Jockey pulley

Discussion in 'Cycling Equipment' started by Doug Goncz, May 8, 2003.

Thread Status:
Not open for further replies.
  1. Doug Goncz

    Doug Goncz Guest

    I have a motor on my bicycle, an electric motor. It's mounted in the center of the main frame
    diamond, and it is currently connected to the rear wheel with a flip flop hub and a 48 tooth track
    cog I made. The motor pinion is 8 teeth. It can also be connected to the pedals, without
    repositioning, since the left crank is a tandem crank, and so, has a chain wheel.

    I made the first 48 tooth track cog from a BMX spider and a chain wheel. It was eccentric and
    wobbled. The second came out great. I soldered a bottom bracket lock ring to the spider to give it
    the thickness of a track cog.

    The chain forms a triangle from the motor to the track cog, and placing the motor in the center of
    the frame diamond makes sure that this triangle doesn't hit the chain and seat stays, because it
    positions the motor on the bisector of their included angle.

    I added a turnbuckle in front, between the head tube and the motor mount disc, to tension the chain.
    I found (post "Ghost Cog", here in rbt) that it requires a lot of tension to avoid chain skips. So I
    added a jockey pulley.

    I removed the inboard pulley and side plate and reversed the bolt to go in from the post side. I
    capped the bolt with an M5 cap nut. I trimmed the remaining cage to look spiffy. I selected a point
    along that bisector I made the bracket from the mating part, freed from the rest of the derailer by
    drilling out the rivets, milling the stamping until it was symmetrical, grooving it, and bending the
    two rivet hole areas out perpendicular to the post.

    I selected a point on that bisector I mentioned, and drilled a hole to fit the outside of the
    bushing that takes the post. I tried hard to get it square to the board. I should have taken the
    board off and used the drill press. It comes off easily with three hose clamps and an electric
    screwdriver fitted with a
    5/16 socket.

    I put the bushing in the far side, and marked, drilled, and screwed in one tab, then did the same to
    the other. Then I removed the whole bracket and drilled out the hole to clear the tensioning spring.

    I removed the board, finally realizing how helpful that would be, and put the jockey, spring, and
    bracket with bushing together with the snap ring, and installed the screws. It dragged horribly. I
    made a few careful bends here and there with a vise mounted bending brake I have, and pliers, and
    got it almost working. To finish, I used my arbor press to cram the bushing down into the board,
    since I had discovered my milled and bent ears were one thickness of sheet steel pround of the area
    around the bushing.

    I fitted the chain and tensioner, and it's ready to ride. Whee!

    The goal of this project is to add virtual mass to the bicycle with the motor and an ultracapacitor.
    It should add more than the mass of vehicle and rider, with a mass cost of, say, twenty pounds. By
    charging up the cap approaching a hill, I should be able to stay in gear right to the top, without
    bottom out on the lowest gear. Believe me, it doesn't matter what that lowest gear is, once I hit
    it, I get very frustrated.

    I have found that, in general, speeding up to approach a small hill is a great technique to get to
    the top with less leg and lung strain. Long hills, you just have to tough 'em out....

    The cap has enough storage to go down a couple hundred feet and have an assist on the other side. It
    costs $3000.

    I wonder if I can rent one somewhere....


    Doug Goncz, Replikon Research, Seven Corners, VA If a computer won't do
    what needs to be done, lie to it. Don't try this trick on people.

Thread Status:
Not open for further replies.