Author Topic: Galloway Castings  (Read 22217 times)

Offline metalmad

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Re: Galloway Castings
« Reply #30 on: December 22, 2013, 09:46:39 AM »
Hi Pat
Have you started the patterns yet?
I'm looking forward to see this one come together  :ThumbsUp:
Pete
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PatJ

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Re: Galloway Castings
« Reply #31 on: December 22, 2013, 09:55:10 AM »
Thanks Jo, Metalmad-

At this point, I am trying to enlist my buddy in CA (the country) to make the patterns for this engine on his new large-format CNC machine.

I could hand-make the patterns and core boxes, but it would certainly expedite things if I had some help.

I don't really have a schedule for this engine.
I work on it in my spare time.

Once I get all the machining allowances added to the model, and define the core prints and core boxes, then the pattern making can begin.
I am using resin-bound sand, and so the fact that the sand sets and hardens should aleviate most of the sand problems that one would normally run into with complex cores and patterns.  I plan on casting the water jacket/passages in the cylinder and head like the factory did it.

Offline steamer

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Re: Galloway Castings
« Reply #32 on: December 22, 2013, 10:25:46 AM »
THAT's the way to make a pattern!....

If you're going to machine a pattern, you might want to consider aluminum.   It isn't really anymore difficult to machine than MDF, ect, and is far more durable should you want to make more that a few castings.....especially patterns in the small sizes that are easy to damage during ramming if made of wood.

Dave
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Offline gbritnell

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Re: Galloway Castings
« Reply #33 on: December 22, 2013, 04:44:08 PM »
Hi Pat,
In regard to your flywheel spoke construction here's a way you can get the shape you need.
1. Create your rim and hub
2. create a workplane through the axis of spoke.
3. draw the profile, taper part way up then the remaining taper I presume at a different angle.
4. do a revolve on the profile and you will get your spoke.
5. fillet the spoke into the hub and rim.
gbritnell
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PatJ

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Re: Galloway Castings
« Reply #34 on: December 22, 2013, 05:34:06 PM »
THAT's the way to make a pattern!....

If you're going to machine a pattern, you might want to consider aluminum.   It isn't really anymore difficult to machine than MDF, ect, and is far more durable should you want to make more that a few castings.....especially patterns in the small sizes that are easy to damage during ramming if made of wood.

Dave

I have considered using aluminum for patterns, but in larger sizes, the cost can get prohibitive, and I think bit wear would be greater.
I have had trouble with both wood and plastic patterns breaking due to ramming, handling, and mainly pulling the pattern from the sand.

One idea I am going to try is to make temporary patterns in wood with double shrinkage, and then cast those in zamak-27, which has a low melting point, good fluidity and is very strong metal for applications that don't require operation at elevated temperatures.

I think zamak-27 is as strong as cold-rolled steel, although not as hard, and it machines and finishes very well.
It does not drill very well, but I don't need to drill it for patterns.

And with self-hardening fine sand, I can make a pretty clean copy of the master pattern, since the sand sets before the pattern is pulled, thus no distortion is added by having to tap on the pattern to release it from the sand, and no distortion from having to ram the cope up against the drag, since the drag sand is set (hardened).

I could use aluminum for casting metal patterns, but zamak is not as gummy as AL356, it saws easier and machines cleaner than 356, melts at a lower temperature, is much stronger than AL, and pours with much more fluidity than AL.

The photo below shows an ingot of zamak-27 with a single pass of a fly cutter, which feels very smooth to the touch, and then on the lower right sanding lightly with fine sandpaper, and upper right with a wire brush.  The light sanding is a good method.
The wire brushing tends to melt the metal, so that is not good, but I don't need to wire brush a pattern.
« Last Edit: December 22, 2013, 05:38:56 PM by PatJ »

PatJ

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Re: Galloway Castings
« Reply #35 on: December 22, 2013, 05:43:31 PM »
Hi Pat,
In regard to your flywheel spoke construction here's a way you can get the shape you need.
1. Create your rim and hub
2. create a workplane through the axis of spoke.
3. draw the profile, taper part way up then the remaining taper I presume at a different angle.
4. do a revolve on the profile and you will get your spoke.
5. fillet the spoke into the hub and rim.
gbritnell

George-
I am not sure why my lofted spoke won't fillet, but I did try extruding an ellipse while using a taper, and the result is not usable, and not the same as lofting through two or more ellipses.

I need to experiment with the filleting to figure out how to fillet a lofted shape without having to fudge it.

I don't know how to draw a profile and then revolve it into an ellipsoidal shape, I would think the spoke would come out circular in section?

Offline steamer

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Re: Galloway Castings
« Reply #36 on: December 22, 2013, 06:12:11 PM »
I think the biggest expense with a CNC is going to be the cycle time....and any futzing around with the part....if they can load it and go, it will get done faster....

If they have to mess with chipped MDF...or whatever, it will take longer...and time is money.....

Just sayin.

Dave
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Damned ijjit!

PatJ

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Re: Galloway Castings
« Reply #37 on: December 22, 2013, 06:34:55 PM »
Dave-

Yep, I hear what you are saying.
I guess if I were going to make commercial kits available I would certainly use aluminum in a CNC for patterns.

