Which model casting kit(s) to get

[Beardy MikeParticipant @beardymike]

I’m looking to get a model engine kit, but I’m not sure how the various UK suppliers compare. I’m looking for something fairly simple, supplied as castings, bar stock and drawings.

It’d be my first project from castings, although I have previously made a simple single acting piston valve engine from bar stock. I’ve also machined all sorts of parts for both home and work projects over the years. I’ve got a mini-lathe, kx3 CNC mill (as well as a 14″ shaper, drill press, bandsaw, and various other kit).

I’m thinking either a single cylinder steam engine (that could initially be run on air, until I took on a boiler project) or a Stirling engine.

Anyone got any suggestions?

Thanks,

Mike

[noel shelleyParticipant @noelshelley55608]

Welcome ! Look at the Stuart Models range, may be a 10V or 10H. There is a booklet on building this series of engines and the principles apply to many of the type. Good Luck. Noel.

[Nicholas FarrParticipant @nicholasfarr14254]

Hi Beardy Mike, Stuart Models and Mac Models Mac Models might have something you are interested in, or maybe Reeves 2000.

Regards Nick.

[JasonBModerator @jasonb]

As Noel says the usual suggestion are the stuart offerings, either the S50 Horizontal or the 10H / 10V. You could also look at teh P M Research kits that are available in the UK from Forrest Classics.

Another alternative are the old Clarkson engines which Blackgates has taken over the supply of. The small horizontal or vertical both of which are 1″ bore x 1.5″ stroke are quite simple particularly the horizontal which is less complex than the Stuarts. Also being a bit larger they may suit better as a first casting set. They don’t include barstocj but that is not a vast amount to allow for and it does give you the option to build in metric rather than imperial as you can buy what you want not what is included in other kits, you also have a decent length of material to hold not the stubs supplied in the kits. There will be a build series of the horizontal starting in ME within the next couple of months to new metric drawings.

Though with the tools you have you should be able to make some good engines that look like they are made from castings but just cut them from solid and/or fabricate

[Clive Brown 1Participant @clivebrown1]

Hemingway does a few steam engine designs, which can be bought as fairly complete kits with build notes, which can be useful. Perhaps not the very simplest projects but attractive models.

[Ches Green UKParticipant @chesgreenuk]

I’ve built Stuart model engines (up to 7″ flywheel dia, limited by lathe swing) and PM Research models.

Stuart uses cast iron castings which can sometimes be a bit challenging due to the hard outer surface, and the black dust produced when machining.

PMR models are mostly Aluminium so easier to machine and produce ‘cleaner’ swarf/dust.

I’ve found both models from these companies to be well worth the price. As mentioned, there are a number of booklets for the Stuart models to assist building.

The drawing sets from both companies can be slightly puzzling, but that’s all part of the challenge.

Ches

[Beardy MikeParticipant @beardymike]

Thanks for all the suggestions folks. I was leaning towards the Stuart horizontal, so looked up a couple of YouTube build videos; the first important measurement was described as some number of 64ths of an inch. While I’m generally pretty bilingual with units, fractional inches at this scale concern me – if I convert every measurement like this then sooner or later I’m going to mess one up!

How much does it limit my options to only go for something with metric drawings? Failing that, decimal inches are massively preferable to fractional.

The Clarkson horizontal is sounding promising – is the bar stock required just basic mild steel, brass etc. or will I need to source specific grades or chunks of cast iron etc.?

Thanks,

Mike

 

 

[BaldricParticipant @baldric]

I have a kit from P M Research, the generator, I have not yet built it, but I seem to think the fixings are UNC o UNF, if that means getting new tools, it maybe worth checking.

Baldric.

[JasonBModerator @jasonb]

Nothing exotic needed for the Clarkson

PGMS or silver steel for crankshaft

Stainless 303 for piston and valve rods

Bit of brass or bronze for the glands for those two rods

ditto for valve and nut & cross head

0.5mm aluminium sheet for cladding if you want to fit it.

Steel round for conrod.

Although I am not keen of “bills of materials” I’ll knock one out later or tomorrow. This will give you an idea, items with their name highlighted are from barstock. I don’t tend to buy hex and square, you can mill that from round bar used for other parts so less sections to buy.

