Casting Kits I would like to see For Sale Again

[GreenTwin]

My thoughts are to cast 356 aluminum match plates with all the runners, gates and sprues on them, using the original patterns to create these matchplates.

One has to remember to 3D print patterns like this with double shrinkage.

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[littlelocos]

My thoughts are to cast 356 aluminum match plates with all the runners, gates and sprues on them, using the original patterns to create these matchplates.

One has to remember to 3D print patterns like this with double shrinkage.

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I did a similar, lower-volume method by taking urethane rubber molds off of the original matchplates for the Parsell & Weed model and then using these and Freeman Repro urethane to produce multiples of the same piece. These were mounted to 3/4" baltic birch matchplates. This method is probably more appropriate for the several hundred of these kits we sold over the last 6 or 8 years. The patterns have held up very well even with machine (jolt-squeeze) molding machines. Repro is an industrial, filled urethane designed for producing foundry patterns. I've done the same thing with printing a master pattern, smoothing it with epoxy, and then duplicating it with Repro; however, I've gotten better with the printing and now mostly just print the patterns and glaze with epoxy.

For some of the patterns I've produced for the foundry's customers, shrinkage gets wild when you have to consider a 3D printed master with double shrink on the pattern, fitting with the single-shrink on the cast aluminum core boxes so that once the aluminum production plate is made the core prints fit with the molded cores. .....and then there are the different shrinkage rates for the aluminum core box and the brass finished part. This makes the project fun tho.

 

[littlelocos]

Hopefully we can meet ways at the Black Hills Model Engineering Show if you still plan to attend. Doesn't sound like it would be a cheap roadtrip for you either. I need to sell a few things to even make it, but it would be great to pick up one of your horizontal Parsel & Weed kits. They sound great for the size.

At this point we're probably in the "maybe next year" mode on the Black Hills Show. We had intended on going, but at this point it's more of a trip than we can really afford.

 

[Jasonb]

Todd, that sounds the same way that Nick Rowland does his buy taking a mould of his master, casting in resin and than mounting on a board, part way through making up boards

The things I have made patterns for were all for small amounts mostly 2 or 3 though the flywheels usually have a few more cast as they come in useful for other projects. Therefore they are not done on boards but if there are a number of small items I do make the pattern as a "stick" which saves moulding time and less likely to go walk about than individual small patterns

 

[GreenTwin]

I recall Maury using a lot of cast resin for the patterns he sent to the foundry.

There is a bit of an art to using those materials too, to prevent air bubbles and such, or so it seems according to the online videos.

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[Jasonb]

I've only done a little bit of csting with PU resin from when I used to make an dpaint model figures for which it is a very popular choice of material along with teh more traditional white metal. Putting it into a vacuum after mixing and again after pouring into the mould is the best way to get rid of bubbles much like you do when pouring investment.

 

[Jasonb]

Pat's current 3D printer thread got me thinking a bit more about the size of casting sets if offered for sale.

I offered him the 3D file for this flywheel that will have a finished diameter of 380mm or 15"

That cost £300GBP to get cast based on a weight of 18kg or 40lbs

Scaling the model in CAD and working out the weights and costings on a pro rata basis

An 11" version would cost £134 and a 8.5" version £50. All other castings likely to have the same volume difference so same cost difference too.

So not only would the market for large casting kits be limited by those who could fit them on their machines and be able to physically manage to handle them it would also be limited to those with deep pockets as the cost of the large kit would likely be close to 3 times as much on the material side so say 2 1/2" times the cost as plans would not cost much more.

On the steam engine front there is also another factor to consider and that is running them. As the bore gets taken up to 2" which may simply be a double up of an original 1" bore the actual volume of steam or air needed will go up by the cube of any scaling factor. If you then also figure in wanting to make the engine work that will require a much higher pressure than a display engine running of say 5psi and that working engine will also tend to be run faster than the display engine ticking over as slow as it will go.

So the builder needs to find a suitably sized compressor or steam boiler that will provide that larger volume of air/steam and be able to maintain the required pressure.

Putting a few numbers to it an original engine with 1" bore and 1.5" stroke if double acting has a volume per rev of 2.3cu in.
Same engine scaled up to the "standard" 2" diameter will have a stroke of 3" and the volume per rev goes up to 18.8cu in
Even with second thoughts about the "standard" making the engine too large and dropping down to 1.6" bore x 2.4" stroke volume is 9.6cu in

So FOUR times the volume at the same given speed but more likely TWENTY times when you get upto a couple of hundred rpm and probably 10 times the pressure to at least get some work out of it.

that is going to reduce any potential kit purchasers even further as not many will have a big enough compressor or steam plant to run a large engine. Even if just a couple of additional sets of castings were produced to cover pattern making costsIt would be hard to find buyers.

 

[GreenTwin]

Here are a few pictures from NAMES 2019.

Very large casting kit offered by Myers, and a very sizeable tractor that someone made patterns for and had cast.

You can't rationalize the size.

