Colson center drop

[Gregor]

Originally Posted by trilogy2826

Small sidetrack first:
2826 has built 11 drivetrains in the four years we have been competing:

Competition:
2009: 3 wheel crab, Wide
2010: 4 wheel longitudinal beam suspension (2 traction in front, 2 omnis in back), Long
2011: Octocanum, Long
2012: 8 wheel, 2 center drop, 5" Colsons, Long

Another sidetrack, but I just want to point out that 2826's most simple drive train coincides with their most successful season. Coincidence? I think not.

[Chris is me]

Jake,
One other thing I'd look into with regards to turning scrub problems would be how rigid your frame is diagonally (cross-corner). A less rigid frame is more likely to flex just a little bit and result in the outer wheels touching the ground when they shouldn't, leading to the problem you described. From what I've seen of your frame this year, it really shouldn't be an issue, but I've seen it happen to a few teams. I think this is part of why the Kitbot has a larger drop than average - the frame is less rigid than a more solid welded frame.

You may be able to avoid the dynamic turning compliance problem with wider Colsons. I noticed at IRI that your drive base was running very thin (7/8") Colsons - experimenting with 1.5 inch wide Colsons, while it will add some weight, could help a bit too. Since the weight of the robot is distributed across more tread, there should be less localized pressure on the tread and thus you might get a bit more freedom turning. I know this sounds counterintuitive, but we've had great results with the wider Colsons and I thought I'd just throw in another data point to test.

[Brandon Holley]

Our 2011 DT was a 6WD, drop cetner w/ 4" X 1.5" Colsons. We dropped the center wheel 3/32". This worked well, but was a little on the too grippy side for us, so we went to 1/8" on our 8WD this past season.

-Brando

[Akash Rastogi]

Have you guys modified the tread pattern at all when using Colsons or flattened down the wheel? (Not sure if they all come with a tapered tread). If so, did you see any benefit in performance/turning?

[Brandon Holley]

Originally Posted by Akash Rastogi

Have you guys modified the tread pattern at all when using Colsons or flattened down the wheel? (Not sure if they all come with a tapered tread). If so, did you see any benefit in performance/turning?

We did cut treads into our Colsons this year and saw improvement, mainly in traction. We were measuring somewhere in the ~12% range for the pattern we used.

Flattening the wheels on a belt sander also appears to be something we'll explore as we move forward. We flattened a few of our wheels this past year. We'd like to try flattening them and then cutting the tread pattern into them and seeing what kind of performance we get.

Even with all these tweaks, we still felt even regular old off-the-shelf Colsons are more than acceptable.

-Brando