The Blackgates catalogue photos do not do their engines justice, this is what you get in the casting set (plus the eccentric strap)

PM about to be Sent

 

[noel shelleyParticipant @noelshelley55608]

If the drawings are in fractional inches then half an hour with a calculator will give you metric or decimal inches. I have a cheap chinese 300mm rule and on the back is the whole run of 64ths into metric, handy ! The metalworkers Data Book is worth its weight, and at about £7 invaluable. I take it you already have calipers, mikes Etc to be able do the necessary measurements. There are calipers that work in fractions !  Old Stuart Models kits did at one time have trouble with hard spots, the Bridport Foundry who took over Stuart Models went to much trouble to solve this problem. Good Luck. Noel

[Neil WyattModerator @neilwyatt]

Always check the flywheel sizes!

There are lots of great designs that are a bit larger and less fiddly with 8″ flywheels, but you can’t turn the flywheel on a 3.5″ centre height lathe like a mini-lathe.

Neil

[JasonBModerator @jasonb]

9″ is more common as that could be swung in a Myford gap.

Still all is not lost. As you like metric then take an old design and scale it to 1/16″ = 1mm and you will get easy numbers to work with and a flywheel that fits a mini-lathe and is also within the Y capacity of your KX3 so any spoke design is possible and it can be cut from a slice of CI bar.

Luckily most of the beginners engines are smaller so it is not until you move onto the more fiddly and detailed designs that you tend to see the larger flywheels.

There is a Bill of materials for the Clarkson 24 x 38 Horizontal in my Document Gallery now if anyone wants to see what is needed on top of the castings.

 

[PeteParticipant @pete41194]

Converting fractional inches to decimals is a very easy process that only takes a few simple key strokes on any or even with the most basic of calculators with a method that many don’t seem to know about. Fractional inches have an upper number (the numerator) and a lower number, (the denominator) ANY fractional inch dimension no matter what it is can be converted to exact decimal inches easily. Take the top number whatever it might be and divide it by the bottom number. Example 1/4″, 1 divided by 4 = .25″ With the decimal equivalent known, it’s then easy to convert that to a metric dimension if that’s what you want since the imperial inch is actually based on it being exactly 25.4 mm to the inch. I’ll use that 1/4″ or .25″ as another example, .25 x 25.4 = 6.35 mm.

Or fractional inches to exact metric almost instantly with a few less key strokes, that same 1/4″, 1 divided by 4 x 25.4 = 6.35 mm. I have a wall chart with the common fractions and there decimal equivalents, for any I don’t already have memorized, I usually won’t walk the few steps to even check it since that calculator method is faster. And the most used tool in my own shop is a calculator, so it’s always handy. Imperial or metric is just a mathematical concept and one verses the other really isn’t any better or worse than the other. Metric is easier without a calculator, threads and there tap drill sizes are certainly easier with metric, but that’s about it for what we might be doing. For myself I was taught in school and can still visualize much better in imperial, so I just use that as my measurement of choice. But I can sympathize with those that have only been taught metric. Imperial fractions probably do seem a bit confusing, in reality it’s all pretty basic if you know that easy conversion method.

[JasonBModerator @jasonb]

The direct mathmatical conversion has it’s limits for the newcomer who may only have metric taps, reamers, drills, etc. which is why I suggest a full conversion particularly if they have a metric machines and just hand wheel dials. Far easier to move 3mm either side of a mid point while compensating for backlash than 3.175mm if your dials are only marked in 0.2mm divisions.

[Bob WorsleyParticipant @bobworsley31976]

A small steam engine is the obvious go to to build, but I would suggest that a Weir type steam pump is a better choice.

Why? Smaller, simpler, only needs a tiny boiler to run, no flywheel, does something, and absolutely fascinating to watch. I bought my castings from Kennions, but there are other suppliers.

 

[noel shelleyParticipant @noelshelley55608]

Building a small weir type pump may be fun but a novice may have difficulty getting it to run. Only very careful and accurate machining and assembly not to mention setting up will see it run. It is much more complicated than it’s simple looks would have you believe. Having no flywheel when getting it to run is not a bonus as there is nothing to carry it over the dead centres, though there were types that did have a flywheel.

Stick with a small horizontal steam engine but note the flywheel size to suit your lathe etc. Good Luck. Noel.

[BazyleParticipant @bazyle]

OP has a CNC mill so that can make a pretty large flywheel, not to mention using the lathe as a mill to machine a flywheel. the latter could make a beginners article for MEW.

