Re: Chain Tensioner
 

If you have the resources to machine to close tolerances and you space your wheels by an integer number, you will not need tensioners until the chain stretches and then you can just replace it. I would personally not run without tensioners but it can be done. I would rather tension then replace but some teams are ok replacing chain more frequently for the weight savings.

Re: Chain Tensioner
 

Assuming you have the capabilities to make either, it is simpler to make as well.

Re: Chain Tensioner
 

we are closing in on 11 months without replacing our chains on our 2008 robot. and not one problem. also as Adam stated it saved us from making all other tensioner associated parts. I predict the drive chains lasting at least 5 years on this year robot.
mike d

Re: Chain Tensioner
 

Wow that is incredible. So are the chains loose now? How did you figure out the spacing to get it so perfect?

Re: Chain Tensioner
 

they were loose to begin with and they are even more loose than when we started but with 180 degrees of wrap they are still working fine. as for the spacing, we use #25 chain so the axle spacing is just a dimension divisible by .250 or 1/4".
mike d

Re: Chain Tensioner
 

Thats what I thought you guys did. I guess since you weren't using a super high force drivetrain the shock load on the chain wasn't great enough to break it. I always thought the reason for chain tensioning on #25 chain was so that it stays taught and doesn't snap when a shock is introduced. This year would be perfect to try going without a tensioner since the forces are so low on the drivetrain.

Re: Chain Tensioner
 

Last year we used a floating sprocket on our launcher. here's a pic.

Re: Chain Tensioner
 

I used to get all the drive train components about where I wanted them, mount the chain, then drill the holes in the right places. No real precision is required, though a good eye helps. Don't over complicate things. It's only rocket science if your robot is chosen for the next mission. You can probably find several good books about chain drives on Google books that were published from 1890 to 1915 or so.

Re: Chain Tensioner
 

We made some UHMW & Ziptie chain tensioners which resembled those of Andymark. They were on 4 chains that were all at a 5-10 degree angle and they worked fine.

You can guarantee they'll work fine so long as the spacing between the chain through the tensioners is smaller than the diameter of your smallest sprocket. That may not be easy to do though.