pic: Drivetrain Side View

This is a side view of half of the drive train that I am designing. The middle wheel is lowered by 1/8 of an inch. Although it is hard to see in this picture, when the bolt at the end of the frame is turned, it moves the wheels and tightens the chain. The robot uses number 25 chain, and 23 tooth sprockets to connect the center wheel to the outside wheels. The wheels are made out of 1/4 inch sheet metal and 1/8 inch sheet metal welded together. They are bolted to a hub made out of aluminum.

Looks like it is inspired from the 254/60/22 drive train.

Why couldn’t the wheel be only two pieces by incorperating the hub into the wheel itself?

I love the button head screw to tension the chain. Nice touch.

Just a few thoughts as 229 had a drive similar to this for triple play. Are you using a solid chain linking all the wheels together. We decided that we should use 2 chains one mid wheel to front wheel and one mid wheel to back wheel. in case one breaks you still have 2 wheels driving. Also if you use this in a game try to keep the robot balanced front to back otherwise you ed up with massive tread wear. But other than that great design, good luck in ‘07’

I modeled the drive train off of ideas behind of 254’s drive train, and 968’s tensioner.

Why couldn’t the wheel be only two pieces by incorporating the hub into the wheel itself?

I designed the wheel so that it could be swapped out easily. All we have to do is to remove the six bolts, and the wheel is free to be swapped out. Also, one of our sponsors is a sheet metal manufacturer. They can easily cut out the 5 pieces of sheet metal that make up the wheel. The wheel has an 1/8 th inch thick rim, a 1/4 inch thick spoked section, two 1/4 inch body sections, and another 1/8 th thick rim. They would then spot weld these together in that order to make the wheel. By incorporating the hub into the wheel, we would have to start with a larger block of aluminum and wouldn’t be able to make the wheel out of sheet metal.

We decided that we should use 2 chains one mid wheel to front wheel and one mid wheel to back wheel. in case one breaks you still have 2 wheels driving.

I am doing the same thing. You can see the two sprockets on the main drive shaft in the other picture that I posted. Thanks for the advice on tread wear

Here is a render of our tensioning device. Once again, it is made out of sheet metal.

Are the wheels being held on the shaft only by the clips, or is there something I’m missing?

It looks like snaprings. Those do a great job, I know 968 (and 254 as well?) used them this year. We also had all six of our wheels held on with snaprings and never popped one.

It seems like it. The clips would be enough to keep on the wheels. 254, 60, 22, 968, 980, and 4 (thats all i can remember) used only clips and they work just fine

well then, I’m convinced. I’ve never used them, so I wasn’t sure how strong they were.

It looks like snaprings.

Yes, those are snap rings. Good call.

Can you show a more detailed look at how the tensioner interfaces with the frame? I’m not clear on how it’s supported.

I’ve been working on a similar design that requires as little complex machining as possible, as I’m the person who does all the CNC work on the team and there’re few things I dislike more than sitting in front of the machine. The tensioning mechanism is one of the few details remaining, so it’s interesting to see how others have decided to implement that detail.

Here is a picture of how the part that I posted earlier fits into the frame. I moved one of the side plates out of the way so that you can see how the part fits in the frame.


Thanks for clearing that up. Are you relying on the tension of the chain to prevent the buttonhead screw and tensioning mechanism from moving outward (left in the picture)?

Also, I like the display style a lot.

Correct, I am relying on the tension of the chain to prevent the buttonhead screw from moving outward.

that my friend is beautiful…i wish i had the patience to design something like that. Very nicely done.

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.


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


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?

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?