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View Full Version : So I'm an Airsoft store tech/manager, let me edjecate yous :)



Electricity
06-30-2008, 06:14 PM
Hey guys, My name is Sam Agger, I'm a manager/tech of an airsoft shop here in baltimore md, I've always been interested in robots, but have never found the time (or money) to get started. I followed Sienna back here from an airsoft forum (www.maapr.com) and became engrossed. You guys do some amazing stuff here!
I'm hopping to be able to afford a Bioloid Beginner Kit (http://www.trossenrobotics.com/bioloid-beginner-robot-kit.aspx), but we'll have to wait and see.
Anyways, I'm hoping I can help clear up some misconceptions as far as airsoft goes.
First off, the little airsoft cannons posted in another thread are utter crap, I feel bad for the dude who bought 5 of um! The metal gearboxes are a bit better, with some upgrades they would perform admirably.
First about bb weight, yes there are many many different weights available.
.12g Used for nothing but the cheapest of guns. Very poorly manufactured, often out of round, seamed, or dented.
.20g The standard round. Almost any gun will shoot the twenty. They arn't amazing, but their ok. The only types of guns that would use a 20 as a standard would be an AEP/GBB (automatic electronic pistol, or gas blow back pistol).
.23-.25g The standard round for almost all AEGs (automatic electric gun, re. Rifles, carbines, machine guns etc). The extra weight over the twenty, while it does delay the travel speed by fractions of a second is far outweighed by the fact that the bb flys much straighter, and further. Better accuracy and brush penetration (re. shoots through small leaves instead of bouncing off.)
.28g + (upwards of .42 sometimes) These are sniper weight bbs, designed for single shot sniper rifles that need all the range and accuracy possible.

Next, let me explain a bit about how the gear box functions, Heres a good animated short
http://www.mechbox.com/data/how-the-mechbox-works
The motor spins the bevel gear, which in turns spins the spur gear, which in turn spins teh sector gear, which pulls the piston back, and then releases it. The sector gear also actuates the tappet plate, that allowes a new bb to be loaded.
To answer the question of velocity, 350 is probably the average for most high end aegs. To lower the velocity (and increase the speed) the easiest way is to replace the spring with a lighter weight spring, or simply cut a bit off the stock spring. There are other ways as well, that that is the easiest, and most reversible.

That all being said, the current gear box is fairly archaic and in desperate need of a revamp. I'm thinking robotics enthusiasts would be the ones to do it :) How about a belt driven mech box..

Anyways, let me tell you about another little goodie we have that I'm sure you guys will find VERY interesting. The m203 bb shower grenade.
http://www.spartanimports.com/IMAGES/PARTS/a075m.jpg (one of many, i wanted to take a picture of the ones we have in store, but my cell phone is dieing).
These little babies are designed to be shot through an m203 launcher, mounted under the gun. But in actuality can be shot by pressing the little plunger on the back. They shoot between 16 and 300 bbs per shell.
http://www.gamershell.com/static/boxart/large/363.jpg
Shoulder mounted perhaps? Or have a revolver style arm..
I debated whether I wanted to mention these, because Would love to built a mech of my own, and the element of surprise is always fun.

As far as the scoring goes, I think you should have something closer to 100, if not more. The reason being that airsoft guns are easily capable of shooting 20+bps (balls per second), with most stock guns shooting 10-15, even upwards of 30, 40, I saw a gas gun that did 80, and I personally have a special model that shoots ~150 rps. :veryhappy:
My point is, at 10 hits to death, I could have your mech down in less then a second with a properly tuned gun.
I would love to help in the planning of an even local to me (Cockeysville, Maryland), and would also be more then willing to help anyone and everyone acquire parts, and understand airsoft, and anything else I know.
As I said earlier, I'm hoping to be able to build a mech of my own (I've got me some ideas.. ), however I have no idea where to begin, is there anyone local who'd be willing to take me under their wing and show me the ropes? Perhaps someone would be willing to start a team/pit crew/project with me for this round of tournies. I'm more then willing to do what it takes, I even have plenty of spare parts and such laying around waiting for something fun to do with them.
I really am looking forward to joining this amazing community, and hopefully building me some robot goodness!

DresnerRobotics
06-30-2008, 06:21 PM
Thanks for the input and welcome! The biggest reason we were looking at those little airsoft tank cannons is size and weight. I realize they are not in the same class as a real airsoft weapon, but they are super light weight and fairly compact.

Since we're looking at walking robots, our payload is very limited. Rapid firing isnt so much something I'm personally looking for, however a very compact and light weight firing mechanism is. Also would greatly prefer something that had an electric firing mechanism. I'm shooting for less than 500grams for 2 weapons total.

Do you have any suggestions as far as a part that would fit that criteria?

Electricity
06-30-2008, 06:51 PM
The m203 shells I would guess to be ~6 ounces, making them about 170 grams, I also have the guts to an mp7 airsoft gun that, with all the extra fluff you wouldn't need, like selector switch, battery etc, but no magazine to be approximately 8 ounces, or 227 grams. It is electronic, and shoots at about 230-250 fps. That would be ideal, you could also look into AEPs, automatic electronic pistols http://www.pointact.com/prod_M81_451_16.html being one such gun, about the same fps, with a much higher ROF. I would guess (don't have one in the shop at the moment) them to weigh approximately a pound all told, so by the time you gutted them, they would be much less. You could also look into gas pistols, while a bit weightier, with some guttage you could probably get them down to spec. They are semi and full auto, most shooting around 300 fps. They have the added awesomeness factor of having blow back, meaning the slide blows back on each shot. With a bit of custom fabrication, you could make one amazing looking gauss rifle, or something similar.
Most gear boxes weigh in under a pound as they sit, but with some customization to the box itself you could reduce that significantly. Then you would just have to fab a feed system of some sort.
Then of course there are the shot guns.. >:)
http://www.airsoftpost.com/product_info.php?cPath=21_47&products_id=27951&osCsid=ed213fab494cc28ba9dd871179ebcbef
Buy it just for the shells, the gun is a trash cloan. I don't know the weight, but I'd imagine less then a real shotty shell. Each shell is filled with gas, and shoots 14 bbs at once at ~280 fps. They have a similar plunger system to the m203 granades. You would just have to fab a firing/loading mechanism.

dcalkins
06-30-2008, 08:34 PM
I'm still a bti concerned about the use of BB's... Ricochets into teh crowd and suddenly I'm trapped in a "christmas story"

How big a play field again? I could grab a few of the old steel-conflict cmobat arena wall modules for protection, but that's a lot of work for this.

JonHylands
06-30-2008, 08:37 PM
I think we should either not allow full auto, or change the targeting system to wait one second in between "hits" before another hit is registered. Simpler to just not allow full auto. I'm not interested in having someone dump 100 BBs per second into my target, just because the mechs can't react that fast, and count that as 100 hits. Seems like whoever spends the most money on a gun wins, in that case.

Maybe one or two rounds, per barrel, per second.

Thoughts?

JonHylands
06-30-2008, 08:40 PM
I'm still a bti concerned about the use of BB's... Ricochets into teh crowd and suddenly I'm trapped in a "christmas story"

How big a play field again? I could grab a few of the old steel-conflict cmobat arena wall modules for protection, but that's a lot of work for this.

Dave, we're talking about having full six-sided protection in the arena. Floor, walls, ceiling.

Personally, I think the front wall should be plexi, and the roof should be fine netting.

dcalkins
06-30-2008, 09:32 PM
>Dave, we're talking about having full six-sided protection in the arena. Floor, walls, ceiling.

I don't think you'll need floor protection! We abuse the Ft. Mason floor a lot, and it hold up fine.

A-Bot
06-30-2008, 09:34 PM
Maybe one or two rounds, per barrel, per second.

Thoughts?

I kind of assumed full auto would be ok, but you make a good point. I was thinking ammunition will be limited on these bots, and I'm not sure target hits are going to come that easily. Bots don't want to be hit. An ammo constraint could be used to force a more conservative approach.

To your point, MechWarrior fans will remember that the mechs easily overheat when weapons are over-used, so I am definitely in favor of a burst-size limit in any case for the realism factor.

Perhaps a five-round burst with a two second delay between bursts? I like Jon's general idea of keeping the complexity out of the target. The builder should have to deal with the extra complexity to get to use auto bursts.

DresnerRobotics
06-30-2008, 10:04 PM
I'm still a bti concerned about the use of BB's... Ricochets into teh crowd and suddenly I'm trapped in a "christmas story"

How big a play field again? I could grab a few of the old steel-conflict cmobat arena wall modules for protection, but that's a lot of work for this.


David, even if we're going the route of an enclosed arena, I was still planning on sticking with airsoft ammunition until we (if we get to this point) go with a full blown battle-bots type arena. The rules still state airsoft only and I would not change that unless I got it cleared with you first.

dcalkins
06-30-2008, 10:34 PM
OK, thanks for the clarification!

