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Broken axle

Discussion in 'Technical Q&A' started by dickvandorm, Jun 24, 2005.

  1. dickvandorm

    dickvandorm Rookie

    May 24, 2005
    36
    Olympia, WA. USA
    Full Name:
    Dick Pierson
    I am in the process of installing a new right rear axle, only to fine out that my car has had this problem before, three times (one left and two right). After talking to Carlo in Tacoma (30 yrs+ working on Ferraris), he says that broken axles are extremely rare. If that is the case maybe I should go buy a Lottery ticket. I find it alarming that this car has had this problem three times. Anybody else had a problem with breaking axles on Mondials? Mine is an 81' Mondial 8
     
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  3. Verell

    Verell F1 Veteran
    Consultant Owner

    May 5, 2001
    7,000
    Groton, MA
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    Verell Boaen
    By axle I assume you mean the rear half-shaft?

    If it was the shaft itself, I concurr, these should be extremely reliable, esp. in a stock car. They haven't come up as a weak spot w/the 400+ hp modified engines.

    If it was a CV joint, I'd wonder if a boot had failed contaminating the lube. Even so, the CV joints are tough as well & don't have a history of failing.
     
  4. Miltonian

    Miltonian F1 Veteran

    Dec 11, 2002
    5,960
    Milton, Wash.
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    Jeff B.
    I'd see if I could find a frame dimension chart to see if something is bent. Or possibly a broken motor mount. I don't know enough about Mondials to know exactly how things are laid out, but if your car is regularly breaking halfshafts, I'd guess that something is crooked.
     
  5. Ken

    Ken F1 World Champ

    Oct 19, 2001
    16,078
    Arlington Heights IL
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    Kenneth
    I agree. Something is out of line. When it broke a second time, someone was a real idiot to just replace it and not figure out that if it broke twice, it was going to happen again.


    Ken
     
  6. milstanselnino

    milstanselnino Formula Junior

    Jan 8, 2004
    573
    MN
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    Jon P.
    I had trouble with my Mondial rear axle, it turned out to be broken bolts which held the whole thing together. Cheap fix.
     
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  8. ferrarilou

    ferrarilou Formula Junior

    Apr 13, 2004
    513
    US
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    Lou Menditto
    Do you have pics of the break and location of the break relative
    to suspension components and frame?
     
  9. Mark 328

    Mark 328 Formula Junior

    Nov 6, 2003
    510
    Orange, Ca
    Full Name:
    Mark Foley
    This shop in Orange, Ca said he could rebuild the half shafts for about $70.
    They generally need a core, but the 328 shafts look pretty much like a Volkswagen beetle's so there may be some common parts with some other shafts.

    Also, they said they could probably do the Rack and Pinions Assy's for about $170.

    They have rebuilt several Alternators for me and they all have worked well at a price that can't be beat. They seem to basically have a wholesale business--there are all kinds of Alts, starters, R&P, etc around there. I just talked to them about doing these yesterday so you may want to give him a call. Note he has a heavy Spanish accent, but he seems to understand English pretty well.

    Reyes Alternator 714-633-4208, 1119 Alvarez Ave, Orange, Ca. the Owner's name is Leonardo.

    Mark
     
  10. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,858
    Dick - the nature of the failure is very important, and might answer your question. First, everyone seems to assume that you are referring to the half-shaft. Is this correct?

    Second, at what point along the shaft did it fail? Inner 3rd, mid-point, outer 3rd?

    Finally, did the failure assume the shape of a 45 degree spiral? A cylindrical shaft that fails as a result of torque will always (almost) break with a 45 degree spiral. For interest, if anyone has a piece of chalk, grab it by both ends and twist (carefully - not applying bending moment, tension or compression - only torsion). The cylindrical piece of chalk will fail with a 45 degree spiral fracture. (Hence - the spiral fracture of the tibia when skiing).

    Based on my and other's experience, it is unlikely that you will see this spiral. These shafts are quite strong, and unless your engine has been modified without your knowledge, a Mondial is unlikely to produce that much torque. On the other hand, perhaps you experienced a bad batch of metallurgy with yield strength below specification.

    We await your observations.

    Jim S.
     
  11. 8valve

    8valve Formula 3

    Sep 3, 2003
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    The past weekend I was at the Zandvoort racetrack, and one of the contenders in the classic Ferrari challenge (a UK series) was driving a streetlegal Mondial on slicks. In one of the fastest corners his left rear axle broke, separating the wheel from the car. The axle had sheared off just on the outside of the main hub. Car and driver got away luckily with just some slight damage to the front of the car when it hit a guardrail. I spoke to the driver, and he said that he had seen it happen a few times before to other Mondials....
     
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  13. dickvandorm

    dickvandorm Rookie

    May 24, 2005
    36
    Olympia, WA. USA
    Full Name:
    Dick Pierson
    #10 dickvandorm, Jun 25, 2005
    Last edited by a moderator: Sep 7, 2017
    The break was exactly at the hub and was a complete shear of the stub axle at the hub. It was appearant that the break had happened "in part" some time ago, there was rust on approx. 75% of the break. The other 25% was all that was hanging on until it let go. It after some examination, it does not appear that the car has been hit or anything is out of line, however that is very tough to determine with the naked eye. I installed the new part last night and road tested the car, seem to be very smooth and feels fine, may be my imagination but it feels better than before. Here is a pic of the axle and hub, (I put the hole in the axle thinking I was going to have to pull on it to get it out).
    Image Unavailable, Please Login
     
  14. chrismorse

    chrismorse Formula 3

    Feb 16, 2004
    2,149
    way north california
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    chris morse
    This is some scary S**T!!! So, does anyone have a good way to avoid this problem. I have seen one or two posts cautioning big sticky tire use on 308s for this same reason.

