Hello all,
I have a cracked flange on a D4 pony motor, P/N 5B5105, and I was curious what the best repair method would be. I've seen some people say that it's cast iron, but it looks more like a steel to me so welding might be better than brazing. What are your thoughts here?
 
Thanks, 
Mike

I have has good luck using 7018 SMAW on larger castings on the old cats, a TIG welder would be very handy for a small item like that, of course grind / v out the brakes and fill, Preheating part to 200F before welding and air cool when your done.

cast iron /cast steel the best method is bronze welding with a oxy-torch soak the part is water based degreaser for a day or 2 rinse well, vee out the joint and bronze it up not it must be preheated first so "borrow" the oven and heat it to around 150 to 200 deg celcius for at least a hour before trying to weld. it will also need slow cooling so a steel bucket or a old drum filled with dry sand dig suitable hole and light a fire in hole to preheat the hole this can be burning while you weld. bury the part in the heated sand and let cool for a couple of days
grind and file the weld so its only just proud of the surface and hose no sharp edges it should last for decades.

the preheat helps prevent cracking and also help dry and pull impurities from the metal. the slow cooling prevent post cracking.

you can use flux coated or plain rods with flux flux coated are easier to work with available in a handy pack for those small jobs

I'd just put a metal plate under it with correct holes, and use countersunk screws to connect metal plate to the casting.
Or use bronze brazing.
Arc welds in cast iron do tend to crack

Everything trainzkid88 said is right on the money - Nicad DC welding or stainless can cause stress cracks. If you heat with wood can use nice warm ashes to imbed piece in.

While you have everything apart, check the shaft and pully. Some of those were made out of balance and that what causes the ear to break. Some have put the pully on the lath and ground out the inside where the weights are to even it up.

I might have a good used housing if you want one.

To determine cast iron or cast steel, hit it with a regular angle grinder and pay attention to the color of the sparks it throws. Bright yellow is steel. The duller orange/red will be iron.

If it’s cast iron and you choose to Ni-rod, first research the proper blend to use. One blend is extremely hard and not very machinable. You may want to grind the welds afterward and you’ll cuss yourself if you use that one. The machinable blend is plenty strong enough for what you are doing. Once you finish grinding your welds smooth, and the workpiece is still fairly hot, hit it with a needle scaler. It will relieve the stress. And it will actually disguise your repairs by adding dimples to the surface to look like the roughness of the original casting.
If it’s cast steel, same concept with the needle scaler to disguise your repair.
Good luck.