Adrenalynn
06-30-2008, 11:12 PM
I can't imagine steel BB's as a good idea. There's just no good argument I can envision for them.

I think the DefCon Bots folks have considered some good points in their rules, which seemed to work pretty unchanged at The 'Games.

Sam, welcome aboard and thanks for your insights!

I'm the "dude[tte]" that bought a handful of those tank guns. Yes, they stink on ice - but they're actually pretty darned educational. With an 8" competition barrel slapped on the front, and cleaning up the gearboxes by getting rid of the gunk in 'em and replacing it with white lithium, they actually shoot pretty consistantly.

I wonder if coming at this from a competition airsoft perspective as you appear to be may not be the best way to look at it. Sure, if you don't move around much I can dump the entire clip from my TM M14 into center-mass from 75'. The entire arena is 15'^2. I just tried it in the lab, and I can hit a piece of paper at-will throwing a 28g airsoft pellet by hand from 12'+. That StinksOnIce tank cannon has no problem with banging on a paper plate consistantly from the same 12'. (My long section of lab table is 12' long). A little inaccuracy is probably a good thing in this particular sport. One bot hiding behind a building and long-balling everyone to death isn't very exciting... CQB has got to be the name of this game, IMHO, also remembering that we're dealing at, what about 1/8 - 1/10 human scale, 1/25-1/40th "mech scale"?

Another thing to consider in the weight is swinging that mass around with a pan-tilt built from servos. There's no worm gear box there, consumer servos slap like mad. Every nanogram you add to those things heightens the negative targeting effect tremendously.

So the upshot is that I'm not trading in my TM M14 for one of these tank guns, but they're insanely cheap, easy, light, and disposable. I don't know if I'm ready to discount them for various projects involving things that go "pop" yet. :)

Your thoughts?

DresnerRobotics
06-30-2008, 11:33 PM
I can't imagine steel BB's as a good idea. There's just no good argument I can envision for them.

I think the DefCon Bots folks have considered some good points in their rules, which seemed to work pretty unchanged at The 'Games.

Sam, welcome aboard and thanks for your insights!

I'm the "dude[tte]" that bought a handful of those tank guns. Yes, they stink on ice - but they're actually pretty darned educational. With an 8" competition barrel slapped on the front, and cleaning up the gearboxes by getting rid of the gunk in 'em and replacing it with white lithium, they actually shoot pretty consistantly.

I wonder if coming at this from a competition airsoft perspective as you appear to be may not be the best way to look at it. Sure, if you don't move around much I can dump the entire clip from my TM M14 into center-mass from 75'. The entire arena is 15'^2. I just tried it in the lab, and I can hit a piece of paper at-will throwing a 28g airsoft pellet by hand from 12'+. That StinksOnIce tank cannon has no problem with banging on a paper plate consistantly from the same 12'. (My long section of lab table is 12' long). A little inaccuracy is probably a good thing in this particular sport. One bot hiding behind a building and long-balling everyone to death isn't very exciting... CQB has got to be the name of this game, IMHO, also remembering that we're dealing at, what about 1/8 - 1/10 human scale, 1/25-1/40th "mech scale"?

Another thing to consider in the weight is swinging that mass around with a pan-tilt built from servos. There's no worm gear box there, consumer servos slap like mad. Every nanogram you add to those things heightens the negative targeting effect tremendously.

So the upshot is that I'm not trading in my TM M14 for one of these tank guns, but they're insanely cheap, easy, light, and disposable. I don't know if I'm ready to discount them for various projects involving things that go "pop" yet. :)

Your thoughts?


Very good points all around. I think airsoft competition type gear is a bit overkill for this given it's scale, and from the sound of it those cannons might work quite well. Don't need them to be super accurate, fast or hard hitting, we need them to be light and compact.

dcalkins
06-30-2008, 11:51 PM
For all those new to humanoids: Don't count on a 12-14" humaniod being able to carry much more than a pound total - including the camera system. The record from FIRA is 1.5 pounds, and that's w/o moving around a cityscape.

So presuming a camera system is around 4oz, that gives you 12 oz (340 grams) for a gun system - including your actual ammo. Presume no batteries though - that the gun get's its power form the native 6VDC 'bot batteries. YMMV

DresnerRobotics
07-01-2008, 12:05 AM
For all those new to humanoids: Don't count on a 12-14" humaniod being able to carry much more than a pound total - including the camera system. The record from FIRA is 1.5 pounds, and that's w/o moving around a cityscape.

So presuming a camera system is around 4oz, that gives you 12 oz (340 grams) for a gun system - including your actual ammo. Presume no batteries though - that the gun get's its power form the native 6VDC 'bot batteries. YMMV


Great information here, I'm going to add this to the site so that people have realistic expectations. I was shooting for the 400-500g max range anyway, I'll probably try to trim that back a bit. Looks like those 70g airsoft cannons are going to be the ticket.

David do you have any additional info on that record? What servo type/torque and what the frame was made of?

Adrenalynn
07-01-2008, 12:07 AM
Here's a fairly high-res photo of what we're talking about, scaled. [Click twice for max zoom]

Adrenalynn
07-01-2008, 12:13 AM
My weights on four: 69g, 70g, 70g, 72g - about 2.6oz.

My 8" barrel was pretty close to that again, but I'm working on a different project needing better accuracy...

0.12g bb's, let's say you carry 50 of them: ~6g.

Call it 160g out the door, worst case, ready to rock-and-roll. That's assuming that you are careful with your hopper design...

[edit] You guys are dropping a lot of weight in your designs with limited upper bodies, right?

DresnerRobotics
07-01-2008, 12:31 AM
My weights on four: 69g, 70g, 70g, 72g - about 2.6oz.

My 8" barrel was pretty close to that again, but I'm working on a different project needing better accuracy...

0.12g bb's, let's say you carry 50 of them: ~6g.

Call it 160g out the door, worst case, ready to rock-and-roll. That's assuming that you are careful with your hopper design...

[edit] You guys are dropping a lot of weight in your designs with limited upper bodies, right?

My upper torso will be fairly limited. One servo for torso rotate that will be positioned in between the two hip servos. The upper torso will consist of a light aluminum frame and only 2 servos total for pan/tilt on both arms.

So, compared the the stock bioloid, mine will be 3 AX-12s lighter and using a Lithium Ion battery instead of the Nimh, plus the weight of the weapon systems. I should be way under the limit and am trying to keep it as lightweight as possible.

Adrenalynn
07-01-2008, 12:36 AM
I think that's a good design tip and adds another layer to consider in ones design. It's an inherent engineering challenge/limitation, which are so much more appealing [to me] than arbitrary limitations.

dcalkins
07-01-2008, 12:45 AM
IRT lifting capabilities:

Yes, you could take off the arms of an off-the-shelf bot (RoboNova, KHR-1/2, Bioloid, etc.), but don't forget that those arms help balance while walking...

You can also upgrade servos (for example, all my RoboNova's have upgraded ankle servos - from the stock HSR-8498HB w/102 oz.in of torque to the HSR-5498SG w/152 oz.in of torque.) for a higher load capacity, but don't forget they pull more amps and thus battery life is decreased. Of course the robotis dynamixel offers 229 oz.in of torque, and the Hitec HSR-5990TG gives you 416 oz.in of torque... so YMMV depending on what servos you use (and of course, these are all mfg specs, I cannot vouch for any of their veracity.)

You can of course build your own bot from scratch (highly un-recommended for a beginner), or go with this tres-cool kit:

http://www.lynxmotion.com/Category.aspx?CategoryID=67

...

The problem with forums is that there's always more talk than action... ;-)

DresnerRobotics
07-01-2008, 12:55 AM
IRT lifting capabilities:

Yes, you could take off the arms of an off-the-shelf bot (RoboNova, KHR-1/2, Bioloid, etc.), but don't forget that those arms help balance while walking...

You can also upgrade servos (for example, all my RoboNova's have upgraded ankle servos - from the stock HSR-8498HB w/102 oz.in of torque to the HSR-5498SG w/152 oz.in of torque.) for a higher load capacity, but don't forget they pull more amps and thus battery life is decreased. Of course the robotis dynamixel offers 229 oz.in of torque, and the Hitec HSR-5990TG gives you 416 oz.in of torque... so YMMV depending on what servos you use (and of course, these are all mfg specs, I cannot vouch for any of their veracity.)

You can of course build your own bot from scratch (highly un-recommended for a beginner), or go with this tres-cool kit:

http://www.lynxmotion.com/Category.aspx?CategoryID=67

...

The problem with forums is that there's always more talk than action... ;-)

Problem with the Lynx scout is that it is a bit heavy material wise, and you couldn't effectively pull it off in this competition with any less than 12x HSR5990s.

