Cheap Short Wheelbase Wood Conversion Recumbent Bike

Step 4 Bottom Bracket

Start off by attaching a 10" piece of 2X4 to another 2x4. This is best done with bolts as bolts mean adjust ability. To ensure there's no chain ring path conflicts, trace the diameter of the inner two chain rings on your 10" piece of 2x4 (I got by, barely, with shear dumb luck) - also mark the center.

Clamp the smaller 2x4 to the longer one and drill three holes (that match your bolts) - do all holes at the same time. Then bolt together (don't forget washers).

You want the smaller 2x4 on the chain ring side

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Now, drill a pilot hole through the marked center for the BB. Be as parallel as possible. Next, use a 2" hole saw (make sure this fits your BB cup) and cut a 1/2 inch deep hole. Don't remove any material yet (just drill the circle). Repeat on the opposite side.

Now, use a 3/4" hole saw and make two cuts to allow reassembly of the 1 piece crank. You need to be able to pass the crank/axle through the wood on that funny angle you used for disassembly. So make the cuts on "top" of each other.

Finally, chip away the 2" recess. Use a chisel, or a screwdriver ;)

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Your cups should now press into the wood (perhaps slightly loose). Assemble the cups and reassemble the crank. You may find that the screw no longer fits with the keyed washer in place. I removed the keyed washer (which will require occasional tightness checks later). Re attach the let pedal.

Laugh at the hilarity of a bike crank assembled into some 2x4's.