Sidecar Design Formula - IMPORTANT!

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

  1. L_Bomb

    L_Bomb Strewth and blimey

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    Does anyone have some suggestions for front wheel trail with a leading link setup?

    I tried searching but couldn't find any recommended lengths.
  2. GearHeadGrrrl

    GearHeadGrrrl Long timer

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    At least Erik Buell was honest enough to admit that they put the fuel and oil in the frame and swing arm partly to save money.
  3. Prmurat

    Prmurat Long timer

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    Very small part of the design ... long after weight distribution. Having the frame holding the gas was a lot more expensive than any roto plastic gas or oil tank.
  4. leethal

    leethal 3 wheel Monarch #37

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    Depends a little on what bike and front tyre but my AT with skinny 21inch wheel has 30mm and light steering.
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  5. robtg

    robtg Long timer

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    I have built several leading link forks and about 1" trail works well for me.
  6. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    And look where that attitude got him!

    Rickman and others have used oil in the frame for years. Honda does it with all of their XR thumpers. The problem with the Rickman style of oil in the frame is that if you have a RUD (Elan Musk's "Rapid Unscheduled Disassembly"), you'll have a hell of a time trying to get all of the little bits flushed out of the frame.
  7. claude stanley

    claude stanley Claude

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    No assembly is stronger than it's weakest point.
  8. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Truer words have never been said
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  9. mthure

    mthure Adventurer

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    I was watching this video on Youtube. Even though the rear mount is triangulated with some pretty heavy hardware it is free to rotate where it is attached to the sidecar, apart from the tension on the bolts. And it appears that the front mounts is the only thing that keeps the sidecar from folding up next to the bike and also fore and aft. Is this considered good practice, or does this guy need to go back to the drawing board?

    sidecar frame2.png sidecar frame.png
  10. DRONE

    DRONE Dog Chauffeur

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    Neither of those two videos will play in my browser. Don't know if others can see them. In any event, I looked up the vid on YouTube and posting it now --




    This is the same one, right?
  11. JustKip

    JustKip Long timer

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    They are screen captures, from that same video
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  12. bete

    bete misguided adventurer

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    My car is attached nearly identical, it's held fast for a year or so, lots of rough roads and over loaded tub at times.
    I'm not saying there isn't a better way but this way does work.
  13. mthure

    mthure Adventurer

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  14. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Yeah but, that bolt in sheer is in double sheer!
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  15. leethal

    leethal 3 wheel Monarch #37

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    Lower mounts on a Ural are just a BALL with clamp. Been working great for Ural for 80 years.
    The two fixed struts forming the triangulation are what prevent the SC folding up to the bike.
  16. claude stanley

    claude stanley Claude

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    The ball and collet type mounts are valid and were also used on various other sidecars with sucess on days gone past. Watsonian and even Motorvation years ago.
  17. claude stanley

    claude stanley Claude

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    Think on this....Not always possible but if the lower mounts are the same distance from the center of the bike and from the ground it is a good thing. Why? If they are not then any change in lean out will change the toe in. The more the mounts vary the more change occurs which requires more adjustments than would be needed if they were inline. Of course this is usually not the case but it is a decent goal on a new build. Catch 22 is that suspension changes on the bike can throw them off a little anyhow but so it goes. It is a good idea to always recheck toe in after adjusting lean out and visa versa until you get to know what YOUR rig does. ...... Upper mounts are best if they are placed on opposing angles when viewed from the side. This gives better rigidity to any fore and aft movement. It is a good goal to try and set mounts in such a way that they all share the load . There have been cases where a given mount was prone to fail over and over. The blame was placed on THAT mount as it was the one that failed but the true culprit was that it was carrying much much more of the load than it would have had to if the other mounts had been designed to share the burden. Many use spherical ball ends ( heim ends) for the lower mounts. These are easy to work with and do work but they are actually designed to rotate. So.... more responsibility goes to the other mounts (uppers) in this case. One design which was common ( and finally changed) would create issues with the upper rear mount at the bike end. That mount was ( on a 1100 GS) A simple pinch block on a small diameter piece of tubing by the seat. Yep...failure after failure was the result. Why? The upper was not on a good point structurally and that in combination with the heim ends down below was handwriting on the wall that sometHing would give. In theory it is a good practice that all mounts share the load equally and are braced when possible laterally to the other side of the bike. Is this possible? Well maybe not but it is a good goal. We may go overboard a little by typically and many times tie the upper and lower mounting points at the bike tobeter on a vertical plane for more SHARED strength. Overkill? Yeah maybe but imho better than taking the risk to save stuff a few more bucks into the profit margin of a build. BTW ,,,,,, Anything built by a human can have an issue. All the cars do not finish the INDY 500 every year. As old friend the late Hal Kendall used to say " Build it stout out of things you know about".
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  18. claude stanley

    claude stanley Claude

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    How many have had or seen an eyenut failure on a strut or mount?
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  19. Strong Bad

    Strong Bad Former World's Foremost Authority Supporter

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    Not the eye nut itself, the bolt passing through, multiple times.

    That being said, all were on off road race cars not on sidecars.
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  20. claude stanley

    claude stanley Claude

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    Been there with the race cars ,,,in my case sprint cars etc as you know as we have discussed this before. :-)
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