Something to keep in mind with the Dynamixels is that they're rated for 229oz torque @ 10v, but they easily run 12v (this is what the wall wart supplies, and also about what 3s lipo provides) which gives them about 275oz/in of torque. That is a lot of torque for very little money, and once we get a control scheme figured out for Bioloid it will be publicly available. Just something to keep in mind for those deciding on what type of servos to use.

dcalkins
07-01-2008, 01:26 AM
This guys seems to carry a pretty big load:

http://www.jdpuddy.me.uk/scout.html

DresnerRobotics
07-01-2008, 01:39 AM
This guys seems to carry a pretty big load:

http://www.jdpuddy.me.uk/scout.html


Very nice. He's still powering the 106 via tether... but I'd actually prefer the old style pvc construction lynx scout over the aluminum version, I'd wager you save some weight there. Wonder what type of servos he is using.

dcalkins
07-01-2008, 01:49 AM
IN my experience, there's negligible weight diff. between the lynx polycarb (not pvc) and the alum. The alum is so much thinner than the ply that it balances out.

GO TO BED.

lamont
07-01-2008, 01:52 AM
That StinksOnIce tank cannon has no problem with banging on a paper plate consistantly from the same 12'. (My long section of lab table is 12' long). A little inaccuracy is probably a good thing in this particular sport. One bot hiding behind a building and long-balling everyone to death isn't very exciting... CQB has got to be the name of this game, IMHO, also remembering that we're dealing at, what about 1/8 - 1/10 human scale, 1/25-1/40th "mech scale"?

As someone interested in other uses for those guns as well, how you estimate the accuracy is on that 12' distance?

My tank guns have not arrived yet, so I'm still wondering how I'll feed them and how well they'll shoot at a distance. For both Mech, and defConBots.

4mem8
07-01-2008, 01:57 AM
I will stick with my 4 airsoft tank barrels to experiment with like adrenalynn, room for experimenting here for the first year anyway.

Adrenalynn
07-01-2008, 01:57 AM
Hi Lamont,

Not terribly great in the sizes we're looking for (<1/2" repeatable) - but the rate of fire may be enough to make up for it, and I'm still tuning barrel selection, so I'll continue to update. It's certainly good enough not to bag a black target by accident, but I figure it would probably take a half dozen rounds to hit a 1/2" target. I'm still thinking about deliberate oscillation or individual shot tracking and correction ala the Phalanx. :)

lamont
07-01-2008, 02:06 AM
Well crap. The 1/2" repeatable would make things a lot easier. Maybe I can make new barrel and give that a shot. (pun, deal with it) I'll have to wait till mine show up to play with.

Thanks for the quick reply.

dcalkins
07-01-2008, 02:06 AM
Maybe we can rifle the barrels? can't be THAT hard.

lamont
07-01-2008, 02:11 AM
Maybe we can rifle the barrels? can't be THAT hard.

Rifling seems to help with larger projectiles, as well as putting baffles at the end (or drilling holes near the end) which lets air escape sideways rather than blow past the projectile and messing up the flight path of the shot.

I can do either, but I'll experiment with air escapes on the end first, as that's easiest.

dcalkins
07-01-2008, 02:15 AM
Want one!
http://www.airsoftgi.com/product_info.php?products_id=1424

dcalkins
07-01-2008, 02:16 AM
Lamont:

Maybe we should have a play-date.

lamont
07-01-2008, 02:19 AM
Last play-date with you I ended up in a park being shot at by roman candles.

Good times, Good times.

dcalkins
07-01-2008, 02:21 AM
Oooo... I got new ones. These ones.... well, the recoil is harsh. About 5x the power of normal candles. Need f-in' welding masks for RC fights if you use these (They're called Titanium's. about 3" thick. Almost as big as a mortar.)

Adrenalynn
07-01-2008, 02:33 AM
Those basically just spray a few hundred pellets in all directions. The shells don't launch (that I've ever seen in an airsoft game) - they're just not that exciting or practical really

In my experience, "hop-up" works better than rifling. Same concept as putting backspin on a golfball.

I'm using a 6.04mm competition barrel, Lamont - it's pretty good - but no hop-up unit on these guns. Building hop-up for them shouldn't be tough...

dcalkins
07-01-2008, 02:42 AM
Those basically just spray a few hundred pellets in all directions. The shells don't launch (that I've ever seen in an airsoft game) - they're just not that exciting or practical really

Probably hit the other guy with one of those hundred pellets though, now wouldn't you?

And the crowd would LOVE it.


I'm using a 6.04mm competition barrel, Lamont - it's pretty good - but no hop-up unit on these guns. Building hop-up for them shouldn't be tough...

Link?

Adrenalynn
07-01-2008, 02:50 AM
And the crowd would LOVE it.


Got me there with my own logic...



Link?

http://www.airsplat.com/Categories/AC-UPI-BARREL.htm

http://steelhawkairsoft.com/barrelsandhopup.html

http://en.wikipedia.org/wiki/Airsoft_pellets#Hop-up_.26_Bernoulli.27s_principle

DresnerRobotics
07-01-2008, 02:57 AM
Oooo... I got new ones. These ones.... well, the recoil is harsh. About 5x the power of normal candles. Need f-in' welding masks for RC fights if you use these (They're called Titanium's. about 3" thick. Almost as big as a mortar.)

This sounds fantastically dangerous, and fun :veryhappy:

dcalkins
07-01-2008, 03:16 AM
This sounds fantastically dangerous, and fun :veryhappy:

Yea... When Simone gives birth in December, we're planning on making "Baby's first proximity suit."

We actually baby-sit for a five-year old. I got her a full face shield. Deal is, if she cleans her plate, we let her blow shit up. Safely, of course.

She's just adorable in the face-shield and flak vest. Safer than a riot cop, but much, MUCH cuter.

Our child, of course, will have his/her very own nomex body suit and balaclava.

Charles Addams eat your heart out. :p

Adrenalynn
07-01-2008, 03:25 AM
The mental image presented is awesome there. . . :)

Alas, it's such a different world these days than it was when I was young. I'm even hesitant to talk rocketry these days...

Congrats to the both of you, BTW!

sthmck
07-01-2008, 09:59 AM
Oooo... I got new ones. These ones.... well, the recoil is harsh. About 5x the power of normal candles. Need f-in' welding masks for RC fights if you use these (They're called Titanium's. about 3" thick. Almost as big as a mortar.)

My buddy wants to know where you got those. Or did you make them?

Droid Works
07-01-2008, 11:17 AM
Hey guys, My name is Sam Agger, I'm a manager/tech of an airsoft shop here in baltimore md, I've always been interested in robots, but have never found the time (or money) to get started. I followed Sienna back here from an airsoft forum (www.maapr.com (http://www.maapr.com)) and became engrossed. You guys do some amazing stuff here!
I'm hopping to be able to afford a Bioloid Beginner Kit (http://www.trossenrobotics.com/bioloid-beginner-robot-kit.aspx), but we'll have to wait and see.
Anyways, I'm hoping I can help clear up some misconceptions as far as airsoft goes.
First off, the little airsoft cannons posted in another thread are utter crap, I feel bad for the dude who bought 5 of um! The metal gearboxes are a bit better, with some upgrades they would perform admirably.
First about bb weight, yes there are many many different weights available.
.12g Used for nothing but the cheapest of guns. Very poorly manufactured, often out of round, seamed, or dented.
.20g The standard round. Almost any gun will shoot the twenty. They arn't amazing, but their ok. The only types of guns that would use a 20 as a standard would be an AEP/GBB (automatic electronic pistol, or gas blow back pistol).
.23-.25g The standard round for almost all AEGs (automatic electric gun, re. Rifles, carbines, machine guns etc). The extra weight over the twenty, while it does delay the travel speed by fractions of a second is far outweighed by the fact that the bb flys much straighter, and further. Better accuracy and brush penetration (re. shoots through small leaves instead of bouncing off.)
.28g + (upwards of .42 sometimes) These are sniper weight bbs, designed for single shot sniper rifles that need all the range and accuracy possible.

Next, let me explain a bit about how the gear box functions, Heres a good animated short
http://www.mechbox.com/data/how-the-mechbox-works
The motor spins the bevel gear, which in turns spins the spur gear, which in turn spins teh sector gear, which pulls the piston back, and then releases it. The sector gear also actuates the tappet plate, that allowes a new bb to be loaded.
To answer the question of velocity, 350 is probably the average for most high end aegs. To lower the velocity (and increase the speed) the easiest way is to replace the spring with a lighter weight spring, or simply cut a bit off the stock spring. There are other ways as well, that that is the easiest, and most reversible.

That all being said, the current gear box is fairly archaic and in desperate need of a revamp. I'm thinking robotics enthusiasts would be the ones to do it :) How about a belt driven mech box..

Anyways, let me tell you about another little goodie we have that I'm sure you guys will find VERY interesting. The m203 bb shower grenade.
http://www.spartanimports.com/IMAGES/PARTS/a075m.jpg (one of many, i wanted to take a picture of the ones we have in store, but my cell phone is dieing).
These little babies are designed to be shot through an m203 launcher, mounted under the gun. But in actuality can be shot by pressing the little plunger on the back. They shoot between 16 and 300 bbs per shell.
http://www.gamershell.com/static/boxart/large/363.jpg
Shoulder mounted perhaps? Or have a revolver style arm..
I debated whether I wanted to mention these, because Would love to built a mech of my own, and the element of surprise is always fun.

