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darkback2
02-19-2008, 12:28 AM
Has anyone tried powering a robot using gasoline? I was thinking of coupling a weed whacker with a 12 volt DC motor. I was thinking I could power a robot that way, and forget about using batteries. That said, the gas tank would probably run out before the robot could do very much. It would be interesting to find out how a gas generator set up like described above would compare with a standard battery.

Any ideas?

jrowe47
02-19-2008, 01:33 AM
More power. Less control.
More complexity... gonna need linkages up the wazoo.
More weight (carrying fuel and the tank.)
More heat. Gonna have to shield any electronics from the heat.

I'd say thats about the only difficulties in using a gas engine. I suppose it would be great for forward propulsion, and you could use some sort of lawnmower clutch system, then have electronics control fuel intake and gearing. Wouldn't be too great indoors, as it would stink (and probably kill things, people included, if you left it running too long inside.)

A great idea for an outdoors bot. Maybe modify a self-propelled lawn-mower? I'm sure there's something on E-Bay or locally that would be within the $100-$150 range.

It would be neat, but there are a few challenges to handle. :)

jdolecki
02-19-2008, 08:26 AM
Have a look at this and all your questions will be answered.

http://botmag.com/articles/06-10-07_Outdoor_Robotics_Power_Plant.shtml

Alex
02-19-2008, 09:19 AM
Have a look at this and all your questions will be answered.

thanks jdolecki! That was the exact article I had in mind, but I couldn't remember where I read it before;)

MYKL
02-19-2008, 09:25 AM
That is what popped in to mine also. Now strap that to a superservo powered biped...

yeah baby yeah...

Matt
02-19-2008, 03:10 PM
You could buy one too :)
http://forums.parallax.com/forums/default.aspx?f=10&m=214032

If you're independently wealthy and REALLY like robots.

kdwyer
02-19-2008, 08:22 PM
For most (not giant) bots, a good SLA battery system is better. Cleaner, quieter, simpler (no conversions or gearing/linkages), and probably alot cheaper. Less parts = more robust.
I've looked into this too, and while the idea is appealing, the tech hurdles are considerable. For a large outdoor bot, this may be workable. Not elegant, but workable. Still, the advantages of using large capacity SLA batteries are hard to top. They work well, supply ALOT of power almost instantly, and are reasonably cheap and easy to charge.

Hell, go for it, and let us know if ya get it up and running reliably. I'll cheer ya on!

darkback2
02-19-2008, 11:02 PM
Ok...so I might give this a try after I get the next version of gepetto completed. To be honest, I really don't think I could go as complex as the guy mentioned above. To be honest I don't really undersand all of the electronics stuff. Thats part of why I tend to rely on the piggy back model.( a computer on the back of the robot) So...given the restrictions my wife has placed me under...IE nothing new until either this summer or after I start selling my previous models. I don't see this even being in the drafting faze until this september or so. But...it will happen...I may just end up stripping out the weed whacker engine and putting a reliable battery in its place though.

One question, if I were to connect a DC motor as a generator to a ESC through a diode(those are the one way thingies right?), and just have the gas engine turning the shaft of the motor at a fairly constant speed, why would I need a bunch of other stuff?

Also there was a gas powered robot on "The Science of Star Wars" on the discovery channel. It was from some australian kid...it looked sort of like the one in the above post.

Matt
02-19-2008, 11:56 PM
I like the idea of gas as an energy source for "long run" bots that could move very fast. It's not a bad idea. I was talking to Dave and Alex today about merging my current passion with another one I hope to get into someday, treasure hunting! :)

There are many loooong tunnels in South America that have legends of Inca gold (http://team-xo.com/grant/pieces/mystical/tunnels.shtml) lurking inside. The problem is that people keep disappearing and dying trying to explore these tunnels. It would be great to create a gas-bot that could explore hundreds of miles of tunnels in a few days. Oh, to dream...

darkback2
02-20-2008, 08:07 AM
If there is treasure involved I might be able to convince my wife to let me get started on this one now.

