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Final drive casting mods

Discussion in 'Racing' started by Dustin Maki, Mar 7, 2021.

  1. Dustin Maki

    Dustin Maki Just got it firing!

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    I've got an idea for a sidecar racing rig with the sidecar wheel driven by a solid axle through the final drive.
    Instead of the rear wheel cush drive fins, the final drive will contain a Rzeppa joint with the axle passing through it, and through the area where the stock axle nut goes. The bike rear wheel will be offset slightly to the left and mounted only to the axle and the sidecar wheel way to the right. The left side of swingarm will be eliminated and the right (single)side beefed up. Essentially becoming like a quadbike single swingarm with solid axle pivoting inside the final drive. The idea being that the sidecar weight and both rear wheels stay planted while the bike and front wheel are free to lean into corners both ways.

    I need to know if the final drive is likely to hold together if I start opening up the area on the (right)outside to allow clearance for the axle shaft to pass and pivot. The bike is a 2000 Jackal with stock final drive. If you know of any more suitable final drive unit, with a lower gear ratio, I'd love a recommendation.

    Are there any known weak points in the Guzzi final drive that need reinforcing? I know this is at my own risk, just hoping to hear any experienced race mechanics to save me a few failed iterations.

    If anyone has performed modifications to the rear drive casting, what welding filler materials worked best?
    Any idea how deeply or how wide I can machine into the axle nut boss before I strike oil? If I do break through, any recommendations for patching it up?

    Any comments on the overall idea, especially expected handling characteristics are welcome.
     
  2. DeadEye

    DeadEye High Miler

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    I would try to get some University Eng. program geeks with access to modeling software to draw this up !

    U of T has a group of keeners
    http://web.utk.edu/~dki/motorsports/ncar.html
    They aren’t working on a sidecar Racer but maybe you could get them interested in some aspect of it.
     
  3. Dustin Maki

    Dustin Maki Just got it firing!

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  4. Moto-Uno

    Moto-Uno Cruisin' Guzzisti

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    Take a close look at a Ural , that's pretty much how they drive the sidecar wheel , mind you , speed
    is certainly not a Urals' forte so to speak . Peter
     
    john zibell likes this.
  5. DeadEye

    DeadEye High Miler

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    Dues U of Memphis have an mechanical eng. group participating in any SAE competition stuff ?
    Maybe getting some them interested in your project would help kick start them on their own ?
     
  6. Dustin Maki

    Dustin Maki Just got it firing!

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    They did SAE Baja I think it was called, on the floor below me. I approached them while they were having belt problems with their CVT testing in the parking lot. They obviously had the driven sheave mounted backwards so it looked aligned at rest, but misaligned at speed. They wanted no input from outside their private little club, so I left them to their own devices.
    I helped a mech build a plasma speaker for a final project, but he's gone now. I think I have an in with engineering technology. They were getting a new CMM(coordinate measuring machine) as I was leaving. That would help map out thicknesses where I can't put a micrometer. Might get someone to run FEA(finite element analysis) on the casting with my changes. Its going to be weird going back, but a good idea I should have thought of.
     
  7. DeadEye

    DeadEye High Miler

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    Who’s your Monkey ? :rofl:
    It would be cool to try, no so cool to go Flying off at a Speed :think:
     
    Last edited: Mar 16, 2021
  8. Dustin Maki

    Dustin Maki Just got it firing!

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    Thank you for the vote of confidence.
    One thing came up. I am not sure if a Rzeppa joint is able to support almost half the weight of a vehicle while also transmitting torque.
    It looks like a giant ball bearing that should be able to take it. But there are only 6 balls. They are mostly stopped or oscillating, not constantly rolling, and have perpendicular grooves. That is a lot of force concentrated at a few small points forced to wiggle a little. https://www.sae.org/publications/technical-papers/content/2016-01-1135/ haven't read it yet. Spalling or galling is likely. I Always forget which is which. I think spalling is when the surface flakes off and galling is when the surface embeds itself in the opposite surface before flaking off.

    I think that calls for a static test before anyone jumps on and goes for a ride. Anyone with insight on this, I'd love to hear it. Not really many Rzeppa joints used in this fashion, especially on bikes. Probably not much out there. So even if you just have good Google fu, I could use that.
     

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