Leaner Sidecar/ Vintage Vespa

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

  1. Charlieman22

    Charlieman22 Adventurer

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    Hi all - allow me to introduce myself.
    intro/background:
    Having coveted a vintage Vespa and sidecar for a decade or so - I came across one last year and pulled the trigger on the spot.
    That was the moment I realized I was completely clueless about 2 stroke motors - not to mention hacks - but hey - no better way then to own one.

    I've since been through this one and had some fun learning.
    Port timings, piston grinding, port grinding, hell - there is pretty well nothing I won't Dremel at this point.
    I've managed to squeeze a whopping 15ish HP out the motor at best guess - so a tad less then you guys are used to.
    Will cruz about 50-55MPH and might reach 60 on a still day, on a slight down hill, with tight clothes on, and a close shave.
    I've modernized the suspension and brakes - but kept it all tucked inside the stock chassis to maintain the basic look that attracted me in the first place.
    I've also done what I could to remove any play from the hack chassis and connection points.
    Mostly - its just a ton of fun to ride and work on.

    That said - I've been intrigued by the leaner concept - and like to tinker.
    At first pass - the whole leaner idea seamed a misfit.
    Anyone still reading at this point maybe nodding their head in agreement.
    1. The floor boards are wide - they nearly touch the ground on a a good corner already.
    2. The attachment of hack frame to scooter has only a short area along the tunnel.

    That second point is a short coming for a fixed hack as well.
    In fact - there is only about 15" to really connect the hack frame to scooter chassis under the floor boards.
    That is less then ideal - especially when I get on it a little through the twisties...

    So I decided I would take the leap, and modify the connection to be leaner.
    Seeing as I'm going that far - I want to make it lock out as well - to allow it to be rigid if I prefer.
    The basic concept is to make the front connection above the floor board - raising it up - and the back connection behind the rear wheel.
    In order to do this - I have added a sub frame in the wheel well - that will support the rear connection - and I am designing a custom mount for the front connection point above the floor board where it turns upwardly into the leg shield.

    Below are a few pics - with some basic data I'm planning to use - which I gathered from others on this forum (thanks!)
    Enjoyed all I've read here - and thought I would wheel out my concept for a good tire kicking. All input welcome. Still thinking through the design/execution so would welcome your insights.

    Many thanks
    -CM

    IMG_9600.jpeg
    Current hack - strange frame was someone's idea of adding protection - just not sure why it is at that height between the scooter and the hack body. Kinda kills the lines in my view.
    IMG_9600.jpeg IMG_9601.jpeg

    Side View.jpg

    Heim joint at rear is connected to subframe welded in to wheel well (paint burns show the subframe line) Front connection will be 6.3" higher about 45" forward of the tail mount- making the angle about 8° between connection points. Green sketched line shows connecting rod from front heim to sidecar frame
    Front view.jpg
    Green dotted line portion would be on other side of leg shield. Bottom green line would be at tail. Top green line would be removable locking bar
    #1
  2. brstar

    brstar Long timer

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    Looks great.
    The drawing looks very neat.
    The photo not so much?
    Not sure how they moved so far apart?
    How does it ride.?
    Ground clearance?
    Left turn clearance on the front mount?
    A few more photos might explain to the simple here.
    As others and myself have found leaners work best as light weights.
    #2
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  3. Charlieman22

    Charlieman22 Adventurer

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    Thanks for weighing in brstar!
    New to forum and it's idiosyncrasies for posting - as you can see. I seem to have posted one of my pics x2.
    Wrestled unsuccessfully with that.
    Not completely clear what you meant by above - can you clarify?

    Photos of hack connected to scooter are as I bought it - prior to tear down.
    It was a rigid connection.
    The sketch is not to scale - purely conceptual.
    Here are my initial thoughts on specs
    Lots to still figure out (hoping for input here):
    - 8° difference between rear and front pivot points.
    - 45" from rear pivot to front pivot
    - 6.3" heigh difference between the two pivots
    - Target lean for scoot - ~40ish degrees (no idea if I can reach this or if the scoot ever leans that far anyway! Have to figure that out)
    - Distance between scoot and side car - still TBD
    - Height of center line of rear pivot from ground ~5.5" to 6" (would put front pivot at ~12")
    - Rear wheel lead <20 % of distance from center of rear to center of front wheel. Ideally ~ 15% of that distance
    - Hack suspension - trailing swing arm with adjustable shock - allow soft setting for when unloaded.
    - Weight of hack - tbd. Frame as light and stiff as I can manage to get it.
    - Left turn clearance will be created by the shape of the connecting bar from scooter chassis to sidecar - it will be bowed to allow clearance with floor board.
    #3
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  4. brstar

