3/4" Scale J1e

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FKreider
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Re: 3/4" Scale J1e

Post by FKreider » Sun Dec 19, 2021 12:33 pm

jeffsmith wrote:
Sun Dec 19, 2021 11:53 am
Jack, don't forget to mention that any moisture and molten metal will cause a violent reaction. Not good.
This really isn't a big concern for investment casting because as Jack said the investment molds have been in a kiln for hours to burn out the wax and bring the mold up to temperature before metal is ever poured into it. Due to this process it would be impossible for any moisture to be left in the investment at that point.

Sand casting is a whole other story, "greensand" is water bonded where you are actually counting on the moisture and clay in the sand to hold the shape of your pattern so that you can pour the molten metal in. This is why greensand is part science - part art because you need moisture but not too much moisture otherwise yes bad things happen!

Master modelmaker Mr. Paul Hamler has a fantastic in-depth video on YouTube showing the investment casting process for a small home shop setup:

https://www.youtube.com/watch?v=06t2_2I2tZk
-Frank K.

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Greg_Lewis
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Re: 3/4" Scale J1e

Post by Greg_Lewis » Sun Dec 19, 2021 1:27 pm

FKreider wrote:
Sun Dec 19, 2021 12:33 pm

Sand casting is a whole other story, "greensand" is water bonded where you are actually counting on the moisture and clay in the sand to hold the shape of your pattern so that you can pour the molten metal in. This is why greensand is part science - part art because you need moisture but not too much moisture otherwise yes bad things happen!

Many years back I made a furnace and got some sand so I could cast aluminum. I did a few castings and one day I was in a hurry and didn't wait for the sand to temper out. I started the pour and the molten aluminum came back out of the sand like a volcano, which was, shall we say, interesting. :roll:
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.

rrnut-2
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Re: 3/4" Scale J1e

Post by rrnut-2 » Sun Dec 19, 2021 1:43 pm

Even putting metal that has a little water on it, into the pot is exciting!

Jim B

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Re: 3/4" Scale J1e

Post by Harold_V » Sun Dec 19, 2021 4:48 pm

What Jim said. And it need not have water on it when it is introduced to the molten mass in the crucible. Cold metal introduced to the discharge from a furnace will quickly condense moisture on its surface, causing a steam explosion when it is submerged (don't ask how I know).
It is good policy to prewarm metal above the dew point before introducing it to a crucible that contains molten metal.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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rmac
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Re: 3/4" Scale J1e

Post by rmac » Sun Dec 19, 2021 7:06 pm

FKreider wrote:
Sun Dec 19, 2021 12:33 pm
Master modelmaker Mr. Paul Hamler has a fantastic in-depth video on YouTube showing the investment casting process for a small home shop setup:
https://www.youtube.com/watch?v=06t2_2I2tZk
Thanks for that link! I now see how it all works. It's interesting that the investment material is porous enough that a vacuum will sort of suck the metal into the mold, but not so porous that it affects the finish on the cast parts.

One more question for Jack: What do you deliver to the foundry? Bare wax patterns? Wax patterns + investment? Or burned-out investment?

Thanks,

-- Russell Mac

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JBodenmann
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Re: 3/4" Scale J1e

Post by JBodenmann » Mon Dec 20, 2021 12:19 pm

Hello My Friends
I only send waxes to the foundry. I used to send my masters and have them make the molds. I lost some masters and molds when foundries sold or went broke. I lost all my 1-1/2 inch scale commonwealth brake rigging, and some 3/4" scale parts like that. I have since learned to make my own molds and as I said I only send out waxes now. If they get lost it's no big deal. I like to make masters mainly from brass. It machines and solders nicely. I do use plastic sometimes if there is an odd shaped part that requires hand shaping with files and such. Here is a photo of a mold for a 1-1/2" scale Sunbeam headlamp part. It is ready to be closed up and have the rubber poured in. And then we have a couple photos of some waxes for a small 1-1/2" scale air pump. This was the pump for the Disney American. No shortage of things to do!
Jack
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Pump1.jpeg
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rmac
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Re: 3/4" Scale J1e

Post by rmac » Mon Dec 20, 2021 2:14 pm

Thanks, Jack, for the extra info. As I said before, this is just fascinating to me.

