pic: Drivetrain Concept

[Andy Baker]

Originally Posted by Tom Line

Also, unless there is a pressing reason for 8 wheels - I would avoid it. Unless you drop the middle 2 sets, you'll have trouble turning, and making 8 wheels the correct heights is really difficult.

I love the simplicity of this design. I too would suggest that the wood be made from plywood.

Another suggestion... if you make the 4 interior wheels have a slightly bigger diameter, that will work too. What I would do is put treads on the 4 interior wheels so that they have a diameter that is 0.2" larger than the outside wheels. This may be easier than varying axle heights.

Andy B.

[JesseK]

Originally Posted by Andy Baker

Another suggestion... if you make the 4 interior wheels have a slightly bigger diameter, that will work too. What I would do is put treads on the 4 interior wheels so that they have a diameter that is 0.2" larger than the outside wheels. This may be easier than varying axle heights.

Andy B.

If all 8 wheels are driven, wouldn't that cause the outer wheels to fight the inner wheels since their smaller circumferences cause slower linear translation than the middle wheels? Is it too minor to worry about?

[AndyB]

Originally Posted by JesseK

If all 8 wheels are driven, wouldn't that cause the outer wheels to fight the inner wheels since their smaller circumferences cause slower linear translation than the middle wheels? Is it too minor to worry about?

Yeah, the difference is too minor to worry about. I've seen teams use this method successfully.

[sdcantrell56]

I like it in general. It looks very similar to my design I posted. I too would switch to plywood, particularly a good 1088 meranti or baltic birch plywood as it is much stronger and more stable than a solid chunk of wood. Also u should look into epoxying the wood to the fiberglass plus screwing. If you do that you will have an indestructible joint.

[Alan Anderson]

Originally Posted by JesseK

If all 8 wheels are driven, wouldn't that cause the outer wheels to fight the inner wheels since their smaller circumferences cause slower linear translation than the middle wheels? Is it too minor to worry about?

Even if it weren't too small of a difference to actually make a difference, there is a wee bit of theoretical benefit to a minor mismatch in speed. If the corner wheels are any less grippy than the specially-treaded middle ones, they'll be slipping slightly. The way friction works, they'll thus slide sideways more easily than if they were in solid lock-step with the rest of the wheels.

But it's not an issue. Andy Baker's suggestion is a proven one. The TechnoKats 2008 robot uses six-wheel drive with in-line axles and extra tread on the center wheels, and it drives great.

[gorrilla]

does anyone use the kit wheels anymore? they work great for all kinds of stuff not just as drive wheels

at TNT i only saw 4 teams that used tham