    brstar Long timer

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    Rigid pictures explains a lot.
    Your mount should look a lot neater.
    I ran an air shock on mine which allowed it to float nicely.
    I think it was at 9deg though I didn't do the sums myself it was just how it worked out.
    I used nolathane bushes which meant they had to be inline.
    The distance apart not so critical
    Pivot points as low reasonable helps to turn easy.
    It will scrub the sidecar wheel a bit.
    It should be a lot of fun to ride but more planning is required as you go along the road.
    40deg lean you wild thing.
    Wheel lead?
    Not sure of the exact best percentage.
    Not sure if anyone else does either.
    The height difference between front and rear pivot makes the sidecar wheel steer a bit.
    Or rather automatically adjust the toe in.
    If you lean into a turn at a low speed at say 20deg and have the same lean angle at high speed then the turning circle is much different.
    Hence the drag on the sidecar wheel.
    The 1st time you take of you will notice a sort of double counter steer.
    I will be waiting to see it.
    #4
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  5. Charlieman22

    Charlieman22 Adventurer

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    Brstar- thanks.
    Curious - why the bushings rather then Heim joints? Are there advantages/trade offs?

    We will see how much lean I can actually get - main question I have - how important are some form of limiters to stop the lean at max?

    Alll - has anyone tried aluminum tubing to cut weight? Wasn’t so much focused on that up until now...

    Tks for all input as I prep for next steps.

    -CM
    #5
  6. brstar

    brstar Long timer

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    Bushes?
    Cause I had some.
    I mean that's the spirit of a scrap metal build isn't it?
    Its now a rigid outfit with the optional pivots still there.
    I have been messing with Ali and while its a great medium, where you are means you can get cut lengths of drawn over mandrel tube (DOM) delivered to your door.
    It would suit your purpose just fine.
    It wasn't a good option in Western Australia that I know of.
    #6
  7. Hellracer.nl

    Hellracer.nl What the hack???

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    I like the idea of the rear connection a lot.
    That's brilliant!
    I don't see how the front connection would work, does't that interfere with the floorboard in a lefthand turn?
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  8. brstar

    brstar Long timer

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    I was wondering when you would weigh in hellracer.
    If the front connection goes up at an angle before bending back down to the sidecar it would work fine.
    Sort of like a question mark on its side.
    It could also become the left side lean stop at 40deg.
    #8
  9. Charlieman22

    Charlieman22 Adventurer

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    Bedankt Hellracer!
    brstar has the concept right.
    Sketch below of a left turn to show it in action.
    Front connecting rod from sidecar frame to scooter chassis is bowed - to allow space.

    Much appreciate the discussion - thank you for jumping in.
    Would welcome some critiquing/ insights on below from anyone who wants to share their perspective.

    1. How important is a stop on left lean? Do I need this?
    2. Is right lean stop also needed?
    3. I have calculated about an 8° difference from rear to front - good?
    4. Best guess is that the front pivot point will be a full 12 inches (305mm) above the ground. (rear will be half that). Will scrub be miserable?
    5. I am planning 1.25" DOM tubing - perhaps 1.5" for the connecting bars from side car frame to scooter. Heim joints are 5/8".

    left turn.jpg
    #9
  10. brstar

    brstar Long timer

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    The left lean stop will most likely be a matter of protecting the running board.
    On my left side rig.
    To the left I had a solid stop at about 40deg.
    To the right I had the ground for a stop.
    How about a photo of the left side of the scooter?
    How much suspension travel is there?
    And how low can the pivot points be?
    Cheers
    #10
  11. Charlieman22

    Charlieman22 Adventurer

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    brtar,
    Good insight on reason for lean stop.
    I am way new to this - which is to say...
    I had imagined that perhaps the stop was there for riding purposes.

    Understanding its purpose better now - I should likely have a stop - to avoid the leg shield hitting the side car.
    Since I wanted to have a lock out on this as an option anyway - perhaps the 45 degree angle bar for locking could have a locking pin that allowed it to telescope - or not... See pic.

    Answers:
    Below is a pic from the left side - from when I first got the scoot.
    Note - the rear tire is temp - and was a bit smaller then the front.
    I do not believe I can lower the pivot points - for my build.
    Is there a standard or a max above ground?
    I assume high means scrub - but not sure how much or what that will translate to for feel.
    Suspension for side car is trailing arm with shock.

    Front view.jpg


    Left side of scoot as requested - below.
    IMG_9599.jpeg
    #11
  12. Charlieman22

    Charlieman22 Adventurer

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    Short addition - spent some time mocking up the mount for the front pivot point.
    It's rough - and I will remake it now that I have done a first CAD model (Cardboard Aided Design... hat tip "project pinky").
    See below.

    Did a quick sketch on the bike.

    IMG_3140.JPG
    Then stripped off the paint and commenced measuring for center - note - due to the nature of other upgrades like front hydrolic disc brakes, the center line is not center on the bike... Have to create an offset mount.
    IMG_3146.JPG

    Then used some cardboard and foam core to build a simple concept model. Work to be done to allow my mount to actually tie in properly to the scoot chassis - but its a start and allows me to think it through.