Mike Walsh
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Re: 3/4" Scale J1e

Post by Mike Walsh » Mon Dec 20, 2021 9:01 pm

Harold_V wrote:
Sun Dec 19, 2021 4:48 pm
What Jim said. And it need not have water on it when it is introduced to the molten mass in the crucible. Cold metal introduced to the discharge from a furnace will quickly condense moisture on its surface, causing a steam explosion when it is submerged (don't ask how I know).
It is good policy to prewarm metal above the dew point before introducing it to a crucible that contains molten metal.

H
Harold is right.

I have seen the aftermath of a "pop," as they call it in the industry. Only, this pop had two pops... The first was a outward vertical pop, there was still metal on the roof of the building a few years later when it shut down. The second pop broke the pot in the furnace and blew out the "weep hole" that is used to detect if there is a cracked pot, with enough force to produce a 3/4" thick slab of aluminum about 8' wide, 20' long. Thankfully there were no team members walking by at that time - that could very well have been fatal for that team member. I won't go into the root cause, but let's just say that warming up your tools prior to handling molten aluminum is a critical factor in safe aluminum foundry practice. As a foundry engineer, I am often up on the pour deck watching team members and their pouring techniques as well as looking for any opportunities for improvement. I had just vacated my usual observing spot about ten minutes before the incident - a blessing at the time. I also keep my head on a swivel - if I see a new tool brought onto the pour deck that I do not know has been properly prepared for use (coated, dried, pre-warmed to dry out any moisture), I take about forty steps back to protect myself.

Thankfully the team member was not injured save for a few minor splatters of aluminum. Pretty sure his life flashed before his eyes, though.

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JBodenmann
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Re: 3/4" Scale J1e

Post by JBodenmann » Tue Dec 21, 2021 8:59 pm

Hello My Friends
Many years ago I was entertaining the thought of my own little foundry. There use to be an advertiser in Live Steam Mag. that sold foundry supplies. You could get the whole enchilada from them. Furnace, crucible, sand ,etc. And easy to follow instructions...I had the order form all filled out and my check book in hand. Ready to write the check. Then I thought to myself, do I really want to do this. I knew there would be surprises, failures, and puzzles to figure out. Few things are as easy as the pro's make it look. I already had far too many plates spinning. I didn't order the foundry stuff. I have fabricated a lot of things since then, and also learned to make molds for investment casting. I get by. :D
Jack
Last edited by JBodenmann on Tue Dec 21, 2021 10:09 pm, edited 1 time in total.

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Greg_Lewis
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Re: 3/4" Scale J1e

Post by Greg_Lewis » Tue Dec 21, 2021 9:12 pm

A wise move, Jack. After making a half-dozen pours, I realized I wasn't enjoying it, and decided there were other things I wanted to learn and to spend my time with, so I sold the furnace and related stuff and haven't missed it.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 35 years of turning perfectly good metal into bits of useless scrap.

Harold_V
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Re: 3/4" Scale J1e

Post by Harold_V » Wed Dec 22, 2021 4:11 pm

Interesting. A great deal depends on one's objective. I personally enjoy the challenges of doing pretty much everything myself. I am just now finishing construction of a non-ferrous melting furnace, one that will accommodate #30 bilge crucibles.

Doing everything in one's own shop results in much slower progress. If you enjoy the journey and don't care if your project never gets completed, doing all of it is a great idea. If you hope to build an engine (or any other involved project) and get it in use as quickly as you can, it's not the way to go.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

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JBodenmann
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Re: 3/4" Scale J1e

Post by JBodenmann » Fri Dec 24, 2021 12:25 pm

Hello My Friends
The hobby is different things for different people. Like Harold, I like doing it all myself. There is a great sense of satisfaction in that for me. Now that being said I will not make everything, such as nuts and bolts, many pipe fittings etc. I had my friend Doug wire EDM the throttle quadrants for the tiny throttle lever. What a cool process. I am a bit of a lunatic and sometimes get hung up on details. But I am having fun, and that's what it's all about. Merry Christmas and
See You In The Funny Pages...
Jack

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