Homebuild leaning sidecar

Discussion in 'Hacks' started by Hellracer.nl, Oct 27, 2012.

  1. kohburn

    kohburn Long timer

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    yes a leaner of the style that has only the motorcycle lean, not the side car.
    when sitting still the stresses applied at the chassis mounts are unchanged, there is only a difference while making turns. but yes the stresses of the load are concentrated at the pivot instead of spread across the frame members under the tub body. one advantage of this design however could be that it would allow the wheel to be placed closer to the center of mass without having any affect on steering effort or scrub.
  2. icebrrg3rd

    icebrrg3rd Adventurer

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    My 2ยข on the pivoting sidecar is with a leaner, you are already putting the sidecar further from the bike to get a decent lean angle in a right turn. With the car pivoting, wouldn't the sidecar's back end be drifting to the left (closer to the bike) in a right turn? That would mean you'd have to have even more space between the bike and the car's body. Mine is already quite wide. Just thinking out loud, that's all.

    -Andrew
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  3. Hellracer.nl

    Hellracer.nl What the hack???

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    That is a very good point.
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  4. kohburn

    kohburn Long timer

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    its a valid concern, how much the sidecar drifts depends a lot on the lead distance of the tire in front of the rear axle, and the distance from contact patch to pivot, and the lead distance of the pivot in front of the motorcycles center of rotation. depending on geometry the sidecar may actually drift the same direction as the turn (meaning you get a little more space when leaning toward it and less when leaning away)

    for example: in that drawing shown, performing a figure 8 inside a 6mx12m box (MSF standard) the tug wheel is estimated to drift 10* or 14cm on a 3m radius turn(2m radius to the side car). When making a left turn inside the same restricted area the side car drifts toward the bike 5* or 7.5cm. This is about the maximum possible because I overestimated the center of rotation for the motorcycle, the reality in testing will likely be half as much drift.
    [​IMG]

    these are low speed turns so they can give you an idea just how much tire scrub is fighting the steering input in a standard rig.

    maybe I'll try borrowing the kids Legos to make a demonstration model. :-D
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  5. Hellracer.nl

    Hellracer.nl What the hack???

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    Hmmm, I'm not convinced. A caster wheel will normally follow the curve, this means that in a right turn, the back of the sidecar will move to the bike.
    But I may be wrong and I'n open to proving that I am!
  6. kohburn

    kohburn Long timer

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    casters normally are placed at the corners and have a very small offset from the pivot to contact patch. what is experienced here is essentially the side car is lagging behind the bikes position. since the contact patch is behind the center of rotation it acts like the rear caster rather than the front caster on a cart.

    that may just make it more confusing but that's about the best visual i can come up with until i make a model.
  7. brstar

    brstar Long timer

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    Not trying to be picky at all.
    I think this drawing is a little shy of the mark in that there would be three circles of differing radii.
    And of course it maybe helpfull if we could see the difference between a shallow upright turn and a hard turn at full lean?
    Not sure how that would be done other than with a go pro :lol2.
    Oh pivot the chair from the middle front?
    Make it pointy?
    With perhaps a centre mounted wheel to go with it?
    Now here us an idea, try it with a scooter frame!
    Oh and you can borrow my mechano set if you want...... If you want it steam driven the engine needs an overhall:y0!.
    Hmm was it 5/32nd whitworth?
    Back to work now. :D
  8. claude

    claude Sidecar Jockey

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  9. brstar

    brstar Long timer

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    Claude so funny.
    Yep above my pay grade.
    Wait I'm unemployed at the mo. Its all above.
    Seems all a variation on the theme.
    But I think we are talking on a slightly different concept than the link you just showed.
    Maybe a little simpler?
  10. claude

    claude Sidecar Jockey

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  11. kohburn

    kohburn Long timer

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    yeah, I deleted extra circular path lines to simplify it a bit, the more upright the bike the closer the center of rotation is to the rear tire and the more lean angle the closer the center of rotation is to the middle. the effect this has is that full upright has the greatest steering drift of the side car.
    a center wheel is fine it just has to be inline with the pivot. I am seriously considering that option but didn't feel like making a bunch of drawings just to show that on here.
    :imaposer
  12. kohburn

    kohburn Long timer

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    yeah, this would be a different variant. more like a steering version of the sidewinder. Its only real advantage over the standard version is limiting tire scrub and turning effort.

    I'm a big fan of the flexit and how it reduces the track width, did see some video of it having serious nosedive in some turns and one wreck from it, made me a bit nervous. But I did get enough construction information to be confident that I could duplicate it if I wanted to.
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  13. dwoodward

    dwoodward Long timer

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    Geez, I look away for a couple days...

    Hellracer, thanks for refresher on the front mount. I just need to find a bike with a full cradle frame and exhaust that's up out of the way. Maybe a used Triumph Scrambler... And then enough working space to start playing with it.
  14. Hellracer.nl

    Hellracer.nl What the hack???

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    Well, as you can see in my pics, you don't need a full cradle frame to build a leaner. And any R BMW will do just fine too, the early ones have a full cradle frame and the newer ones use the engine as a stressed part.
  15. Hellracer.nl

    Hellracer.nl What the hack???

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  16. Hellracer.nl

    Hellracer.nl What the hack???

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    Even on a leaner, you can haul some weight:
    [​IMG]
    This is a Goldwing 1200 engine that I'm transporting to a fellow sidecarrist.
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  17. Turbomachine

    Turbomachine Stirring the noodle

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    Some parts of the world (like 'murica) use third-angle projection, and some use first-angle. Its really confusing when you are reading a drawing as one that was drawn in the other.

    My welder buddy uses neither, and the first attempt at putting it together per my drawings resulted in a left-handed sidecar rather than right. Easily fixed with a grinder.

    Regarding the geometry and steering / scrubbing calculations, I build a spreadsheet for my "conventional" leaner to calculate all of that. PM me and I'll send it to you, modify however you see fit. It is more complicated than the triangle tire videos shown above, as the bike rolls around the tire contact patch. Mine is only set up for centerline pivots.
  18. kohburn

    kohburn Long timer

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    Yep

    [​IMG]
  19. Hvymax

    Hvymax Been here awhile

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    This is an amazing thread!!! I'm thinking something like this for my KLR!!!
  20. Hellracer.nl

    Hellracer.nl What the hack???

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    And if practice a little bit, you can ride with a leaner on very loose sand without any problems.

    [​IMG]

    [​IMG]
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