As far as the scoring goes, I think you should have something closer to 100, if not more. The reason being that airsoft guns are easily capable of shooting 20+bps (balls per second), with most stock guns shooting 10-15, even upwards of 30, 40, I saw a gas gun that did 80, and I personally have a special model that shoots ~150 rps. :veryhappy:
My point is, at 10 hits to death, I could have your mech down in less then a second with a properly tuned gun.
I would love to help in the planning of an even local to me (Cockeysville, Maryland), and would also be more then willing to help anyone and everyone acquire parts, and understand airsoft, and anything else I know.
As I said earlier, I'm hoping to be able to build a mech of my own (I've got me some ideas.. ), however I have no idea where to begin, is there anyone local who'd be willing to take me under their wing and show me the ropes? Perhaps someone would be willing to start a team/pit crew/project with me for this round of tournies. I'm more then willing to do what it takes, I even have plenty of spare parts and such laying around waiting for something fun to do with them.
I really am looking forward to joining this amazing community, and hopefully building me some robot goodness!
I like the m203 very much. Do you have a link so I can buy one. It would look great on the shoulder of my mech.

Electricity
07-01-2008, 12:00 PM
I can't imagine steel BB's as a good idea. There's just no good argument I can envision for them.
Neither can I, all airsoft bbs are made of plastic, or starch in the biodegradable ones.
Infact, you'll note that steal/copper bbs are actually much smaller than airsoft, and can't be shot.


I think the DefCon Bots folks have considered some good points in their rules, which seemed to work pretty unchanged at The 'Games.

Sam, welcome aboard and thanks for your insights!

I'm the "dude[tte]" that bought a handful of those tank guns. Yes, they stink on ice - but they're actually pretty darned educational. With an 8" competition barrel slapped on the front, and cleaning up the gearboxes by getting rid of the gunk in 'em and replacing it with white lithium, they actually shoot pretty consistantly.

I wonder if coming at this from a competition airsoft perspective as you appear to be may not be the best way to look at it. Sure, if you don't move around much I can dump the entire clip from my TM M14 into center-mass from 75'. The entire arena is 15'^2. I just tried it in the lab, and I can hit a piece of paper at-will throwing a 28g airsoft pellet by hand from 12'+. That StinksOnIce tank cannon has no problem with banging on a paper plate consistantly from the same 12'. (My long section of lab table is 12' long). A little inaccuracy is probably a good thing in this particular sport. One bot hiding behind a building and long-balling everyone to death isn't very exciting... CQB has got to be the name of this game, IMHO, also remembering that we're dealing at, what about 1/8 - 1/10 human scale, 1/25-1/40th "mech scale"?
Firstly, thank you, I'm glad to be here. :)
I suppose its really what your looking for in a competition, and what the robots are capable of doing. I really don't know, my experience with robots consists of picking up a little hexbot thingie from Rat Shack for ten bucks and letting it wonder around my desk. I'll have to learn more about bots in general before I can render more of an opinion.


Another thing to consider in the weight is swinging that mass around with a pan-tilt built from servos. There's no worm gear box there, consumer servos slap like mad. Every nanogram you add to those things heightens the negative targeting effect tremendously.
[quote]
Which, from an uneducated stand point might not be a bad thing, sure you can't aim worth crap, but you can sure keep some heads down! :p
Again, I was not (and still am not) aware at all of design limitations, and will have to learn more about your side of things before I can hope to render an educated opinion.
[quote]
So the upshot is that I'm not trading in my TM M14 for one of these tank guns, but they're insanely cheap, easy, light, and disposable. I don't know if I'm ready to discount them for various projects involving things that go "pop" yet. :)

Your thoughts?I guess maybe I'll have to pick one of these guys up and do some playing arounds with it, see what I can come up with.


Hi Lamont,

Not terribly great in the sizes we're looking for (<1/2" repeatable) - but the rate of fire may be enough to make up for it, and I'm still tuning barrel selection, so I'll continue to update. It's certainly good enough not to bag a black target by accident, but I figure it would probably take a half dozen rounds to hit a 1/2" target. I'm still thinking about deliberate oscillation or individual shot tracking and correction ala the Phalanx. :)
Might I suggest you try .20g weight bbs instead of the 12s your currently using. Not only will you see better accuracy, you will note that the manufacturing on the 20s is much much better then the crap they produce in 12s.

Those basically just spray a few hundred pellets in all directions. The shells don't launch (that I've ever seen in an airsoft game) - they're just not that exciting or practical really

In my experience, "hop-up" works better than rifling. Same concept as putting backspin on a golfball.

I'm using a 6.04mm competition barrel, Lamont - it's pretty good - but no hop-up unit on these guns. Building hop-up for them shouldn't be tough...
You got the right idea there. For small round pellets, hop up works much much better then rifling or porting, a properly tuned hopup will produce as much as 3x the standard range.
The way hopup works is thus.
At the back end of the barrel is a little slit, around the barrel is a rubber sleave with a nub that sits inside of the slit. Ontop of the barrel is the actual hopup chamber that has an adjustable arm that pushes down on the nub, making to go further into the barrel. When the bb is shot, it hits the nub, giving it back spin. The bb then 'floats' through the air, similar to an airplane wing (more air pressure above, less below) and travels in a much straiter line, rather then arcing. However in a 15x15 arena, I can't imagine hop up doing a whole lot.. :p

I like the m203 very much. Do you have a link so I can buy one. It would look great on the shoulder of my mech.
http://www.airsoftpost.com/index.php?cPath=23_58&osCsid=e94c73964dc973510b967172544cf932
Take your pick.. :) We don't have any m203s in stock, but can usually get them. That link has just about every kind available.
Theres a vid of one shooting..

Edit: heres said link
YouTube - Chad hit with M203

DresnerRobotics
07-01-2008, 12:09 PM
Just wanted to say, really appreciate your input on this. Its awesome to have an airsoft professional chiming in as its certainly not most of our area of expertise. Like I said- we picked the RC Airsoft Tank cannons due to their compact size and light weight, as in <100g per cannon... and I wasn't aware there was a pro-airsoft equivalent in that size/weight class.

Electricity
07-01-2008, 12:17 PM
Just wanted to say, really appreciate your input on this. Its awesome to have an airsoft professional chiming in as its certainly not most of our area of expertise. Like I said- we picked the RC Airsoft Tank cannons due to their compact size and light weight, as in <100g per cannon... and I wasn't aware there was a pro-airsoft equivalent in that size/weight class.
Glad to be apart of this! I'm really looking forward to learning all I can from you guys, and sharing whatever small bits of info I might possess as well! I hope that I can afford at somepoint to make a robot of my own, maybe even a mech!
Heres a question, is there a program available that would allow me to learn/practice some aspects of programing a robot, without actually having one available to test?

Adrenalynn
07-01-2008, 12:33 PM
Thanks again for your insights!

I understand that you're coming at this from a "new to robotics" perspective - you've been gentle with "us", I'm sure we can return the consideration!

Lamont and I are working on a different project - an autonomous weapon platform designed to shoot targets. We have some overlap with this project, so we're sharing our research. Have a look at defconbots.org - you might enjoy a readthrough, and my apologies for any confusion this might have caused.


Might I suggest you try .20g weight bbs instead of the 12s your currently using. Not only will you see better accuracy, you will note that the manufacturing on the 20s is much much better then the crap they produce in 12s.


I tried the 28's that I shoot in my "real" airsofts and they were just too heavy to get any muzzle velocity. The 20's are a good recommendation, splitting the difference, but I didn't have any laying around. I had some 12's that came with my first spring airsoft pistol, so they got pressed into service. ;)

Yup, hop-up leverages the Bournelli Principle and Magnus' Law [assuming the effect exists in the real world] [sorry, I'm a science geekette ;)]. Even over shorter distances I suspect it would help keep the ball from curving (a "slice" in golf) which is something that I observed with these tank guns. I flared the end of my barrel a tiny bit and it seems to have radically impacted how straight it shoots for the 10-15' I'm playing in. Vice mounted, it will pound a 2" circle all day (cycling in the background as I write) and seems to put about 30&#37; into my required <0.5" circle. I would like to experiment with a chopped-down hop-up barrel, even non-adjustable, and see what happens. Do you have any suggestions? I see them out there on fleaBay, but...

I'd like to not pay a huge chunk of money for it, and it doesn't need to be uber-grade, recognizing I'm going to be cutting it down and experimenting.

I'm sure this doesn't concern you, but as a note for others, any playing with these tank guns does require some "smithing". There's no seal inherent at the exit port, and every one of the ones I picked-up had bad solder joints on the noise capacitor. They also only use single cap noise filtering (sigh), so that should be improved for robotics use. The gearbox should *really* be torn down and the junk gunk lubricant replaced with something like white lithium or teflon suspended in lithium (which is what I'm using). It makes a differences on motor load, probably on the gear life, and added nearly 10fps to the muzzle velocity [as chrono'd].

