Leaner Sidecar/ Vintage Vespa

Discussion in 'Hacks' started by Charlieman22, Jan 14, 2020.

  1. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Agreed.
    Time to build and test to see what feels best. you guys have given me a good sense of what to look out for.
    One other question as I proceed:

    what is considered a safe low point under ur bikes? ( I see pictures that look so low to me). Is there a standard/ what height did you use for your low points?
    #41
  2. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    #42
  3. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Some formatting issues - user error undoubtedly - in my last post.
    Here was my response to davet2


    davet2 - to address the foot and leg issue, I would arch the connecting bar and curve it forward away from my leg and close to the leg shield. When I mock it up, I’ll post a pic. Thanks!
    #43
    Bobmws likes this.
  4. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Some progress and some learning.
    Mostly just tacked together to get a sense.
    And what did I learn?
    Well - now I understand scrub due to the lever effect of the ground level "hinge" and the pivot point height - but the ground hinge moves - as the tire contact (tire patch) shifts when leaning.

    With a little testing in the garage - I could see that the sidecar tire moved laterally away from the scooter - about 3"/75mm.
    That is a lot of sideways movement.
    Additionally - with only 4° of differential between rear and front pivot - there was only a small amount of steering.

    With this better appreciation - I decided to take a more radical approach to getting the rear pivot as low as possible.
    I have disassembled and am re-working the rear mount to take it as low as possible.
    Some testing suggests this is approximately 3".

    Observations/questions:
    1. Can you guys share with me how high you and others put their lowest mounting point from the ground?
    2. Why not mount the sidecar wheel with no lead = to the rear wheel of the scooter? As the rear pivot point is the low one - this would create more "steering" effect and less "pushing" or scrub effect.

    What say you?! (A few pics below)
    IMG_3435.JPG

    This is the original rigid hack frame - to speed things along - I robbed the suspension portion. See next pic...
    IMG_3463.JPG

    1.25" DOM tubing bent to allow scoot to lean without hitting sidecar frame.
    You can see the bit I stole from the old frame.
    IMG_3466.JPG
    This mount was approximately 4" from the ground. The sidecar wheel is about 10% ahead of the scooter rear wheel. When the scooter leans to about 45°, the scooter wheel moves to the blue line - about 3"/75mm to the right of the wheel.
    #44
    Flyin' Monkeys likes this.
  5. brstar

    brstar Long timer

    Joined:
    Aug 17, 2007
    Oddometer:
    2,133
    Location:
    Shoalwater Western Australia
    [QUOTE="brstar, post: 39229712,
    Rear pivot point.
    With the suspension compressed and the pivot point as close to the rear wheel as feasable.
    Being then shielded by the tire it only needs to be high enough to clear speed bumps gutters/potholes and curbs.
    That could/should be your starting point.
    Just cover it with a mudflap.[/QUOTE]

    You have some nice work there.

    With the rear pivot that far back from the wheel it's bound to get hung up on something.
    Mostly in an embarrassing way.
    Though with a small wheel mounted on it it could make a great wheelie bar.
    I would aim for an inch clearance on the wheel and a couple of inches ground clearance with the suspension/ tire fully compressed.
    Hopefully you could still then get the wheel of and on again.

    Wheel lead is another thing.

    At zero lead it would not benefit from toe in.
    I believe the early sidecars on ridgid framed bikes had no lead or toe in.
    I'm thinking zero lead would cause problems with any steering effect as well.
    While no one seems to get the concept that a motorcycles turning radius is affected as much or more by speed than the lean angle.

    It's the centrifical force generated by the amount of speed that requires an angle of lean.
    Turning radius x speed = lean

    On a leaner like yours it's different.
    Lean angle of bike = turning radius of sidecar wheel.
    So it's all a comprise like politicians.

    And that's the reason for much of the excessive scrubbing or tire wear on a leaner.

