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Thread: how to increase axle strength

  1. #1
    Associate Engineer
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    how to increase axle strength

    Building small cart to portage canoe(72 pounds). I'm 77 years old and no longer strong enough to put it on my shoulders. Would like to increase axle strength. Axle is 1/2"schedule 80 PVC pipe, not tubing, with 1/2" aluminum rod(41" long)inside. Clearance between inside of PVC and aluminum rod is ever so small. If I can find some kind of epoxy or glue that I can coat the aluminum rod with before sliding it into the PVC, will that substantially or even at all increase the strength of the axle.

  2. #2
    Principle Engineer Cragyon's Avatar
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    Quote Originally Posted by mjpt3800 View Post
    If I can find some kind of epoxy or glue that I can coat the aluminum rod with before sliding it into the PVC, will that substantially or even at all increase the strength of the axle.
    Depends on the rigidity, strength characteristics and sticky-ness of the epoxy or glue. Know that where the strength increase matters is at the load reaction locations.

    First thought - have you considered upgrading the axle to Schedule 160?

    https://www.engineersedge.com/pipe_schedules.htm

  3. #3
    Principle Engineer
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    An increase in the outside diameter of the axle is the fastest route to increased stiffness.

    If practical, I suggest that you put a length of 1" PVC over the 1/2" and use a reducer at each end to connect the 1" to the 1/2" pipe.

  4. #4
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    yes i understand the greater the diameter the greater the strength and that's what i'm trying to do while trying to stay as small and light as possible. a hollow tube over another bigger holow tube i don't think increases the original tubes strength if they only make contact on each end for 3/4". i'm not sure. however, i am pretty sure if i can get my 1/2' aluminum rod to be welded(glued/epoxyed) to the pvc pipe i will have done what you suggested, maybe stronger in that it would be solid full length not just solid for that 3/4" on each end. hence my original question-if i can figure out what kind of medium to coat 1/2" rod with to fill some small 1000th difference in dia of aluminum rod and inside of pipe will it indeed make it enough stronger to make it worth the money to find the medium to do so?

  5. #5
    Administrator Kelly Bramble's Avatar
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    Quote Originally Posted by mjpt3800 View Post
    yes i understand the greater the diameter the greater the strength and that's what i'm trying to do while trying to stay as small and light as possible. a hollow tube over another bigger holow tube i don't think increases the original tubes strength if they only make contact on each end for 3/4". i'm not sure. however, i am pretty sure if i can get my 1/2' aluminum rod to be welded(glued/epoxyed) to the pvc pipe i will have done what you suggested, maybe stronger in that it would be solid full length not just solid for that 3/4" on each end. hence my original question-if i can figure out what kind of medium to coat 1/2" rod with to fill some small 1000th difference in dia of aluminum rod and inside of pipe will it indeed make it enough stronger to make it worth the money to find the medium to do so?
    If you can identify a bonding medium that ensures that the shear load and adhesion is maintained between the ABS Plastic tube and aluminum rod - then yes, the axle will be stronger and carry more load.

    However, I do not have any suggestions on what medium you need. Moreover, even if a filler is identified I doubt it would be less costly then a thicker or different material axle..
    Tell me and I forget. Teach me and I remember. Involve me and I learn.

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