My team is toying with drivetrain ideas .. .
 

you be the judge. This is the most radical (that we are considering)


You have two wheels in front. They are your drive wheels. They are powered through a differential . . . . .

You have one 'wheel' in back. like monsieurcoffee's teams omniwheel from the gallery:

http://www.chiefdelphi.com/forums/pi...&quiet=verbose

the wheel is perpendicular to your direction of motion . . or whatever, its just sideways. Ours would probably not by that robust as it is not going to support very much load.



Anyway, the pluses we see with this drivetrain are as follows:
1- low energy turning. We only need to spin a smaller motor to turn, unlike a tank tread bot where you need to use the same power to turn as you do to go full speed.

2- need for only one transmission . . Your wheels are not driven independantly, so only one transmission/gearbox is needed.

3- your axis of rotation will be the midpoint between your front wheels when you are stopped. with some designs we are playing with this will allow us to spin aroung a box to acheive a better angle without even touching our main drive.

4- did i say you only need one transmission? cheaper.



possible drawbacks

1- you need to build/aquire a differential. If you aquire it and it fails, diffiult/impossible to replace/repair.

2- the three wheel design may be prone to tipping, especially when on the ramp.

3- an omni wheel, as monsuier(however thats spelled) coffee calls it, will need to be machined. . . . we would probably use rollerblade wheels or something, tho, it would need to be able to get across those little 'lips' on the start of the ramp easily.

So, did I just describe something you already have been using?

is it feasible?

should we do it?



I really agree with my physics teacher: he saw us turning our edubot (4 wheel drive version) by reversing one side . . and laughed at how inefficient that was.

My (newbie :) ) assessment:

I agree with all of your plusses :)

"1- you need to build/aquire a differential. If you aquire it and it fails, diffiult/impossible to replace/repair."

I would agree with you, there.

"2- the three wheel design may be prone to tipping, especially when on the ramp."

Add two caster wheels on the two previously "un-wheeled" corners!

"3- an omni wheel, as monsuier(however thats spelled) coffee calls it, will need to be machined. . . . we would probably use rollerblade wheels or something, tho, it would need to be able to get across those little 'lips' on the start of the ramp easily."

If your omni is behind your main drive wheels, it will have more traction than it would on a level surface. Roller blade wheels would potentially grip relatively well if you made little nicks in them, I would think...

Overall, it sounds like a cool idea :)

did I miss how it was going to turn? Steering brakes perhaps? Or was it that the omni wheel is powered and sideways?

I don't remember the rule number exactly, but i'm pretty sure this year you can't use metal on your wheels. (well metal studs, but i think the sideways rolling sections would count.) That would require that you make those sections out of rubber. Which i think is slightly tougher, but is probably still possible. Good luck on making them though. My team is probably sticking to the inflatable rubber wheels.

Not metal wheel things, but rollerblad wheel type stuff . . . we can find em at used sports stores for cheap.

yah, the back wheel is powered, thats how it turns. Actually, things are looking up for us, we ca probably do this.

(original chassis! WOO FOR US!)

Any type of wheels are allowed this year... and by any manufacturer.

You could buy Omni Wheels if you can find them... just do a google search for "Omni Wheel".

I got outvoted, my team opted for standard 4 wheel drive.

They have no sense of adventure.

And I'm lead designer. #%#%#%#%. Most of their protest centered around the omni wheel, maybe if they knew we could buy em they would change . . . . . some of the wheels are like 50 dollers tho. Heavy duty, tho, probably all we need and more. we have 1000 extra as of now, hoping for more, later.

Maybe I can talk them into it . . . this design is just soo, cool.

ah well, maybe next year when we are not a rookie team. I'll be a senior them, maybe captain, if im lucky.

I'm sorry to hear that but keep this in mind. A really cool design might not be the one that will have you place highest in the Qualifying Matches. However a really cool design could get you picked for finals. This is something jumbling in my head right now but I can't say a whole lot about it. Top-secret stuff.;)

<edit>On second thought, your design would be very maneuverable but essentially have only two wheel drive and a caster in the back (the omni would be a little better than a caster). This could be a problem for going up the ramp. But a very cool design none the less</edit>

some of the omni's I saw on sale have pretty big contact wheels . . . should be no problem . . . you could put both chiaphua/atwoods and both bosch drill motors/transmissions into your differential, and that way you could go anywhere with torque to spare.

Bah. They don't want to even build a stacker. Cowards. We settled on a boring bulldozer/4 wheel drive bot. Man, I wish I was in charge (so that we could show up at regionals with a half-completed bot).

i am probably going to get killed for saying this, but our team is going to do a walker this year... dont ask, but u will have to see it to believe it:);)

No Differential Required
 

You really don't need a differential to do what you want. A while back I used to own a Suzuki 4-wheeler. At the time, virtually no 4-wheelers existed with a differential (I don't know about these days). The point is, you can have steering with no differential - it's not that bad.

For cars, the differential makes the steering a bit more stable, but one of the biggest reasons for the differential is for tire wear. Since you're building a short lifespan robot, I wouldn't worry about one side slipping a little bit.

In fact, I would argue that a differential could be a bad thing. Have you ever seen a car with a standard differential on a slippery surface? What happens is that the differential causes more power to go to the wheels that have less traction (that means you'll have one wheel that's spinning like crazy while the one that has tractions is sitting there doing nothing). That's not good for this competition.

read the design. the differential is a crucial, vital part.

Anytype of wheel that doesn't violate rule M17.