Anyone want to speculate as to why this axle broke? The stub was very tight in the hub. The hub has an excellent taper. I find it curious that it broke inside of the hub. The hub is of the kind that has the surface turned flat. Might this have contributed to the problem? It seems this kind of hub would support on a smaller part of the axle.

Looks like it had several cracks in it before it broke.

Tom,

Give Don Lang a call. There was a car on the cross country tour which kept braking axles and I believe it was inside the hub like this. It was something to do with the hub. Don can give you the details.

Dave S.

One lucky fellow Tom...

I tried to pinch the pic to mark it up and show, but for some reason it won't let me pinch it.

Pictures and shadows can show false positives, but I think you caught this in good light.

In your picture 1, There was a scratch or a gouge on the surface that started at about 1205, kept at bending fatigue for a while, made it to the keyway and stopped. There was also a scratch or a gouge at 600 that also started bending fatigue and grew upward until it met the other one.

the keyway shows there was a third crack that started down and I believe this occured before the 1205 one made its way down and why the 1205 one stopped. Your last few miles were only held together by that little crescent shape that goes from about 630 to 900. LUCKY GUY.

Now that I told you where they started, care to look at your own picture and tell me why? Picture an oyster shell in your mind before you begin.....

I've reposted the pictures. The picture of the hub has been flipped and rotated as this may make it easier to see what happened.

p.s. This is not from my car.

I broke an axle inside a wire wheel rear hub. I always thought it was because I had let the nut get a little loose and the hub wobbled and eventially the axle broke. That hub doen't look like it fits well to me,but that may be my bifocals..

Jack, it was a wonderful fit. No wobble at all.

Looks like there are lines radiating out from the key way. Is that D shaped part in the photo the key? If it's not the key then it all most looks like the key way was cut too deep and a filler piece pushed in.

I agree with George, looks like more than one problem from the start, just took many years and miles to show up. Dave

George said: "Now that I told you where they started, care to look at your own picture and tell me why?"

I have no idea. Please elucidate.

Mark, that is not the key. It is just the way the metal broke. Keyway looks like the correct depth to me. I will double check. There was no "filler piece".

The oyster rings (Called beechng BTW) will ALWAYS have a central point as to where the crack began and grew over time to fatigue. I've spent a good portion of my career finding beech marks in some pretty sophisticated stuff and my eyes know what to look for.

Look at your shadows and cheat if you want, look where I said the cracks began and then watch the shadows turn arched and 'wash' away like a stone thrown in a pond. Each arch is an individual break that occured over time.

The top crack PROBABLY was first and longest duration as the steel is etched dark with oil and grease.

The keyway was hard to spot but I do see hints of rings about 1/2 way down.

The series of ring section defines slow and over time...a rough tear-away called 'catastrophic' is simply the point where the steel gave up in the final 'break'.

Now I will add...those initial surfaces may have been smooth and proper, and a sliver from the keyway, however microscopic may have worked to that 1205 and the 600 position...that we can't tell by just looking at pictures. As long as the volunteer metal sliver was harder than the other material, material will scratch and gouge, then again it could have just been a lather groove at that point.

I would suspect that the axle had a very slight bend right where the taper starts, and the unequal pressure as the wheel rotated caused it to slowly fatique and fatique and ....
Ask the owner if that wheel ran true, or did it have a very slight wobble to it?

The keyway runout is a stress raiser. There is more moment at the axle bearing, but more stress at the keyway. You have a fatigue failure. I don't see anything abnormal or strange about it.

An Axel that is not tight, and it dosn't take much, will break more axles then any thing. The stress point is where the Hub stops, and the Axle bearing begins. If the Bearing outer end cuts, or grooves the axle in any way, it acts like a piece of glass, and will break at that point. If the Axle nut is allowed to run loose, it will wear the taper, it can break the taper of the axle half way down in the hub, as all the stress is now on the key, and Axle. A loose Axle nut will also wear out the key ways, in the Axle, and worse the hub. A loose Axle nut will also wear the Axle, and Hub taper to where they don't come close to matching, and when that happens, there is no way to keep a wheel tight, or make one run true. The wheel in the picture was not tight, as the hub key looks over size from the picture, the inside of the hub, was hitting brake shoes, and or bolts. With an Axle, and hub key way wore, they are both junk, and not of service! I have read in two places years ago, in some applications of driving, it was recommended the Axles be replaced once a year! Herm.

