Author Topic: Pattern for a small oscillating steam engine  (Read 6154 times)

PatJ

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Pattern for a small oscillating steam engine
« on: November 27, 2013, 04:15:05 PM »
Here is a pattern I made for a small oscillating steam engine a few years ago.

The original pattern was modeled in 3D, and printed in plastic on a 3D printer.

The pattern was then filled with Dap multipurpose spackling compound, and painted with Krylon spraypaint (because I had some on the shelf, most pattern makers use another product, the name of which eludes me at the moment, getting old, shellac perhaps?).
The filler added some curvature to the surfaces, and helped get some draft angle to make pattern release from the sand easier.

The sand used was petrobond.

The pattern was coated with paste wax (wipe it clean, don't leave wax residue on it) to allow it to release cleanly from the petrobond.

This was one of my first casting efforts, and I had a little gassing, but overall, it was a good learning effort.
« Last Edit: November 27, 2013, 04:21:36 PM by PatJ »

PatJ

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Re: Pattern for a small oscillating steam engine
« Reply #1 on: November 27, 2013, 04:20:04 PM »
I did not have much draft angle on the sides, but the pattern pulled ok after I put screws in the bottom, and tapped it in all directions to get a little clearance around the pattern, and to help break the sand from the pattern.

Just before pulling the pattern from the sand, I sort of walk it around in the tiny clearance beteen the sand and the pattern to sort of firm up the sides of the mold.

Here are the rusults.

Like I said, one of my first attempts at casting, so anything at all would have been ok with me.


PatJ

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Re: Pattern for a small oscillating steam engine
« Reply #2 on: November 27, 2013, 04:24:01 PM »
This is a bar stock version of the same engine.

I stuck my hand in there to give a sense of scale.

Offline b.lindsey

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Re: Pattern for a small oscillating steam engine
« Reply #3 on: November 27, 2013, 04:45:33 PM »
Very nice Pat. Did you make one from the casting as well? I have know about the use of 3D printing for patterns for some time now, but yours are the first I recall actually seeing. Looks like they turned out quite well too.

Bill

PatJ

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Re: Pattern for a small oscillating steam engine
« Reply #4 on: November 27, 2013, 05:14:53 PM »
Bill-

I have been in the learning curve since 2009, trying to learn machining, engine design and assembly, and more recently setting up a foundry and learning how to use it.

My tiny little brain has been through extreme confusion on many fronts about model making, how is it best done, how do I want to do it, etc.
Luckily my brain is so small that it does not have enough critical mass to self-explode, or else it would have already.
(Less is more as they say).

A good description of my efforts would be a blind man stumbling through a mine field that is littered with boulders.
You get the idea.

So no, I never built the engine from castings because once I learned 3D modeling, I wanted to take an entirely new approach to modeling, which is to create 3D models from scratch, with the design taylored for making patterns and then castings.

I had to toss everything about bar stock construction that I had learned over a two year period and "think outside the bar" to coin a phrase.

So my attempts now are for engines with cast passages, etc.
I don't like to drill passages, and I really only want minimal machining and finishing after the castings are made.

I have yet to complete a cast engine, but I have one in the works, and NAMES is approaching fast, so we shall see if the weather and the modeling gods will smile on me or cast me into the gates of foundry hell (foundry work can go either way).


PatJ

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Re: Pattern for a small oscillating steam engine
« Reply #5 on: November 27, 2013, 05:20:47 PM »
I have found that the best way to make a 3D printed pattern of high quality is to send it to a place in Knoxville TN that has a high-dollar 3D printer that uses powder deposition that is fused together somehow.

The 3D printers that use the plastic extrusion process are not ready for prime time (in my humble opinion), and are a waste of time and money until they improve.

My ultimate goal is to make patterns hand made in wood, but for small models with lots of tiny details, the high-resolution printing is really the way to go if you want the ultimate patterns.  3D printed patterns are not very strong or durable though, so best to cast them in bronze if you intend to reuse them indefinitely.

