Sidecar Design Formula - IMPORTANT!

Discussion in 'Hacks' started by Get Back, May 25, 2009.

  1. Bobmws

    Bobmws Curmudgeon At Large

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    Telelever......:pot
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  2. Hvymax

    Hvymax Been here awhile

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    Here's where I am with my leaning sidecar frame. I'll be going with a torsion axle and trailer tire. Another great thing is I can throw a link in for winter riding. IMG_20181008_150757411.jpg
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  3. sebwiers

    sebwiers  

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    That front is a LOT higher then the rear to my eye... is that really how the math works out for "steering" the car wheel?

    Also wondering about the rod ends... they are being side loaded, which is not the orientation that their load rating is for. All the ones I have looked at are simply not rated for such applications, though I suspect given the hardware sizing they are plenty beefy for such use. Not really being critical, just wondering if anybody has seen any load specs for such use, or tested them, or if it is just common enough practice to be known to work? Any rules of thumb for what "correct orientation" load rating translates to a safe "side loaded" application?

    I'm looking at using suspension bushings in a similar application, partly because I also want the wheel (and pod) to be articulated, which quadruples (or more) the number of pivots, making cost a bit more of a consideration. Not really expecting any gain from the tilting wheel vs a non-tilting wheel, just doing it because I think it'll be fun / look cool. As in the above case, I figure I can lock it rigid for winter / slow speed use. In fact, I'll probably mount a brake system on the articulation so I can lock it up on the fly - I figure I'll want that if I come up against the bump stop when learning into a corner.
  4. sebwiers

    sebwiers  

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    Hmm, in that case elastomer bushings may not have the compliance I need at that connection. Thanks. Guess it makes sense you'd need at least as much compliance as the total steering angle...
  5. Hvymax

    Hvymax Been here awhile

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    The Math comes in with how much higher to make the front. The big factor for mine is the 9" of ground clearance of my lifted KLR. There is a lot more swing than on a lower bike. also how far between pivot points. The next big challenge will be finding the ride height sweet spot.
  6. steam powered

    steam powered just a regular punk

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    I wouldn't get too hung up on the clearance under the leading link, a motocross leading axle front fork hangs lower than the axle on many set ups and doesn't seem to create too many issues. A leading link shouldn't be significantly wider.

    A longer distance between the axle and pivot will mean less change in trail over the full suspension travel at the disadvantage of pushing the pivot lower.

    Using a 300mm distance between the pivot and axle will place the pivot just beyond the edge of the rim alongside the tire (based on a 90/90x21 tire).

    For minimum change of trail over the full travel the suspension the leading link should be perpendicular to the rake angle (28 degrees on the KLR according to Mr Google). This means the axle should be 140mm higher than the axle, this gives a distance of 230mm from the ground to the centre of the pivot (based again on a 90/90x21 tire).

    As an alternative you could go for minimum change in trail in bump and accept that trail will increase in droop, this isn't as bad as it sounds as the tire is inevitably unloaded in droop and so the increase in trail shouldn't adversely effect feel at the handlebars.

    So using the same 300mm from axle to pivot and working on 150mm vertical suspension travel, with 2/3 (100mm) in bump and 1/3 (50mm) in droop (from loaded ride height) - the leading link wants to be at 17.5 degrees slope, the axle will be 90mm above the pivot. This gives a distance of 280mm from ground to the centre of the pivot.

    If your tire size or desired suspension travel differs from the above, I will happily redo the numbers for you.
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  7. Hvymax

    Hvymax Been here awhile

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    Decided that I need to reverse the front joint to looking down from the bracket to allow for rotation which seems to be integral to the way it moves. Trial and error.
  8. Turbomachine

    Turbomachine Stirring the noodle

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    I published a spreadsheet calculating all the geometry for a leaning sidecar a few years back when I designed mine, based on a college text book for motorcycle design. You want to balance the turning effect with the scrubbing of the sidecar tire, and target a balanced Cg location. It is dependent upon a number of geometries of the particular bike, and what you can fit for a sub-frame. https://advrider.com/f/threads/sv650-sidecar-homebuilt-leaner.992940/

    The loads on the rod ends are so low for reasonably sized quality joints that you have a huge safety factor in both radial and axial directions. Plus acceleration and braking loads in an actual leaning application are really low, the primary loading is in radial direction of the joint due to gravity and the moment arm of accel/decal to the rig Cg.
  9. Squily

    Squily Squily Supporter

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    You still have the spreadsheet and want to share it?

