Packard Forum Index » Pre-War (1899-1942)

Hello all, Recently during a drive to a Display day, I noticed a burning smell from the LHR wheel. I pulled over and jacked the wheel up, grasped it firmly to check for looseness, etc. The wire wheel and brake drum very gently came off the axle in my hands. Very lucky not to have been involved in a nasty traffic incident. I was wondering if the forum has some stress engineers who might offer some advice on why this over 90 year old part failed. I repacked the wheel bearings and replaced the inner seal and brake linings in 1974. Have attached a few snaps of the item. I have no idea why the pics rotated on posting. They unrotate when you click on them. beats me.

Peter Toet

Attach file:

---

  (54.22 KB)


  (35.03 KB)


  (35.43 KB)


  (82.79 KB)

I assume it's not covered under Packards warranty anymore?

I'm sorry I couldn't resist, I have no idea what could of causes thay. I see you carry that motorcycle on the back, could the added weight have something to do with it?

Peter,

I know we're "down-under" but this is ridiculous! Instead, try these.

Photos taken with a mobile phone?

Attach file:

---

  (74.28 KB)


  (54.13 KB)


  (55.29 KB)

Thanks Mal, Yes, taken with a mobile phone.

The Indian and other bikes have been on the back for around 30 years. The bikes are Road registered and I do remove the bike and ride it around from time to time. I relieve the load on the springs when not travelling. I am fairly certain that the extra 300kg did not cause the failure as the drive is through the taper and key. Perhaps I overtightened the nut. I generally torque them to around 225 ft lbs, then maybe a bit more to fit the split pin. PT

It is hard to tell without examining the grain structure at the break. I would guess it experienced a low cycle fatigue failure caused by the threaded section flexing in relationship to the taper shaft. Possible cause a slight mismatch of the tapers. Could the key have been to high and prevented the two surfaces from forming a good contact on both surfaces?

Looks like a typical fatigue break, indicated by the "beach marks". When it comes to fatigue, sharp corners greatly increase the stress concentration and are areas where a crack can initiate, and then spread. When this happens you'll see telltale marks left in the broken parts, that look like beach marks. The attachment goes into this in depth.

Looks like the root of the thread ended in the corner. Since the thread comes to a point in the root localized stress here is going to be high.

For a fastener you always want to have it in tension so it is loaded higher than what will be seen in the application. This way the fastener is never subjected to cyclical reverse loading, which can eventually fatigue the fastener.

Attach file:

---

Size: 1,230.23 KB; Hits: 132

Over my 50+ years in the hobby I've seen that type of failure may 5 or 6 times, and more often on Chrysler products than Packard, not that that can be statistically significant.

I've no real knowledge of metallurgy or failure analysis, I always attributed it to a poor fit between the taper of the shaft and that of the drum. PS - I'm reminded that what at least two of the failures had in common was the use of a lubricant or antisieze compound on the taper.

That the shaft itself isn't bright and shiny leads me to believe, as others have said, that it didn't have a tight fit with the drum so was constantly moving a little which eventually fatigued the shaft to the point of breaking off. During my years as a prototype machinist, we would do districtive stress-testing and this type of break looks to be of the type described.

I had the exact same thing happen to me in a 1940 "110" I owned when I was in my 20s. Was doing about 35 mph and people in cars passing by were pointing and waving more than usual. Then suddenly I felt a thud and could tell the RR wheel was locked up and dragging. Pulled over and found the whole wheel and tire were jammed up into the fender. Went to a pay phone and called my dad who arranged for towing. Luckily the car was a'40 so the wheel remained contained and upright and didn't fall off completely or the car would have been skidding along on the fender.

Later examination showed the nut was still on the threaded end of the axle shaft which was rolling around inside the hubcap. A look at the break showed crystallization of the metal. As I recall I'd previously used a heavy hammer on a wheel puller to get the stubbornly stuck brake drum off the axle and figured the blows had caused the metal to crystallize, but was never certain. I was however very grateful I wasn't doing 65 on the freeway at the time.

Reviewing the pictures again I see some of the pictures show signs of rust on the male tapered shaft. The rust tends to further support that opinions that the male and female tapers did not have the correct fit. The picture with the key in place also shows signs of rust. Thus allowing the hub to flex slightly on the shaft.

If there is a lesson to be learned from this post, one should ensure that the wheel hub and tapered shaft are very clean and free of any lubricants. While not very experienced in this type of wheel fitment, I would guess that when gently sliding the drum on the shaft without a key as a test of the fit they should mate up with a snug fit. If not, then the reason should be investigated before doing a final installation with the a key.