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Casting a Model Westinghouse-Type Twin Steam Engine in Iron

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tom osselton:
I’ve been watching “ Windy hill foundry “ on YouTube and he seems to anneal everything that needs machining.

vtsteam:
Yup, me too, just working up from the earliest videos so far. Though he calls it "stress relief", which would make sense for larger castings, but doesn't for much of the small stuff he does. I think the real advantage is he's probably annealing which is a legitimate benefit since he uses disk rotors as melting stock. I see he adds a lot of ferrosilicon, too.

Maybe he gets better in the later videos, but wow, IMO he over-rams stuff in the early ones, and then you definitely need vents, which means more cleanup and rougher castings. On the other hand he doesn't seem to get any side packing near the pattern at all so he gets a lot of flash and breakaways.

I really think Ironman has got the most impressive molding finesse, and beautiful looking castings as a result. But Windy Hill is good fun to watch, and he has some good and interesting ideas (I like the long screw for pulling patterns, and his disk crusher is cool) and he gives a good idea of what's required for a small production business.

vtsteam:
Had high hopes for the second round of heat treatment for the third casting attempt, but milling showed it still had some hard spots on the thinnest part of the casting -- the lower crankcase around the base flange ( < 0.25", 6mm thick).

The upper flange machined nicely, and the exhaust boss did as well so there was improvement. But I have to face it, there's no saving this casting. For thin casting sections, disk rotor metal appears to have been a poor choice -- unless additional ferrosilicon might have made a difference. But .35% was already a substantial amount. I do think steam radiator iron might have been a better metal to use, and If I had done, the casting might have been successful.

But another possible approach would be not to core out the crankcase and bores at all, and just open out those spaces after casting. That might actually be easier anyway because coring leaves hard to remove inner surface sand inclusions and scale particularly on a small size casting. And those rough surfaces would requiring milling anyway. So there's not much savings in machining.

Also, small cylinder bores in a twin are unlikely  to be perfectly centered and aligned when cored, that makes a milling cutter the only way to adjust those locations. If machining a solid casting, however, the centers can be accurately located by drilling.

I think it makes sense to core larger cylinders because they can be more easily cleaned and bored afterwards, and you're eliminating a lot of excess metal in the casting, but these were only 3/4" in diameter. Better to drill that out from the solid.

So, one more lesson learned....well several lessons learned!  :coffee:  I may try a solid casting of the twin next.  :dremel:

vtsteam:
Fourth attempt:
1/3 Disk brake rotor iron
2/3 Radiator iron
increased ferrosilicon to 0.45%
no cores
About 8 lbs charge
Melt time 40 Minutes to pour

Slag was quite fluid and tended to reform quickly

Pour went well, 1 small ingot left over.

This ingot broken in half shows very fine grained gray iron throughout.

tom osselton:
That ingot looks good but the ferro silicon seems way high. It would be interesting to see how the two types of cast turn out with the regular amount of ferro silicon and I wonder if the fluidity of the slag is a indication of pouring temp or ferro silicon needed.

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