Looking for direct drive high torque motors

[billy gunn]

Been a while since I've done any crawling, but figured you guys could probably answer my questions as well as anybody. I am in the process of making a project for school. I'm using my TLT axles and am trying to direct drive them, the problem is that even running a couple 75 turn lathe motors they are stalling out when they bind up. I am running tires that are 80mm or about 3.15 inches in diameter. The main reason for direct drive is space. Everything has to fit in a 10"x10" square, and the axles, tires, two servos take up most of the space, there isn't enough space and clearance to fit a gearbox.

I'm limited to a 7.2V battery, I can create a circuit to bump the voltage up if i have to, but I don't want any more speed. I really want less speed and more torque. I figure my options right now are either to try a couple 75 turn motors from Axiom, or custom wind a couple old lathe motors. What I would really like to find are some 80-100 turn motors to tame the speed and hopefully get some more torque so it doesn't stall as bad. Only problem is I haven't found any so I don't know if they exist.

 

[Thorsteenster]

good luck, id be surprised if you achieve that with no gear reduction. have you seen rc4wd's inline gear reduction units? they just might be the ticket.....

 

[rockwerks]

give us some more specifics of the peramiters of what the project is and how it need too function. 10x10 is a ton of space, if you know how to use it

 

[Reflection]

No gear reductions.....BIG outrunners are the answer. My final drive ratio is 24.7:1 and it'll pull my heavy Super sized crawler at a snails pace all day long through the rocks. The beauty of it....as soon as I need to git it,just stab the throttle and it's burning rubber hitting the gates air born:twisted: Get the best of both worlds"thumbsup"

 

[billy gunn]

give us some more specifics of the peramiters of what the project is and how it need too function. 10x10 is a ton of space, if you know how to use it

Basicly its a mini-DARPA challenge. For everyone that doesn't know, DARPA is a part of the Department of Defense, you can read this PDF , http://www.darpa.mil/grandchallenge/docs/Urban_Challenge_announcement_updated.pdf if you want to know more about the full-scale challenge. It has to be a fully autonomous robot that can make it through a series of all-terrain obstacles, including rocks, water, tight turns, etc. One of the obstacles being a 6 inch steps.

Controls are provided through a handyboard, which is a microcontroller system that can control multiple motors, servos, and sensors. The navigation is going to be done with IR sensors, sonar sensors and such.

the problem with the 10 inch by 10 inch footprint is this. The battery must be a 7.2Volt stick pack, The handyboard is about 3.75x4.15 inches. The tires are limited to 80mm, 3 inches, in diameter. In addition in order to make it up the step, there are two additional servos and an assembly to help "assist" it up the steps. So right now in the proto-type there is the TLT axles with tires. A basic "stick" chassis to keep it simple, and 2 steering servos, as well as 2 motors to drive each axle, plus the step assembly. If it was possible to fit a tranny in so we could use one motor that would be nice, but in order to fit a stealth or pede, or any gearbox that I have found it would hang to low, and it can't make it over some of the other obstacles.

Sorry for the long post, hope this kind of shows you what I am after and what help I am after.

 

[billy gunn]

No gear reductions.....BIG outrunners are the answer. My final drive ratio is 24.7:1 and it'll pull my heavy Super sized crawler at a snails pace all day long through the rocks. The beauty of it....as soon as I need to git it,just stab the throttle and it's burning rubber hitting the gates air born:twisted: Get the best of both worlds"thumbsup"

I have actually already thought about that, but this project is fully autonomous, and the microcontroller we have been given is much to slow to process the data, and send signal to another microcontroller to run the brushless motor.

 

[Reflection]

I swear I believe with a little ingenuity you could fit a modded Twin tranny in there. The design of the Twin tranny can be manipulated several different ways to fit alot of different set ups. I'll go get a few pics of mine real quick and post up. The rigs apart right now on the workbench....be back in a minute.

 

[rockwerks]

the step mechanism? is that your design or generic for all entries?. during operation does the vehicle have to remain in the 10 x10 configuration or can it change shape during operation?

 

[billy gunn]

the step mechanism? is that your design or generic for all entries?. during operation does the vehicle have to remain in the 10 x10 configuration or can it change shape during operation?

Mechanism to get up the step is the design of each team, and it doesn't have to stay in the 10x10 footprint, it has to start and finish at that size, during the course it can change shape.

Pretty much the only things that are set in the rules are:
1) Tire size limit
2) Footprint size, and it can change during the competition
3) Must use the supplied 7.2V stick pack
4) Have to use the handyboard controller

Other than that, each team can design it how they like.

 

[rockwerks]

Mechanism to get up the step is the design of each team, and it doesn't have to stay in the 10x10 footprint, it has to start and finish at that size, during the course it can change shape.