Offline metalmudler

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Re: Pattern for a small oscillating steam engine
« Reply #6 on: January 26, 2014, 04:12:55 PM »
Hey Pat,
I think you should build a few small engines from castings, then you will be able to better plan your patterns.There is shrinkage and the need for extra material in places to machine.I too have a home foundry. My own engine is also on the agenda.
Ambitious you are..
If you can afford to make or build a 3D printer for your patterns, rather than make some wood ones......   You can certainly afford castings/plans and material kit or two...   Make one or two, bang up some pics :ThumbsUp:

Paul
It's not done, until it's DONE... Even then there is something else to do to it !..

PatJ

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Re: Pattern for a small oscillating steam engine
« Reply #7 on: January 26, 2014, 04:37:49 PM »
Hey Paul-

Good to hear from you.

The engine above was one of the first things I cast in aluminum, and that was way back in 2011 I think.

At the time, I had only a vague idea of pattern making and casting.
Seems like I have progressed in light years since I did the engine above.

I have really made a lot of progress since then, successfully casting gray cast iron, and machining it, and I have figured out draft angle, machining allowances, shrinkage, pattern making, etc., and generally make patterns from wood these days.

It is winter, so I am not doing any pouring right now.

I generally design and build small workshop type engines, and prefer to do my own design and casting, since the engines I want to build cannot be bought in casting kits, or not in the quality and size I would like.  And there is nothing quite like seeing a design go from the computer screen to real life in metal.

Here is the latest item I cast last fall.

Good luck with your castings.
Post some pictures so we can see what you are buiding.

Pat J
« Last Edit: January 26, 2014, 04:41:26 PM by PatJ »

Offline chucketn

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Re: Pattern for a small oscillating steam engine
« Reply #8 on: January 26, 2014, 04:45:11 PM »
Pat, is that flywheel cast iron or aluminum?
Nice work,BTW.

Chuck

Offline metalmudler

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Re: Pattern for a small oscillating steam engine
« Reply #9 on: January 26, 2014, 07:10:59 PM »
Pat,
 That flywheel is bloody cool as mate! Pattern draft is improtant.. Your using that petrobond, lucky bugger!(fire clay and sharp sand and a secret quantity of moisture).. Ally, just carve out a channel in the outside and load it with lead if ya really have to or heat fit a steel rim.. Nice F@#Kn casting Bro!

Paul
It's not done, until it's DONE... Even then there is something else to do to it !..

Online Jasonb

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Re: Pattern for a small oscillating steam engine
« Reply #10 on: January 26, 2014, 07:39:53 PM »
Thats an iron flywheel so no need for added lead.

J

Offline metalmudler

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Re: Pattern for a small oscillating steam engine
« Reply #11 on: January 26, 2014, 07:51:38 PM »
Ohh, its iron, who said?.. Thanks for replying with the info on the flywheel Pat.... and Jason..
Nice work again mate, keep it up :)
It's not done, until it's DONE... Even then there is something else to do to it !..

Offline ian cable

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Re: Pattern for a small oscillating steam engine
« Reply #12 on: January 26, 2014, 08:10:36 PM »
hi pat a really nice piece of casting nice and clean. Ive found the best ally to use are Nissan cylinder heads , it machines beautifully cast easily and very strong for intricate parts it will cast down to 3mm wall thickness so ideal for engine sumps fins and lugs. Also very cheap from the scrappy ian c

PatJ

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Re: Pattern for a small oscillating steam engine
« Reply #13 on: January 27, 2014, 01:00:27 AM »
Hello all, thanks for the replys.

The flywheel is gray cast iron, as is the engine that will go with it (twin osciallator workshop engine).

I found a resin binder and some commercial round grain fine sand, and that mix is specifically designed to work at iron temperatures, and it works well.

I have only done two cast iron pours, then winter set in.

I started with aluminum, then went to brass, bronze, and then gray cast iron.
Cast iron is tricky, and more difficult and expensive than aluminum by a factor of about 10.
It takes a ton of heat to melt (a serious oil burner) and some high temperature refractory, as well as iron-rated crucibles.

I prefer machining gray cast iron to any other material, and so I hope to cast all my future engines from it.

Here is last fall's iron pour.

I can't wait until the weather improves and I can get back to it.
I still have a lot to learn about iron, but getting there.

Pat J

Pat J