pic: Full robot, half way through the season - back view

[Jon Stratis]

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[Ty Tremblay]

Might I suggest putting traction wheels in the front of your robot as well? You'll still have a small enough wheel base to turn effectively, but you'll also have more resistance to being turned by a defending robot. At the very least, it looks like all 6 wheels are the same diameter, making it possible to switch them out if necessary.

[thefro526]

To Echo what Ty said, I would switch at least one set of wheels, either front or rear to traction wheels like the center wheels. Also, are you using the C-Base? If you are, is your center wheel dropped? If the center is dropped you could get away with running 6 Traction wheels without a problem and still be just as maneuverable as you are with 4 omnis.

[Jon Stratis]

Yes, we're using the C-base, and the center wheel is dropped. We used this same wheel setup in 2007 (highest seeded rookie award) and 2008 (regional finalists) successfully, and have never used traction wheels for any of our robots... I don't even know if it occurred to the students. Regardless, I've made sure your suggestions were passed on to them so they can compare the pro's and con's of the current setup versus traction wheels. We'll see what they decide!

[Ty Tremblay]

Sounds like you know what you're doing. Just for clarity, what I meant by traction wheels was not-omni wheels. You could just use the same wheels as your center wheels.

In my opinion, unless all 6 wheels are traction (aka not omni) wheels, you don't need to drop the center. The purpose of dropping the center wheel is to shorten your wheel base. This way so you don't have to counteract the moments from the traction wheels on BOTH ends of the robot that are preventing your robot from turning. If you have omni wheels on the front, back, or both ends of the robot, that moment is no longer there.

I apologize if I'm overstepping any boundaries, simply trying to pass on my knowledge. I'm sure the team will be successful with whatever it decides. Looks great guys.

[sgreco]

Originally Posted by Ty Tremblay

In my opinion, unless all 6 wheels are traction (aka not omni) wheels, you don't need to drop the center. The purpose of dropping the center wheel is to shorten your wheel base. This way so you don't have to counteract the moments from the traction wheels on BOTH ends of the robot that are preventing your robot from turning. If you have omni wheels on the front, back, or both ends of the robot, that moment is no longer there.

I agree that all traction wheels is better than omnis on the end, but if you stick with omnis you should still drop the center. An omni wheel theoretically has the least friction when going completely sideways. When you turn, you sweep out an arc, you don't strafe sideways, so you still get drag from both sides of the robot. If you drop the center wheel, you essentially cut the wheelbase in half and reduce the drag. (Omnis wheels have a lot less drag then a traction wheel, but it is still helpful to drop the center). Either way it's not a big difference with omnis whether you drop or not, but I think it's a little better with the drop. I'd go with all traction wheels though...

[Jon Stratis]

Originally Posted by Ty Tremblay

I apologize if I'm overstepping any boundaries, simply trying to pass on my knowledge. I'm sure the team will be successful with whatever it decides. Looks great guys.

Not at all - we always appreciate constructive feedback like this!

Even with Omni's, we've found that dropping the center is still a good idea. Getting 6 wheels to all hit the ground evenly is fairly difficult... and you definitely want the KoP wheels in this setup to have firm contact - otherwise, you'd end up sliding sideways at the slightest breeze from an open door. Ok, that may be a little exaggeration Regardless, you need some traction side to side, and the easiest way to do that with this design is drop center.