    IMG_3173.JPG
    #12
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  13. Bobmws

    Bobmws Curmudgeon At Large

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    Your optional sliding lockout bar might bind due to the wheel scrub of the sidecar.
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  14. brstar

    brstar Long timer

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    I would not go with a sliding pin lock because of the of chance of it sticking at an inopportune moment.
    Ideally the pivot point would be at ground level so the scoot does not drag the sidecar sideways as you turn.
    Probably possible to make a fancy linkage to achieve that but my brain only conceived the concept but no practical way to achieve that.
    At least when you pull up at the lights the drag of the sidecar slows the scoot from falling over.
    #14
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  15. Charlieman22

    Charlieman22 Adventurer

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    Couple of good ones there.
    Now I better understand the scrub issue.
    I was thinking of it as a toe in or out vs the scooter's line of direction.
    Sounds like it is more a pushing or pulling sideways of the side car.
    Thanks guys. Sliding pin probably not a good solution for me.

    The really low points on scoot or side car scare me a little.
    I would hate to catch one of them on something while riding.

    Couple new questions then:
    If my configuration keeps the sidecar wheel in as close to the scooter as possible (narrow track) will that help reduce scrub in my case?
    Does scrub also work to make it slow or difficult to return to straight up and down out of lean - or just fights lean?

    Tks.
    -CM
    #15
  16. brstar

    brstar Long timer

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    With a rigid, toe in of the sidecar wheel along with leanout of the bike counter the drag of the sidecar.
    So there is always some tire scrubbing happening.
    With a leaner travelling in a straight line it theoretically be a similar wear rate.
    But where is the fun in that?
    It's the transition from upright to lean and back that causes the drag/scrubbing.
    The faster the speed means the less you notice it.
    Claude did have a moment on his 1st leaner outing I believe. (He believes to).
    My paraphrasing is that he stuffed it down in a tight turn and got a surprise when it didn't pop straight back up.
    I have only ridden the one leaner that being mine.
    It seemed to handle well enough to me anyway.
    But to be critical the comparison in my mind was between a graceful adult/solo bike and a still gangly teenage/leaner.
    It's a bit like riding an old type shaft drive bike.
    Setup early for corners and keep it smooth.
    You will adapt or change.
    Narrow is good as it reduces the drag effect.
    Achieving your 40deg lean with clearance will dictate the width.
    But side scrub will still be there. So long as your sidecar tire is cheap it's not a biggie.
    Cheers
    #16
  17. Charlieman22

    Charlieman22 Adventurer

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    Will keep these in mind...
    Thanks for the input.
    Am trying to develop the front mount so that it bolts on bolts off - meaning - I could experiment with some different height differentails from front to rear.
    Will post pics - and of course - any other musings welcome from all.
    Thanks gents.
    -CM
    #17
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  18. Hellracer.nl

    Hellracer.nl What the hack???

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    I see that the front pivot point is above the centreline of the frontwheel axle. That's very uncommon. Normaly a leaner will have the pivot points as near as possible to the ground, that way the weight of the bike pushes the sidecar into a corner without demanding to much extra force. The higher the pivot points, the more force it will require.
    Since the Vespa has very little own weight and the wheels are so tiny I'm not sure if it will influence the required steering force a lot.
    But I do know that you will get a hell of a lot of sidecar wheel scrubbing with high placed pivot points.
    That will make steering at low speeds heavy and probably cause for steer slapping.
    #18
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  19. brstar

    brstar Long timer

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    Hellracer I think you have some good points there.
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  20. Charlieman22

    Charlieman22 Adventurer

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    Hellracer - thank you.
    Good catch. Center line of front axle is lower than front pivot.
    Had never imagined that CL of front wheel was related to scrub?
    I have struggled to fully understand the dynamics of what causes scrub tho - so no surprise there.
    This lack of clarity makes problem solving a bit more of a challenge...

    The scooter chassis has limitations - but there might be some creative work arounds if I better understood the dynamics.
    Would welcome some comments from those that better understand.
    (I've searched but failed to find a complete explanation of what geometries create the scrubbing effect)
    Does the front axle height vs front connection pivot point have any specific relation?
    I can be a little thick - so welcome a layman's explanation if anyone wants to give one.

    There are gives and takes - but at first glance, here are some levers I have at my disposal.
    1. Bring the front mount down lower - closer to CL of front axle. This would decrease the differential front to rear of pivot points to about 4 degrees instead of 8 degrees - where I now have it targeted.
    2. Move the front pivot LOWER then the rear - though this would put it closer to the ground then I think I am comfortable with it would work in reverse of how I see the motorcycles do it - but seems like it would also work?
    3. Move the side car wheel backwards or forwards

    Lemme know what you guys think.
    Interested to hear your insights.

    Edit: see clarification on #2 above.
    #20