Crushing Aluminum

Discussion in 'Motorized Bicycle General Discussion' started by MysterySandwich, Jan 6, 2014.

  1. MysterySandwich

    MysterySandwich New Member

    Joined:
    Jun 30, 2012
    Messages:
    196
    Likes Received:
    0
    What's the general consensus when it comes to the strength of aluminum?

    Will clamping some steel plates onto an aluminum frame bring up some problems? (Staton-inc FD on aluminum frame)

    I'll be careful and not torque down the bolts too much, but what's the right amount? Would some rubber or some other kind of cushion help protect the aluminum frame? I know that that's really not a good idea when it comes to mounting 2 stroke engines in-frame...
     
  2. rustycase

    rustycase Gutter Rider

    Joined:
    May 26, 2011
    Messages:
    2,746
    Likes Received:
    0
    Yes, it will cause problems eventually, but if that's what you gotta do... well...

    Use the largest possible bearing surface, and Not so it would encourage a direct break-off line.
    I would use some quality gasket material sooner than rubber. Garlock?

    The problem with aluminum is that it suffers from fatigue which leads to catastrophic failure. This was learned in a spectacular fashion in the aircraft industry.

    Just my opinion... perhaps someone will have information of a long term success.

    Good luck
    rc
     
  3. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,684
    Likes Received:
    24
    It won't be a problem bolting that U bracket and plate to your frame.

    Put thin pieces of rubber between the steel brackets and your frame and don't over tighten the bolts.

    There is no comparison to putting rubber under a 2 stroke motor mounts.
    Your friction drive motor channel is also secured by by 2 aluminum stays that go down to the axles.

    Install a tire liner like Mr Tuffy and a thick thorn proof tire because the roller will drive any sharp objects into your back tire.
    Carry a spare tube with you too because FDs get lots of rear wheel flats.
     
  4. rogergendron1

    rogergendron1 New Member

    Joined:
    Sep 18, 2013
    Messages:
    882
    Likes Received:
    0
    crushing aluminum.......

    sounds like a new heavy metal rock band !!!!

    but srly ..... u bolts are one of the best ways to mount a motor to a frame ! keep tightning it till you see the frame start to crush a tiny bit and thats how you know its tight enough !
    i have a 35mph bike and the motor is held on by a u bolt in the rear with a plate going to the case bolts and a single 5/16ths through bolt, bolted through a steeel plate on the frames down tube and the motor boltas to that. have not had a single problem ever and the motor is as solid as a rock !

    the bolt that goes through the frame in the front mount is has large washers bent in a curve to match the frames curve and its tightend so tight it crushes rthe frame slightly, this means the fram is crushed in just enough to want to push or spring back out and it keeps tention on the bolt to stay tight.
     
    #4 rogergendron1, Jan 6, 2014
    Last edited: Jan 6, 2014
  5. rustycase

    rustycase Gutter Rider

    Joined:
    May 26, 2011
    Messages:
    2,746
    Likes Received:
    0
    lol

    I never did consider the FD wheel driving thorns into a tire, with enthusiasm!
    Tnx for that tip!
    rc
     
  6. MysterySandwich

    MysterySandwich New Member

    Joined:
    Jun 30, 2012
    Messages:
    196
    Likes Received:
    0
    Great, thanks guys!

    So some nice gasket material in between the steel mounting plates and the aluminum frame. This Mr. Gasket 9615 should do the job well, yes?

    I already regret buying a bike with 24" tires hah... hard to find some heavy duty inner tubes or compatible Mr.tuffy, contacted bikebuyers, hopefully they can help.

    And as for torque'ing down the bolts until I see the frame crush slightly... is that really a good idea? makes me nervous!
     
  7. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,684
    Likes Received:
    24
    The Staton U clamp and plate are wide and just need a little cushioning so they don't rub on the seat stays.
    A piece of thin inner tube is just fine for the job.

    26" Tire liners are easy to cut to length for a 24" wheel with scissors.
     
