Drive train suggestions

Technical Technical Discussion
1

Rookie Team 3992 here,

We currently made a drive train which is as so:
4 Wheels;
The two front wheels are 10 inch pneumatic wheels from harbor freight.

The back two “wheels” are 3.5" diameter swivel casters.

We thought this would allow for good maneuverability, but instead it’s harder to control with the casters on the back.

However, we have been driving it:

  1. On painted concrete floor (more slippery than the carpet)
  2. With no weight on the drive train (pneumatics get more traction with weight, and casters may act differently)

So I ask you,
Are our two testing factors giving us the unsatisfactory result, or is our drivetrain design not very efficient and we should change it?

Thanks!

2

Your problem can be summed up in one word.

Casters.

Use omni wheels if you possibly can. If you must use casters, use ball casters.

While weight and the fact you aren’t on carpet may have something to do with your problem (and if I were you, I’d test on carpet), casters are your problem right now.

Casters tend to do exactly what you’re finding out that they do: mess up maneuverability.

3

We’ll try to test soon, but otherwise, what are the cheapest yet best omni wheels you can recommend?

We’d obviously need two dualies.

4

There’s a blue-and-white dually type I’ve seen around. That’s pretty decent; I want to say it’s a 4" size. I don’t know any more about it, sorry.

Or you can go shopping AndyMark’s collection.
4" dually http://www.andymark.com/product-p/am-0381.htm
All of AM’s plastic omnis (which are cheaper than the Al ones) http://www.andymark.com/Omni-Plastic-s/69.htm

5

The only problem I see is leveling them with our 10" giant pneumatics. I’m thinking 8" dualies.

Does that sound good?

6

We did a 4 wheel driver with 2 8inch traction and 2 8inch non-dualie omin wheels.
It worked out fairly well in the end.

You probably need an bracket to get the omins even with the 10inch pneumatics.

7

We’ll probably use an FTC stunt, by using a 3 unit channel attached to the bottom of our C-Channel to displace the 8 inch wheel, therefore leveling it with the pneumatic

8

Easy solution to omnis, you will need the following:

  • A kit wheel of your choice.
  • Pool tube.
  • Zipties.

Take the pool tube cut to go around the outside of the wheel. Cut down the middle and put over the outside of the tube using zipties every so often to hold the tube in place. Cut the ends off of the zipties and tada! You have a poor man’s omni wheel.

My old team used these in 2005, 2006, and 2008 with much success. Good luck!

See an example wheel here!

9

Whatever you need to use. See the AM page, or just start browsing AndyMark’s wheels.

10

Another solution might be adding a gyro to the bot so it will maintain a directional heading. (Read: drive in the direction you want it to)