Odd 8 Wheel Tank Drivetrain Idea

[Henrique Schmit]

Originally Posted by Bryce Paputa

The idea is that when turning, the traction wheels are high enough off of the ground that they don't interfere. They would only engage when rocking from high acceleration or torque. I don't really want omnidirectional movement, the mecanums would just be an interesting experiment. 971's chassis and bumpers are very interesting and things that I'll also look into, however, we like having a standard chassis that will work with all games so we can create the same one quickly after kick off. The diamond shape may be an option next year, however it may also not be one.

Interesting, i got what you want to to, it's pretty much like a drop center wheel and it'd probably work in the situation you described above, but since the traction wheels would only be touching the ground at high speeds or high torque
your wheels wouldn't touch the ground if someone got you from the sides, i believe it's very important to consider that when deciding to use or not this idea, personally i believe that the agility you get from that won't overcome the bullying you'll suffer at the field, but that's up to your team. Also, here is a good way to increase your agility without any major modifications to your drivetrain design http://www.chiefdelphi.com/forums/sh...hreadid=129276

[Abhishek R]

We used a setup similar to what you're describing. We had an 8WD West Coast Drive with 4 Colsons on the outside wheels and 4 omni wheels on the center, Depending on your drop, center of gravity, and gearing for acceleration speed, you may or may not drop back onto the traction wheels when accelerating, or in a pushing match. For this reason, you would need to actuate at least one end to ensure the traction wheels are touching the ground.

Now that I think about it, that's exactly what we experimented with this year.

[Bryce Paputa]

Originally Posted by Abhishek R

We used a setup similar to what you're describing. We had an 8WD West Coast Drive with 4 Colsons on the outside wheels and 4 omni wheels on the center, Depending on your drop, center of gravity, and gearing for acceleration speed, you may or may not drop back onto the traction wheels when accelerating, or in a pushing match. For this reason, you would need to actuate at least one end to ensure the traction wheels are touching the ground.

Now that I think about it, that's exactly what we experimented with this year.

Have you guys tested your drivetrain without the actuation? Or did you start out with it? Your drivetrain actually was what gave me the idea and what I'm trying to get is the same result in the lightest, simplest form possible.

[Abhishek R]

Originally Posted by Bryce Paputa

Have you guys tested your drivetrain without the actuation? Or did you start out with it? Your drivetrain actually was what gave me the idea and what I'm trying to get is the same result in the lightest, simplest form possible.

Yes we've tested it, and it really depends on how likely your robot is ever to recline onto the back wheels. You generally want a low CoG, so if it's low enough you will never have the back wheels touch the ground while accelerating. You could definitely experiment with the drop though and may find different results. We found it works best to actuate one side, and it was still pretty light, at about less than or equal to 30 lbs.

[Bryce Paputa]

How much use did your strafe wheel see? How much power did it have? I've been pursuing this more for turning ability than stafeing, but in a game like 2011 it could be very helpful for sure. How helpful was it in this game?

[Abhishek R]

Originally Posted by Bryce Paputa

How much use did your strafe wheel see? How much power did it have? I've been pursuing this more for turning ability than stafeing, but in a game like 2011 it could be very helpful for sure. How helpful was it in this game?

We used it in autonomous to get the second hot goal. During tele-op, we mainly used it to get out of t-bones; we could easily spin out of a perpendicular friction pin. For actual maneuverability on the field, it never saw too much use other than maybe adjusting for shots near the one point goal.

If I would change something about what we did this year, it would probably be to not use the center wheel and instead go for a 6 CIM single reduction with the same setup of omnis and traction wheels. We ran 4 CIMS this year because two were being used on the center wheel.

In a game like 2011, it could definitely be useful, and I believe 148 had originally planned to use a nonadrive again that year, but then left it off and went with what became known as butterfly, or now "Tex-Coast Drive." Why they chose not to use it I'm not sure, maybe someone from 148 can expand on that.

If we ever get around to it, something I would like to see is putting the traction wheels in the center and omnis on the outside; the idea being you can still turn on a dime even when in traction for more controlled turns.