What Drivetrain?

So I made a thread like this last year and I’m once again curious what drive train did your team use for Ultimate Ascent. Here is a link to the old thread I’m curious how the two compare. http://www.chiefdelphi.com/forums/showthread.php?t=106347&highlight=2012+drivetrain+poll

So, officially, my team used a 4 wheel tank but that was result of the products of the new robot dimensions and a wide orientation yielded a small enough track length for a 4WD.

  • Sunny G.

I love how you added Mecanum as the only choice in italics

Actually, the italics denote the choice you voted for. For example, on my screen, ‘4-wheel tank’ is italicized, as it was the choice I selected.

Guess I learn something new everyday.

Personally, I LOVE 6 wheel tank and think it can work for a lot of games.A lot of systems like swerve, west coast, ect are robot specific and strategy specific, while I think tank is easy to build, fix, and operate.


Erm, west coast drives are a form (in my opinion the best form) of tank drive.

It would be interesting to compare the pit scouting data from CMP and IRI, FiM and MAR, or any other sets of tournaments or regions to see how different regions or events compare in drive train usage. I’m familiar with the CMP division pit-scouting and am anticipating something similar for IRI, but is there a giant Google Docs spreadsheet of pit scouting?

I agree, wholeheartedly! WCD is a great drive-train choice, but it is tank, executed well.

But I am a Swerve-Drive guy at heart. Yes, it is expensive (time, machining, weight, $s,…) and it is exceedingly difficult to execute well (and very easy to execute poorly). But well-executed Swerve-Drive is hard to beat as an FRC drive-train (this judgment is, of course, game dependent).

Swerve combines true 2-d drive capabilities with excellent traction. Since direction of travel is independent of chassis orientation, it does not telegraph intent like tank does. Its ability to vector drive force in any desired direction makes it formidable in defense as well as offence.

But this comes with a high price tag, which includes extensive and continuous driver training. This never stops for us.

Could someone please explain “butterfly” or “nonadrive”?

A butterfly drive is a drive train with four omnis in the corners and then a pair of deployable traction wheels to allow you to drive staiter and not being pushed, while also giving you a quick and nimble drive train with the omni wheels. Most these ive seen drive the two sets of wheels at different speeds resulting in a “shifting” drive train. ALthough some teams (148 maybe?) run all the wheels at the same speed allowing them to have omnis down on one side and traction on the other changing where the robot rotates. Here is some info on 3928’s butterfly drive http://www.teamneutrino.org/seasons/ultimate-ascent/robot/butterfly/

A nonadrive is a butterfly drive but with a center set of omni wheels positioned perpendicular to the other wheels allowing for the whole drive train to strafe from side to side. Heres a video of 148s 2010 nonadrive you can see the drive train specifically at 1:10 and 1:33 http://www.youtube.com/watch?v=_hTyXQUgYLE


About them being the best, what do you qualify as WCD. They aren’t the best for every team though. If I mainly used sheet I wouldn’t be cantilevering wheels.

We used a 6WD West Coast Drive this year for several reasons:

Note: we have a square robot (27.5" x 27.5")

  1. The field had no raised obstacles, so no need for mechanisms like in 2010 or 2012 to traverse the field.

  2. It gives you the widest wheelbase/track possible for the size. (I suppose wheelbase is debatable because of the dropped center.)

  3. Our drive base is very simple and easy to fix, just a piece of extrusion, bearing blocks, chain, and wheels. (Don’t trust hex bearings.)

  4. It gave us more room for electronics and other mechanisms because of how little space the entire drive system takes up.

  5. The drive base is very maneuverable, the added ability to shift allows us to go around or under the pyramid quickly, in addition to being able to push through defenders.

I am sure there are other reasons, these are just the ones I can remember off of the top of my head.

The “standard” definition of a WCD is a 6WD drop-center, cantilevered wheels, live-axle, center directly driven off of the gearbox (usually a 2-speed gearbox), outside wheels chain-driven off the center axle.

I don’t necessarily agree that WCD is the best of the tank drives, partly because it does take some precision to make and thus might be rather difficult for some teams, but it is up there if a team can build it properly.

What if your team switched drive trains through the season…

No, it didn’t end well.

Last year, our team changed drivetrains at Championships. Try to avoid that.

Actually… Switching drivetrains is something you could get away with, IF you’ve planned correctly. For example, if you’ve got the extra hole(s) drilled already, it’d be relatively simple to go from 8WD to 6WD, or vice versa, or 4WD to 6WD, or 4WD to mecanum (with a pair of transmissions added). Planning correctly means that you built the robot to be able to switch–though it does not necessarily mean modularity.

330 did that back in 2005–the competition robot had an extra set of transmission slots so we could swap to mecanum from 6WD if we thought it was a good idea. The testbed–a Kitbot–ran mecanum. We didn’t have the weight that year to switch. To this day, 330 has yet to run mecanum on a competition robot.

When you say extrusion, did you use something other than the normal 2X1 tubing?

Also whats up hex bearings?