Chains for 6 wheel drive

We are building a prototype to test 6 wheel drive. Could someone tell us the best way to arrange the drive chains?

Can you put up a picture of what your current drive configuration is?

-RC

Depends. Where is the gearbox?

here are are a few photos of our rookie year drive train. You might get a few ideas from this:

http://www.chiefdelphi.com/media/photos/27588

http://www.chiefdelphi.com/media/photos/27587

does this method of chains work well?
i’ve been prototyping chain drives and never though of 6-wheel power but it seems like a good design. do you use 3 chains per side? you could extend the drive chain so that it wrapped around the first two wheels, like on a caterpillar. that way you’d only be using two chains.

two chains were used. 1 drove two wheels and was powered by one CIM. The other chain drove the front wheel getting power from the middle.

330’s setup has typically been 2 chains off the gearbox, one to rear, one to middle, and 1 chain from middle to front. Gearboxes were aft, which helped the robot settle on that side for slightly more stable driving. (6WD drop center)

We used a similar setup this year. Two chains from the gearbox (to middle and rear wheels) and one chain from the middle to the front. Again, gearboxes were aft of center, but tensioning was a nightmare (we were using #35 chain).

Our set was way easy to tension. All we had to do was slide the motor shaft fore or aft to tension the back chain. The front chain was tensioned by sliding a small PVC pipe along the length of the chain and zip tying in place.

Have you been following the discussion in this thread? Static (ie non-rotating) tensioners are not receiving a favorable assessment over there.

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It’s a lot easier to use one chain per connection than it is to use a single chain for multiple wheels. So 2 chains off the box and one chain from a wheel to another wheel.

Another alternative that I don’t believe has been mentioned yet is:
Direct drive one set of wheels, then use chain to drive the sets.
For instance, direct drive the center set, then run a chain from center set to the front set and another from the center to the rear set. This can also be done by driving either the front or rear set of wheels and then chaining up the remaining sets. If you use #25 chain, this will also yield the lightest use of chain.
We have used this setup, as well as many other teams, with great success. The one caveat is to make certain your alignment and tensions are correct.

One not so obvious advantage to this design is that a single chain break will not cripple your drive train. In fact, multiple breaks might not either.

You can really route your chains just about any way that you want, provided you have enough chain wrap around each sprocket. Teams have had success with just about everything.

My favorite method so far is a using just a single chain to provide power to all the drive wheels on one side (example here). It makes for a nice simple system that’s easy to work on, but if the wheel sprockets are slightly eccentric it can be a pain to tension correctly.

We used that same approach for Lunacy. it worked very well.

We did 6wd for Lunacy.

We drive the center wheels directly. Fronts and back wheels were driven by individual chains each slaved to the center wheel master. The center wheel, in addition to being directly driven, had dual sprockets. This worked well, kept chain lengths short, and limited the impact of losing a chain in a game (which never happened, anyway).

Spacers on the sprockets kept the chain runs straight.

just a quick question, I see you bolted into 80/20 for your wheels. did you have any problems with the two outside wheels coming loose during competition?

No. This was not a significant problem.

We did check chain tension in the pit. If loose, we utilized the 80/20 grooves to tighten the chains (loosening the bearing block bolts; shifting the blocks to tension the chain; tightening the bearing block bolts). This was probably a once-per-competition event.

We used economy nuts in the 80/20. We have generally found that these do not tend to slip if they are tight. In fact, they tend to bite into the 80/20’s aluminum and need to be tapped with a hammer to move after loosening the bolt.

A small caveat to Clem’s post I would just like to point out is that Lunacy drivetrains tended to be much more forgiving in terms of chain tension, and things coming loose. This was due to the slickness of the floor/wheel interface. Wheels can only exert so much force on the ground, and in the case of the Lunacy game, it was much smaller than usual.

Just wanted to point that out, the sliding tensioner blocks may have worked great for Lunacy, but for games with more aggressive surfaces (ie: carpet), they may not work as well. Thats not to say it cannot be done, it just will require some extra effort.

-Brando

I really, really like the simplicity of using extrusion and sliding blocks to tension chain like that. Have any teams successfully implemented this in a high traction drivetrain? Machining bearing blocks out of solid and making a reliable mechanism to hold them in place and adjust them as needed is difficult, and this looks too simple.

I wouldn’t say it is difficult at all. Any team with a manual mill could EASILY pull it off.