I was thinking along the lines of plywood that does not have many or any knots in it, if there is such a thing, and glued up in layers if necessary.  Plywood has pretty good dimensional stability, but does break out sometimes.

Plywood avoids the fuzzy finish, and holes in the plywood can be filled easily enough.

The guy with the CNC is retired, so not really a time is money thing, but even he does not want to have to repeat a run.

It is something to think about.
I guess I will get whatever he decides to use, if he decides to make these patterns.

I can make patterns manually in wood, but for things like tapered ellipsoidal spokes, CNC or 3D printing is nice, and for tight tolerances where you are trying to maintain a uniform wall section like in the cylinder/water jacket area, you need all the accuracy you can get.

Offline Jo

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Re: Galloway Castings
« Reply #38 on: December 22, 2013, 06:42:10 PM »
I guess if I were going to make commercial kits available

Is the Galloway market not already saturated? George B did a wonderful job in sorting out the original model design and they are already available in four different scales.... I am not sure how big the fine scale market might be  :shrug:.

Jo
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Offline steamer

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Re: Galloway Castings
« Reply #39 on: December 22, 2013, 06:47:57 PM »
Dave-

Yep, I hear what you are saying.
I guess if I were going to make commercial kits available I would certainly use aluminum in a CNC for patterns.

I was thinking along the lines of plywood that does not have many or any knots in it, if there is such a thing, and glued up in layers if necessary.  Plywood has pretty good dimensional stability, but does break out sometimes.

Plywood avoids the fuzzy finish, and holes in the plywood can be filled easily enough.

The guy with the CNC is retired, so not really a time is money thing, but even he does not want to have to repeat a run.

It is something to think about.
I guess I will get whatever he decides to use, if he decides to make these patterns.

I can make patterns manually in wood, but for things like tapered ellipsoidal spokes, CNC or 3D printing is nice, and for tight tolerances where you are trying to maintain a uniform wall section like in the cylinder/water jacket area, you need all the accuracy you can get.


If you go the plywood route.....stick with BS 1088 marine plywood, or Birch Aircraft plywood.    BS1088 guarantees there are no knots or voids...

But both are pricey....MDF would be the next choice I think....


Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Jasonb

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Re: Galloway Castings
« Reply #40 on: December 22, 2013, 06:49:33 PM »
I did not read it that way Jo, "if I were" suggests that Pat would use aluminium if that were the case but he is using ply and likely to cast one or two parts from the pattern.

Also no one makes a kit of a 7.5HP at the moment which is what Pat is modeling

J

PatJ

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Re: Galloway Castings
« Reply #41 on: December 22, 2013, 07:18:41 PM »
Dave-

Thanks for the tips, I have not tried to get any patterns CNC'ed yet, and so am new to that.

Jo-

I would say that the market is saturated, and the market is small too in my opinion to support someone anyway; two good reasons not to offer a casting kits for sale.

But my idea was to make 1/3 scale castings of my dad's 7.5 hp round rod, and those kits don't exist.
And I am not aware of any kits having a one-piece frame and cylinder casting with water jackets like the original engine, or water jackets in the head, or tapered ellipsoidal spokes shaped like the original engines, etc.

So the argument can be made "Would anybody notice that sort of thing, would anybody care, and would anybody pay extra for these features"? and the answer is "probably not".

But since I remember my dad's engine well, remember how it was built, and have photos of it, then it seems logical to make the castings exactly like that.

Some casting kits these days have superb quality, and some are lumps of metal that only vaguely resemble the part to be made.

It is pretty easy to make better castings yourself than some of the kits that are available, but not necessarily all the kits; some kits have superb quality and are very difficult to match in quality.

I am no casting expert, lets make that clear.
I am a casting expert wannabe, but my progress so far is very exciting, especially in cast iron, and cast iron parts with cast passages.

I guess everyone has a level of accuracy that they want to work towards.
« Last Edit: December 24, 2013, 07:13:29 AM by PatJ »

Offline Jo

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Re: Galloway Castings
« Reply #42 on: December 22, 2013, 07:23:04 PM »
I can understand the need to make a model of your Dad's engine and to make that an accurate model 8).

Like I have had a number of "offers" to make my 1/6th S&P commercial.. that is not the point of why I am doing it, its personal  ;)

Jo
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PatJ

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Re: Galloway Castings
« Reply #43 on: December 22, 2013, 07:25:52 PM »
Yep, that pretty much sums it up, "its personal".

And there is the chance that I will fail miserably, but I would rather try and fail then not try.

PatJ

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Re: Galloway Castings
« Reply #44 on: December 24, 2013, 06:40:14 AM »
I was thinking about why I design and cast engines, and about all I can come up with is that scene in the movie "Forrest Gump", where he keeps running and running, and finally the newscasters start running along side him, and they ask him "Why are you running....it this for world peace, the homeless, women's rights, the environment, animals....?".

And Forrest replies "I just felt like.......running......."

And so that is how it is with me and designing/casting engines.
My motivations are not exactly what you would consider complex.


Here is a core box for the cylinder, and also the core that this core box will produce (with the bore core shown inside of it).

Edit:
The tabs extending up towards the water hopper should not go all the way up.
And the cylinder and frame will be cast in a single piece, but I modeled them seperately because I was having shell issues with the frame when I combined them.
« Last Edit: December 24, 2013, 07:16:43 AM by PatJ »

 

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