Chain Slack

Does anyone know of a chain and sprocket distance/length where the chain has no slack? Specifically with the 18 tooth sprocket.

i mean, odd numbers of holes between the sprockets are how vex intended them ( I think), or you could add chain tensioners or zipties for custom tensioners, a tensioner is just a standoff or something that the chain runs over to increase the length of travel, and zipties are good for chainbars

I never knew about the odd number of hole thing or the zip tie idea. Thanks!

I have found out that you only want the chain tight enough so that the sprocket does not slip. Any more tension than this only causes more friction. If you are making a chain bar then use as much tension as you can to reduce play in the mechanics.

You should never have no slack on a chain. If you actually test it without motors a system with more chain slack will have less friction.

This is correct, however you might want to keep the chain tight if you are using it for a chain bar.

We had a partially tank drive robot in Round Up, and for the first 80% of the year, we had our tread bow string tight. Then we added one link and doubled our speed.

What do you mean by an 80% tank drive

I agree that it reduces friction, but you want friction for a chain bar to keep the sprocket still.(Correct me if I am wrong.)

Also I do not think that it increases the drive train’s speed by twice.

Depends on your definition of tight. I would agree that you do not want it hanging lose, maybe gently rubber band tight. If you have it as tight as ours, it would not move. We had enough tension to pull our bushings out of alignment and chew our drive shafts apart on the metal hole’s edge, and we broke tread any time we hit a bump. We got ours in a connected loop, then forced the drive shaft through the holes we were using. It definitely doubled the speed when we added slack.

The only way you could have doubled the speed would be because of taking off weight, or was itonly your drive train. There is definetly no way that it reduces that much friction still.

Just saying I have once tried adding one piece of chain to a tight piece of chain and I still get a small difference in the speed.

I still think we have different definitions of “tight”.

Your logic is unsound. If you had chain that was so tight, the drive train did not move, then loosening the chain would increase the speed infinitely. Thus, it is possible that a reduction in friction could merely double speed.

I didn’t say it was insanely tight did I?

Right now my chain isn’t so tight and it has tons of weight on it and it moves very well, so I will try testing it. I’ll tell you the result.

Maybe you are misunderstanding me. I am making no claims of what your personal issue is, only a statement that in my experience, excessive chain tension has a significant impact.

I am not trying to convince you that your robot will get twice as fast if you add slack to your chain.

I tested it and it seems the same to me. But I guess I am going to keep my keep that to myself.

I am not 100% sure what you are asking…

We had 10-ish inches of tank tread in the front with omni wheels in the back.

For the first portion of the year, we had the tank tread VERY tight. Enough to be on the verge of stalling out our motors. It was our first time making a competitive robot. We were not good at anything yet.

Sometime between the second to last qualifier and worlds, we added one (or more) links to our tread, releasing the binding forces that were destroying our robot.

I disagree. I’ve see drivetrain chains so tight the robot barely moved.