Restoration Qs...Shackle's

[BRENT in 10-uh-C]

Originally Posted by Glenn C.

Brent, sometime back in postings on the fordbarn....someone posted pictures of repo shackles that had fractured during installation. Granted original shackles should not be compared with original shackles as far as metakurgy is concerned, but I just have a hard time dealing with the fact of welding on any forged component, that even momentarily during installation could fracture, possibly ruining someones day. Possibly for ever. I am not a metalurgical engineer, but I am cautious about the possibility of upsetting the molecular structure of forged components by welding, and heat treatment to original specs. At the end of the day.....does a points car really mean that much ?

Ok then, I now understand your position and your advice of caution. Thank you as I now feel better about what we are trying to accomplish. I also think the reference about the repro shackles was from Vince about 10 years ago. See if THIS jogs your memory regarding those broken shackles. At that time there were a few batches that had issues however that was corrected a long time ago much in part to Vince making others aware of this, ...but also note where this one broke in the pictures below. Like Doug mentioned above, the amount of heat that would be transferred into the piece during the build-up process would likely anneal or normalize the shaft making it soft, --not brittle like in the pictures below.

I would want to study the effects of the Casenite a bit more because I was under the impression it only case-hardened the surface area to resist abrasion or wear. When they were originally heat treated, maybe that is all the treating did too?? So, ..if the unit was originally forged, what affect did the heat treating after they were machined have on the forging? If none, what is the difference of using TIG weld to build up the shafts?

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[Glenn C.]

Tig welding may be the best solution Brent. I wish an engineer with a metalurigical background would jump in here with his opinion.

[BRENT in 10-uh-C]

Originally Posted by Glenn C.

Tig welding may be the best solution Brent. I wish an engineer with a metalurigical background would jump in here with his opinion.

IMHO, someone pretty close in my mind already has above.

[RockHillWill]

Has not anyone considered using a hollow mill tool to turn the OD of the shackles and use a brass sleeve?

I saw a pair of these shackles done this way, but for the life of me I cannot remember who showed them to me.

I just acquired a hollow mill that was long enough to do the shackles from McMaster-Carr. I used it to cut thru the studs in a manner that saved both the rear hub and the drum, as I was looking for good steel drums.

I also use hollow mills to turn down the diameters on rebuilding shifting levers. I built a fixture that holds the shift lever in the tool holder and insert the hollow mill into the head stock.

It would seem that if the wear was not excessive, using a hollow mill and a thin sleeve would work as the load would be distributed evenly along the length of the shanks, and welding would not be required.

It has been my experience that Casonite, as applied by an amateur (me!), has little depth, and should only be used to provide a marginal increase in wear characteristic, and not be counted on to provide much in the way of additional strength-especially over welding!

[Roger V]

When I restored my first fine point project (a long time ago), I couldn't find good original rear shackles. I had our Tool Room (a Ford stamping plant) rework the excessive wear. I don't remember what they did welding-wise but I had full confidence with them. I do recall that they turned them in a four-jaw chuck with a boring bar. They came out great. On another note I had a driver Tudor with apparently the shoddy repro rear shackles of a couple of decades ago. One time I was checking the rear end lube and happened to notice one of the shackles was broken. Unlike Brent's it broke diagonal across the bar through the grease fitting hole. It was a testimonial to the strength of the removable cross bar(nut end) which carried the weight for who knows how long! Based on both of these situations I wouldn't be overly worried.

[Bick in New Zealand]

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I have some unmachined double script shackles cast in silicone bronze by the late Fred Gooding. Maybe this is the way to go, at least you know what you are dealing with from the start.

[Tom Wesenberg]

Originally Posted by Bick in New Zealand

I have some unmachined double script shackles cast in silicone bronze by the late Fred Gooding. Maybe this is the way to go, at least you know what you are dealing with from the start.

I wasn't aware of these.
How did they work out in the long run?

[RandyinUtah]

I welded up a set of originals and turned them between centers with the a boring bar. They have been in service over 20 years with no problems and no heat treatment.

[k24556]

OK, I don't know much at all about Model A's, but I can help in the metallurgy department. Just because this is a forged part does not mean it is not weldable. For steels, the amount of carbon in the steel dictates the potential for strength. The use of other alloy elements such as chromium, molybdenum, etc will dictate the DEPTH to which the strength can be achieved.

In the 1920's steels that were used for forged parts such as a shackle which would see both wear and heavy impact type loads were generally medium carbon, (0.45 to 0.6% carbon) and were heat treated with respect to the intended use. If the part was a wear part, like a gear, then it would be surface hardened and maybe case-carburized to increase the carbon content on the surface, and thus the hardness upon heat treating. A part like a shackle, would probably be quenched and tempered to try to get the hardening (strengthening) as deep into the part as possible.

So how do you tell what you have? a bench grinder will work. If you grind on a low carbon bar (or tube steel) you will get a long shower of sparks with lots of (what I will call bursts). If you have a medium carbon or high carbon steel, the shower of sparks will be shorter and wider (grind on a broken drill bit, for example), If the sparks are orange, you have cast iron.

So as a rule of thumb, weldability goes DOWN as the carbon content goes up. I would put a cutoff of 0.30 carbon max as my point where welding would not be performed. There are NO high carbon content weld rods to produce a high carbon content weld deposit. thus any weld metal will not have the same wear and strehgth properties as the original part.

My guess is that shackles started as 0.50 or 0.60 Carbon steel and were forged and heat treated to last. Welding them could pose a risk of cracking, but there is some skill and luck associated with welding such steels. You can preheat the item being welded, or the next weld layer can be used to temper the material hardened by the first weld layer. This tempering approach is falls on the LUCK side.

I'm about a week away from taking the springs off my A. Unless there is something mystical about the shape of the shackle, and I was not concerned about originality, I would probably make them from high strength steel, probably AISI 4140. I would make two studs threaded on both ends and two clevises. I would machine a radius in the diameter transition of the studs to avoid stress concentration.

Hope this helps