Broken casting – Best repair?

[John McCullaParticipant @johnmcculla]

<p style=”text-align: left;”>I appreciate that this is not exactly model engineering, but I thought it worth asking anyway.</p>
My 1957 FE35 tractor has a broken casting. The rear diff housing has four threaded holes around the PTO shaft which takes threaded studs and secure mounting plates which hold check chains for the link arms. At some point in its life one of those chains appears to have experienced a shock load, breaking the stud out of the casting. Can anyone suggest a viable repair method? It isn’t worth replacing the whole housing, the tractor works fine as it is, but I would like it fixed. I don’t think I could weld it, the part is too large to preheat. It can’t be helicoiled, because half the hole is missing. Any ideas?

[halfnutParticipant @halfnut]

Welding is the only way to fix that with sufficient strength. You might be able to bodge it up by making a square plate held by the existing 3 studs and having a 4th stud in that plate. Is it really that necessary?

[noel shelleyParticipant @noelshelley55608]

I have one in the garden ! Halfnut has beaten me to it, A square plate on 3 studs and the forth welded in would be the way I would go. I would only weld the diff case for the look of the thing and not expect any great strength in it. Good luck. Noel.

[DiogenesParticipant @diogenes]

JB Weld – same end result as outlined by Noel & Halfnut but without the necessity to heat the case / disturb the seal &or bearing.

 

[Robert Atkinson 2Participant @robertatkinson2]

Replace the existing plate (seal retainer?) with a larger / thicker one with 6 holes (3 for bolts) one threaded for new stud. The stud could extend into the broken casting and be built up with metal filled epoxy so it get a bit of support and looks nice.

Robert.

[VicParticipant @vic]

I was gifted an old Motorcycle many years ago. When I removed the carburettor to work on it I noticed one of the two wings for the mounting bolts had at one time been completely snapped off. It had been repaired with some type of metal loaded epoxy? The repair was surprisingly quite satisfactory.

[Bo’sunParticipant @bosun58570]

Another vote for an additional plate as halfnut & noel have suggested.  That’s always assuming the remaining two studs can be extracted for longer studs or bolts.  With a bit of thought, it could be made to look as if it were meant to be there.

Good luck John.  These fine machines (for their day) are worth preserving.

[Clive FosterParticipant @clivefoster55965]

A weld repair without preheat is possible with an arc welder using the old “field expedient” puddling technique. Once upon a time this was an official method.

The fine current control possible with modern inverter welders has made this technique much easier.

Basic idea is to build up several thin layers of weld using minimum current on the cast iron surfaces to separate the cast iron from the weld joint proper. Low current minimises the heat input significantly reducing the carbon transfer from cast iron to weld metal that causes a hard, brittle joint. Peening the weld using the chipping hammer as it cools removes most, hopefully all, of the cooling contraction stresses. 5 to 8 thin layers should do it. On an old casting like that expect to be burning out soaked in oil and, possibly, excess carbon. Probably have to grind back the first couple of layers and start over.

Use the most ductile rod you can find. The inexpensive ones sold for amateur use can be surprisingly good. I was given an unmarked box of China sourced rods that absolutely aren’t what the code on the rod claims but are remarkably good for this.

Before starting the initial weld build up you need the joint well Veed out so there is room to make the final joint with several layers at a lower than normal current. Do the final joint with several thinner than normal layers peening after each run and waiting for things to cool between runs.

Takes forever but the joint is decently strong although I’d not risk a pure tensile loading.

Whatever you do never, ten thousand times never, use a rod for cast iron without preheating. The result will be uber hard, often brittle and liable to shock failure.

Clive

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