Ok...so more realistically...I'll get to work penning a design for a cave exploring robot powered by gasoline as soon as I can get my hands on a working little 2 stroke:

- Less than 6 cubic feet 1.5*2*2 or so.
- Can carry a payload of 30 lbs
- Treads for increased mobility?
- A drill and bucket for getting samples of rock
- An arm for manipulating treasure
- An automated "explorer" mode
- A metal detector
- Some way of getting a signal out of a cave... possibly a relay system that it would drop out of its back as it went along.
- A wireless camera
- Anyone think of anything else?

Matt
02-20-2008, 09:38 AM
I would look at weed wacker & leaf blower engines

- Some way of getting a signal out of a cave... possibly a relay system that it would drop out of its back as it went along.

I was pondering this same thing and I came up with the same answer. Make cheap repeaters that can be dropped every X meters.

It would also need a roll cage that can right itself after wipeouts.

Dave
02-20-2008, 09:48 AM
I would look at weed wacker & leaf blower engines

Call me a tree-hugging hippie, but two-stroke engines are really really dirty. You'll be smogging up all those nice caves you want to explore.

Matt
02-20-2008, 09:49 AM
PS: I've met David Childress. His home base is only an hour drive from here. Maybe we can give him a bot to send down a tunnel on his next adventure! LOL. Or he can take us along and we'll all get rich and famous.

MYKL
02-20-2008, 09:56 AM
The idea is to find the treasure right? Send in a swarm of smaller or more maneuverable 'bots to map out the cave and document mineral and metal content. When a high concentration of whatever your looking for is found then send in a bigger beastie with the cameras and the manipulators.

Why not power a generator with one of those little R/C airplane motors? They are quite peppy and you could attach them to a smaller generator thus reducing the whole package size of the powerplant. Send in a mobile platform with the swarm bots. The little bots could be snake shaped (there is one that can swim and ambulate on the ground, great for spelunking) and battery powered. The Mobile platform(s) could contain your relays and a generator for on demand recharging.

Brainstorming is fun...

I wanna go spelunking too-Whaudya do this weekend? I robo-spelunkded and you?

^_^

Matt
02-20-2008, 02:22 PM
Call me a tree-hugging hippie, but two-stroke engines are really really dirty. You'll be smogging up all those nice caves you want to explore.

Dear tree-hugging hippie :)

These are tunnels dug through the dirt by humans not nature made crystal caves, and besides there's gold to be found. Screw nature :P

Sincerely,

Matt robo-pirate Trossen

darkback2
02-20-2008, 11:43 PM
I found the following motor online.
Thunder Tiger PRO-120RP RC BB

Specs: Weight: 35.5 oz, Power: 3.7 hp
@15,000 rpm
Ok...so help me out here if I'm wrong.

1 HP = 746 watts.

so 3.7 HP = 2760 or so watts...

So if Watts are amps * volts, and I'm producing 12 volts, then ...that would mean 230 amps @ 100% efficiency. I don't have an amp meter...but say I'm getting %25 efficiency, then I would have 57 amps...

Given that the ML50 DC gear head motors have a stall current of 3.3 amps, and I run 4 of them...so thats about 14 or so...that leaves...plenty to run a camera and arm. Given the draw of some drills, that may have to go.

Oh wait...I just realized...The limitation in amps would be on the end of the generator. So I would have to use something like a $300 NPC-T64 Gearhead motor which has a stall current of 100 amps @ 800 and change inch pounds of torque. Which I think the gas motor could do easily...

This may be doable. Though I would prefer using something like the HG62 Geared Motor 62:1 just because its only about $50, and the Thunder Tiger TTR61 which is just under $100. So for under $200 I would have a decent power system...if my math is right.

kdwyer
02-22-2008, 04:58 PM
Just a thought on the roll-cage / self-righting stuff...

