pic: Concept Drive

[Jrizo]

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[Sohaib]

With the Omni-wheels in the front, I'm not sure if a drop center would help. Drop-center's are used to reduce turning scrub by effectively making your robot into two sets of a 4WD. The Omni's already do this for you in terms of turning scrub. I'd suggest go either or, but not both.

[Ether]

What performance benefit are you expecting by adding a set of drop-center wheels in this configuration?

[Richard Wallace]

3620 ran 6 CIM 6WD with four 4" blue nitrile performance wheels and two 4" dual omnis. No drop. Handled like a dream in five events: two Michigan districts, MSC, CMP, and WMRI. Our drivers are hard on tread (like a good driver should be!) and we went through a couple sets per event. Even had to change omnis once. But no problems with control or reliability.

I am with those who recommend against drop-center in a setup like this.

[RonnieS]

I would flip your gear boxes so that you are at least direct driving one wheel then running chain runs off of that. It would be more reliable and less chain. Also agree with everyone else on the drop center topic.
-Ronnie

[nathannfm]

Originally Posted by Ronnie314

I would flip your gear boxes so that you are at least direct driving one wheel then running chain runs off of that. It would be more reliable and less chain. Also agree with everyone else on the drop center topic.
-Ronnie

Agreed, you could even direct drive all 4 traction wheels and only chain in the Omni, assuming you are not planning on a sprocket reduction. This would ensure popping a chain will never hurt you. Whatever the setup ends up being I would recommend having (possibly redundant) chains between all wheels on a side so that if you are lifted onto 2 or 4 wheels by another robot in a pushing match you will still have full 4 CIM power to the wheels that are touching the ground.

[RonnieS]

I would flip your gear boxes so that you are at least direct driving one wheel then running chain runs off of that. It would be more reliable and less chain. Also agree with everyone else on the drop center topic.
-Ronnie

[Jrizo]

Originally Posted by Ronnie314

I would flip your gear boxes so that you are at least direct driving one wheel then running chain runs off of that. It would be more reliable and less chain. Also agree with everyone else on the drop center topic.
-Ronnie

Thanks for the feed back. We are going to scrub the drop center and stick to the omnis up front. This has been extremly helpful. We will keep you posted on how it turns out.

[Jrizo]

Here is the actual cad file I work better in 3DS max but I realized that some of the measurement's were off so I redid it in Inventor. I have only done the actual drive train and not the whole frame. The center wheel is driven from the front omni by #35 chain. The performance wheels will have blue nitrile on them.

https://www.dropbox.com/s/n4nnbleo11...b2015.iam?dl=0

[BBray_T1296]

Why have you chosen to put the omni wheels up front? I would personally make the omnis at the back (seems like no effort at this point, just declare the other side front) to give whatever manipulator/etc the benefit of more fine control.



perhaps this is moot for more reasonably dimensioned robots


.

[Jrizo]

Originally Posted by BBray_T1296

Why have you chosen to put the omni wheels up front? I would personally make the omnis at the back (seems like no effort at this point, just declare the other side front) to give whatever manipulator/etc the benefit of more fine control.



perhaps this is moot for more reasonably dimensioned robot

.

The dimensions of the original drawing are off the actual dimensions are 32x24. I see your point about switching the front and back, we may just do that if our drivers can get the feel for it .

[BBray_T1296]

Originally Posted by Jrizo

The dimensions of the original drawing are off the actual dimensions are 32x24. I see your point about switching the front and back, we may just do that if our drivers can get the feel for it .

Of course I made it super long to show the effect. for a robot that is of standard squarish it is indeed significantly less of a concern