Re: pic: Drivetrain Side View
 

If anyone is interested, here are the Solidworks files for the drive train and transmission. If you end up using any part of them durring the season, I would love to know about it. Please let me know if there is a problem with the files, or something doesn't make sense.

http://www.boardsailor.com/austin/CDExport12-28.zip

Re: pic: Drivetrain Side View
 

It also clamps onto the 1x2 frame rail I assume.

Re: pic: Drivetrain Side View
 

Correct.

Re: pic: Drivetrain Side View
 

Thanks for making the model available. It's always fun to get in and dig around somebody else's models.

I've been curious about how you're planning to attach tread material to your wheels. Because they're made from several layers, it seems like it'd be difficult to rivet the material down. Can you give any insight into how you're going to do this?

Re: pic: Drivetrain Side View
 

I have always wondered if it is possible to avoid using any sort of tensioning whatsoever for roller chain. If you properly calculated the measurements for the location of the sprockets you would never need to tension the chain. I reference this website: http://www.battlekits.com/
This drivetrain uses no tensioners, though granted, they do use #35 rather than #25. Smaller chain stretches more than larger chain. I really like the Battlekits design and function, and simplicity. What do others think about not using tensioners?

Re: pic: Drivetrain Side View
 

I haven't looked too far into this, but I was assuming that since the wheels will be tig welded together pretty solidly, we would be able to ignore the fact that the wheels are just layers of sheet metal, and just drill holes for the rivets. We would of course try to drill the holes through the centers of the layers and miss the gaps between the sheets, but I don't see anything wrong with drilling in the gaps between the sheets. If the wheel breaks because we drilled a couple holes in the wrong spot in the rim, we have MUCH BIGGER problems.
Thanks for your feedback.
Did I use the PEM nuts correctly? Our machinist recomended PEM nuts instead of threading metal, but since I have never used them before, I don't know if I used them correctly.
Also, I sent the design to our machinist for inspection, and he thought that I needed to strengthen the transmission case by making it more of a box. Is his concern valid?
(PEM nuts are cool parts that are pressed into a special sized hole in a piece of metal and presto, the hole now has threads. http://www.pemnut.com/)

Re: pic: Drivetrain Side View
 

After watching our 2004 robot go from having tight 35 chain, to 35 chain with around a link and a half of slop in the chain without driving it very much, I would be hesitant to get rid of chain tensioners.
Theoretically it is possible, especially with short chains, but I don't feel comfortable without a chain tensioner.

Re: pic: Drivetrain Side View
 

Look at how 22 (maybe), 60, 254 an 968 have been doing it. You have no problem with the curved plates.

Re: pic: Drivetrain Side View
 

The captive nuts looked fine to me; just make sure the ones you use are sized properly for the sheet metal thickness.

I think your transmission will be fine as long as it has the spacers across the top, though I was curious why you decided to use sheet metal spacers instead of simple tube. It may be heavier to have a bolt run through tubing, but it'd also be a lot easier and might alleviate some of the sheet metal production time.

Did your machinist express any concern about the bearing holes lining up from one side the the next? The limited experience I've had with sheet metal parts makes me concerned that you may not get bends that are accurate enough to keep the shafts orthogonal to the plating -- especially if you're bending something as thick as 1/4" plate.