Why bother? Just make it invertable, a wheel diameter (or track) taller than the bot. Then a simple sensor to tell if the bot gets flipped on its' back, and the drive controls get inverted when the bot is inverted.

And I'm still not a fan of using a gas engine. (Gas is explosive, especially in confined spaces.) A good tether provides:
1. power in and data out, real time.
2. a way to retrieve a malfunctioning bot (No! Our bots never malfunction!) or a stuck one.
3. if it is good enough to explore the pyramids, its good enough for me. Why re-invent the wheel? (see Dicovery Channel etc.)
4. no exhaust fumes. You may want to sample air or vapors in the cave, without contamination.
5. almost silent operation.

That said, I'd probably be first in line for one of these that worked well.

Matt
02-22-2008, 05:07 PM
>>> Why bother? Just make it invertable, a wheel diameter (or track) taller than the bot.

That's a good idea.

>>>A good tether provides:

Well, in my case I'm talking about potentially miles and miles into tunnels. I can't see a tethered solution there.

It's all just too difficult. Now I'm just sending Alex in with a torch, a string around his ankle, and a ham sandwich.

Alex
02-25-2008, 09:20 AM
Just make it invertable, a wheel diameter (or track) taller than the bot. Then a simple sensor to tell if the bot gets flipped on its' back, and the drive controls get inverted when the bot is inverted.

you mean like this:


http://www.youtube.com/watch?v=GmPMlT6XpHM

Sure, it's not Gas powered, but still pretty cool, huh;)

Alex
02-25-2008, 09:22 AM
It's all just too difficult. Now I'm just sending Alex in with a torch, a string around his ankle, and a ham sandwich.

Sounds like fun Matt, so long as Survivorman (http://www.survivorman.ca/) can tag along;)

Where do I sign up?

kdwyer
02-29-2008, 05:54 PM
Good video. And yes, that's exactly what I meant when I said "wheel diameter taller than bot".

It does constrain design in other areas. Any extensible masts or arms means... non-invertible. Unless they are retractable. Even then, I think it may be un-doable.

An invertible bot may only be good for surveillance, it seems. No manipulations.

cmmguy
03-02-2008, 11:06 AM
If your going to go with a gas engine.... why not make it a hover vehicle instead of wheeled? More challenges but more versatile... add a couple sensors...

http://a330.g.akamai.net/7/330/2540/20071210160019/www.designnews.com/articles/images/DN/20071210/CA6509000_B.jpg

Matt
03-03-2008, 12:09 PM
Holy crap, what is that? Any links for info?

cmmguy
03-03-2008, 04:00 PM
Military UAV for recon... supposedly has thermal imaging... I read Design News and they had a whole section on Military UAVs and robotics. It is a great magazine that allows full online access. http://www.designnews.com/article/CA6509000.html

http://a330.g.akamai.net/7/330/2540/20080206165944/www.designnews.com/articles/images/DN/20080206/CA6529364_A.jpg

indy007
06-02-2008, 10:04 AM
The parallax setup looks good, but what about those of us that are basically just coders, and not electrical engineers? I thought of a solution using off the shelf bits, but have no idea if it would work effectively. I know it's definately a heavier, and a bit more expensive, solution, but those are minor issues for a build I'm working on.

Hypothetical setup:

2000w surge, 1650w continuous gasoline powered portable generator (runs 8hr on 2 gallons of gas at half load, so right now $1/hr at half-load running cost)
12v smart charger
12v lead acid battery (say.. 25aH, even though I think you can go much smaller)
A pair of SyRen 25 amp motor controls running some banebot RS-500s (not full power, but lets just pretend for a moment. don't have a list of DC motors in front of me)
Phidgetts servo controller & mini-itx pc

Probably add a capacitor to handle motor surges, but beyond that.. would it work? would it not? if not, why? What would have to be changed?