George said: "As long as the volunteer metal sliver was harder than the other material, material will scratch and gouge, then again it could have just been a lather groove at that point."

So if I understand correctly, a piece of material may have gotten between the hub and axle? What is a lather groove? I have studied the axle more and I am sure that everything you have said is entirely correct. The oldest break is at 12:00.

Ken: Maybe so. I have followed this car, and don't remember any wheel wobble. That is not to say that it didn't though.

Ted said: "I don't see anything abnormal or strange about it."

It seemed weird to me that it broke well inside the hub. It seemed weird that it didn't break at the end of the keyway, or some other "natural" place.

Herm said: "An Axel that is not tight, and it dosn't take much, will break more axles then any thing."

Good point. Although this axle was very tight at the time of failure, that is not to say that it may have been run loose at some point in its career.

Herm said: "The wheel in the picture was not tight, as the hub key looks over size from the picture, the inside of the hub, was hitting brake shoes, and or bolts."

Not true. None of it. Hub was tight, keyway correct size (I measured it) and no hitting of bolts. Taper on both axle and hub are good.

Tom,

Do you know the type of service this axle experienced - i.e. were there accessory brakes (disc), was it on a speedster, or other "go fast" vehicle that underwent rapid acceleration and abrupt "wheel skidding" stops?

My eyes aren't as experienced as George's, but when cracks originate or terminate at the keyway slot I have to wonder what sort of extreme stress (if any) the axle endured. Wouldn't the keyway be the point of greatest impact of directional change - the point that has to endure and absorb the greatest kinetic energy?

True these parts are extremely durable, but not indestructible, and some folks put the items thru a lot more stress than the designers foresaw - "back in the day".

Dave

Dave, as George pointed out (if I understand correctly), and I believe him, the crack didn't start at the keyway, but about a quarter of a turn away. The car is a stock-motored 26 roadster. No speed equipment, no outside brakes.

OK, Thanks
Dave

Tom, you must have took the axle nut off then, and the stub axle shaft is loose in the hug in your picture? It looks like it wouldn't be even close to a 50 percent fit, from hub, to axle, and the inside of the hub taper looks like it is shiny, or a polished effect. The greatest stress on the axle should be the little space from the end of the bearing, to the begining of the hub. Also, just because the Nut can't be pulled tight any more, and you can't wiggle the wheel in the air, doesn't mean the wheel hub, is a good fit on the axle taper, and won't let it work to crystalize the axle, either inside the Hub, or out. Herm.

Tom,

sorry, I didn't mean 'lather' grove, I meant the type lathe!

Scracthes and gouges, even those left by a lathe with too pointed a tool, have a habit of being a magnet and concentrate all of the nearby streeses at the point of 'defect' The same thing holds true for things that are radiused for size change. Get the radius too small and all of the forces want to gather there.

Do look the break over carefully. Like I mentioned sometimes the pictures throw light and shadiows that can confuse. Even saying that I'm pretty sure at least one crack started at 12:05. But then it stopped which would suggest the keyway crack beat it to that location. You can tell by the color of the 'sugared' steel between the rings...the darker the color USUALLY the older the crack!

Thanks George.

Herm, yes the stub is just sitting in the hub to give an idea as to the break location. It actually goes in a little farther. I should have mentioned that at first.

Thanks Tom, Herm

The microstructure of steel is crystalline. Although a fatigue failure looks like it "crystallized and broke", it didn't. It just failed in fatigue.

Ford had a lot of problems with axles. That's why there's so many versions. I skimmed the thread and didn't see but did any one asked the date of the axle? Are there any markings like "FORD" inside the keyway? Outside? Does it show the hardness test marks in two places?