Some "Groovy" Half Shafts - need advise

[Stephen B.]

I soaked these half shafts in a solution to remove rust. As you can see, a groove was created by the solution. I wonder if these half shafts are ruin, or are the still safe? I was also thinking of seeing if someone locally could install the flanges on a new shaft. Thanks in advance.

[Michael W.]

Re: Some "Groovy" Half Shafts - need advise

What makes you think that the groove is not actually a crack?

[Stephen B.]

Re: Some "Groovy" Half Shafts - need advise

Both half shafts were not cracked before I left them in the solution. The lines coorelate with the level of the solution in the 5 gallon bucket. I was surprised that the solution ate into the metal.

[Chuck S.]

Re: Some "Groovy" Half Shafts - need advise

Stephen...If it were me, and these were for my restoration, I would find some good used shafts, or check out those repros someone mentioned. What happened?...Did you leave your half shaft in acid overnight?

Material loss is not significant enough to be a concern in my opinion, but that groove nicely scored the tube...it would have to blended smoothly with a die grinder as a minimum. I believe the grinding would pretty much compromise the "restoration potential" of the halfshafts.

Another concern would be the fact that the OTHER yoke was immersed in the solution, and the universal joint "fits" in the yoke may be enlarged enough to cause future problems for you. Mechanical cleaning may be the better way to go in this case.

[Stephen B.]

Re: Some "Groovy" Half Shafts - need advise

I left them in the solution too long. My plans are to restore the half shafts to NCRS specs even with the grooves for practice. I have two 1970 cars, and these are to be installed on the driver. I occasionally have the driver car judged to see how well my restoration techniques hold up to scrutiny. I bet those grooves are worth a point or two. lol.

I just don't want to step down on the gas one day and they break.

[Joe R.]

Re: Some "Groovy" Half Shafts - need advise

Stephen,

Sorry, but those half shafts were gone long before the acid treatment. It would take you more than several hours to grind those pits out and make them presentable. Attend the next swap meet and see if you can find some that are not rusted beyond help.

You can purchase new half shafts (reproductions) from Bair's. They will not receive full points because they have been turned on a lathe rather than using electric weld pipe. But they are safe, look nice and require no backbreaking labor.

JR

[Keith L.]

Re: Some "Groovy" Half Shafts - need advise

What did you soak them in and how long did you leave them?

[Steve L.]

Re: Some "Groovy" Half Shafts - need advise

This looks like a crack to me. ...a torsional crack since it is at an angle. I think the acid treatment only made it show up. I wouldn't trust this shaft.

[Alan S.]

Re: Some "Groovy" Half Shafts - need advise

Hi Stephen,
Your pictures are very interesting.
I left (forgot) about some bolts in a rust removing solution from one Saturday to the next. I was amazed how little of the bolts was left.
I also like you're statement about having your car judged to see how your restoration techniques are viewed on the field!!!!
Regards,
Alan

[Dennis C.]

Re: Some "Groovy" Half Shafts - need advise

I also think it looks like a crack. It's possible the crack was not visible until the rust was loosened. I would think if it was the result of the solution, it would appear more evenly along the shaft.

Have you tried examining it under a magnifying glass? Also, try probing it with a pick to gauge the depth.

Regards,

Dennis

[David S.]

Re: Some "Groovy" Half Shafts - need advise

It almost looks like an arc strike that preferentially etched being metallurgically "different" than the parent material. I'm not familiar with what welding technique was used in production so this assessment may be incorrect. Do you have access to anyone who could take a photomicrograph of the anomaly?

[Edward C.]

Re: Some "Groovy" Half Shafts - need advise

Take them to a machine shop and have the groove magnafluxed and that will show if it is a crack if you really want to use them. It should not be an expensive test. Good used shafts would be the best option in my opinion. Ed

[Chuck S.]

Re: Some "Groovy" Half Shafts - need advise

This looks like a crack to me. ...a torsional crack since it is at an angle. I think the acid treatment only made it show up. I wouldn't trust this shaft.

My instinct tells me the mode of failure for a tubular carbon steel half shaft would not be torsional cracking.

The steel in the tube is too ductile to fail by cracking. Steel has a yield strength where it begins to stretch and elongate before ultimate failure. More likely, the shaft would twist significantly before failure.

Fatigue failure would produce such a crack, but it would not be as obvious as this, with or without acid cleaning. A fatigue crack would be virtually invisible to the naked eye without magnaflux or dye penetrant testing,

It is not a crack...Stephen left the shaft in a bucket of cleaning solution leaning at an angle. It was pretty easy for him to connect the "groove" to the angle of the solution when he removed it and observed the damage. Also, notice the darkened area immediatedly above the "groove" before the area was wire brushed; the darkening is from fumes related to chemical activity...there is no explanation for one side of a crack to darken like that, and it would have been obvious before cleaning.

The curious thing is why the "cleaning" activity was so much more vigorous near the solution surface. If the solution activity is accelerated by oxygen from the air, that could be an explanation. That's why I was interested in the solution used.

[John H.]

Re: Some "Groovy" Half Shafts - need advise

Here are a couple of photos of the "torsional" failure mode, incipient and complete. The pair on the bench, showing a pronounced twist, came off a slightly modified '67 L-89 on stock tires (sheer luck they were spotted before they failed), and the ones on the floor were on a '67 with a 540 Merlin and 8" slicks.

[Joe R.]

Re: Some "Groovy" Half Shafts - need advise

John has just shown examples of what can happen when the short shafts are rusted beyond help.

Scrap these puppies! They cannot be helped.

JR