Overkill Rear Mount on Happy Time Motor

Discussion in 'Frame Mounted Engines' started by Molotov256, Jun 19, 2010.

  1. Molotov256

    Molotov256 Member

    Having moved the same HT motor between 4 or 5 different frames, I've come to the conclusion that I hate the stock motor mount system. As pointed out by member Al.Fisherman, the engines are intended to be mounted in a frame with a 75 degree angle, which just isn't too realistic.

    Anyhow, I got an idea from another MB forum to use hockey pucks and U bolts. If you're interested, a couple members on that forum have found success with the hockey puck method. It didn't work well for me, though, because the give of the rubber allowed the motor to torque side to side to some extent, and that of course leads to chain issues, so I went back to the drawing board.

    First of all, I drilled and tapped the rear mount stud holes to take Metric #8 bolts. Then I picked up a length of 2" wide 3/16" thick welding steel, cut off an 8.5" piece, and carefully measured and drilled holes to bolt the steel to the existing mount holes. I also had to grind a little bit off one side to clear the guard around where the chain feeds into the drive cog. After that, I again carefully measured and drilled holes to accommodate some 1" u bolts. For rust protection, I spraybombed it, and then bolted it all together. Pictures below.

    To use this method on a bike with wider frame tubes, one would have to find some wider steel to work with, and more cutting and grinding would be required to fabricate a piece that can attach to the OEM mount stud holes and still clear the chain and other engine contours. Still, it's working REALLY well for me so far, and if it saves the heartache of thrown chains and broken motor mount studs, I think it'd be well worth it.

    So is it overkill? Possibly. But there's absolutely NO lateral sway in the motor now, so I consider it a victory. It was also a very cost effective solution. About $9 for the steel, and the 1" U Bolts were 85 cents each. Woot!

    Attached Files:

  2. Hawaii_Ed

    Hawaii_Ed Member

    Very nice job! There is room for all kinds of improvements on these llittle machines, that is perfect!
  3. give me vtec

    give me vtec Active Member

    yeah I agree... you pretty much perfected the flaw there. That is a lot of vibration to focus in one point... its really hard on aluminum frame bikes.

    What you did is awesome, definitely not overkill...
  4. moonlake3

    moonlake3 New Member

    great rear mount

    what size u bolts did you use.. did you use short studs in engine or bolts..did you get u bolts at hardware store..good job..great idea...:bowdown:
  5. GearNut

    GearNut Active Member

    It looks very strong and very adjustable. I like it!
  6. Al.Fisherman

    Al.Fisherman Active Member

    Although I've never had a "REAR" mount issue, I sure like your idea. Anything that can be fabricated and as inexpensively as this certainly isn't "Overkill". Although I made a fix for the twisting of these engines on a frame due to torque.
    OH, and thanks for the acknowledgment...
  7. V 35

    V 35 Member

    I like your mount, a lot. One thought, seems to me, the Hot Setup would be to
    start with a frame stripped of paint, and Braze the mount in place, after aligning, and bolting down. Drilling and bolting through frame makes sense too. U Bolt, drill, through bolt, braze, that should hold.
  8. Molotov256

    Molotov256 Member

    Thx V, you may be on to something there with the brazing. I don't have a lot of tools to work with myself, so I was just doing what I could with a hand drill and an angle grinder, heheh... most anybody could replicate this setup, and there's plenty of room for improvement. It'd be super cool if somebody with a nice drill press and a few motors kicking around could do a small scale production of plates to mount various HT motors, but I'm not sure if there's enough consistency with OEM measurements from motor to motor for a "one size fits all" approach to work.

    I've heard a lot of folks don't like to drill through the frame for fear of losing structural integrity, but to each their own. I also know of several folks with a hole and a bolt through their oversized downtubes, and the vast majority of them have had many hours of happy riding without structural failure. All depends who you ask.
  9. GearNut

    GearNut Active Member

    Ask Al.Fisherman. He knows all about that.
  10. Molotov256

    Molotov256 Member

    Yeah, snapped frames like that are what convinced me to keep drills away from mine. I don't want to be the one in a hundred that has that happen, and with my luck, I would be. :rolleyes7:
  11. V 35

    V 35 Member

    I'm agreeing, don't Drill, any thoughts on Silver Brazing ? Cut down U Bolts after
    Brazing cools ? Plan to build up a ' Mild Steel ' Cheapo . Wanted to drill, tap,
    thread on Coupler nuts, braze coupler nuts to frame tube to have a clean looking way to add accessories, like Frisco Pegs, for Cases and Deraileur ? Wanted to power my
    Schwinn Sidewinder, but now want to start with cheapo, build from there, keep
    Bike intact, for what it is. [ for now ]