    #7 MotorBicycleRacing, Jan 6, 2014
    Last edited by a moderator: Jan 6, 2014
  8. MysterySandwich

    MysterySandwich New Member

    Joined:
    Jun 30, 2012
    Messages:
    196
    Likes Received:
    0
    Hey guys, thanks for all the good help!

    Anyway, got my bike today and looks like there's a bigger:confused: problem.

    So the mount right behind the seat post... There's no room for all three bolts to bolt on, only for the middle one. I COULD move it up right behind the seat post and bolt the two on the side and not the middle, but then there'd be no room for the saddle.

    See pics... : https://www.dropbox.com/sh/9e48n7ipqmddulz/Zp_1g3deJo
    (disregard the first picture)

    I'm not too excited about the idea of only mounting the middle (the steel plate would probably end up bending in) so the only thing I can think up of is getting some kind of extensions (see picture) but I don't know where I'd buy those...

    OPEN TO ANY CREATIVITY!
    :-||
     
  9. Mike B

    Mike B New Member

    Joined:
    Mar 23, 2011
    Messages:
    2,256
    Likes Received:
    1
    I tried to warn you...

    I even showed how it goes on my bike.

    You are going to have to fab up a custom bracket. It's gotta be strong too, that motor bracket takes the entire thrust from the engine driving the tire.
     
  10. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,684
    Likes Received:
    24
    Flip the bracket around and only use the center hole.

    Then drill 2 more holes in the bracket on the inside of the seat stays.

    Or you could notch the bracket in the middle removing the center hole
    then re drill 2 outside holes higher up on the outside of the frame.

    Then re drill the center hole below the notch.

    Actually would be better to forget the middle hole and drill 2 more holes
    on the inside of the frame so there would be 4 bolts, 2 on each side.

    Of course you have to match the holes in the backing plate.

    [​IMG]
     
    #10 MotorBicycleRacing, Jan 8, 2014
    Last edited: Jan 8, 2014
  11. MysterySandwich

    MysterySandwich New Member

    Joined:
    Jun 30, 2012
    Messages:
    196
    Likes Received:
    0
    Yeah I know :/

    Hey thanks, those are some good ideas -- I'm not exactly sure what you mean by the third option.

    But here are some crude drawings I did, is this what you meant by #1 & 2?
    I like option #2 the best.

    [​IMG]

    EDIT: Oay so I did some measurements and what not, #2 won't work, the steel in the middle will have to be grinded to the point where it is too thin, See pic

    SO I think I'll have to go with #1 -- Will this be stable, even though there are no bolts holding on the outside of the seat stays?
     
    #11 MysterySandwich, Jan 8, 2014
    Last edited: Jan 8, 2014
  12. MotorBicycleRacing

    MotorBicycleRacing Active Member

    Joined:
    Jul 28, 2010
    Messages:
    5,684
    Likes Received:
    24
    Mark the new holes on the actual bracket with felt tip and take pic
    with it on the frame.

    forget about the middle hole as there is nothing in the middle to clamp
    around and it will only bend the U bracket and plate.

    Put a hole on each side of the 2 seat stays in the U bracket so you are using 4 bolts to hold it on.
    maybe you can use the 2 outside holes.

    That is a large diameter strong aluminum tube to clamp to so no worries
    about crushing it.

    [​IMG]
     
  13. Mike B

    Mike B New Member

    Joined:
    Mar 23, 2011
    Messages:
    2,256
    Likes Received:
    1
    That would be ideal. If you can get those outer bolts to clear the frame and drill 2 inner ones, you are golden.

    Yeah, forget the center bolt.

    You need to clamp from both sides of the stays or the bracket will move.
     
  14. MysterySandwich

    MysterySandwich New Member

    Joined:
    Jun 30, 2012
    Messages:
    196
    Likes Received:
    0
    Okay So I actually already drilled the holes... See pics

    Theres no room to drill holes on the outside of the seat stays.
    Buuut.... We can combine the ideas -- What do you guys think about grinding off the middle/top hole to create leeway for the frame which would let me raise the ends a bit higher so I can drill holes on the Top left and right corners for 2 bolts? I'll just have 2 holes unused.
     

Share This Page