    A part of the wheel lead equation is load distribution and capacity.
    On a rigid frame the center of mass needs to be well inside the triangle of the 3 wheels.
    Scooters tend to be rear heavy already.
    Zero lead could make the sidecar the same.
    Wheelie bar?
    So one way or extreme would be.
    So zero lead zero steer effect caused by equal height pivots set as low as possible.
    I:E hard behind front and rear wheels.
    Probably work fine.
    Load and distribution depending.

    A silly alternative is 100% wheel lead.
    Probably no toe in and a serious amount of steerabiliy required.
    Not viable without clever electronics and servos etc.

    So somewhere between and some scientific WAG as to the setup.
    Anyway in two weeks I'll be on the plane to Cambodia again.
    So there's workin to be done.
    #45
    Flyin' Monkeys and Bobmws like this.
  6. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    brstar - thank you.
    On quoted advice above - actually - I already did that.
    On Saturday - here in the states - ripped down bike and frame and created a new rear mounting point.
    See pic below.
    It is tucked in very snuggly behind rear wheel as low as possible
    It has very little clearance from ground when suspension is fully compressed.
    However - it is so close to the rear wheel - unless I am driving off a curb, I do not think it can hit anything.
    To be tested...
    So I am at the lowest possible position at rear pivot with the latest rendition.

    I'm not sure I followed your reasoning on rear wheel lead though.
    Currently when I lean the bike right - the sidecar wheel moves significantly to the right (scrub) and has some toe in toe out effect.
    This is of course caused by the pivot points height from the ground.
    Theoretically (in my mind...) if the back pivot was on the ground, the front pivot was elevated, and sidecar wheel had no lead, wouldn't that cause the steering effect I am looking for with almost no scrub?
    If I wanted more or less steering - I could raise or lower the front pivot.

    I plan to test this a bit with the next iteration.
    More to come.
    -CM
    (Note - my welding is Frankenstein ugly - but effective...)

    IMG_3487.JPG
    #46
    brstar likes this.
  7. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Spent the day fabricating the front mount.
    Came up with a three point scheme that will allow me to shim the rear mounting points to elevate or lower the front pivot point.
    Welding remains like emergency room doctor's stitches: your happy to have them when you need them - but they are gonna leave a scar.
    IMG_3510.JPG
    Fabricated this front mount from a square piece of tubing and a U bolt exhaust clamp
    IMG_3507.JPG If I shim the rear two U bolt clamps, it will raise the back and lower the front - tilting the connection point toward the leg shield. I can now adjust the pivot point height about 25-30mm up or down.
    IMG_3508.JPG This front mount will now be welded to the scooter body underside.

    star, hellracer. how high off the ground were you front and rear mounts?
    #47
  8. Hellracer.nl

    Hellracer.nl What the hack???

    Joined:
    Aug 25, 2012
    Oddometer:
    1,213
    Location:
    Netherlands
    I'll have a look tomorrow when it's light again.
    #48
  9. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Thanks hellracer! Of course - that assumes it will be light in the Netherlands tomorrow...
    .
    #49
    Bobmws likes this.
  10. Hellracer.nl

    Hellracer.nl What the hack???

    Joined:
    Aug 25, 2012
    Oddometer:
    1,213
    Location:
    Netherlands
    In centimeters: rear 17, front 25.
    In inches: rear: 6,7 , front 9,83.
    #50
  11. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Very helpful.
    Thanks for the precision as well.
    Gives me some confidence I am on the right track.
    Know I will have to adjust for my own geometry - but happy to have something to compare to.

    For fun - sharing a pic below of iteration II of my frame.
    It's a little ugly - I have a hacked portion of my old rigid frame in it.
    1.25" .095 wall thickness DOM tubing. Seems plenty rigid and strong.
    Significantly lighter than the old frame.

    Front pivot is about 8" - will have to measure carefully when I assemble again.
    Rear pivot it about 4"
    Distance between the two is about 54"
    IMG_3534.JPG
    This is a temporary frame that will allow me to test the geometry and adjust.
    #51
    Bobmws and brstar like this.
  12. Hellracer.nl

    Hellracer.nl What the hack???

