Dynamic chain loading in multi-pilot drivetrains
Posted: 07 Aug 2012, 10:27 am
Good news:
My new 4-seat tricycle survived its first public trial - a 1-1/2 mile parade last Saturday. That may not sound remarkable, but the parade route is a 3-6% uphill grade for its entire length! Our loaded weight with pilots was over 1,500 lbs and average speed was around 2 mph. That's the equivalent of pushing a 60's Volkswagen uphill for 45 minutes.
During the ride, we experienced something that I hadn't anticipated. Oscillating dynamic loading of the chains. My machine has two independent drivetrains. One per side, each turning its own wheel. In each, two pilots are seated in tandem. Each pilot powers a standard bicycle style setup. Each of those is connected via fixed sprockets and chains to a jackshaft. The jackshaft then connects to the axle 1/2-shaft with fixed sprockets and a #40 chain.
While riding, the power impulses from the pedaling pilots were not synchronized. That caused the jackshaft sprockets to load and unload several times per rotation as each power impulse tried to speed up the jackshaft. The problem occurred as each power impulse caused the input chains to tension and slacken. When one pilot applied power, the other's input chain would momentarily go slack.
This problem was absorbed by a good chain tensioner in the left drivetrain. But the right side wasn't applying enough pressure to soak up the impulses and let the long forward chain whip a little too much. The result was a chain that jumped off the sprocket. No big deal in this ride. But definitely something to pay attention to and keep in mind when building.
Dr. scott Diabolical
evil genius
My new 4-seat tricycle survived its first public trial - a 1-1/2 mile parade last Saturday. That may not sound remarkable, but the parade route is a 3-6% uphill grade for its entire length! Our loaded weight with pilots was over 1,500 lbs and average speed was around 2 mph. That's the equivalent of pushing a 60's Volkswagen uphill for 45 minutes.
During the ride, we experienced something that I hadn't anticipated. Oscillating dynamic loading of the chains. My machine has two independent drivetrains. One per side, each turning its own wheel. In each, two pilots are seated in tandem. Each pilot powers a standard bicycle style setup. Each of those is connected via fixed sprockets and chains to a jackshaft. The jackshaft then connects to the axle 1/2-shaft with fixed sprockets and a #40 chain.
While riding, the power impulses from the pedaling pilots were not synchronized. That caused the jackshaft sprockets to load and unload several times per rotation as each power impulse tried to speed up the jackshaft. The problem occurred as each power impulse caused the input chains to tension and slacken. When one pilot applied power, the other's input chain would momentarily go slack.
This problem was absorbed by a good chain tensioner in the left drivetrain. But the right side wasn't applying enough pressure to soak up the impulses and let the long forward chain whip a little too much. The result was a chain that jumped off the sprocket. No big deal in this ride. But definitely something to pay attention to and keep in mind when building.
Dr. scott Diabolical
evil genius