Recumbent trike – idlers and longer ride
The trike is now mostly done, but the drive train was giving me grief. The idlers were not working out and I replaced the rear cassette due to the chain skipping. The previous owner of the components had beat the bike more than I initially thought with damage to the cassette and outer crank chain ring , both of which had to be replaced. Maybe there was a good reason he cracked his Trek carbon fiber frame?
After having problems with:
- Metal pulleys as idlers . These were garden tractor style A size v-belt pulleys form Northern Tools. There were metal shavings everywhere and the chain would pop off.
- Hybrid pulleys. I used sprockets from the old gear cluster and 3D printed nylon sides and spacer to center them over the ball bearings. They held together, but after 5 miles were wobbling badly and the low gears were skipping. The chain would rock off the sprockets, ride on the sides or pop off all together. The nylon withstood a huge amount of force and merely deformed without breaking. However with a 9/32″ wide bearing, there was too much lateral force.
- Hybrid pulleys versions 2&3. I used PLA for the test models. However, it blew apart under stress in less than 3 miles. There were problems with geometry and the bearing to sprocket interface. I was not thrilled with the thought of making new parts out of aluminum to withstand the stress and support 2 bearings per pulley. Nylon flexed too much and I would have needed to bake the spool again due to the humidity. to drive off the absorbed moisture prior to printing.
I then again turned to Google. This lead to Terra Cycle idler pulleys. http://t-cycle.com/idlers-chain-management-c-41/idlers-c-41_9/sport-power-idler-p-134.html They were highly recommended on the AZ website and elsewhere. I ordered a couple of these and one of thier 28″ chain tubes as an upgrade from the garden hose. With the research, I also decided to redo the chain tube supports and let the sprockets and chain tube slide freely on the shaft rather than being held side to side in a fixed location. The resulting setup is seen below. I used 1/16″ x 3/4″ aluminum stock and bent it to match the chain tube. This was easier to make and the integral chain retention is a huge benefit.
You can also see above, that when the old front idler shattered, the chain was then rubbing on the underside of the handlebars.
With these installed, I dressed for cycling (cycle shorts, not my regular cargo shorts) so as not to appear to be flashing the passersby. The padding of the cycling shorts was not necessary but the snug fit was. I then did an intermediate length “shake down” ride. Just shy of 20 miles and nothing fell off or bound up. I still need to do some derailleur adjustment (some skipping under hard stress) and front brake fiddling (some squeaking/ rubbing of he disks) and front wheel toe-in adjustment as well as tying down the right front brake cable which is rubbing my calf.
However, it rode very well overall. It was comfortable and fun. There were plenty of interested looks on the bike trail, as you might expect. Max speed was 26 MPH and average was 12. Still below my road bike, but I hope with a bit more tuning and remembering to top off the tires, I should break even. My back, wrists and hands felt much better than on the road bike. Conversely, my shoulders and biceps were a bit stretched as my hands are below and behind my back due to the reach for the handlebars. Legs were pretty good, but my shins are a bit sore tonight. I expect that there will be some “human break in” for the new riding position.