pic: New Drive System for 703

[mtaman02]

My honest opinion is that looks way cool. Judging by the picture it looks relatively light - did you guys weigh that assy. to see how much weight you have left to play with. Looks like its about 20 - 30lbs. Do you plan on having all the wheels be driven by a motor on each side or only half of the wheels gonna be driven.

[Elgin Clock]

OMG! What the...

For those that ask why: Why not?

But seriously.. what the heck are you thinking?

You are definately not in the running to be forklifted for extra points in the end of the match (no clearance at all under that chassis), so unless that's your main purpose of the missing components (making a ramp out of yourself or something) again I have to ask why???

[Jak DiGriz]

Here, have this piece of chalk. There's the drawing board. Use it.

How inefficient! Get rid of half those wheels; you ain't getting any better friction than you would with six wheels! The normal force is distributed more evenly with your design, and you end up with a sliding... brick.

Sorry if I'm blunt, but that's how I roll.

[sanddrag]

I've been sitting here looking at this picture, and I've been reading through the responses, and thinking hard. And I still can not find any reasonable explanation for the massive quantity of wheels. While Jak's post may not have been delightfully articulated, what he said is basically true. You're not really gaining anything here, except for a lot of un-necessary weight and more failure points.

If there is some big concept I'm missing here, please enlighten me.

[Billfred]

Originally Posted by sanddrag

I've been sitting here looking at this picture, and I've been reading through the responses, and thinking hard. And I still can not find any reasonable explanation for the massive quantity of wheels. While Jak's post may not have been delightfully articulated, what he said is basically true. You're not really gaining anything here, except for a lot of un-necessary weight and more failure points.

If there is some big concept I'm missing here, please enlighten me.

I see a few potentially desirable attributes, depending on their strategy.

1) Spur gear drives have been proven to be quite effective in past FRC competitions, both in reliability, serviceability, and performance. (25's been doing it for years, although they choose ginormous wheels instead of 703's smaller wheels, which means they can get away with fewer intermediate gears and wheels.)
2) If they are choosing to climb other teams' ramps, there's functionally no way they'll be able to bottom out even on the steepest of ramps. Combined with those relatively short overhangs and the end patterns, I foresee them climbing anybody they want.
3) They've been drawing a lot of tread comparisons in their posts; if you want wheels to emulate treads, particularly on non-uniform terrain, this is probably the way to go.

Now, there's a possibility that it is entirely far too much weight and so on, but I'm willing to give 'em a shot.

(And besides, they could go "normal" 6WD if they wanted by dropping out a few wheels and bolting up some sprockets. I, for one, hope they don't have to do it, but flexibility wins.)

[MattB703]

Billfred is right on track. 703 has not used chain or belt in our main drive system since 2003. We love the reliability and ease of maintainance that comes with an all gear drivetrain. Could we have done the same with a 6WD and got most of the benefit? Sure. But then we would have needed a whole bunch of idler gears to get the power from the gearbox to the front and back wheels. Besides, we wanted to keep all of the charactoristics of our treads but not have any broken belts. This does that. And it is cool.

The weight is a little more than our previous system. We figure that the running chassis with all the motors, wiring, controls, and battery will be about 52lbs before we add any game playing features. We're not worried about it for this year's game.

The cost is actually less that the breco-flex belt system we have used in the past. The gears are cut from pinnion stock, and we make all the wheels in our school shop.

Matt B.

[jcatt]

Very Nice, Very Nice.

Cowmankoza-
very nice, i like the design, im assuming the bottom wheel is offset?, and do i spy geardrive?, my team was contemplating doing something similar, kudos to making it work

One thing that our mentors noted aboout this design and what in the end discuraged us from doing it is. That if one of your gears fails or binds then you loose all on your wheels. The only way to insure this doesn't happen is to design some fail safe into each gear.

At least with chain, if you chain each wheel indiviualy then if one chain breaks you still have the use of some of your wheels.

But still great work, We wil have to take a better look at the design, during the off season.

[groves]

If the center wheel is offset, then you have a really complex six-wheel drive. making 8 of the wheels either not touching the ground or not effectively getting traction. If they are getting traction then turning will become pretty tough depending on the amount of motors your using and then battery use comes into play. ignoring what I just said I really think it's a neat drive system.

[James1902]

This looks really cool and I really want to see it drive. But just some quick questions.
How many motors are you using to power either side?
Can it climb a ramp efficiently?
How easiley repaired is it if a gear or wheel breaks or becomes unalinged?
Otherwise SWEEEEEEEET

[cbale2000]

You have the problem of something breaking or falling off with any drive system, last year it was treads, this year wheels but we think that we have taken necessary precautions to eliminate, or at least minimize the chances of that happening.


The center wheel is offset but only VERY slightly, the other wheels still grip the carpet (though, granted not as well). We have done the same thing with all of our tread drives in the past so there really isn't much difference in terms of functionality.




We're using 4 CIM motors to power it (2 on each side) as well as a two-speed transmission that we've cooked up especially for it.

It should be able to climb a ramp as well as any other robot with tank treads (Assuming their ramp isn't made with slippery lexan or something; then it might be a bit more difficult).

If a wheel breaks, it is VERY easy to pull off and replace (takes about 20 seconds), the gears are a bit harder and require pulling off the side panel but it's no more complicated than replacing a tread on one of our previous robots.



Some time within the next week we hope to have it wired and running, if and when that happens I'll post a video of it for you all to see.

[Donut]

I have to say that even if this doesn't turn out to give any real advantage, it will still look impressive just having that many wheel on one robot.

I just hope it doesn't weigh too much for you guys.

[optimusfugii45]

you have got to be kidding me.that cannot work well. i doubt it will even turn that well-you might want to modify that design quite a bit- maybe take out a few dozen wheels.

[EricH]

Originally Posted by optimusfugii45

you have got to be kidding me.that cannot work well. i doubt it will even turn that well-you might want to modify that design quite a bit- maybe take out a few dozen wheels.

They only have fourteen wheels all told, and the center one on each side is slightly lowered. These guys aren't kidding! I just hope that it works as well as they think it will.

[Guy Davidson]

That looks quite cool. One thing I thought about when I saw your design is that your wheels might be in some sort of V with a very big angle, such that at each point in time either the front eight, the middle two, or the back eight wheels touch the ground.

All in all, that looks like a really cool replacement for tank-treads.

-Guy

[MattB703]

Originally Posted by sumadin

That looks quite cool. One thing I thought about when I saw your design is that your wheels might be in some sort of V with a very big angle, such that at each point in time either the front eight, the middle two, or the back eight wheels touch the ground.

All in all, that looks like a really cool replacement for tank-treads.

-Guy

They are actually in a large arc (this ain't our first rodeo)