[JasonBModerator @jasonb]

As I mentioned earlier his Y axis will be the limiting factor on his CNC which is the same as mine. He won’t be able to mill a circle much over 140mm outside dia but he has a 7x $$ lathe so easier to turn a larger casting than to mill it.

 

As he wants to make an engine from castings I’m not sure what milling would be required to be done on a lathe?

[Pete]

On Pete Said:

Converting fractional inches to decimals is a very easy process that only takes a few simple key strokes on any or even with the most basic of calculators with a method that many don’t seem to know about.

True, but beware.  The problem is the process is tedious and a big plan may require lots of conversions.   The combination makes numeric conversions error prone.   Unfortunately double checking is even more tedious, so annoying mistakes still slip through galore.   It helps to be numerate, to have practised mental arithmetic, and knowing the common conversions off by heart makes it easier to spot sillies.

 

 

…. Imperial or metric is just a mathematical concept and one verses the other really isn’t any better or worse than the other.

Not so!  The problem with Imperial is it’s riddled with internal conversions.  Imperial units were derived in isolation, when measuring the weight of spuds hand no obvious connection with measuring length or time.  And before electricity, of which it has no concept!

In a home workshop, there’s rarely any need to calculate using derived units, so all seems well.   But Imperial behaves badly when engineering calls for grown-up maths because Imperial requires multiple internal conversions.   Look at this simple example:

Applying the formula is easy enough and the answer is 10,800 lb. per sq.in.  But hang on, my question to the friends of Imperial is, what’s the 6 in the formula for, and where does it come from?

It’s a ‘magic number’ resulting from mixed units.  The Imperial system being internally incoherent means that it’s littered with them, and they turn anything other than basic maths into a minefield. They’re an extra complication making more work and causing mistakes, definitely not a good thing.    In contrast, Metric was designed to eliminate ‘magic numbers’ and other faults.  Much simpler, and far better suited to maths based engineering.

Fortunately for Imperial fans, Model Engineering rarely calls for the more advanced calculations that expose the systems shortcomings.   Advanced calculation is unlikely to be needed unless a ME is doing design rather than following an existing plan.

As all conversions are bad, converting Imperial plans into Metric, or vice versa, is risky.  Small projects aren’t too awful, but converting a big one quickly turns nasty because bored people make mistakes.  Well I do!

If it has to be done, a slide rule is surprisingly effective because the numbers don’t have to be typed in.

Dave

[BazyleParticipant @bazyle]

My thought for the CNC mill was to mount the flywheel horizontal and ‘off centre’ on a spigot through the bore (previously drilled and reamed on the bench drill). CNC mill say 1/4 of the rim, rotate, repeat. There might be a slight discontinuity at each transition which could be trued up with a file or something when complete and running under its own steam.

The milling in the lathe I was thinking of was how to machine a large flywheel by mounting horizontally on a spigot on the saddle and rotating manually against a small flycutter in the lathe spindle. Fifty years ago this would have been a no-brainer to the old modellers but why I thought it might need a MEW article nowadays, if it hasn’t been covered before.

[Beardy MikeParticipant @beardymike]

I think I’m going to go horizontal Clarkson 👍

Each to their own on units, but I know that if I convert all the drawings sooner or later I’ll do something daft like swap digits. E.g. 17/32″ should be 13.49 but I’ll absent mindedly cut 13.94.

Bazyle, thanks for the suggestions on larger flywheels. I won’t need them at the minute, but I’ll try to file them away in my mind as they will probably come in handy one day.

[JasonBModerator @jasonb]

I’ve got you now. I came close to doing a flywheel pattern by the way you suggest indexing it around and milling a pie shaped segment at each setting but ended up CNCing separate spokes that were glued into a rim that was “turned” by mounting on the rotary table and rotating against a milling cutter.

 

[DalboyParticipant @dalboy]

Why go for a kit with castings, how abut one from plans. Like some of these by Jerry Howell

[Beardy MikeParticipant @beardymike]

A few reasons for castings:

• Avoids me getting carried away in ‘planning paralysis’ when I start tweaking things to match what I have on hand
• I’ve not done much with castings and fancy giving them a go
• People are asking what I want for my birthday and it’s easier to say “this casting kit” than trying to brief them on what to buy from a bar stock supplier!

That said, some of those Howell ones look interesting; I might consider one of those once I’m done with the Clarkson one.

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