pic: Offseason Gearbox

[Chris is me]

Originally Posted by rponmalai

Am I correct in assuming that you need a larger pulley to keep the belt from slipping off of the pulley?
The more I hear about this I am starting to lean towards chain drive to run through the tubes. My only draw back is keeping the chain tensioned. What would be the best way to keep the chain tight while it is in the tube?

Slipping off, no, ratcheting or failing, yes.

That said, you never have to tension a properly dead spaced belt in tube drive. It has its pluses. It's just not

If you have the proper center-to-center distance on the chain, it should stay tensioned.

Maybe in certain applications depending on load, chain length, etc, but this just isn't a blanket statement you can make. Both chain stretch and sprocket wear are very real phenomena that shouldn't be ignored. The 118 solution does an unconventional but effective job at containing this chain stretch to prevent failure, but in most cases you're going to want a tensioner. Optionally, you could replace the chain once it's stretched to the point of giving you problems.

For a very extreme example, our chain elevator this year had a nice 13 foot long loop that was dead spaced, and it stretched noticeably over the course of a few hours of low to no load testing. It is a function of sprocket diameter, chain length, and several other factors. At the size of sprockets used in west coast drives, it's a factor.

Originally Posted by Abhishek R

If it's nice and tight properly upon installation, you shouldn't need any form of tensioning for the chains.

The other important caveat here is that your chain and sprocket should be constrained by the tube itself for this to work (very close to inner walls of tubing). One of the reasons chain in tube seems to work so well is that there is nowhere for the chain to go when it does stretch, preventing the jumping problems found with looser chains.