Swordman's Electric Recumbent

[Swordman]

In 2006, I added power assist to my home built recumbent. I ordered a motor, controller, and twist throttle from Oatley Electronics in Australia for $110. I originally used two 12V 17AH lead acid batteries but have recently switched to a single 24V 8AH NiCd battery I got from ebikes.ca for $95. I got some good ideas from the "Bikes & Pedelecs" section of the now-defunct "V Is For Voltage" internet forum in a thread entitled "Bottom Bracket Drive."

This design drives the smallest chain ring for the front pedals. The advantage to this approach is that you have the other gears (10 in my case) to shift through to give you fast speed and decent hill climbing ability. The disadvantage, if you think of it as a disadvantage, is you must pedal along when the motor is engaged.

I tried first to mount the motor above the chain ring on a single bar. This approach proved problematic. When the motor got loaded down, it would slightly turn and the chain would loosen. This was mainly due to the thin metal I built the mount out of and that I could never get the u-bolts tight enough to where they wouldn't turn around the bar. I scrapped the first approach, built a mount out of aluminum angle, and relocated the motor underneath and behind the chain ring. This approach so far has proved to be excellent.

Behind the motor is a battery box containing the 24V 8AH NiCd battery pack. Under the battery box in a black project box that houses the motor controller and a relay to control the power. A kill switch is mounted on the handlebars to control the relay.

Originally, the motor did not freewheel. It was possible to pedal without the motor engaged, but it had a good bit of drag and was not something you wanted to do for very long. I recently added a freewheel to the motor by using a left hand drive, 13-tooth, BMX freewheel and an aluminum motor shaft/freewheel thread adapter made for me by a nice Australian man named Dom. The bike now pedals fine without the motor engaged and I find I pedal more and use the motor only for when I encounter hills or get a bit tired. It also has a higher top speed since the original 9-tooth drive gear has been replaced by the 13-tooth freewheel.

Top speed with this approach is around 30 mph with a range of just over 15 miles assuming moderate pedaling.

 

[TylerDurden]

Excellent!

The BB drive is nicely configured. I only realized recently that a BB drive would keep the pedals spinning under power (duh).

I might enjoy having a set of footpegs for cruising under power... like sitting at a player piano.

What is it like to shift under power?



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[Swordman]

Tyler,

Thanks. Glad you like it. Answers are below.

What is it like to shift under power? I don't shift under power. I let off of the throttle, shift the gear, pedal until it is engaged, and I then reapply throttle.

I might enjoy having a set of footpegs for cruising under power... like sitting at a player piano.

I've thought about foot pegs, but I find I like to pedal. I do this for exercise and fun, so having to pedal is a plus for me.

 

[Swordman]

Attached is a howto on how I built my recumbent. It covers all aspects of the design and has a section on MAPP gas brazing.

 

[TylerDurden]

Very nice, Swordman, an excellent and generous contribution!

THAT is the catz-pajamaz...

Thank you!

 

[D-Man]

Thanks very much swordman. Thats a lot of information to ingest. I saved a copy. Took awhile to download though. Excellent job! I'll be reading it over and trying to figure it out.

 

[Swordman]

Feel free to ask questions. Going the do it yourself route for the bike probably isn't for most people, but I enjoyed doing it.

 

[Rassy]

Really nice job on the recumbent. I like how you mounted all the heavy stuff down low. My first E-bike project was with 24 volt scooter parts mounted under the bar just ahead of the crank sproket wheel. It worked real good until I burned up the motor on my steep hill. Just had to learn/remember to pedal before hitting the throtle or my feet would start flying.

One comment on u-bolts (which maybe is obvious) but I always tighten them on with the large hole crosspiece they come with which will bend around the tube some, and then attach the solid mounting plates to the bolts. Slippage was never a problem, but my motor was much smaller than yours.

 

[Swordman]

Really nice job on the recumbent. I like how you mounted all the heavy stuff down low.

One comment on u-bolts (which maybe is obvious) but I always tighten them on with the large hole crosspiece they come with which will bend around the tube some, and then attach the solid mounting plates to the bolts. Slippage was never a problem, but my motor was much smaller than yours.

Thanks for the compliment. I originally had lead acid batteries above the bottom bar but changed it when I went to NiCad since the battery is so much smaller. I really like everything down low on the bike also. As long as the bike is, it's not like I didn't have plenty of room.

I probably could have made the initial motor position work, but the place I have the motor now works really well.

I really need to add a new picture of my bike. I'm riding it to work now (only about 1.2 miles each way) and I added a plastic toolbox as a trunk on the back. I'll try to snap a new pic this weekend and add it here.

 

[Swordman]

As promised, only a week late, the new and improved Sport Utility Recumbent. $8 Wal-Mart toolboxes can hold a lot of stuff.