First Lost-Foam Casting

[Hawkeye]

I'm replacing the exhaust system on my 1965 Honda Trail90. I haven't found one, so I'm making one. The muffler will consist of a 2" metal tube with two cast end bells. I made up the foam pattern on the lathe early in the week and coated it with drywall mud.
   

This morning, I fired up the foundry and melted down some scrap casting aluminum. Meanwhile, the pattern was spending a couple of hours in the oven at 150* to make sure it was very dry. The pour went well. I had a fan blowing across the top of the casting bucket, so the smoke and flames were kept out of the way. I had plenty of metal in the crucible to get a good head pressure.
   

Went to a coffee meet with the other old bikers and came back in the afternoon to shake out the casting. No bubbles or voids.
   

Machining was pretty straightforward. I got the forward bell pretty much done.
   
   
   

[Mayhem]

Looking good Hawkeye. Is the pot on the top your crucible or is that a reservoir for the mould?

[EdK]

Those castings turned out nice.

Ed

[the artfull-codger]

(03-16-2013, 11:22 PM)Hawkeye Wrote: I'm replacing the exhaust system on my 1965 Honda Trail90. I haven't found one, so I'm making one. The muffler will consist of a 2" metal tube with two cast end bells. I made up the foam pattern on the lathe early in the week and coated it with drywall mud.


This morning, I fired up the foundry and melted down some scrap casting aluminum. Meanwhile, the pattern was spending a couple of hours in the oven at 150* to make sure it was very dry. The pour went well. I had a fan blowing across the top of the casting bucket, so the smoke and flames were kept out of the way. I had plenty of metal in the crucible to get a good head pressure.


Went to a coffee meet with the other old bikers and came back in the afternoon to shake out the casting. No bubbles or voids.


Machining was pretty straightforward. I got the forward bell pretty much done.

Nice castings Hawkeye, love the tip about a fan blowing the smoke away,each time I've done lost foam castings you can't see to finish the pour & end up with it all over the place,never occoured to to me to use a fan!!! btw what's drywall mud?? is it the filler you use on the joints when dry lining with plasterboard?
Graham.

[DaveH]

Turned out great

DaveH

[ETC57]

The casting looks great Hawkeye and I'm envious of you having a tc90,
I keep looking for a couple of 70 vintage tc 90s or 100 for the wife and I.
Jerry

[stevec]

(03-17-2013, 11:09 AM)the artfull-codger Wrote: btw what's drywall mud?? is it the filler you use on the joints when dry lining with plasterboard?
Graham.

Graham, if I understand "dry lining" yes.
Does dry lining mean the procedure of speading the "mud" then applying the joint tape and then blending over with more mud to finish the joints of plasterboard.
(Dryboard's called Gyproc here)
Boy! local terminologies can be tricky on the WWW.
Oh, if I'm right about the above, why would it be called "DRY lining"?

[Sunset Machine]

"Taping mud" or "joint compound" here, used on "sheetrock". But I'd like to learn what purpose it has in lost foam casting...

[stevec]

Sunset, don't get mad at me, but did you read post #1?

[Sunset Machine]

<chuckle> We're pouring the metal on top of the foam, correct? Burning it out with a smoking fury, from inside of the mud shell? What's the mud do that the sand doesn't?