RECUMBENT BICYCLE TRANSMISSION

[jw9976]

looking for a cure to what ails me...... I am designing a drivetrain for a front wheel drive, front wheel steering, recumbent HPV. I am currently trying to set it up like the cal berkley transmission which uses a jackshaft, two chains, and four gears. The main gear is the bike cranks then directly behind the main is the secondary gear which is coupled to a bigger gear. The second chain runs from the bigger gear along the pitch of the fork to the 16t sprocket which is attached to the internally geared hub. pics at

http://calhpv.berkley.edu/pics/frontdrivetrain.jpg

THE PROBLEM THAT I HAVE IS THAT THE WESTERN HPV'S ARE MEANT TO GO FAST AND STRAIGHT. WHEREAS THE ONE WE ARE DESIGNING IS GOING TO HAVE TO TAKE TURNS AS WELL. SO HOW DO I REDUCE THE CHAIN FRICTION THAT WILL BE CAUSED WHEN STEERING AND KEEP THE CHAIN FROM POPPING OF THE HUB.
THANKS

 

[alexit]

First chain from crank gear to secondary gear, then universal coupling on shaft supported by frame to third gear on fork, second chain to wheel sprocket.

 

[BillPSU]

You will lose HP going through the secondary shaft and more through the universal joint. My recommendation is to direct drive the rear wheel(s). I drove the front wheel in a great moonbuggy competition however because the machine was a 4-wheeled vehicle with A-arm suspension with steering. With A-arm suspension you must use two universal joints and keep your pivot points of the A-arms and the driveshaft at the same plane. I also had the steering pivot points in alignment with the outboard universal. The buggy was 2-wheel drive the front left and the rear right drive wheels.

My moonbugy took second place and the following is a link to a photo of it in action. It was not my moonbuggy but my team's but I designed the frame, suspension, and drivetrain. By the way, I was a non-traditional student and was asked several times if I was a professor which I quickly corrected by saying I was a student.

http://www.nasa.gov/centers/marshall/multimedia/photos/2005/photos05-045.html

 

[griffengm]

jw,
I agree with Bill about using the driven rear wheel.
While neither pro nor professor, I have build a couple hp trikes and found that the KISS principle holds very true.
My winter project this year is to move to a fully drive-shaft driven vehicle with a transmission.
Recumbents are meant to be laid back!
Griffy