Author Topic: AOGís Stuart S50ish completed  (Read 858 times)

Offline AOG

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AOGís Stuart S50ish completed
« on: December 27, 2018, 07:57:00 PM »
Itís finished and it runs but Iím not super happy with it. I set out to build a Stuart S50 but the final product is more fabrication than Stuart casting. I should be happy that Iíve come far enough in my model engineering skill set that I can fabricate replacements for the armor piercing castings from Stuart. (Thanks Elmer) but I wanted to build a Stuart S50. I will be revisiting this design.

Here is the video:



Here are some pics:







Till next time

Tony


Sent from my iPad using Tapatalk
« Last Edit: December 27, 2018, 08:04:09 PM by AOG »

Offline Gas_mantle

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Re: AOGís Stuart S50ish completed
« Reply #1 on: December 27, 2018, 08:13:18 PM »
Looks great to me Tony, and seems to run well :-)

Congrats  :cheers:


Offline b.lindsey

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Re: AOGís Stuart S50ish completed
« Reply #2 on: December 27, 2018, 10:52:05 PM »
I agree...looks and runs well. Sweet sound too....what's not to like?  :ThumbsUp:

Bill

Offline AOG

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Re: AOGís Stuart S50ish completed
« Reply #3 on: December 27, 2018, 11:23:26 PM »
For some reason my inability to rescue the hardened castings is really sticking in my throat and I canít even tell you why. I guess that I have come to see the fabrication as taking the easy way out. As someone with a closet full of Stuart castings on his build list, this is something I need to be able to address without access to a heat treat oven. Time for a little research.

Tony

Online Kim

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Re: AOGís Stuart S50ish completed
« Reply #4 on: December 28, 2018, 12:08:43 AM »
Tony, nice work on the engine!  It seems to run quite well :)

Sorry about the hardened castings.  I can't help you much there, others will have to comment.
Kim

Offline crueby

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Re: AOGís Stuart S50ish completed
« Reply #5 on: December 28, 2018, 12:55:20 AM »
Many years ago I built that same engine, and had a couple hard spots in the base that ate some drill bits for breakfast.  :censored:

At the time I was able to get Stuart to replace the base casting - is that still a possibility today? I think they have changed hands since then, dont know their current policies on that problem, but it could be worth asking them.
I have never tried annealing cast iron parts (at the time I did not have any torch setup either) - question for those who know: what IS the procedure for it? How hot for how long, any special cooling required? For the most part I have gone to bar-stock fabrication for everything, but once in a while I still do one from castings, and if its do-able it would be good to know.
Chris


Offline 10KPete

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Re: AOGís Stuart S50ish completed
« Reply #6 on: December 28, 2018, 01:20:35 AM »
Converting "white" cast iron to grey is really simple. Heat the part to a good red then let it cool slowly. I've done this in the charcoal grill, a wood stove, a forge and a potters kiln. Oh, and a torch worked well too. A bucket of very dry sand, or better, wood ash will blanket the part for slow cooling. Vermiculite, pumice, etc.

Use what you have....

 :cheers:

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline crueby

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Re: AOGís Stuart S50ish completed
« Reply #7 on: December 28, 2018, 01:52:27 AM »
What do the terms White and Grey cast iron mean?

Offline 10KPete

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Re: AOGís Stuart S50ish completed
« Reply #8 on: December 28, 2018, 03:35:02 AM »
Grey iron is what you are used to. White iron is very hard and is created when a grey iron pour chills too fast somewhere.

Quenched, so to speak...

So, like most metals with lots of carbon, annealing softens it up.

 :cheers:

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline AOG

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Re: AOGís Stuart S50ish completed
« Reply #9 on: December 28, 2018, 04:06:53 AM »
Thanks Pete, thatís what I was looking for. So if I understand you correctly. I should get a Webber and bed the castings in some sand. Then burn some hardwood charcoal over it for a few hours and let it cool to ambient and they should anneal.

Tony

Offline 10KPete

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Re: AOGís Stuart S50ish completed
« Reply #10 on: December 28, 2018, 05:32:36 AM »
The iron should go right in the middle of the fire and be brought up to a good red heat and kept at that temperature so the heat is all the way through. Longer is better.

If you do this in a furnace or kiln, you can then let the temperature come down on it's own after you turn off the furnace or kiln. The furnace/kiln/forge what ever must have enough mass to hold the heat and let the temp down slowly. Example: a 5 pound piece of iron should soak at heat for about an hour and then be cooled over night.

If heated with a torch, you'll need some way to insulate the part so it will cool slowly. A bucket/barrel of pumice like is sold in nurseries for plants is excellent. Make sure it's dry!

So out of the heat and instantly into the media for cooling...

Hope this helps,

Pete
Craftsman, Tinkerer, Curious Person.
Retired, finally!
SB 10K lathe, Benchmaster mill. And stuff.

Offline Jo

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Re: AOGís Stuart S50ish completed
« Reply #11 on: December 28, 2018, 08:50:01 AM »
We have been successfully heat treating suspect Iron castings in my log burner this month. They are put in before I start the fire and left in over night and taken out once cooled with the ashes in the morning. Even the thin flashing has been soft enough to attack with a file :)

Jo
Usus est optimum magister

Offline Jasonb

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Re: AOGís Stuart S50ish completed
« Reply #12 on: December 28, 2018, 12:37:34 PM »
I think the temp is about 750 to 775 degrees C at which point the iron will no longer be magnetic.

I've had mixed results, mostly I can get it soft enough to machine though it is still not as soft as iron bar. Flat or turned surfaces are not such an issue with carbide tipped tooling but that does not help if you need to drill or tap the offending area. I usually use a propane torch on smaller items but may have a go with a fire if Jo has had good results when I next find some hard castings.

Offline ShopShoe

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Re: AOGís Stuart S50ish completed
« Reply #13 on: December 28, 2018, 01:11:00 PM »
Congratulations on a good project finished.

Runs Well, Looks good. You did well dealing with what you had.

Thank You for posting.

ShopShoe

Offline rjconway

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Re: AOGís Stuart S50ish completed
« Reply #14 on: December 31, 2018, 10:19:04 AM »
Nice looking model int he end...
Which castings caused you the most trouble ?  I have just started and the flywheel (the only part besides the base) took a number of tools to the grave.  It turned out OK in the end however I am concerned with the cylinder the most.   HSS tool I could see vanishing before my eyes before I tried a carbide tool which again struggled.

The base machined very easily and I used a high speed router table.  (actually its my CNC router)