pic: CAD Chassis



Just to satisfy the public posting of a CAD design requirement, I’m throwing this out here. Credit to 973 for the gussets and 973/RC and 1323 for the gearboxes. That cad may or may not eventually get replaced with our own parts.

Highlights:
2x2 1/8" tube
1/16 AL belly, hole pattern tbd
Bumper mounts not final, will likely lose the middle two
weighs ~35lbs including CIMs
will eventually have cross support in location tbd after kickoff

That is a beautiful render… but one question how do you tension the chain?

Jack, is this an iteration of your 2011 drive? http://www.chiefdelphi.com/media/photos/36832

We are actually using 15mm belts with center to center spacing, which does not need tensioning. One belt run is actually inside of the tube, and the other belt run is outside of the tube, and you can see those pulleys on the front wheels.

Yes and no, there are a lot of changes (wider belt, different size tube, gussets instead of welding, AL not PVC belly pan, moving to two belts, different reduction, and different bumper mounts) that make this significantly different from last years chassis. It is still without bearing blocks and a few other staples of the standard 254/973/1323 WCD, but it is closer to that design than ours from last year.

How do the belts work for y’all, do they skip at all? (I have never used belts) Also if you’re running belts on the inside of the tubing how do you get them on and off? Last thing, why gussets over welding? (so you can repair more easily?)

For some teams welding isn’t a good enough resource to rely on. For 973 we completely switched over last season because we didn’t have a person who could weld in house or a sponsor who could weld overnight.
Gussets allow for a margin of error, if it is a little off you can redo the rivets. And everything can be assembled in house in 1 day.

Marc hit the nail right on the head, our welder has a three day turn around time and our machine shop has a one day turn around time.

Belts don’t skip at all. Although, our 9mm belts did ratchet when we changed direction last year, and we are switching to 15mm belts to try and alleviate the problem.

Akash posted a photo of last year’s belt access system (was a one belt system.) This year, we are still experimenting with access window size and location and we plan on using a similar system.

Why wait until after kickoff to finish an offseason project?

My apologies if this comes out worded funny. Rather than making individual sub-assemblies independently rigid and then finding ways to connect them together, sometimes we like to use other parts of our robot to add stiffness to parts. In this case, the robot would probably have at least decent cross support before we added another cross member. But there’s no point in adding a cross member if we’re about to add, for example, a box tubing lift on top of the chassis. If the game calls for an arm, our mast support would be the cross member. For an intake game, we’d have to redesign anyway as the chassis is closed front.

So it’s less not finishing it and more waiting for game specific design. There are other loose ends to finish, like chassis specific gussets and gearbox standoff mounting, but since changes will be needed in just two short weeks anyway to meet the game…

A 1/4" Plywood carbon or Fiber glass coated board would allow the team to develop some experience with composite construction methods. A way to get some fiber into the robot’s diet. YouTube is full of videos on how to do it.

We actually built our '09 robot almost exclusively out of fiberglass, and our 2010 and 2011 robots both sported some fiberglass and pvc. This is the first year we are looking to go almost entirely metal.

Looking forward to putting an iteration of this on the field in 2012.