The Kneeslider

Doers Builders and Positive People

Radial Motorcycle Engine Modifications

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Mike Redpath (on the left) and radial engineThe radial engine powered motorcycle Jesse James built and displayed at the recent concours drew a lot of attention, as it should, you just don’t see radial motorcycle engines every day, or any day for that matter. But for those of you who are more mechanically inclined, you might look at the bike and say, “Hey, wait a minute. The prop is powered from the front of a radial engine, how do you drive the bike from the back?”

Good question, and the answer is you find a radial engine mechanic and ask him to extend the crankshaft out the back where the auxilliary drive is usually located. Enter, Mike Redpath.

Mike (that’s him on the left in the photo, the engine owner on the right) has been restoring and repairing old airplanes for about 20 years and a fellow with this radial engine has the bright idea of putting it in some kind of motorcycle. He heard about Mike and his aero motor skills so he brings the engine over, points to the front and says, “Wrong end.” Mike, who is getting a little bored only doing things the FAA will approve, scratches his chin and says, “Hmm …, gimme a wrench.”

Taking an engine designed to drive a prop from the front and reversing everything takes some disassembly and reengineering but Mike pulled it off. The engine eventually found its way into the hands of Jesse James who built the motorcycle around it. The photos below show the starting and end points and a few shots in between. Awfully neat and all pretty ingenious.

Mike got the itch to stretch the envelope a little bit after this because he told me he’s planning to open a speed shop very soon. It will be named, Musclerodz and Customz. His web site isn’t up just yet but as soon as it is, we’ll point you over in his direction. Nice work, Mike!

All engine photos courtesy of Mike Redpath. Lots of photos below:

     

Photo #1: This is the front starting point, notice the prop drive.

Rotec engine front before modification

Photo #2: This is the front partially disassembled.

Rotec engine front

Photo #3: This is the back before modification.

Rotec engine backbefore modification

Photo #4: This is the back partially disassembled.

Rotec engine back

Photo #5: This is the back finished, note the drive extension from the crank.

Rotec engine back finished

See also:
The Kneeslider: Radial Engine Powered Motorcycle

Posted on Filed Under: Engines, Motorcycle Builders, Workshop & Tools

Comments

  1. beautiful piece of art – not so motorcycle but a good looking what-if 🙂

  2. Wonder if ithe radial could be balanced with bottom two jugs removed? Sure would lower the center of gravity wheather it was mounted north-south or east-west. Radials make for something new and different in the motorcycle world even if it is a novelity.

  5. Since there is no propeller to act as a flywheel, does another component act as a flywheel or does it run well without a flywheel?

  6. radials don’t really need flywheels since the power pulses overlap. Basically the next cylinder fires right after the previous one (approx 51 degrees in this case) and then the next and the next… There is never much need for the inertia of a flywheel. it does require a bit larger starter though since it can’t rely on the momentum of the flywheel to light off the first ignition. Maybe they use shotgun shells to start it?
    -todd

  7. Wishing out loud…
    could we get a picture of sandra sitting on this beast?
    could ya put the prop back on it and jump something…
    something really wide…inverted…maybe royal gorge?

  8. Interesting project. But really just an exercise. Who could ride it. It appears to have no front brake and the torque would be scary. Another crazy plot by Jesse. Remember his bike with the semi engine. Still I guess it keeps him off the streets.

  9. Mounted north and south this engine makes way more sense. This bike is doomed to that old Honda CX 500/650 syndrome. When you have to gas it while in a corner or curve, the engine will stand your bike up out of any kind of shape to make the turn. Come on Jesse, you know that.

  10. Nice bike but I’ve seen a better layout that was built a year ago at http://www.jrlcycles.co The crew used form and funtion and the sound is” like god walked ito the room and made all right with the world” (a quote from American Iron) check it out…

  11. In revisiting the website I should have mentioned in my earlier comment that what we are seeing is a fixed radial engine. In the original radial engines (WWI aircraft) the entire engine spun and the prop was attached to the engine. Very effective for cooling, not so good for actual flight. When the gas was opened (That was the throttle in the early engines, gas on or gas off) The huge torque made the planes turn from a straight line to one side or the other depending on the direction of the particular engines rotation. The fixed radial was a great improvement in that regard and simplified the fuel feed as the engine remained fixed to the airframe.

  12. Looks like this might work as a great hair dryer. Just ride a few blocks with that breeze blowin’ through those cooling fins then directly into your face…and could probably ride through a Chicago blizzard in the buff and be real comfy.

  13. That just looks like FUN. Radials are the most awe inspiring powerplants ever created by mankind. (and that SOUND!) I wonder what, if any, provisions are made for keeping that monster cool, besides not letting it run very long with the bike stitting still?

  14. In reply to DOUGLAS that would be a rotary engine you are referring to
    during WWI usually either Le Rhone or Oberursel depending on which side

  15. I’ve been an aircraft mechanic for 25 years, and a motorcycle lover and rider for 40+. When I saw this “bike” I absolutely fell in love with it. GO Jesse GO!! He’s got to be one of the only guys that is trying to build something different. Custom is not bolting on somebody elses’ store bought goodies.
    Yea, this machine would scorch the Hide off the Devil even with really good baffling. Torque would be a major issue, no worst that cracking the throttle on one of the Boss Hoss creations. If you mounted the engine transverse would be interesting…might be worth persuing….
    Shaving 2 to 3 cylinders off the bottom shouldnt be a major issue, Harley-Davidson did it years ago.
    Thanks for covering and chasing down the authenticity of this incredible machine, I’m fixin’ to go check out Jesse’s site next!!!!!

  16. In Reply to Steve July 16th.

    Hi Steve. No, not a rotary they did not come along until much later. There were two developments in the Radial engine the original one I described that the entire engine revolved and the propellor was fastened to the front of the engine. Later the engine was fixed to the airframe and the prop turned on the crankshaft similar to current engines. Both had multi cylinders and the fixed radial was (and is) still around and flying.
    Rotary engines have no conventional cylinders and pistons.

    Cheers

  18. Well, there was a radial-engined motorcycle before – simply enter the search word “Megola” into any search engine. The engine sat in the front wheel. Saw one live approx. 30 years ago at a vintage bike meeting in Germany, but with only 10 (of 2000 built) remaining in a usable condition these things are “as rare as rocking horse droppings”. I remember the owner push-starting the engine and stalling it when he had to come to a stop.
    Visit: http://en.wikipedia.org/wiki/Megola

  19. Douglas, Steve is actually right. The WWI engines were (and, in those circles, are still)considered rotary engines. Maybe a difference in perspective, but no reference to the modern rotary. I always thought the whole idea was stuped to have the engine turn about the crankshaft, but I wasn’t there.

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