Thanks for that Neil, I'll give them a call.
Yes, trying to cast an exhaust port insert to extend the duct, then another casting of a jacket to surround and water-cool said extension.
All attempts so far have been very poor, with much pitting on the surface, and unacceptable shrinkage.
I'm using the lost wax method, and the shrinkage of the wax is the main problem.
It has to be cast, as there's no way to machine a billet to exactly match the weird contours of the port, which I need to ensure the inner part of the insert makes good contact wth the existing water-cooled surface.
With the latest attempt, I've dipped the wax mold in more wax to add some bulk to counteract the shrinkage. Probably lost some contour definition in the process.
Nothing is easy...
bees wax, much less shrinkage.
Mate. I hear it's the same as the aussie stuff. Storm in a Teacup. With coperate Egos attached.
Sorry about that.
Don't you look at my accountant.
He's the only one I've got.
Storm in a Tea tree!..
Sorry about that!
Quick Update: Kero/Oil burner has been fired up a few times with dramatic & inconsistent results. (Sorry, no Video)
The fuel needle valve had been re-tapered in the past by someone with a grinder!!!
Removed it and turned it in the lathe, hoping for better results now.
Still not too sure on the required supply pressure (somewhere, I guess, between 7 & 30 psi.??)
Cheers, Daryl
RISERING TO THE OCCASION:
A friend who mucks around with pumps and other hydraulic/fluidic related gizmos had the need for some design of a mixing chamber and wondered if we could machine up a part for him. As it was a relatively simple job and he was in no real hurry, I volunteered to try casting it for him. Silly mistake.
So, printed up a pattern and cleaned it up and primer surfaced it. The easy part. Basic casting size is 20 thick and Ø110. A bit chunky really.
Trial 1. Used classic runner gating system designed using Foseco guidelines (thanks MM) with 5 risers. Filled easily, but huge shrinkage around the central boss.
Call this a FAIL.
To be continued...….
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
RISERING TO THE OCCASION:
Forgot to say that I am using CO2 for the sands. Using Superfine sand for the facing sand and coarse Foundry sand for the backing. Must say the CO2 process is really convenient.
Trial 2. Moulded it upside down, with a huge sprue/riser in the middle. That should do it. Nope, Similar shrinkage, not as bad though.
Call this a FAIL
To be continued.
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
how a feeder should work, should be the last metal to freeze off so as to feed the shrikage occuring in the mold. Technically the 'freeze' line should start at the bottom and finally finish freezing over at the top of the riser. Thermal sleeves help for this and the magnesium powder that is sprinkled on the the riser as the metal is still molten. This fires up to ensure the riser solidifies last. When all is finished and you are breaking open the mold you should see a large depression under the remains of the magnesium powder, the result of the sum total of all the shrinkage in the whole casting. If you see this you know you have a sound casting. If you don't, you will find shinkage voids within the casting as its machined. The shrinkage is there wether you want it or not, just have to control it and put it out of harms way, top of the riser / feeder.
RISERING TO THE OCCASION:
Trial 3. Stuff these fails, I know better (?) he says. Because the section is so thick, I think a chill is the order of the day, this being a preheated 10 mm steel plate on which the mould sat. The idea this acts as a cool, high conductivity piece of the mould cavity, causing the metal that contacts it will freeze off first. Being on the bottom, this will create a “directional solidification” effect, and the risers just feeding a gradual rising frozen level. Just as Fletto explained in his post above. It was filled down the centre sprue/riser.
Well, sort of worked, but the thing leaked and still had shrinkage. Thinking this was then a lack of feeding (ie riser size) the plan was next to do the same, but with larger risers.
Call this a FAIL
To be continued…
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
RISERING TO THE OCCASION:
Trial 4 & final. It was fail & go CNC or just go success. Went for the latter. Same as 3., but increased the riser effectivness by both increasing their size and also adding more mass by interconnecting them. She says it’s like holding hands. Plus a hold down weight. We tried some time ago to get some magnesium flux, but the local Foseco dude has fallen off, so will get some via Sydney, seems to be the go. In its absence, I just set up an LPG torch and played a healthy flame onto the top of the risers.
Anyways, all going thru heat treatment so will see what the man says when he does initial machining.
Morale of the story is to only do thin wall stuff or be prepared to add shitloads of risers & magnesium fluxes...
Call this a success..
End of story…
"Success is the ability to go from one failure to another with no loss of enthusiasm.”
The local foundry guys made a little casting for me that had similarities to that. They had the shape at the bottom of a depression in an open mold and just poured aluminium into it. Nice and simple and worked great. I'm no expert, obviously, but it seemed you complicated it more than needed, by comparison.
I use these things for the risers. Thermal sleeves.
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