Adrenalynn
06-02-2008, 10:50 AM
If you're going to use a generator, get rid of the charger and the battery. The generator has an invertor. Just put in a switching power supply and call it a day.

I think that generator is going to be pretty heavy though.

I have a 6HP Nitro-burning truck (Cen Racing) that would be trivial to turn into a robot. It has three channels of PWM out to the receiver - steering, gas/brake, transmission.

It'll climb a ramp up to the top of my garage and lauch off of it at 30+ MPH...

indy007
06-02-2008, 02:49 PM
The generator's inverter on that size doesn't have enough power. They're only about 8amp. The more I think about it, the only real difference is the parrallax setup generates DC, whereas I'll generate AC and convert to DC. Extra step, a bit more weight, a bit more expense, but safer & much easier for me as a project.

ooops
06-02-2008, 04:38 PM
Forgive me, maybe I missed it earlier, but why won’t the standard off the shelf NAPA auto parts alternator work for you? It’s already at 12v, it is easily adaptable to what ever engine you find via belts, gears, or coupled, it is light, and assuming your able to spin it up will handle most reasonable amp loads … in the "real world" it will keep the engine running, burn all the lights including halogens and crank the 4hp electric winch and lift the 1 ton lift gate all while thumping a stereo. Of course if you go with the Ronco brand it will do all the above while slicing and dicing the French fries:veryhappy:
As for the cave … I would keep it cheap … what goes in may not come out:wink:

Adrenalynn
06-02-2008, 04:46 PM
8amp - at 120v. 80A at 12v (minus losses, which is why you shouldn't generate ac and convert to DC but rather use AC motors if you're gonna do that)

indy007
06-02-2008, 06:40 PM
It would work just fine... but one I can do right now (generator) and one I'm still reading about how to do (alternator). The alternator is definately the better option and I'll pursue it eventually.

ooops
06-03-2008, 08:34 AM
Just a quick follow up. The alternator solution won’t actually carry a large amp load by itself. It works in conjunction with the batteries to “keep the current flowing”. You would want to determine the most efficient battery/batteries for battery only operation, then add the alternator to keep it “charged” and handle the nominal amp loads. That way when the Spelunker runs out of petro it could head back to the pre-determined fuel station, where I assume it will use it’s built in “One-pass” to fuel up quick, and get back to the cave!:D

darkback2
06-03-2008, 11:08 AM
Ok...Lets start compiling a list of parts and costs...dimentions would be good. Maybe we can actually build this thing.

DB

Adrenalynn
06-03-2008, 11:17 AM
I knew someone once that actually thought they'd invented perpetual energy by tying an alternator to a motor powered by batteries and then feeding the output from the alternator back to the batteries. Seriously. That's what they "thought"... Even worse, they actually managed to convince investors. Even worse, the vulture capital firm I worked for asked me to do due diligence on it. I almost died when I aspirated my diet soda...

darkback2
06-04-2008, 12:14 PM
If we were to go with an alternator charging a battery, would the alternator be on costantly? or would it just be on periodically when the battery got low. In anycase, I figure we could use a phidget servo mechanism to control the throttle of the motor, but would we use a volt meter to determine when the motor should turn on? Also...wouldn't a DC motor working as a generator be better? Then it could double as a starter motor which I'm not sure an alternator could.

Could you use a phidget 8/8/8 to detect a drop in voltage, and would that mean that the gas motor needs to rev up?

Adrenalynn
06-04-2008, 12:18 PM
If you're looking to go into mines, have you considered yet how you're going to keep the sparks generated by the alternator from blowing everything up, or how to keep the gas motor running when it's in an oxygen-depleted environment?

And how about water proofing? I know most of the caves/shafts/mines I explore are under 1-30ft of water for at least 50% of the floor.

ooops
06-04-2008, 06:54 PM
If you're looking to go into mines, have you considered yet how you're going to keep the sparks generated by the alternator from blowing everything up, or how to keep the gas motor running when it's in an oxygen-depleted environment?