Some folks build HUGE stuff.
Why? Because they can.
There is no logic to it.
Its like climbing Everest.
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[Jasonb]

Yep they do but there are not that many of them and the $2700.00 guide price for the big Ryder would be more than most would want to spend on a kit or have the ability to build. As I said as they get bigger the market gets smaller (not non existent) so anyone putting a kit out there for sale would have to take that into account

At least with the hot air engines and tractor you don't have the boiler/compressor issue and the aluminium they use does make it a bit easier to hump them around

 

[Vietti]

Don't know if its been mentioned but weight becomes an issue as we age. I built a number of larger engines but boxed up and ready to transport they weigh +/- 40#s. The smaller ones I now build are easily lifted by on hand! I think the smaller engines are fussy to build and run but worth it.

 

[peterl95124]

Don't know if its been mentioned but weight becomes an issue as we age. I built a number of larger engines but boxed up and ready to transport they weigh +/- 40#s. The smaller ones I now build are easily lifted by on hand! I think the smaller engines are fussy to build and run but worth it.

Agree, and I only build models that can fit in my bookcase,
EG my Kozo A3 switcher is scaled down so the loco and tender fits in my 34" internal width
bookcase, and its reasonably light too.

 

[minh-thanh]

He has trouble with his eyes..., and had problems with making small details so I think we shouldn't talk about size
Homemade engine : making engines according to preferences, abilities ..., satisfying the passion for self-made is enough.

 

[Jasonb]

But the thread title is about kits not what one person chooses to make so as kits will be sold to builders with a range of preferences then anyone making them for sale again needs to consider the market which will be influenced by size of machine needed to build it, cost of the kit and physically being able to handle, store, transport and run the engine.

Take the Galloway kits as an example, these were available in 1/3rd, 1/4, 1/6 and 1/8 scale. Anyone taking on that range would probably be best to start by making the 1/4 and 1/6 scale engines available first as the 1/3 is quite a sizeable engine and the 1/8 quite small an needs to run too fast. maybe offer those two just as "cast to order" but still need to work out how soon you would get your money back to cover any reworking of patterns, drawings, etc. Th e1/4 scale would suit those with a 250mm or 10" swing lathe and the 1/6th those with mini lathes which is what a lot of people have.

 

[GreenTwin]

Well, it would be BIG kits I guess; not for an ordinary model engine builder, but for a BIG model engine builder.

One thing I think is certain is that there will be little chance to "get your money back".
I have heard that many kit builders break even, if lucky.

So I would not make kits for the masses, but kits for those who want a BIG kit.

Limited production runs, such as 10-20.

With mass production of multiple sizes, it would not longer but a fun hobby, but a difficult job, and a great deal of potential to lose money.

So think BIG kits.

And the title says "Casting Kits I Would Like to See for Sale", with the emphasis on "I".
I would like to see BIG kits.

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[minh-thanh]

@GreenTwin !

I know your difficulties in making small engines
So, Another option
You design and You can invest in someone who can make small diameters ( 20 , 25 mm ) . After the engine runs, he will send you the engine and the plan is yours and you cast and sell the casting.

 

[GreenTwin]

There are many options down the road, so we will see how it all goes.

There is much to do first, such as finishing various 3D models, figuring out the new Prusa XL, printing patterns, etc.

We will play it by ear, and see where it goes.
I have not ruled out any options yet.

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[Jasonb]

And the title says "Casting Kits I Would Like to See for Sale", with the emphasis on "I".
I would like to see BIG kits.

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You completely missed out the AGAIN bit of the title which would apply to engines like the Galloway, Monitors etc. that were previously available Not new one off engines or new kits be they large or small

But you have already shown that the Big engines you want to build are not practical. You have had to reduce the Creators No6 down in size as you can't cast it if built to your "standard 2" bore", the bottle engine has been reduced down each time you have tried to make the pattern for that over the years, etc

 

[GreenTwin]

"Rational" was never my strongpoint.

I do have fun imagining though.

I like to question the limits of what is practical/possible.

Without questioning things, one never really knows what one is capable of building.

I have never been a "do this because everyone else is doing it" type person; quite the opposite actually.
I try to do stuff that few are willing to attempt, because.........well why not ?; its fun.

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[minh-thanh]

If someone asks me: What size should a homemade engine be? . My answer is : Do whatever size you can .
"Casting Kits I would like to see For Sale Again" : that's a big problem
Choose the size, the machining cost, the casting cost, casting material costs, the shipping cost...., and the people who buy the casting set need what size machines to make...
If selling 1 or 2 sets is only for fun - no matter the money : Do it
If selling to recover part of the invested capital or the whole invested capital (not to mention making a profit), all the above costs must be reduced and suitable for the majority.
Processing costs, casting costs, casting material costs: are a huge barrier for manufacturers
Shipping costs are a huge barrier for buyers
And can't buy bigger machines just to process one set of castings
.........
Everyone has different thoughts, ...so I'll stop here

 

[ajoeiam]

Here are a few pictures from NAMES 2019.

Very large casting kit offered by Myers, and a very sizeable tractor that someone made patterns for and had cast.

You can't rationalize the size.

Some folks build HUGE stuff.
Why? Because they can.
There is no logic to it.
Its like climbing Everest.
.
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Very impressive - - - - - I wonder where the tires for those models were obtained from - - - - anyone with ideas?