IGH on a fully?

[toro1978]

So I found a full suspension old bike for cheap and would love to replace the wheels - I have a Shimano Nexus (or Inter?) 7 with a coaster brake.
Has anyone put an IGH in a fully frame? Can I use the original tensioner (this derailler type) or do I need some other - I assume that the swingarm action would change the chain length when flexing?

 

[Dr. Tankenstein]

As long as your chain maintains it’s tension, you should be fine. Unlike a derailleur, the ‘effective’ length of the chain doesn’t change as you shift gears or as the suspension flexes. It’s still the same arc.

For a simple tensioner, I run one of these
https://rover.ebay.com/rover/0/0/0?mpre=https://www.ebay.com/ulk/itm/163629279590


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[HuffnPuff]

If you are running a coaster brake pedalling backwards might play havoc with a tensioner. They are typically only designed to work under forward chain tension while having slack in the chain ‘undrneath’ when you pedal backwards it tensions up the other side of the chain.

 

[Dr. Tankenstein]

Mine brakes fine, I keep about 1/4”-3/8” slack in the chain. Instant forward pedal response as well.


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[toro1978]

At a closer inspection it turned out I won't have to worry about the suspension flexing:

The other single pivot designs I know have the BB on the frame before the swingarm joint. This bike has the bottom bracket BB on the swingarm, so no problem. Worst case scenario is I would need a half link chain.
Thanks for the input and for the chain tensioner links, guys.
I will post a regular build thread when I start working on it these days.
P.S. The mock up showed the derailler can't work with the coaster brake.

 

[horsefarmer]

Is that design common? Seems it might be the cure for excessive bounce when pedaling uphill.

 

[toro1978]

Well that's the compromise with the full suspension bikes. When going uphill it is the same with a suspension seat or a suspension seat post or a suspension fork - which is why most modern bicycle forks and rear shocks have a "lock out" function; also one reason why there are no road bicycles with suspension forks, the other being the added weight of course.
I think this is less of a problem with expensive bikes though, they have more elaborate suspension design.
So I don't know if it solves the problem, it will always occur when your body changes its position because of handlebars, seat and BB changing their relative position. We'll see
Taken from wiki:
"The main advantage of the single pivot design is its simplicity. It has few moving parts, few pivot points, is relatively easy to design and has good small bump compliance. Challenges with this design are brake squat and chain growth.
Due to its simplicity, many inexpensive department store bikes use this design."

 

[HuffnPuff]

Is that design common? Seems it might be the cure for excessive bounce when pedaling uphill.

It was the solution for pedal bob back in the late 90s. Constant chain length meant pedalling didn’t affect the suspension characteristics. Biggest problem was that when you stood up the suspension effect dramatically cut back because your weight shifted from the saddle location to the bottom bracket. It was also a cheap design to make requiring few pivot bearings.

I have a ‘96 Trek Y-11 which was the ducks guts when built, but the design didn’t last long in premium bikes and now it looks like a million cheap and nasty dept store bikes.