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Thread: Welding axle stubs into axle...how tight a fit?

  1. #11
    Join Date
    Nov 1999
    Location
    SE OZ
    Posts
    2,112

    Default Tacky welding???

    Quote Originally Posted by winchman
    I've been asked to weld some axle stubs into a piece of schedule 80 pipe to make an axle for a trailer. The stubs look like this:



    The fit is going to be rather sloppy. The OD of the stub is 1.75" and the ID of the pipe is 1.94". He wants to put several pieces of 3/32" welding rod lengthwise around the stub to fill the gap while welding.

    That seems pretty shaky to me. I'd rather make a sleeve or put some weld beads around the stub and turn them down. Something that'll give me at least a tight slip fit.

    What's the accepted procedure for doing this?

    Roger
    While I'd agree that the quality and placement of weld is a high priority - which has been dealt with previously - I'd be just as concerned about a few other things before I actually started welding that stub axle to the main axle.

    I'd be cleaning off that scale on the un-machined part as well as making sure no weld or spatter got onto the journal and seal surfaces - as it sure won't do them any good.

    I could not be certain that the machined section of the stub was accurately concentric with or aligned to the machined parts of the stub.

    I'd want enough clearance or "play" between the sub and the bore of the axle so that I could accurately set the camber and "toe in" (if any) as well as the centralising and tracking by reference to the towing ball or hitch. There is nothing worse than a trailer that tracks either off to one side or swings/yaws from side to side - or both.

    I guess that the alignment of the stub and main axles, springs/suspension etc. as an assembly are the main objective.

    Having enough clearance between the stub and main axle will allow for a final "tune" and alignment to cancel out any other/previous errors.

    When-ever I've had to do this I always spend a lot of time either making an alignment jig or double-checking my alignment - or both - and than tack and check extensively. I do a "dry run" towing the trailer with a small weight/load in it at the "tack-weld" stage. If there are any errors I can correct them then. If all is OK, I proceed to the first of the final welds. I check it again and if OK, I finish weld it.

    I try to minimise those damned "I wish to f**k I'd have .............. (fill in your own here) .............!!!!" as I am equally damned sure I'll never entirely eliminate them!!!

  2. #12
    Join Date
    Aug 2002
    Location
    Menlo Park, CA
    Posts
    968

    Default

    Quote Originally Posted by oldtiffie
    While I'd agree that the quality and placement of weld is a high priority - which has been dealt with previously - I'd be just as concerned about a few other things before I actually started welding that stub axle to the main axle.

    I'd be cleaning off that scale on the un-machined part as well as making sure no weld or spatter got onto the journal and seal surfaces - as it sure won't do them any good.

    I could not be certain that the machined section of the stub was accurately concentric with or aligned to the machined parts of the stub.

    I'd want enough clearance or "play" between the sub and the bore of the axle so that I could accurately set the camber and "toe in" (if any) as well as the centralising and tracking by reference to the towing ball or hitch. There is nothing worse than a trailer that tracks either off to one side or swings/yaws from side to side - or both.

    I guess that the alignment of the stub and main axles, springs/suspension etc. as an assembly are the main objective.

    Having enough clearance between the stub and main axle will allow for a final "tune" and alignment to cancel out any other/previous errors.

    When-ever I've had to do this I always spend a lot of time either making an alignment jig or double-checking my alignment - or both - and than tack and check extensively. I do a "dry run" towing the trailer with a small weight/load in it at the "tack-weld" stage. If there are any errors I can correct them then. If all is OK, I proceed to the first of the final welds. I check it again and if OK, I finish weld it.

    I try to minimise those damned "I wish to f**k I'd have .............. (fill in your own here) .............!!!!" as I am equally damned sure I'll never entirely eliminate them!!!
    I think you're over-complicating this:

    The amount of mill scale really doesn't matter as long as you're using welding rod that will weld through it alright - in the States, 6011 or 6010 w/ DC are just fine.

    The stub axle is close enough to concentric & straight.

    To make sure the trailer tracks straight the important thing to keep square is the line across the trailer connecting the two front spring hangers with the long axis of the trailer. If the trailer is crooked, don't fix it in the axle - move the spring hangers. Make the axle straight.

    If you're building this trailer from scratch, place the rear axle so that the proper 10-15% of the trailer load ends up on the hitch. This is the most important factor in insuring safety, since it prevents most instability problems.

    Keeping the weld spatter off of the sealing surfaces IS important; I usually wrap the axle stub in heavy tape or similar during welding.

    If you're worries about alignment, bolt up the hubs & wheels while stubs are just tacked in place and spin the axle w/ the wheels resting on the ground. Any out of alignment issue will show up as wheel wiggle. If you can't see/feel any problems, it's close enough to straight not to matter. Do remember that nothing is perfect in an analog world, but it's often good enough. Most commercial axles are straight; toe-in and camber really aren't needed.

    - Bart
    Bart Smaalders
    http://smaalders.net/barts

  3. #13
    Join Date
    May 2009
    Posts
    157

    Default

    The stubs are CNC turned with bar feeders, they will be concentric with the mill scale surface on the unturned portion. Which is to say, plenty precise.

    The manufacturer previously mentioned did the welding with short arc MIG, not known for digging through recast or deep penetration. Any stick will do the trick.
    Otherwise, what Barts said.

  4. #14
    Join Date
    Feb 2006
    Location
    Ontario, Canada
    Posts
    72

    Default

    I have fabricated many trailer axles, never had a problem with any of them. I agree with most of what Bart has said above with the exception of this

    "Most commercial axles are straight; toe-in and camber really aren't needed."

    All that I have built have been straight, never had a problem.

    A lot of commercial axles I have seen lately have a quite noticeable bow in the axle tube, not sure if they have camber or toe built in as I have not had my hands on one to measure. That said, I have been told that a small amount of negative camber (top of tire tipped in) is desirable, that it makes the trailer more stable. Toe in or out I think is not necessary. I have always found that tongue weight and position of the axle relative to total trailer length, have the most effect on how stable the trailer is. Get those two things right and you will have a stable easy towing trailer.

    Ed

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