Electricity
07-01-2008, 01:11 PM
Well, you could probably fabricate your own hopup assembly with little effort.
I don't know what your using for a barrel, but I've found that hobby brass tubbing works just fine for certain applications. the ID is way way to wide for accuracy (you really need something 6.08mm or smaller, but probably no smaller then 6.025 or so) but could be used as a base if nothing else. I forget the diameter tubing that fits airsoft pellets, but I'm sure if you take one in to your local hobby shop, they'd let you stick it down a few tubes and see what fits :p
Anyway, lets pretend you have a pretty good barrel, to make a hopup assembly is really not that hard.
You begin by cutting you a small notch into the back of the barrel, just like with a real as barrel. I don't have any proper measuring tools on hand, but I'm gonna go ahead and guess that it doesn't matter all that much. I used a bb to estimate the size, the bb fits into the notch perfectly, leading me to believe it to be ~ 6mmx6mm on the top, and extending 2.5mm into the barrel itself.
here is a picture of a stock barrel's hopup end.
http://i31.tinypic.com/2a4z9kg.jpg
http://i32.tinypic.com/9gats0.jpg
Sorry for the blur, cell phone pic..
Anyways, once you have that notch, you would wrap it tightly with electrical tape with the first layer being reversed, so the sticky side doesn't end up in teh barrel, then you could experiment with wrapping it with a bit of wire, pushing the tape into the barrel at different depths to see which works best for you.
Now, that might not work quite right, because your missing the nub still. You could also try with a bit of rubber (say a bikes inner tire), and a small bead or something, placing the rubber around the barrel, and the bead directly over the hole, then wrap it with electrical tape at different preasures to get the best angle.

If you don't mind spending a few bucks, then You could always pick up a stock, or tight bore barrel (stock is usually around 6.08mm id, and tight bores go from 6.04-6.01)
http://www.airsoftpost.com/index.php?cPath=24_72&osCsid=89637114c1ad695f798156c4073bb12e
$20-100 bucks, depending on your tastes. Just cut the barrel down with a pipe cutter to the required length. Personally if I where going that road I'd start with about 8 inches and start cutting of 1/4" segments to see which gave you the best range/flat pattern in the smallest package.
You can then pick up the entire hop up assembly, including the feed port for $20-$30 bucks
http://www.airsoftpost.com/index.php?cPath=24_71&osCsid=89637114c1ad695f798156c4073bb12e
Or just pick up the bucking (the rubber sleeve) for about $5.
Just remember, the hopup nub has to be at the TOP of the barrel, otherwise you will get curve balls left and right, or even down. (which.. if you could rotate your barrel/gun, would give you limited around a building shooting ah lah Wanted, for this thought you'd want an adjustable hopup that your mech could tune itself).
personally I've always wanted to experiment with putting the hopup at the FRONT of the barrel, not the rear. It seems to me it would work a lot better if the last thing the bb did was catch a back spin, rather then entering the barrel with a spin, and having the entire length of the barrel to loose it/change directions.

dcalkins
07-01-2008, 01:16 PM
My buddy wants to know where you got those. Or did you make them?

New Mexico. You can get ANYTHING there.

Adrenalynn
07-01-2008, 01:44 PM
Awesome, thanks for saving me from disassembling my TM. :D

I just notched an 8" tight fit barrel and put a rubber grommet over the hole. The highspeed certainly shows backspin now that didn't exist before. I have to do some real work, so I can't test too much more at the moment, but that's a GREAT start, thank you!

A-Bot
07-01-2008, 05:31 PM
I just notched an 8" tight fit barrel and put a rubber grommet over the hole.

Can we see a pic of your assembly?

Alex
07-01-2008, 09:39 PM
I haven't read all of these Mech threads, so be gentle with me if this has already been addressed:D

Matt and I built a pan and tilt firing range using an airsoft gun, some phidgets and a SES P&T and showed it off at Maker Faire in 07. The problem that we kept running into is the plastic bbs breaking occasionally. This wouldn't be so bad, but we were reusing these bbs. Ideally, we wanted to somehow collect all of them into a trap in the bottom of the setup, but we opted for the lazy way and put a sheet at the bottom of the range, stopping every once in a while to empty it;)

Anways, my question is if there are any airsoft pellets out there that are less susceptible to breaking? Is reusing pellets even done in the airsoft world? I'm not sure on the weight of the pellets that we have at work, so I'll have to check that when I get in tomorrow. Also, has it been discussed on if there was intention to recycling the bbs? I can imagine how many bbs there'd be that are reusable at the end of the day.

Adrenalynn
07-01-2008, 09:48 PM
Don't let any airsoftie hear you ask about reusing BB's unless you're wearing your nomex...

At the very least you can't expect ANY consistent accuracy or muzzle velocity from reused BBs. And really, imho, they're too cheap to bother.

dcalkins
07-01-2008, 10:51 PM
Another point to think about during matches: Your robots gonna trip over BB's on the ground. count on it.

better be able to get up...

DresnerRobotics
07-01-2008, 11:04 PM
Another point to think about during matches: Your robots gonna trip over BB's on the ground. count on it.

better be able to get up...

Check out this foot design: http://forums.trossenrobotics.com/showpost.php?p=13287&postcount=9

I'm hoping that will partially alleviate the BB problem.

4mem8
07-02-2008, 03:05 AM
I like that design, It's similar to GwJax mech design, we will also make our to suit our mech.

Alex
07-02-2008, 07:59 AM
What about a slight angle to the arena floor which will help funnel the bb's to one area or in a trap underneath? I still see the floor getting covered in bb's after only a few matches and even that slick foot design won't be able to move around that...

A-Bot
07-02-2008, 09:08 AM
What about a slight angle to the arena floor which will help funnel the bb's to one area or in a trap underneath? I still see the floor getting covered in bb's after only a few matches and even that slick foot design won't be able to move around that...

Yeah, there needs to be a shopvac or some brooms and dustpans to keep it clean. I don't think it will be that much work though.

The BBs on the floor are less of an issue for quad feet.

JonHylands
07-02-2008, 09:10 AM
Sounds like we need a WALL•E robot, with a vacuum cleaner, rolling around between (or even during) matches, scooping up all the fired BBs. Would add an interesting dimension to the whole thing...

Adrenalynn
07-02-2008, 10:12 AM
I already have the perfect 'bot nearing completion. He would not only vacuum the bb's up, he'd scrub the floor clean. :)

Electricity
07-02-2008, 03:25 PM
Never ever ever ever ever reuse bbs! Aside from the grit and grime you're needlessly introducing into your gun, every time the bb is fired it becomes malformed, cracked, dented, completely broken etc. Its just asking for trouble! Just buy more bbs!
As far as the floor, the ol' over analyzing is kicking in again I notice. Just send somoene in with a broom/shop vac in between matches, should take less then 5 minutes, especially if you just make the next two competitors clean it up. Best way to ensure a quick, thorough job.. ;0

Adrenalynn
07-02-2008, 03:39 PM
See? ^ Toldja.

Don't let any airsoftie hear you ask about reusing BB's unless you're wearing your nomex...
Fools rush in where Angels fear to tread... :p :robotsurprised: :p

I think the autonomous vacuum is great, 'cause it's totally in-character.

Alex
07-02-2008, 03:43 PM
Aside from the grit and grime you're needlessly introducing into your gun, every time the bb is fired it becomes malformed, cracked, dented, completely broken etc. Its just asking for trouble! Just buy more bbs!

Fair enough:D


As far as the floor, the ol' over analyzing is kicking in again I notice.

Yeah, engineers tend to over analyze things "sometimes":p Sending someone in between matches is probably the easiest solution. I mean, if you think about combots, how long does it take in between matches to get everything/everyone setup? During that time in Mech game, a couple of peeps could easily have gone in a vacuumed everything up.

DresnerRobotics
07-02-2008, 03:49 PM
I like the idea of the vacuum bot for concept alone :D

We could even mount some of your airsoft cannons on him just for fun ( I was going to suggest the BBs get vacuumed up into it's ammo hopper, but then remembered the advice just given about reusing BBs)

Adrenalynn
07-02-2008, 04:15 PM
Are you TRYING to pick a fight? :eek::p:robotindifferent:

ScuD
07-10-2008, 08:33 AM
What happens to those used bb's btw?
I mean, not in a "they go to heaven to be with their long lost puppy" kind of way, but is there like a recycling programme (or whatever) thing for these?

It's just that in belgium you could get a big fine even for just putting the last piece of pizza in the same bag as an empty plastic coke bottle.

Electricity
07-10-2008, 12:08 PM
Huh really? We actually have a huge bucket full of used bbs. We're not really sure what to do with them. The boss wants me to figure out a way to reuse um. Which I don't think would work, their different weights, and a ton are shattered/dented.

Adrenalynn
07-10-2008, 12:21 PM
The biodegradable ones just melt away.

