Tandem Cycling - short (160mm) rear cranks

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jm81
08-09-09, 02:06 PM
So, I've been looking for a 160mm rear crankset. I know these are hard to find, and anything will be at least $100. But, I think I have a good idea that I'm going to throw out there, to see if it anyone has tried or thought of this before.

I could buy two regular 160mm right cranks. Then, take one of them and drill out the threading for the pedal. Find a counter-clockwise threaded sleeve with a lip around one end. It would be inserted into the pedal hole from behind, so the lip would keep it from being pulled through as you screwed the left pedal into it.

Get it? I can draw a picture of what I'm talking about if needed.

PMK
08-09-09, 02:14 PM
There are folks that don't even bother with the insert. Just rethread the existing hole so it has clockwise and anti-clockwise threads.

Some suggesting it have tested the idea by applying recommended torques and seen no failures or loosening issues.

PK
jm81
08-09-09, 04:24 PM
PMK,

I can't imagine this leaving much material behind. Do you have any links?

Ben There
08-10-09, 08:11 AM
buy a longer crank and cut it off, drill new hole. I did this myself and then took it to bike shop to have it tapped, so I did'nt have to buy a tap.
Some ref info http://bikesmithdesign.com/Short_Cranks/shorten.html
zonatandem
08-10-09, 09:18 AM
All good suggestions . . .
jts125
08-10-09, 05:32 PM
have you looked at SJS cycles website? Their house brand Thorn cranks come in a wide array of lengths.

http://www.sjscycles.co.uk/default.asp
prathmann
08-10-09, 05:44 PM
SJS also sells a 'crank shortener' that you bolt onto an existing crank. If you start with 175 mm it could be adjusted to about 160 mm or shorter.
jnbrown
08-10-09, 06:07 PM
have you looked at SJS cycles website? Their house brand Thorn cranks come in a wide array of lengths.

http://www.sjscycles.co.uk/default.asp

I noticed some interesting 10 speed cassettes there, a "Mars" 11-34 and Shimano CS-6700 11-28
reversegear
08-11-09, 11:56 AM
I have used some kids single bikes for parts to put our kids on the back of our tandems.

Not always the most efficient way to go about it, but if you can locate an old single at a garage sale or similar with the correct size crank arms you might be able to buy the whole bike for cheap and get a seat and some handlebars thrown in for less than the cost of new. (Maybe even a couple of spare tubes and tires for your trailer.)