01-07-2010 14:14

sgreco

Re: pic: 6 wheel drive train concept picture one

Looks like a nice concept. I like it.

A few questions though. The Gearboxes appear to be floating in space, do you have a planned attachment method yet?

I'm not personally a fan of running the chain over 8020 cross bar on plastic. I've seen it done before, and it works, but my team had issues in 2008 where we broke through some plastic this way. Make sure you get a strong delrin to rest on the 8020 bars.

How do you intend to tension the chains with the plastic blocks? If you slide them, you'll shorten the chain on one end, and lengthen it by the same amount on the other side, and it won't tension.

I like the use of 8020 for a test bed, nice and versatile and easy to work with.

If your unsure of using e-clips or cotter pins, definitely use e-clips. Cotter pins are relatively bulky (for this purpose) and believe it or not they're harder to remove than e-clips. Cotter pins are also a pain if the bend because they stick out. e-clips are a lot cleaner.

01-07-2010 14:27

Eugene Fang

Re: pic: 6 wheel drive train concept picture one

I'd go with snap rings, which are much stronger than e-clips.

01-07-2010 14:53

Chris is me

Re: pic: 6 wheel drive train concept picture one

Snap rings are the best! They weigh nothing and are easy and quick to install.

I've seen Delrin, HDPE, and nylon guides successfully used in this application before.

01-07-2010 15:10

ttldomination

Re: pic: 6 wheel drive train concept picture one

I too am interesed about your gearbox attachment methods.

01-07-2010 16:10

s_forbes

Re: pic: 6 wheel drive train concept picture one

We have used what are effectively plastic blocks to tension our drive chains for the past four years without any issues. We usually use oil impregnated nylon, turned on a lathe so that it has a lip sticking up where the chain will ride over it. This way the chain rollers are supported rather than the connecting plates.

This method of tensioning can be seen clearly on our 2008 robot, here. In that photo you can also see the use of UHMW Polyethylene chain guides, purchased from McMaster.

I think it's worth noting that I was a little skeptical of plastic tensioners and guides at first, but after seeing our 2008 robot run around with its ridiculous serpentine wrapping of the chain and no noticeable drag in the drivetrain, all of my worries vanished.

01-07-2010 22:28

kinghashbrown

Re: pic: 6 wheel drive train concept picture one

I plan on replacing the front face of the gearbox with a plate that has all the holes and extends off and inch and a half to the left and right of the box. Four aluminum spacers will run from the plate to the 80/20, 1/4"-20 bolts will go through them and screw into t nuts in the 80/20 t slot profile. However I am somewhat concerned that if someone hits the center wheel it could cause the SS to move out of place. I haven't really worked much with 80/20 before, so I don't know if that is a legitimate concern.

p.s. Picture two will have this in it. It should be up tonight, right after my laptop is done making it.

01-07-2010 22:41

kinghashbrown

Re: pic: 6 wheel drive train concept picture one

Thanks for the info. I found it helpful.