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ArduTank
04-26-2014, 10:22 PM
Hey, I currently have HS Walker in this state:

55235522

I plan on layering light material (foamboard or metal) over the middle deck (easier to see it in second pic).

However, I have no clue where BB's normally hit in a match, so I am asking if you 'mech vets could let me know if you guys see any other places that would be a good idea to add some "armor" to.

BTW, he is walking:


https://www.youtube.com/watch?v=FY-Xd1bAOvI

jwatte
04-27-2014, 12:11 AM
That's really cute!

My take on armor/cladding so far is "I don't want the weight if I can avoid it." Other than the LiPo battery, there really isn't anything that is sensitive to pressure enough that BBs could damage it. The BBs are lightweight plastic and can't carry a whole lot of energy. I could be proven wrong, though...

If those white legs are 3D printed plastic, then maybe they are thin enough that a barrage of BBs could crack them -- that's the first thing I would worry about after making sure the LiPo battery has some protection.

Xevel
04-27-2014, 07:29 AM
Nice!

In terms of protection, I would suggest the battery like jwatte, but also all electronics. If a BB hits an SMD resistor for example, the BB is going to win. You don't need metal plates for that though, anything that will not be penetrated by the BB should be good enough, go with the lighter material you have around that fits the bill.
Cables should not be much of a problem but I would also protect small connectors just in case.

You still have the gun to put on it, and it's weight enough, don't add anything heavy that you can avoid.

ArduTank
04-27-2014, 07:38 AM
Okay. Already planning on covering the middle deck (electronics) but will cover the battery as well. Foamcore board it is then. Thanks

PS: Jwatte, no 3d printing for me. Those feet are hand shaped PCL.

ArduTank
04-27-2014, 03:37 PM
Anybody measured how much force those AEGs put out?? I would rather not have another mech equipped with an AEG shred my armor.

Xevel
04-27-2014, 04:52 PM
I haven't tested, and I can't talk for all the guns that could be used, but I would expect serious damage to thin foamcore used 'as is' in the worst case scenario (multiple point blank shots perpendicular to the surface).

If I were you, I would :
- add some kind of tear-resistant adhesive tape on the outside of the armor to compound the effects (vinyl tape? duct tape? maybe some tape with fibers in it...)
- make two or 3 sets of plates in case it is damaged too badly during the competition
- when you arrive at the competition, find someone with a powerful gun and test. If it's not enough, maybe double the plates or add more tape.

tician
04-27-2014, 06:34 PM
3mm (1/8") polypropylene twinwall available at most big box stores survives the manual mode of a crosman M74DP fired point-blank and perpendicular without the slightest visible damage. The plastic is less prone to tearing than the paper of foam-core and maybe also be a bit easier to build the walls of a box to surround the electronics and turret than if you were using <0.25" foam-core.

jwatte
04-27-2014, 07:59 PM
I've been mounting my electronics with the "back" side out, to protect the components.
But from what you say, perhaps a thermoformed lightweight PETG or polycarb shell isn't such a bad idea...

ArduTank
04-27-2014, 08:23 PM
I'm using 1/4" foamcore board mainly because I have three full sheets of it, and I'm still working on getting the money for an airsoft gun (likely that m74dp you mentioned). I guess I'll try double layers of the foamboard with a duct tape outer layer, and have Tyberius hit a sample of it with Envy's guns, which appear to be some of the most powerful allowed ones used so far.

kamondelious
04-27-2014, 08:49 PM
I tested out foam-core with my first mech and it didn't stand up to well being shot from 6' away with a gun that's not as powerful as the AEGs. An AEG shooting fully automatic would shred it pretty quickly unless you reinforced it like Xevel suggests. What I used was 2mm card stock. It's basically cardboard, but it is hard enough to withstand a pretty good beating and can also be reinforced with your favourite form of tape. It also held up very well to all the falling involved in building a biped.

ArduTank
04-28-2014, 05:52 AM
Nice. Worst comes to worst, I can use 1/16" sheet steel to cover the electronics deck. I am going to try making the armor angular first though. Fewer perpendicular walls the better it deflects

Added thought: Is there any way to clear load errors without disconnecting then reconnecting the power to the servos???

Xevel
04-28-2014, 07:55 AM
Doesn't clearing the Torque Enable register then putting it back to 1 work for that? I can't remember ><

jwatte
04-28-2014, 11:54 AM
I believe the specific function of the shutdown alarm is to disable the "torque enable" register (24? something like that.) Thus, re-enabling that register clears the alarm, assuming that the alarm condition doesn't still exist...

1/16" steel is way too thick. You can easily use 1/32" (which is approximately 22 gauge) and probably go thinner. Weight matters. A lot!

KevinO
04-28-2014, 12:10 PM
1/16" steel is way too thick. You can easily use 1/32" (which is approximately 22 gauge) and probably go thinner. Weight matters. A lot!

Especially since those appear to be AX-12s. The gun will add weight as well, can't forget the gun.

ArduTank
04-28-2014, 03:22 PM
Main reason I get the load errors is because the servos hit the ground fast and hard. I can't soften that without slowing him down.

On the steel, I looked again and what I have is 22 gauge.

Xevel
04-28-2014, 03:55 PM
maybe use soft rubber feet to soften the steps and get better grip at the same time (with the risk of making waling much harder if the bot is too unbalanced) ?

If you want to test if it's the hit on the ground that is responsible for the error or the dynamics of the robot, you could put the robot on two legs and have it do "push ups" on these legs (with help to maintain its balance, it's not the subject of the test). If after a few push ups the servos are not happy, you know they doe not like the load you put on them and it's not the shock.

If the steps are symetrical in the "lifting the leg" and " lowering the leg" movement, a practical way to do it could be to suspend the bot head down, with two strings, one on each selected foot (the point where the string s attached should be as far from the servo as the foot to have a significant result).

Also, I personally would shorten the legs to avoid having too much stress on the servos. Don't do it now (the bot walks fine as is, so there's no need yet) but keep that in mind if you have servos overheating in the future.

Finally, you probably want a slower (and more durable!) bot than a fast bot that dies quickly of being overweight, so if slowing the movement is the only way you manage to run the bot for as long as the battery lasts, it's probably what you should do. All the more if having spare servos is a problem.

ArduTank
04-28-2014, 04:04 PM
The reason I say that it's the shock is because when I walk him at full speed for long amounts of time, he gets the load errors, but under any other movement pattern he does not. And it's not overheating because the servos do this without even being warm.

To counteract this I added a bit of code that checks each servo's torque enable register and sets it to 1 if it is set to 0.

KevinO
04-28-2014, 05:14 PM
To counteract this I added a bit of code that checks each servo's torque enable register and sets it to 1 if it is set to 0.

Be careful doing this "force" method. If they are throwing that error it usually means something is wrong. You could run into actual hardware failure if you push them to hard.

ArduTank
04-28-2014, 06:46 PM
Oh, I know. I'll add an alert that it'll throw up if the error is found and cleared. That way I can ease off the walking speed to give them a break.

cire
04-29-2014, 04:08 PM
I'd recommend some 1/32" or even 0.02" polycarbonate over steel for armor, it is much lighter and easier to work with. You can cut it with scissors and I believe BB's dont penetrate it, since it is very resistant to impacts.

ArduTank
04-29-2014, 08:08 PM
Problem is, I'm currently under a very tight budget (I may not be able to buy the target panel system in time for this year's competition) so I'm trying to use what I have. I already have access to sufficiently large quantities of 22 gauge sheet steel, among other materials.