Speaking of melting away, I've been thinking about melting the non-biodegradable pellets down and trying to use them for casting...

DresnerRobotics
07-10-2008, 12:43 PM
What happens to those used bb's btw?
I mean, not in a "they go to heaven to be with their long lost puppy" kind of way, but is there like a recycling programme (or whatever) thing for these?

It's just that in belgium you could get a big fine even for just putting the last piece of pizza in the same bag as an empty plastic coke bottle.

I'm going to round them up, fly them into the upper stratosphere and burn them using pure crude oil in hopes to weaken the o-zone even more. Welcome to America.

Electricity
07-10-2008, 01:12 PM
I'm going to round them up, fly them into the upper stratosphere and burn them using pure crude oil in hopes to weaken the o-zone even more. Welcome to America.
Will you wrap them in bacon and serve them with a side of fries and diet coke?

A-Bot
07-10-2008, 02:10 PM
I'm going to round them up, fly them into the upper stratosphere and burn them using pure crude oil in hopes to weaken the o-zone even more. Welcome to America.

Ok that's funny.

ScuD
07-10-2008, 03:11 PM
Don't blame me for the environmentalist hype we have here :tongue:

I figured they might be remelted or something, i dunno..

ScuD
07-10-2008, 03:21 PM
Question for the airsoft enthousiasts: the O-rings that nest the BB in the barrel, what size are they typically? ie. inside / outside diameter.
I just turned a simple piece of "barrel container" which would hold the o-ring and bolt, slipped in an O-ring and tested with one of the crappiest BB's ever (can't seem to find any decent ones anymore) but i had to push it pretty hard to get it past the O-ring.

Seems like a good thing, just not sure if i could build up enough pressure

Electricity
07-10-2008, 05:41 PM
Search for hopup bucking.
its not actually an o-ring.

ScuD
07-11-2008, 06:04 AM
Ah, i thought the hop-up was meant to provide only the "rolling" trajectory of the BB.

I'll look into it, thanks!

MSpurk
08-13-2008, 08:19 PM
Electricity, I'm building my own firing mechanism (think baseball pitching machine). In theory I could put 2,000 rounds a second through the gun. That calculation is purely a theoretical maximum based on motor RPM, wheel size, bb size, and assuming the bb's are touching each other, blah blah blah.

Anyway my question is how do the guns with the highest rate of fire ball hoppers work. I have a little pistol and it has a spring with bb's pushed in a straight line up into the gun. That's great for a pistol with 30 shots, but I want some firepower with this bad boy. In practice I'd like to be over the 500 RPS mark.

-Matt-

ScuD
08-14-2008, 04:36 AM
I have drawn a design for a "gatling gun" thingamajig that, in preliminary tests, seems to work, however I haven't had time to complete the build (needs quite some machining) plus I designed it for use with CO2.

I'll try to upload a few pics of the design over the weekend

sam
08-28-2008, 05:49 AM
Anyway my question is how do the guns with the highest rate of fire ball hoppers work. I have a little pistol and it has a spring with bb's pushed in a straight line up into the gun. That's great for a pistol with 30 shots, but I want some firepower with this bad boy. In practice I'd like to be over the 500 RPS mark.

-Matt-

500... Oh my god. I better install a good armor. :rolleyes: How big/small will be your wheels in the mechanism. It has to be pretty small, no?

Electricity
08-28-2008, 10:47 AM
Electricity, I'm building my own firing mechanism (think baseball pitching machine). In theory I could put 2,000 rounds a second through the gun. That calculation is purely a theoretical maximum based on motor RPM, wheel size, bb size, and assuming the bb's are touching each other, blah blah blah.

Anyway my question is how do the guns with the highest rate of fire ball hoppers work. I have a little pistol and it has a spring with bb's pushed in a straight line up into the gun. That's great for a pistol with 30 shots, but I want some firepower with this bad boy. In practice I'd like to be over the 500 RPS mark.

-Matt-
All airsoft guns use a similar mechanism. Anything in the 'mid cap, or low cap' categorizes use that same spring design, sometimes in a U shape for higher capacity. There are also high cap magazines, that will offer you from 200-5000 round capacity. unfortunately I think the feeding mechanism is going to be the slowest part of your setup. You could try to take a page from paintball's book, and make an aggitated hopper like the revolution, or a force fed hopper like the halo2, empire B, etc.

MSpurk
08-30-2008, 07:36 PM
Currently as Electricity explained the hopper is the slow point. I need a better way to get the balls into the gun. They really need to be forced into the wheel to get the RPS up. I was using gravity feed with vibrating motor to aggitate the balls, but it didn't work well. I would say the balls were merely perturbed. ;)

I may build a smaller hopper with a gatling barrels to feed into the gun. Gotta start worrying about height though. :( I originally thought building the gun was going to be the easy part.


500... Oh my god. I better install a good armor. :rolleyes: How big/small will be your wheels in the mechanism. It has to be pretty small, no?

The current wheel is a foam 1-3/8" diameter wheel. The foam expands too much at high speeds, so I'm planning on switching to a 1.7" diameter O-ring wheel.

-Matt-

Electricity
09-12-2008, 09:25 PM
yeah.. That is a problem. Gravity feeds at ~13.5 bps. Consider a large gravity feed. if you're firing mech can take balls at multiple locations, consider just sticking inside a large tube, with a ton of balls that feed into it.

Vsions
09-15-2008, 07:45 PM
Hi electricity, I am relatively new to this hobby, but I am interested in mounting dual airsoft cannons to my machine. I was interested in using a system that is powered by traditional bbgun co2 cartridges as well as fully automatic at about 400-500 fps. I would like to keep it compact but do have a decent sized platform to work with. If you get a moment please check out my design on the project showcase thread and I would appreciate your reccomendations. Thanks

Dennis

dcalkins
09-18-2008, 04:01 AM
Just to remind potential contestants - the scoring system will only record one hit per second. No more. All this talk of 500+ rps is just... gah. I don't even know what it is.

Adrenalynn
09-18-2008, 05:19 AM
All this talk of 500+ rps is just... gah. I don't even know what it is.

Brainstorming? Talking through a design? Exploring design/physical limitations? "Talking Game"? Having fun with low-end projectile "weapons"?


Now you do. ;)

MSpurk
09-19-2008, 01:55 PM
Just to remind potential contestants - the scoring system will only record one hit per second. No more. All this talk of 500+ rps is just... gah. I don't even know what it is.

It's strategy. I'm thinking these things are going to be impossible to aim. A 3"x3" target at 10', fired through a servo controlled gun, viewing the whole thing through a webcam, is becoming more and more challenging as I work it. Plus, from my childhood experience with BB guns they are horribly inaccurate. BB's don't always fly straight, and plastic BB's made in a mold with tool part lines on them I imagine will be worse. No practical knowledge here just guessing. My stragety is spray and pray. If I get a lock on an opponent I can dial it down. It's not glamorous I jsut hope it's effective.

-Matt-

gdubb2
09-19-2008, 02:37 PM
I'm sort of looking at it the same way.. only a little different. I have 1 fully auto gun, but the mechanism is BIG.. so I got a bunch of the tank mechanisms from Mato Toys in Canada. Much cheaper than from Hong Kong. I'll mount 2 guns on Bheka, and hope they fire random enough to get 2 or 3 shots a sec. They operate a 1 shot per sec, at 6 vdc. If I run them a 9 vdc. they should be OK. Oh yeah..laser sight too..:wink:.. not that it helps with the accuracy, but I have a bunch of laser pet toys from Petco.

Making barrels today.

Good Luck
Gary

Sienna
09-19-2008, 05:52 PM
Plus, from my childhood experience with BB guns they are horribly inaccurate. BB's don't always fly straight, and plastic BB's made in a mold with tool part lines on them I imagine will be worse.
Accuracy depends on the quality of BB you are using, the weight, the tightness and length of the barrel, etc.

For instance, my M4 Patriot (airsoft gun) has a barrel thats probably around 200mm, 6.08mm inner diameter. I use TSD Bio* BBs, at 0.2g. Firing the gun, the BBs will spread to about a foot after 40 or so feet. Put the same BBs into a 500mm barrel, they will go 80 feet before spreading out a foot. Put them into a 500mm barrel, but one that is only 6.03mm inner diameter, they will go even further without spreading, etc.

Whatever you do, don't use any BBs from walmart, sports authority, etc. Those will fly every which way. Instead, stock up on some good BBs from an airsoft dealer. Look local if you are that lucky, or online. I like TSD fine, they are cheap. Others recomend the Airsoft Elite BBs. Use 0.2g in most normal guns.

*The outdoor fields near me require Biodegradable BBs, so thats what I stock


My stragety is spray and pray. If I get a lock on an opponent I can dial it down. It's not glamorous I jsut hope it's effective.
Personally, I don't plan on anything different either.

