Friday, February 17, 2012

Cable problem solved...On the trainer with the handcycle...

The handcycle on the trainer -- and an hour and a half workout went well after some adjustments.  I still have to get a longer (118mm) bottom bracket axle.  The current length is only 107mm and causes the chainline to hug the carbon fiber too much (see the white tape).  I think this is a small problem.


Handcycling and cables (brake, shifting) are not very compatible.  The handcyclist, unlike the bicyclists, rotates the shifter and brake cables that are connected to the handgrip's levers.  Therefore, the handcycle must have a method of keeping the cables out of the way.  I have run two of the cables within the frame itself (right brake and shifter cables).  But there still must be quite a bit of cable exposed in order that the cables do not break quickly with the 10,000 revolutions that I average per workout.

Here is the problem in pictures.


As the crank spins, the handgrip must stay vertical and the cables must stay out of the way of the cranks/grips. I used the end of a carbon fiber fishing rod (as a test) to see if the rod has the strength (but also flexibility) to maintain the excess cable above the handgrips.  The rod must bend down some when the cranks are at the bottom of the cycle.  The fishing rod works quite well:

 You may ask, "Why the excess cable?"  If the cable is too tight, then the rotation will cause the bending of the cable to be confined to a smaller length of itself.  Thus, the cable will break sooner as compared to if the excess length is longer. It is a balancing act.  I expect to change these cables every 1500 miles or so.

3 comments:

  1. interesting problem - seems tailor made for electronic shifting so as to avoid the entire cable problem altogether with an electric brush on the crank and a Di2/EPS equivalent for a hug gear. this is one cool looking bike - can't wait to see you at granfondo!

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  2. You are so right. I looked into Arduino, Gageteer, and other toolkits with bluetooth interfaces for which I might be able to program the controller to work with motors with proper gearing to power gear shifting. Downshifting takes little power. Downshifting (on the I-Motion 9 speed hub), appears to happen by merely releasing more cable. I suspect that the hub moves to first-gear on a broken cable.

    I would probably keep the motors and gears on the inside of the main portion of the fork (you can see in the pictures above that there is a lot of room there) and run a cable to the hub. The reason for this is that I can build a carbon fiber holder/support for it within the fork; the controller can be larger than a store-bought one; the contraption may take a few motors for which I would have plenty of room; and the battery can be protected.

    My next project... if this works.

    GranFondo... I hope my "training wheels" work. I can already see myself going up those 2 mile/20% grades with my odometer reading 0 mph -- albeit, I would still be moving. If this works, I will be going over 50mph downhill though.

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  3. BTW, I found a 118mm bottom bracket axle -- 11mm wider than my existing axle. The chain is not clacking against the carbon fiber fork nearly as much (see picture above where white tape covers the area where chain was hitting),

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