Tensioning a final drive train

[Deanwvu]

Hello all,

My build will almost certainly have a Rohloff hub at the wheel, and likely a terracycle idler to take up chain slack.

My question is--how do I know how much chain tension is enough? My setup will be like this, but with a mid-drive motor, so I will be tensioning between the drive motor and the Rohloff. I think the concept is the same whether using pedal power or a mid-drive, and that is, how much tension??

Example setup:

 

[Wheazel]

I have not tried one of those crossing tensioners, but my approach would still be put a mild tension on the chain. (Typically when the chain becomes a "straight" line, and then a tiny bit more) then check how much the chain dances during load and adjust until its ok. Totally unscientific approach but works for me.

 

[crossbreak]

it is enough if you do not loose your chain frequently. a slack of of +/-5mm is still acceptable

 

[jtrops]

For pedalpower it is generally considered 1/2" of play. This is 1/4" up and down. The Rohloff manual says 10mm's of play, 5mm's up and down. Crossbeaks suggestion about being tight enough to not lose the chain is spot on. Keep in mind that this is for the tightest spot in your drivetrain. There is usually a spot that runs tighter due to small differences in roundness, and concentricity of the various parts. Running too much tension on an IGH can lead to premature wear on the hub internals, and that gets pricey. If you have your chainline dialed in you can run less tension without dropping the chain.

As an aside, I'm running a spring tensioner at the end of the boom tube on my Dummy, and i never drop the chain with my Nuvinci. I've only recently installed the BbS02 on it, but so far no chain skipping. I think the long distnce from the tensioner makes it so that by the time the rear cog is engaged the angle of the chain is more direct than a sprung down tensioner would normally produce.