    Maybe pullig both stubs and shipping them to a good race shop for magnaflux or x-ray inspection would be a good idea???

    Any racers or engineers care to offer an opinion about the worth of shot peening, particularly the radius where the stub joins the flange????

    Could the failure on this Mondial be due to a bearing or spacer with a sharp shoulder pressing on the radius cause a failure???

    chris
     
  15. samsong

    samsong Rookie

    Jun 8, 2005
    39
    Los Angeles area
    Full Name:
    G-man
    Hoping to have a mech engineer with more experience in metal failure would reply, but that looks like a classic fatigue failure. It starts from a void or imperfection and progresses cyclically until it fails. It appears that its not a torsional load causing this, but a cantilever load. If the shaft were loaded, either through mis-aligment or imbalance, it would exert such a load. Beats me, though, how this could happen if its a good part and properly installed. I like the idea of magnaflux, though...would find an imperfection in a part.

    my 2 cents, but material science wasn't my thing in school.

    G
     
  16. Sloan83qv

    Sloan83qv F1 Rookie
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    The big sticky tire issue on the 308's is that the outer bearing housing will fail not the half shaft. That halfshaft failure is not common by any means.
     
  17. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
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    I am curious what type of construction this part is, if it is one peice, or built up of two peices. From the picture it looks like the shaft slides down inside a bore and that it broke down inside the bottom of the bore. Or maybe I am seeing something wrong in the picture. For almost eight years I have been actively involved in trying to understand these cars, and I have never heard of a stub axle failure. Three times You may want to check the alignment of the bearings, in particular the outer one, as if I am correct that is the point where it broke. If the bearing is not aligned in the housing correctly, it could cause binding at that point, although I would imagine the bearing failing long before that would happen. To much camber in the rear? Seems the car should be more capable than that.
    Perhaps the part could be looked at by a good race shop, maybe a good reweld, remachining, and heat treat would be less than a new part, and potentially stronger.
     
  18. Artvonne

    Artvonne F1 Veteran

    Oct 29, 2004
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    Paul
    One other thought: Could the nut on the back side be getting overtightened? There is a sleeve between the bearings, so no amount of tension would effect the bearings, but if someone is using to much torque on the nut by either a faulty wrench, miscalculation of conversion, or using a air impact wrench, something will fail. Usually at the weakest link. Three failures on opposite sides of the car leads one to think in another direction than simple poor quality part failure.
     
  19. dickvandorm

    dickvandorm Rookie

    May 24, 2005
    36
    Olympia, WA. USA
    Full Name:
    Dick Pierson
    Needless to say, I am hoping part failure. When I took it apart all bearings appeared to be lined up fine and as far as I could tell everything in the car was lined up correctly. However, again that is with the naked eye and that is not necessily the best way to tell. I did have the new part taken to a shop and reassembled there, I put it back in the car in one piece. One thing for sure, I have found out that this is a problem that is not common and therefore am feeling better adout the whole thing. Thanks to all of you for such good conversation about this, I feel very lucky to have had this huge network to bounce problems off of.
     
  20. Gary48

    Gary48 Guest

    Dec 30, 2003
    940
    Metallurgy 101 states that whenever a part such as an axel transends from shaft to flange, that transition is where the stress risers can be at their greatest. Large radius conditions lessen stress while small or sharp radius increase them, this shows clearly on the picture. Often radii are polished to further lessen the stress risers. This is just a measure of a heat treated part resisting large stresses put upon it. Normal conditions put little stress on the part and they remain in service for lengthly periods until slicks or severe loading occur and the part designed for normal service, fails. Probably nothing wrong with the part, just loading beyond its design capacity.
     
  21. 8valve

    8valve Formula 3

    Sep 3, 2003
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    Two so far this past week....
     
  22. Sloan83qv

    Sloan83qv F1 Rookie
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    Wow! Seems like you have a problem there.
     
  23. 8valve

    8valve Formula 3

    Sep 3, 2003
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    Hi Paul,
    Please see my post#9 in this thread, that was the first one, and now also Dickvandorm's situation (number 2!)
     
  24. 8valve

    8valve Formula 3

    Sep 3, 2003
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    Paul, I was actually referring to stub-axle failures, not half-shafts. Sorry about the confusion...
     
  25. Sloan83qv

    Sloan83qv F1 Rookie
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    I think alot of us thought you were talking about the 1/2 shafts. Thanks for clearing it up.

    Paul
     
  26. Just_some_dude

    Just_some_dude Karting

    Apr 1, 2004
    114
    Classic fatigue failure, with spalling around the center also.
     
  27. ricrain

    ricrain Karting

    Nov 1, 2003
    195
    Dallas Area
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    Ric
    At a track event, back when the 348 challenge series just started, I spent a good 20 minutes talking to Umberto Masoni, the (then) Technical Liaison for FNA about this problem. He told me that this problem originated back in the days of the early 308's. In the case of 308's, it was mostly, according to him (and the official FNA line), due to the fact that owners were buying aftermarket rims with incorrect offsets. This put undue stress on the 'T' intersection of the axle and hat, and resulted in "premature" failures. It was his contention that anyone racing 3X8's, especially with track or race tires, have the stub axles inspected annually. He said that magnafluxing would not typically reveal the problem, but X-raying would.

    YMMV
     

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