    Nice build btw
  10. sebwiers

    sebwiers  

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    So... if you are making an articulated sidecar (one where the wheel tips along with the bike, likely connected via a set of parallel arms) is any of this relevant? It seems like a lot of it goes out the window because the wheel is already self steering (to a variable extent that would be hard to calculate, making other calculations like resulting scrub equally difficult). In fact, it seems like with such a setup you might validly put the wheel fairly far forward, even maybe forward of the midpoint.
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  11. Hvymax

    Hvymax Been here awhile

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    I'm pretty sure that's the one I used.
  12. Hvymax

    Hvymax Been here awhile

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    No the hack wheel will just be mounted using a torsion axle. The steering will be imparted by the differential linkage to the car.
  13. Hvymax

    Hvymax Been here awhile

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    I have the mounting brackets complete! IMG_20181123_132247252.jpg
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  14. sebwiers

    sebwiers  

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    I think you missed my point. I didn't mean "you = Hvymax", I meant "you = any hypothetical builder". In fact, the hypotehtical builder is ME, which I why I'm trying to puzzle out what sort of steering effect / wheel position makes sense for a fully articulated setup.
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  15. Turbomachine

    Turbomachine Stirring the noodle

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    I still have the spreadsheet. Will convert to a google doc and post it publicly.

    Regarding the wheel position, the problem is as it moves forward the scrub will increase due to the front geometry of the bike. This will increase steering effort at a minimum. Think of the bike as pivoting about the contact patch of the rear tire in a top view as it turns.
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  16. Old Mule

    Old Mule Long timer

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    Once again I am disappointed that no new developments in sidecar technology have appeared for months!
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  17. NikoRedStar

    NikoRedStar Adventurer

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    Noob sidecarist. Currently designing/farkling out my first rig on a Gen 1 KLR650/Trashy Velorex 562. Planning a future build...

    Can any of you direct me to a successful sidecar build utilizing the rear end of a KLR, Enduro, or dirtbike?
    I have a rolling chassis of a Gen 1 KLR that I don’t have much use for after using/parting it to build/complete another bike/rig, which I’ll soon unveil and plan to partake in some adventures on with my dog. Currently finalizing (waiting for parts) on an engine I’m rebuilding. (IG: redstarsidecar)

    The best of the basics for a sidecar build seem to be all there. Suspension, breaks, fairing, lighting, even the ability to mount panniers. Gearing towards a modular off-road hack. Just bouncing ideas around on how to build subframe and mount to the frame. Any leads or input would be much appreciated. Thanks Hackers!

    Here’s some test footage I shot of my rig with my dog. You can fast forward to 3:10/:15 where it shows the rig. Planning silly adventure skits for my own amusement. It’ll give you an idea of where my current build on #creaturekiller1 is/was:
  18. bk brkr baker

    bk brkr baker Long timer

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    Gear that thing down , you're killing your clutch quickly.
  19. NikoRedStar

    NikoRedStar Adventurer

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    Are you talking about the sound of the engine in the vid?
    I usually run a 14tooth front sprocket with sidecar. In that vid I had the 15, as I was trying it out.

    That sound is a rod arm bearing in crank crankshaft and crank shaft bearing failing. I knew thy were failing and needed to get those shots before they did, as I already had planned a complete lower half engine rebuild, which I’m in the middle of. Discount bike and I’m paying the price...but learning more than I ever imagined I would about the KLR and loving it...mostly

    What sprocket are you running in back? I currently have the stock. Any suggestions? Currently I’m about 70% on road 30% off, but want it to be a beast off-road...as much as is possible. However, realistically my journey this summer will probably be mostly Highway.

    Trying to figure out how to mount a winch, but this flimsy velorex frame isn’t giving me many options.
  20. bk brkr baker

    bk brkr baker Long timer

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    Roller bearing motors don't live long being lugged. They really don't get an adequate oil supply below 3000 rpms,if your motor makes sounds like those in the video , it won't last long at all.
    Off road 14 on the counter shaft and 47-49 on the wheel helps , but , it still won't be happy below walking speeds.