Engines > From Kits/Castings
Strictly.... “ Hot Air “
Alyn Foundry:
After a serious mishap with my latest build the foundry went into overdrive after a call for help.
My castings are ready 24 hours after the call. They sent me photos of the moulds. Take a good look at the second picture, what do you see ? ;)
Cheers Graham.
Twizseven:
Distinct lack of a route for the poured metal to reach its destination.
Colin
Jasonb:
I think they have scooped a bit out in the first photo though maybe Graham did not want to to feed the underside of the cylinder rather than the foot?
The foot and underside of the cylinder look concave, understandable where sand has been scooped out and meets the cylindrical part of teh cylinder but foot should look flatter. The shadow may be fooling us, the two green bits are the only uncut part and look straight, the red marks are exaggerated scallops where they have cut the runners
J
PS We also need full details of this mishap :LittleDevil:
Alyn Foundry:
--- Quote from: Jasonb on September 09, 2021, 06:24:14 PM ---
PS We also need full details of this mishap :LittleDevil:
--- End quote ---
Well, as we all make mistakes from time to time…. Not so much a mistake in this instance but an un noticed problem with the highly “ chilled “ top mounting lugs. It took several attempts to drill and ream the 3/16” hole and the bit must have followed the easiest route. The problem only became apparent after fitting the link motion.
The “ chill “ effect had also found itself in the three legged base. Even after several minutes in the gas Forge at around 850 degrees C followed by a very slow cooling ordinary HSS drills wouldn’t even mark the surface.
This casting has to have three holes at 120 degrees for 1/4” Whitworth tapping, 5.1 mm. The solid Carbide drill bit I ordered from eBay got lost in the post so I re remembered an old trick from my days at Chester UK.
Masonry bits are cheap as chips, with a really tough Carbide tip soldered onto a softer backing. Using my trusty Diamond in Borozon wheel I carefully re profiled the top cutting edge from the triangular top form to a single cutting face then gently removed the sides to get the desired 5.1 mm diameter. Back to the rotary table under the big drill press and within seconds the holes were through. I’ve never worked with such a tough casting, ever!!
Putting the threads in was also a serious challenge using a first taper Presto tap. Needless to say I will be needing a new one. I just managed to get a three to four turn start in each hole ( 1/4” thickness ) before risking a breakage. This foundry is definitely NOT on my Christmas card list….
Cheers Graham.
Jasonb:
Temp sounds OK but would have thought a bit longer heating time needed.
Would the pivot on the top of the cylinder be less likely to give problems if you did not core the slot, makes it a bigger lump so should not cool as fast and easy enough to mill the slot.
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