BauerMECH
09-19-2008, 09:24 PM
For instance, my M4 Patriot (airsoft gun) has a barrel thats probably around 200mm, 6.08mm inner diameter. I use TSD Bio* BBs, at 0.2g. Firing the gun, the BBs will spread to about a foot after 40 or so feet. Put the same BBs into a 500mm barrel, they will go 80 feet before spreading out a foot. Put them into a 500mm barrel, but one that is only 6.03mm inner diameter, they will go even further without spreading, etc.

My goodness, what's the total footprint of the playing field? I can't imagine our bots poppin' caps much further than 10' from one another. :cool: My crappy auto does a fair job of being consistantly accurate at that range.


My stragety is spray and pray. If I get a lock on an opponent I can dial it down. It's not glamorous I jsut hope it's effective.


One thing's for sure, it'll make it tough for we bi-pedder's to get back on our feet after a fall... I'll be making snow angels in the mounds of bbs that litter the field. :veryhappy:
Seriously though ...perhaps gridded/pocketed soles as a work-arround?

DresnerRobotics
09-19-2008, 09:47 PM
My goodness, what's the total footprint of the playing field? I can't imagine our bots poppin' caps much further than 10' from one another. :cool: My crappy auto does a fair job of being consistantly accurate at that range.

One thing's for sure, it'll make it tough for we bi-pedder's to get back on our feet after a fall... I'll be making snow angels in the mounds of bbs that litter the field. :veryhappy:
Seriously though ...perhaps gridded/pocketed soles as a work-arround?

Probably around 10x10 feet, maybe even 8x8.

As far as feet design go, I'm going for something like this:

http://forums.trossenrobotics.com/gallery/files/1/4/9/2/isoconcept2_topdown.jpg

http://forums.trossenrobotics.com/gallery/files/1/4/9/2/iso_concept2_back.jpg

Minimal contact to the ground, but contact points widely spread out for stability.

MSpurk
09-19-2008, 10:05 PM
Accuracy depends on the quality of BB you are using, the weight, the tightness and length of the barrel, etc.

For instance, my M4 Patriot (airsoft gun) has a barrel thats probably around 200mm, 6.08mm inner diameter. I use TSD Bio* BBs, at 0.2g. Firing the gun, the BBs will spread to about a foot after 40 or so feet. Put the same BBs into a 500mm barrel, they will go 80 feet before spreading out a foot. Put them into a 500mm barrel, but one that is only 6.03mm inner diameter, they will go even further without spreading, etc.


So using your gun in stock configuration with a 7.87" barrel (coverting to normal units ;)), and some simple trig your system is accurate to within 3" at 10'. So at max range most of your balls will be on target. I was planning on compensating for having a less accurate gun by firing more balls. Plus, as I stated above I'm aiming with hobby servos through a webcam, a little variation in where the balls go may be needed.


One thing's for sure, it'll make it tough for we bi-pedder's to get back on our feet after a fall... I'll be making snow angels in the mounds of bbs that litter the field. :veryhappy:
Seriously though ...perhaps gridded/pocketed soles as a work-arround?

Definitely need some type of knife-edged walking surfaces to counteract all the BB's.

Thanks,
-Matt-

PS I'm firing Wally World BB's WooHoo for spray and pray.

gdubb2
09-20-2008, 11:02 AM
The barrels I'm making for Bhekas guns are only 4 in (100 mm) long. I'm boring them to .238 in (6.04 mm) in hopes of improving the accruacy a little. Really won't know for a few days.

The foot problem was on my mind for a minute or so. I was going to make larger feet to allow for a little smoother walk cycle, But then came the realization that those little half inch square feet won't trip on BB's. :veryhappy: (advantage of a quad)

havin fun
Gary

Sienna
09-21-2008, 10:03 AM
My goodness, what's the total footprint of the playing field? I can't imagine our bots poppin' caps much further than 10' from one another. :cool: My crappy auto does a fair job of being consistantly accurate at that range.
Oh no! I was simply trying to add in some field experience on how plastic BBs fly. It had nothing to do with MechWarrior, except to provide some limited insight into airsoft accuracy.
(And airsoft fields run anywhere from a 50'x50' warehouse with obstacles to a intraforest field many football fields in size.)


So using your gun in stock configuration with a 7.87" barrel (coverting to normal units ;)), and some simple trig your system is accurate to within 3" at 10'. So at max range most of your balls will be on target. I was planning on compensating for having a less accurate gun by firing more balls. Plus, as I stated above I'm aiming with hobby servos through a webcam, a little variation in where the balls go may be needed.
Yeah, again, sorry for the misinterpretation. I was explaining how my "big girl" toys performed. I don't know yet what is going to happen with my cheap walmart toy in terms of accuracy. The types of internals you find on a "real" airsoft weapon are probably too heavy to be put on anything less then a quad.

MSK Mech Commander
01-13-2009, 07:29 PM
Just to remind potential contestants - the scoring system will only record one hit per second. No more. All this talk of 500+ rps is just... gah. I don't even know what it is.

dcalkins has a good point. No need to waste rounds if only 1 out of 500 is going to score.


It's strategy. I'm thinking these things are going to be impossible to aim. A 3"x3" target at 10', fired through a servo controlled gun, viewing the whole thing through a webcam, is becoming more and more challenging as I work it.....My strategy is spray and pray. If I get a lock on an opponent I can dial it down. It's not glamorous I just hope it's effective.

-Matt-

MSpurk also has a good point, as the servo-aimed guns can be quite innacurate

So there's two options being weighed here: increase rps fired, or, decrease rps fired.

I'm thinking that I'm going to have a rate of fire around 5 rps. This way, I can save ammo while giving myself a higher chance of hitting the opponent. That's the simple approach to things.:rolleyes:

The other complicated approach is going through the tedious and complicated math to improve the aiming system. The Army's done it. Their tanks can hit a target accurately around from over a mile away. If we can somehow copy their technique or whatever else is involved, we won't have to put so much weight on our mechs. That way it will also be cost effective as you won't have to buy that much more ammo.

And then the other simple approach: The web. Most likely, somebody's already solved this problem.
So if anybody actually knows this technique for improving mech aim, or comes across it on the web, please let me know!:D

Still, if you're gonna go for the scatter shot, use multiple cannons so that the scattershot is more effective.

Adrenalynn
01-13-2009, 07:32 PM
The math is trivial. The construction of a gun with repeatability isn't.

MSK Mech Commander
01-13-2009, 07:33 PM
True. Just reasoning out the possibilities.

Dementedwombat
01-13-2009, 10:10 PM
To the best of my knowledge (although I may very well be wrong) the military gets accurate aim on tanks by having a battery of electronics that automatically adjusts aim based on speed/terrain. That, and having a stabilized turret that's really bloody heavy.

Neither option is really feasible on a mech, although with a lot of math and some fancy code it may be possible to create a second "floating cross hair" on the computer screen that automatically adjusts to your mech's walking gate. Kind of like that Fire Controll Computer in the Mech warrior games that showed you where to aim in order to get a hit. You know, with a ranging device and a couple gyros, a system like that might be doable PC side. The question is weather anyone wants to attempt it.

Adrenalynn
01-13-2009, 10:17 PM
A fire control system is easy. It was hard when all we had was big platinum-tipped relays.

Tank shells are a lot more regular than airsoft pellets. They're also a crud-load heavier and leave with a crudload more energy. Their barrels are a fair bit longer, and the tolerances faaar finer.

Airsoft is a crummy little toy. Even a highly modified *real* 9mm pistol can't put round after round in the same hole at 25' even when mounted in a vice and barrel-sighted with a bore laser, even with the finest competition ammo - I wouldn't expect a $10 toy firing fraction of a penny ammo to even come close to that performance, let alone hundreds of millions of dollars of the finest engineering money can buy?

I'd think the first step would be to get a few foot long barrel onto the mech with a custom machined firing mechanism. Then cast your own BBs with higher precision.

Figure a couple hundred million for a cheap tank. 1:20 scale, about. So scale the dollars too. $10M should get you a comparable shooter. ;)

Oh - did I mention the rounds are sabboted?

Dementedwombat
01-13-2009, 10:26 PM
Forgive any misunderstanding. I thought I made it clear in the beginning of my post that tank level fire control isn't remotely feasible in this application.

That being said, an aiming system that automatically adjusts aim to remain stationary as the mech moves might be a tad more doable and could eliminate the "run and gun" problem altogether. It could be something as simple as "at point X in the walk cycle, gun A is Y degrees away from parallel. Rotate gun servo A Y degrees." This wouldn't improve the inherent accuracy of the airsoft gun, but it would make that accuracy constant no matter the mech's position.

I don't have nearly enough coding experience to be participating in this conversation, so tell me now if a system like this isn't possible. I won't take offense.

Adrenalynn
01-13-2009, 10:49 PM
I suspect that wouldn't be terribly accurate since neither the gate, the servos, nor the surface is. It might help some.

Naw, if you wanna do it justice, you need a turret-mounted IMU [Inertial Measurement Unit]. Not just for missles anymore - ask Tyberius. :)

I have an IMU [Gyro and two accelerometers] on my soon-to-be-born DIY Segway knock-off. Gyros and accelerometers are surprisingly reasonable these days.

