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Friday, January 31, 2014

Some Philosophy of Bike Building

Suspension Block and Packer for Aluminium Bike

From right to left we have * Existing suspension block from old pedal rubbers, cable ties and a plastic bike tyre lever, * Raw material for new block is an engineered Mackay multicushion industrial damper * which was cut up and combined with a small piece of "Unimold" and some cable ties to make the new block.

The block in place.  Not tested yet!  The extra width of the cable ties keep the block in place.
This blog post is just a bit about replacing a suspension block in my aluminium recumbent with something (hopefully) a bit better.  But really it illustrates some of my bike building philosophy as well.  If you are trying to build something new, you don't have to solve all the issues concerning it at the start.  Once you build it, you will probably find an answer to the issues, and if that fails, and you scratch your head a bit, you will eventually find a better answer.

So at the start of the project to build my aluminium recumbent, I winged it to make the suspension block, and this blog is old enough and nerdy enough to have this process documented.  Since then I have used bits of bike pedals put together to make suspension blocks for the aluminium bike.  This works fine except when it gets hot, say 30 plus degrees like it has been lately here.  A lot.

Then the rubber gets mushy.  For goodness sake, what would you expect?  It was designed as a Chekoslovakian bike pedal, and when being used as an Australian bike suspension system, it just says "Bugger Off" and starts to crumble.  Then it has to be replaced or rearranged so the pressure's on a less crumbled bit.  Which is not really good!

So the new solution was a happy coincidence,
* my (slightly worse performing but still cool) wooden recumbent is heaps good enough for riding around town, so I can use that, and rest and repair my aluminium bike. 

* the build of the wooden bike involved a (fully designed in, woo-hoo) Mackay suspension block, and I bought a few of same dimensions but different spring rates (ie kg/mm deflection) to try on the new bike.  It turned out the softest of these was good on the wooden bike.  The Mackay block handles hot weather fine.

So with 2 harder blocks left, I finally had some material for a long lasting suspension block for the aluminium bike, and a week or so ago when I had some time I set about making it to the template of the pedal suspension block.  This involved hacking off about 2cm of width to make it fit in the pocket in the frame, and bolstering it by 15mm or so with plastic to make it the right height.  You can see the results.  Now I hope the damn thing works!  Will report later.


Steve Nurse

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