And how about water proofing? I know most of the caves/shafts/mines I explore are under 1-30ft of water for at least 50% of the floor.


Very valid points ... I was thinking you might through a coil and spark plug in the exhust and have a nice bright torch to light the way.



If we were to go with an alternator charging a battery, would the alternator be on constantly? or would it just be on periodically when the battery got low. In any case, I figure we could use a phidget servo mechanism to control the throttle of the motor, but would we use a volt meter to determine when the motor should turn on? Also...wouldn't a DC motor working as a generator be better? Then it could double as a starter motor which I'm not sure an alternator could.

Could you use a phidget 8/8/8 to detect a drop in voltage, and would that mean that the gas motor needs to rev up?


Cave dangers aside, one thought is if the battery voltage is low, then using the low battery to start the engine could prove troublesome. But, either could work, myself, I would lean toward the alternator for simplicity, but that’s just me and what I am familiar with.

As for the throttle, depends on your engine. Generators, and pressure cleaners use a mechanical load throttle and rev up as the load increases. It is pretty much at idle or wide open with no thought required. If you go with a manual throttle then some linkage and thought required.

As for the engine, if you are going to have it for charging anyway, it is a shame it couldn’t be put to use for other utilities.

metaform3d
06-04-2008, 08:48 PM
Sorry, I haven't followed this thread in detail, but I recall there was an article in Robot magazine a few months ago about a hybrid robot project. It was a gas engine plus alternator used as mobile power source. I could dig it up if that would be helpful.

EDIT: oops, sorry again. I see it was linked in the first few messages in the thread. Nevermind!

darkback2
06-04-2008, 11:52 PM
If you're looking to go into mines, have you considered yet how you're going to keep the sparks generated by the alternator from blowing everything up, or how to keep the gas motor running when it's in an oxygen-depleted environment?

I remember having a talk with a friend of a friend who works at JPL about using O2 and H tanks, for fuel cell powered robots on Mars. that way they could run at night and use the sun to recharge the tanks during the day. He basically said it would require too much weight, and not give that much of an advantage given the increase in complexity.

I suppose we could seal the system with the exception of a snorkel and an exhaust pipe. for underwater use there could be a small O2 tank, and the ability to shut off the snorkel when needed.

As for sparks blowing the whole place up, isn't that why we are using a robot? Just kidding.

No really though, that simply suggests that internal combustion isn't the best power source for exploring caves...it would be good for exploring/patrolling over great distances...

ooops
06-05-2008, 08:49 AM
Although this isn't practical it is worth mentioning in a hypothetical type discussion. I have always wanted to get my hands on some “pure” Hydrogen peroxide. Basically, the “fuel of choice” for torpedoes at least in the old days. That would provide the ability for a truly “sealed system”. Of course the homeland security folks might take issue.

Adrenalynn
06-05-2008, 11:46 AM
Yeah, I was going to suggest how simple that chemistry is, then you reminded me about homeland security. Sigh. :P

How about a hydrogen fuel cell?

ooops
06-05-2008, 06:19 PM
Is there a good link on the H fuel cell? I understand the principle, but haven't actually read up on them. They seem pretty straight forward.

darkback2
06-06-2008, 12:19 PM
http://www.horizonfuelcell.com/store/h_cell.htm

http://www.youtube.com/watch?v=wVIvsdSyhFY&e

Here is something...the price is a bit steep though.

Adrenalynn
06-06-2008, 12:27 PM
I have a link around here that I shared awhile back for a pretty beefy milspec fuelcell. In the $5000 neighborhood. I live almost across the street from Jadoo Power. I've popped by there once or twice, but haven't built a connection... I might have to pop back by there. Their site is talking about robotics hobbyists now... http://www.jadoopower.com/hobby.html