Incidentally, that's the heart of a run-and-gun M1's targeting system - IMU's. http://www.sparkfun.com/commerce/product_info.php?products_id=8193

Basically, it addresses what you propose above. It measures pitch/yaw/roll/rotate-xyz (6DOF). All you do is sample the IMU, then correct your point, rinse/lather/repeat.

FryGuy
01-13-2009, 10:49 PM
From my limited testing of guns for the defcon event 2 years ago, the $20 guns are accurate to about 4-5 inches at 10'. The larger ones are only slightly better. We ended up making what amounts to a blow tube with a 6" barrel and 100 psi behind it, and it was accurate to about an inch at 15'. The $200 gun we bought (Tokyo Marui) for last years event (we didn't want to carry around a compressor again, and it was a PITA for other reasons, like jamming) was roughly the same.

Given the fact that the targets are 3"x3" and the other robot is 5-6 feet away, it shouldn't be unreasonable to be relatively close, assuming that you can aim it within some tolerances.

DresnerRobotics
01-13-2009, 10:57 PM
Naw, if you wanna do it justice, you need a turret-mounted IMU [Inertial Measurement Unit]. Not just for missles anymore - ask Tyberius. :)

I have an IMU [Gyro and two accelerometers] on my soon-to-be-born DIY Segway knock-off. Gyros and accelerometers are surprisingly reasonable these days.



Heh. Surprisingly reasonable. Tell that to my $600 ADIS 16355 (http://www.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=ADIS16355AMLZ-ND) :robotindifferent:

Adrenalynn
01-13-2009, 10:58 PM
Thanks, Fry! Good observations, and they jive with what I'd expect too, nice to have the theory vetted by your practical experience. :)

I think making ones own competition high-precision BB's with very finely tune barrel, you might see even better accuracy yet.

But, practically, my [genuine] 9mm Sig with thousands of dollars of work in a vice doesn't shoot much better than a couple inch groups at 35'.

Adrenalynn
01-13-2009, 10:58 PM
The six axis I linked is only a little more than half that

Dementedwombat
01-13-2009, 11:00 PM
Naw, if you wanna do it justice, you need a turret-mounted IMU [Inertial Measurement Unit]. Not just for missles anymore - ask Tyberius. :)

I'll be sure to. That might be an interesting conversation :).


I have an IMU [Gyro and two accelerometers] on my soon-to-be-born DIY Segway knock-off. Gyros and accelerometers are surprisingly reasonable these days.

Incidentally, that's the heart of a run-and-gun M1's targeting system - IMU's. http://www.sparkfun.com/commerce/product_info.php?products_id=8193

Basically, it addresses what you propose above. It measures pitch/yaw/roll/rotate-xyz (6DOF). All you do is sample the IMU, then correct your point, rinse/lather/repeat.

I see. That is exactly what I proposed in a gift wrapped package. It's a little too much money for me to justify spending right now, but I'll be sure to remember that. Now I know something like that exists it opens up all kinds of fun applications. But then you already know that, don't you ;)?

Just a quick question. Due to the nature of the device it would need to be mounted as close to the gun as possible correct? It appears that the actual gun assembly itself is the optimum mounting place to get the most accurate reading.

Adrenalynn
01-13-2009, 11:03 PM
Yup! All kinds of fun toys. Crawl around Sparkfun for awhile, it grows hair on people just starting. :)

I'd put it on the turret myself. You really want to measure what the turret's doing -the gun is attached to it. That means you can address space and balance.

FryGuy
01-13-2009, 11:17 PM
At my work they have some of the gyros of the $300k Fiber-optic variety. I think that wins the conversation :)

DresnerRobotics
01-13-2009, 11:26 PM
At my work they have some of the gyros of the $300k Fiber-optic variety. I think that wins the conversation :)

Yeah.

So I'll stop bitching about my $600 ADIS now.... :P

Adrenalynn
01-14-2009, 12:49 AM
Oh - you can bitch all you like, Tybs. No one pays any attention to you anyway. Nuttin' worse than a whiny Yeti with a $10,000 robot... :tongue:

Sienna
01-14-2009, 06:22 AM
One could always "perform barrel inertial compensation" with a laser pointer duct taped to the barrel as well... requires no fancy gyros or complex software! :p

Dementedwombat
01-14-2009, 09:36 PM
One could always "perform barrel inertial compensation" with a laser pointer duct taped to the barrel as well... requires no fancy gyros or complex software! :p

That's probably the way I'd end up doing it. Much simpler, but not nearly as cool.

jes1510
01-14-2009, 10:27 PM
One could always "perform barrel inertial compensation" with a laser pointer duct taped to the barrel as well... requires no fancy gyros or complex software! :p

That's exactly what I plan on doing (sans the duct tape). It will also have a biologically augmented firing algorithm. In other words, the dot is there, my gun usually shoots x inches lower, I should aim here.

FryGuy
01-15-2009, 01:08 PM
That's exactly what I plan on doing (sans the duct tape). It will also have a biologically augmented firing algorithm. In other words, the dot is there, my gun usually shoots x inches lower, I should aim here.

A carbon-based closed loop control system?

ooops
01-15-2009, 02:37 PM
This system isn't alcohol fueled is it?

jes1510
01-15-2009, 03:33 PM
This system isn't alcohol fueled is it?


Actually it runs on either alcohol or caffeine. I've noticed that the accuracy is inversely proportional to the amount of fuel used when run on alcohol. I suspect a memory leak.

Surprisingly, the opposite seems to be true when running the system on caffeine.

ooops
01-15-2009, 05:26 PM
It has been my experience that these systems are best optimized by a fair balance of both, not necessarily at the same time though.

Alucard
02-14-2009, 12:53 AM
As a random question, how hard would it be to get a setup that can vaccum up used BB rounds and feed them into a specially modified gun designed to be able to use the bad rounds effectively? One possible idea would be to have them bunched up in a cluster inside the barrel then launch those. If gravity pulls them into the barrel at roughly 14/second, then designing the barrel to have room for 6-8 should be perfect. It would be mainly a mid/close range weapon, same with a normal shotgun. It also would help counteract the otherwise uselessness of a spent round; it doesn't have to fly particularly well, it just has to stay in the air out to 3-4 feet or so. I think that something like that used in a stealthy manner would be very effective, especially if you could get into point blank range.

DresnerRobotics
02-14-2009, 12:57 AM
I think that has been brought up before... the biggest problem is going to be weight. Is it worth installing a vacuum powerful enough to suck up spent ammo and shoot it back out when it would weigh vastly more than an additional 1000 rounds? I mean, you're not going to be able to pick up *that* much ammo off the ground.

Alucard
02-14-2009, 01:18 AM
I think that has been brought up before... the biggest problem is going to be weight. Is it worth installing a vacuum powerful enough to suck up spent ammo and shoot it back out when it would weigh vastly more than an additional 1000 rounds? I mean, you're not going to be able to pick up *that* much ammo off the ground.
They already have developed some pretty strong AND lightweight vaccums. Shouldn't be exceedingly difficult to reroute the destination to some sort of hopper. It might even be possible to use the excess air pressure to help do a little refueling of some of the air tanks, depending on how strong it is. THAT one is unlikely, but you never know.

DresnerRobotics
02-14-2009, 01:43 AM
But the bottom line is, you could carry thousands of airsoft BBs for the weight of even a lightweight vacuum, making the entire concept pointless. There wont be thousands of BBs on the floor, nor would you have a perfect recovery rate. Refueling a CO2 tank with any standard vacuum would be impossible, you need enough pressure to compress pure co2, neither of which is available with any standard vacuum.

Adrenalynn
02-14-2009, 01:47 AM
Not to mention the effects of reusing ammo. Having it break apart in the gun, out of round BBs flying all over everyplace but where you're aiming, and the worthlessness of doing it at all.

Oh come on, Tybs, don't you have a 3oz vacuum that generates 3000psi? I thought everyone did. I keep mine next to my perpetual motion machine. ;) :tongue:

sthmck
02-14-2009, 07:49 AM
I keep mine next to my perpetual motion machine. ;) :tongue:

Dude you have perpetual motion machine! I am sooo jealous. rofl

A_Clawson
02-24-2009, 08:15 PM
Is there an advantage to using two airsoft weapons v. 1?

lnxfergy
02-24-2009, 08:17 PM
Is there an advantage to using two airsoft weapons v. 1?

If one jams, you aren't dead in the water?

-Fergs

Adrenalynn
02-24-2009, 08:22 PM
Twice as many rounds in the air at once? Half the recycle time? Twice the ammo?

A_Clawson
02-25-2009, 05:46 PM
I was thinking that a single gun would decrease the payload and enable faster locomotion. Also, I figure that it would make a vision-based tracking system more accurate.

Adrenalynn
02-25-2009, 09:30 PM
Then go for it!

This even has never been run before - so no one has any answers as to what is "best" - only ideas.