Pretty much the only things that are set in the rules are:
1) Tire size limit
2) Footprint size, and it can change during the competition
3) Must use the supplied 7.2V stick pack
4) Have to use the handyboard controller

Other than that, each team can design it how they like.

adjustable wheelbase would be the hot ticket. and Id hate to say it clod axles

 

[billy gunn]

adjustable wheelbase would be the hot ticket. and Id hate to say it clod axles

I thought about clod axles, but I didn't think I would be able to get them under 10 inches wide. But if you know a way, let me know....;-)

Adjustable wheelbase might be the way to go we thought of it, but we were trying to keep the robot as simple as possible, but I with an extending wheelbase, we can probably get up the steps without an extra stuff on the robot. Right now its too top heavy to make it up the step, and if you can get the front tire to lip over, the output yoke on the diff catches on the edge of the step.

Oh, and thanks for the ideas you've come up with so far rockwerks. Talking with other people kind of gives me new perspectives on getting this project done.

 

[rockwerks]

I love junk like this.............Ill be thinking about it all night.......about 2am is when my best ideas hit......I will write em down LOL

 

[Reflection]

Heres a pic of my modded Twin tranny. The main shaft has been cut down shorter and can be cut even more if needed. The second pic is the lower section of the chain drive. Mine is a custom unit to replace the plastic setion with aluminum and add a link mount. It's a hair smaller than the factory unit but not much.

Sorry they are kinda blurry,just snapped them real quick.


Oops,got the pics reversed:lol:

 

[Thorsteenster]

yeah that sounds fun, post the results, maybe some vids? what about a clod axle with 14mm adapters and some maxx dish wheels? i got some proline maxx wheels that are dish wheels, that might keep it under 10" but then it might be too big for tire wheel combo.

 

[billy gunn]

Heres a pic of my modded Twin tranny. The main shaft has been cut down shorter and can be cut even more if needed. The second pic is the lower section of the chain drive. Mine is a custom unit to replace the plastic setion with aluminum and add a link mount. It's a hair smaller than the factory unit but not much.

Sorry they are kinda blurry,just snapped them real quick.
Oops,got the pics reversed:lol:

Looks possible, I might have to look into it, just curious, about how thick is the tranny where the outputs are.

Just to give you guys an idea, of the space I'm working with, If we don't do any kind of thing to extend the wheelbase at the start of the competition, there is about 3.75 inches between the pinions on the axles. So in order to do a transmission or something the tranny outputs and drive-shafts would have to fit in that space.

 

[billy gunn]

yeah that sounds fun, post the results, maybe some vids? what about a clod axle with 14mm adapters and some maxx dish wheels? i got some proline maxx wheels that are dish wheels, that might keep it under 10" but then it might be too big for tire wheel combo.

I was thinking about the clod axles and the few people who have run 2.2 clods here in utah are pushing the 12" wide limit, think they have been around 11" if not more, I haven't played with clods too much but couldn't think of a way to narrow them to under 10". Plus the tire size limit kind of hurts, right now I am running Proline Badlands buggy tires that have been cut down to size. and mounted on some extra stampede wheels I had laying around. And the limit puts maxx wheels out, they are 3.2 or something like that inches in diameter for just the wheel.

I'll let everyone know how this goes and of course will have my camera at the comp, but this is kind of a long project, its over 2 semesters, so the competition is not until late april. We're just trying to get this physical part built, so that we have more time to do the actual programming of it, which is going to take much longer.

 

[Reflection]

Well,the two tranny plates are roughly 3/4" outside to outside,maybe a hair less. Your driveshafts would be very short now that I know what your pinion to pinion measurement will be. Just an idea,hope it helps.

 

[billy gunn]

Well,the two tranny plates are roughly 3/4" outside to outside,maybe a hair less. Your driveshafts would be very short now that I know what your pinion to pinion measurement will be. Just an idea,hope it helps.

Thanks for the ideas raptorman, wish I still had a Twin, too bad I don't have one anymore, I'll have to look and see if i can't find a tranny.

I have also looked at the rc4wd inline gear reduction for 540s, that looks like an idea, but would rather not blow the budget by buying $100 in two little gear reduction units. but if worse comes to worse, its worth a shot i guess.

 

[JohnRobHolmes]

You could mount a small outrunner brushless with a reduction unit to each axle. it would be a tight fit, but its workable. It just needs enough power to climb up a step face?

The only problem would be money.

 

[billy gunn]

You could mount a small outrunner brushless with a reduction unit to each axle. it would be a tight fit, but its workable. It just needs enough power to climb up a step face?

The only problem would be money.

Took what we have out for a quick run today, the terrain that its going to see is dirt/sand, rocks, water, grass, and the steps. Grass and the steps are the places that it really just bogged the motors down. Through the dirt and rocks it did pretty well.
And we do have a budget, so brushless would probably not be ideal, but me working in a hobby shop is the only way that we have kept it under budget so far.

I'm in the process of posting pics. Should be up in a few minutes, so you can see what we have to this point