Hub to Mid conversion for a trike - talk me out of it.

[ccihon]

Latest update - I swapped the 9-speed derailleur/cassette for an Alfine 8-speed hub. With the attached 20T sprocket, I am getting a very similar set of gears I had with the previous 11-32 cassette. I kept the shift sensor, and am using the Alfine chain tensioner as I have "near" vertical frame dropouts. This also let me keep the same basic chain length, easing return to original setup, though doubt I will go that way.

Mt main reason to move to this was to allow shifting while stopped, or nearly any time really, and to eliminate the noise and chatter while turning corners in lower gears, which was induced by frame/hub twist that tended to cause chain misalignment in the bigger cogs.

TBD: reliability with the BBSHD - I treat it fairly gently and so far it shifts surely and silently. The hub is also silent while coasting, which I appreciate. Common logic is to use the much more expensive Rohloff or other IGH with this much torque, but others say this one will do just fine for my application. I also dislike twist and trigger shifters on a trike, so the bar-end that works with Alfine is a plus.

 

[amberwolf]

With any IGH, it's not the universal cause for failure, but a major one is shock loading (gear lash) from a stop or after having shifted gears if there is any slop in the gearing so teeth are not always meshed.

If you can ensure that there aren't any times when the motor starts up that there is slack in chain or in IGH gears, such as by taking it up with your pedals first, it should minimize the chances of a problem from gear lash shearing teeth off at the roots, at least.

Wear on the gears over time, or shearing any torque-limiting devices (cotter pins, etc) within the hub are other issues to look into. If the hub has a shear pin, etc., then it will probably be rated to fail somewhere not too far above the specified torque limit of the hub--it might not for significantly above that, but I'd try to assume the limit is the limit, to prevent being stuck wherever you happen to be when it happens (since you won't have any drivetrain at all at that point, as your pedals would also be going thru it) and you'll be walking home.

So you would want to setup your gearing into the hub so the system can't apply more torque than the limit. Higher speed into the hub would be fine, most likely, but higher torque isn't.

 

[ccihon]

One of the few knocks against the Rohloff seems to be the slack or wind up to engagement after shifts. This Shimano, at least out of the box, seems tight.

I will be testing it, as this is a heavy trike with a heavy rider. If the hub internals hold up, I know the chain line is more solid and reliable. This is a long chain with idler and chain tubes, and some frame flex. Early on I snapped the chain with a derailleur upshift.