A Full-body Exercise Recumbent: The Omnidyne 3P

 

My readers will recall that I previous did a post on my experience adding arm power to my Avatar recumbent.

http://lefthandedcyclist.blogspot.com/2012/03/arm-power-and-avatar.html

Now to recap, the Avatar approach used a bolt-on rocking-handlebar and a freewheel added to the left side of the crank axle. Pulling on the handlebars pulled on a chain passing under the crank freewheel moving the pedals forward. A spring attached to the other end of the chain moved the handlebars backward when the pulling force was removed. The linkage connecting the handlebars to the steering was designed to decouple the rocking from the steering.

This arm-power-mechanism worked fine for riding on the flats but was not efficient for climbing hills. Since the handlebars moved at about half the speed of the pedals, the force from pulling on the handle bars was applied every other pedal stroke. On hills this resulted in there being more torque than needed for half the cycle and less for the other half.

The solution was to be able to push the handlebars as well as pulling them. The arms would contribute torque on each  pedal stroke.

 I would need two freewheels to accomplish this and couldn't fit them both on the left side of a single crankset. This meant I would have to add a second bottom bracket with three chainrings on the right side and two freewheels on the left. On the right side, innermost chainring would be connected to a single chainring driven by the pedal crankset.  This would be mounted in front of the second bottom bracket. Back to the right side, the middle and outer chainrings would drive the rear cassette in the conventional manner. 

The presence of a second bottom bracket required that I build a new frame to support it. And I realized that if I mounted the pedals directly over the 16" front wheel, I could shorten the wheelbase of the new bike by 12" when compared to the Avatar. The steering decoupled handlebars would be transferred from the Avatar but modified to facilitate the dual drive.

The freewheels used were the same size as used on the Avatar. Since the force produced by the handlebars with the Avatar was well matched to the pedaling, the goal was to keep things the same for the Omnidyne. The rocking handle bar has two beams attached to it, one on either side of the freewheel  pair. Pulling back engages the outer freewheel while the other freewheel ratchets. Pushing forward engages the inner freewheel while the outer freewheel ratchets. The beams started as the same length used on the Avatar, but since a greater force could be produced pushing compared to pulling, the pushing beam was lengthened. The distal end of each chain is attached to a spring to keep them taught.

As of late I haven't painted the parts and the Omnidyne has not been ridden outside. I like the new motion so much I have been using it as an exercise bike for the last year. I am confident that the push, pull, pedal motion, (3P), will drastically improve the bike's hill climbing.

Hephaestus