    Joined:
    Aug 25, 2012
    Oddometer:
    1,213
    Location:
    Netherlands
    That's the way to go. Build and adjust.

    And don't forget to have fun!
    #52
  13. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Ok gents.
    Finished the test frame.
    Thanks to everyone who chimed in.
    Here is a video of me testing it if interested.
    Note: I had torn down the scoot motor and done a tuning job on it.
    Never had it back in before I started this process.
    So I am dealing with new motor, new transmission, new fuel delivery, and of course - new side car concept...
    What could possibly go wrong?

    Here is a vid of it in action:

    No animals were injured or bothered during the making of this video.
    Toy stuffed animal however was a casualty of a little too spirited test ride...
    IMG_3553.JPG
    #53
  14. ErictheBiking

    ErictheBiking Been here awhile

    Joined:
    Feb 28, 2008
    Oddometer:
    300
    Location:
    Queensland, Australia
    Well done.
    I thought it was winter over there.
    #54
  15. Hellracer.nl

    Hellracer.nl What the hack???

    Joined:
    Aug 25, 2012
    Oddometer:
    1,213
    Location:
    Netherlands
    Wow!
    Looking good!
    How much lean do you have towards the sidecar?
    No trouble with steering slappers?
    #55
  16. brstar

    brstar Long timer

    Joined:
    Aug 17, 2007
    Oddometer:
    2,133
    Location:
    Shoalwater Western Australia
    Sad the dog not trainable.
    Is the missus any better???
    Looks like a fun jigger.
    A full load will be the test.
    #56
  17. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Well - this is our winter.
    Dog: as usual - the issue is the owner not the pet...
    Angle: Best guess, it will go to about 40° from vertical. I plan to adjust to allow for an additional 5°.
    I did not experience any steering slap - but as I increase speeds and test breaks - I will keep an eye out.
    brstar - I will add weights to the bucket and test some more. This should help me tune in lead and toe in.

    My general sense is, I could use a little more steering by raising the front pivot a bit.
    I can do this quickly with the set up I have and will try it - once I have tested this current set up with some weight.
    Thanks to everyone for input and help along the way.
    Not finished by any means - but seams promising based on first tests.
    Cheers,
    -CM
    #57
    Bobmws, Jimr80gs and brstar like this.
  18. brstar

    brstar Long timer

    Joined:
    Aug 17, 2007
    Oddometer:
    2,133
    Location:
    Shoalwater Western Australia
    I like your keep on attitude here.
    Enjoy the process.
    #58
    Bobmws likes this.
  19. Charlieman22

    Charlieman22 Adventurer

    Joined:
    Jan 14, 2020
    Oddometer:
    34
    Location:
    California
    Added the side car body today so I could feel what it was like with a bit more weight.
    There really is very very little pulling - compared to the fixed model.
    I think I just naturally compensate by leaning left.
    The push on braking is similar to the fixed.

    With that said, at low speeds, It wants to lean right - towards the side car.
    I have a foot position on the sidecar frame - if I put my foot on it - I can balance nicely.
    But it is one more thing to remember - and I would prefer to make the set up more neutral.

    I have an idea.
    I would like some feedback.

    The connection points are dead center on the wheels currently - but on a vespa - the engine is off to one side (same side as sidecar) and it naturally wants to lean that way. I am considering moving the pivot points off the scooter's center line - towards the opposite side of the motor and sidecar. In this manner, the weight of the side car would be pulling the bike upright - at least in my brain.

    * Can anyone comment on the likely effects of moving the pivot points (front and rear) off center like this?
    relocate pivot points off center.jpg
    #59
  20. brstar

    brstar Long timer

    Joined:
    Aug 17, 2007
    Oddometer:
    2,133
    Location:
    Shoalwater Western Australia
    How much toe in do you have?
    At what speeds is it an issue?
    Maybe just move your butt over a bit?
    The engine offset just doesn't strike me as being a serious issue.
    Though the whole thing is probably fairly lightweight.
    So maybe you have something here.
    I do know that moving the pivot points off centre creates other issues.
    #60