Bearing Blocks/Chain Tensioning
 

My team has never used chain before, and I'm doing some last minute research to ensure we will be able to this season.

I was looking into calculating the C-C distance, and found this calculator. How do I use this correctly? The example I was looking at was if I had a #25 chain, a 36t sprocket and a 12t sprocket, and I wanted to run chain over a 10" distance. According to this, I would need 104.36 links. Clearly, this is physically impossible. Should I just play with the number of links up top until I get a number close enough to 10"?

Secondly, my team doesn't have a mill. Therefore, we figured the best way to use chain would be to utilize Versablocks. Of course, I can measure the distance I need to put the sprocket centers from each other using a tape measure, but I won't get a super high level of accuracy. How do I determine that my versablocks are sufficiently spaced, such that my chain is tensioned?

Re: Bearing Blocks/Chain Tensioning
 

Don't worry too much about getting the exact center-to-center distance correct. The chain will stretch over time anyways, so you will need active tensioning (what I mean is something you can adjust from event to event) regardless of how well you get it the first time. Here's one solution to that: https://www.mcmaster.com/#chain-tensioners/=15qqcpa

Re: Bearing Blocks/Chain Tensioning
 

To that end, how do I know if it is tensioned or not?

Re: Bearing Blocks/Chain Tensioning
 

If the chain isn't skipping over the sprocket when you apply load to it, then the tensioner is doing its job.

Re: Bearing Blocks/Chain Tensioning
 

Could you also use VersaBlock with a cam instead? We're also fairly new to chain and lack a mill, but were planning on using the cams instead of a chain tensioner. Is one better than the other?

http://www.vexrobotics.com/bearingblocks-g.html

(And as a secondary request, if anyone has a picture with a VersaBlock and WCP Cam installed, that'd be much appreciated. It's hard to tell how the CAM mates with the VersaBlock online.)

Re: Bearing Blocks/Chain Tensioning
 

You can usually tell if chain is tensioned correctly just by moving the strung chain up and down. It should never be too tight in that you can't move it at all. But it shouldn't be sagging on its own.

I, depending on the center distance and size of sprockets, allow for around a third to half an inch of flexibility in either direction (up and down). I usually allow less flexibility with smaller sprockets and a shorter center distance, and more flexibility for large sprockets with a longer center distance.

With that ideology, I haven't experienced any chain issues. However, if people have done more scientific testing that disagrees me, I am willing to change my ways.

Re: Bearing Blocks/Chain Tensioning
 

http://www.wcproducts.net/versachassis

Under tech specs -> drawings -> cam and versablock

Re: Bearing Blocks/Chain Tensioning
 

4901 made it through two regionals, SCRIW, and demos with dead-spaced #25 chain, no tensioners in use. There were teething problems, but we got it together once we started using links without clips and pins and instead used a DarkSoul tool to assemble the chains. So: sometimes, you can get away with not using them.

And yes, we did fiddle with the distance until we had an integer number of links. It's better if you aim for an even integer number of links. Miles better. Half links are the devil.