# STRUART S50 Mill finished.



## Tony Bird

Hi,

Over the last 6 months or so along with other projects I have been making a Stuart S50 horizontal mill engine for someone. It was finally finished last week and I thought members of the HMEM might like to see the photographs taken during its construction. The Stuart S50 like most of Stuarts products is machined from castings which come with all the other bits and pieces i.e. screws etc. to complete the model.

With this sort of model I usually start with the cylinders, first the cylinder casting is face on its valve surface it is the mounted in a chuck and bored and one end of it is turned a little over size. A shellac mandrel is then made a piston fit in the bore of the cylinder and the cylinder is the held on to it using shellac. The shellac mandrel is mounted between centres to finish machining the cylinder still on the mandrel the cylinder is mounted on the milling machine to mill its remaining flat faces.

Next the flywheel was machined which was found impossible as it had been cooled to quickly it had also sagged around its boss. The steam chest and its cover were then tried and also found to be hard. But before these three casting were returned to Stuart for replacement, the engines bead was machined and drilled to see if it as well was defective. It wasnt.

While waiting for the castings the eccentric and its strap was machined along with the fly crank was machined which was straightforward.

New castings arrived, the flywheel was OK but the replacement steam chest and cover were hard. So the flywheel was machined and while waiting for the second set of steam chest castings a start was made on making and fitting the slide bars after which the connecting rod was made. It was found that the connecting rod wasnt at right angles to the axle so the flycrank had to be thinned down a bit. The crosshead was next and straightforward to make.

The new steam chest castings arrived and machined, they werent hard as in chilled but had some bits in them that were fortunately not enough to worry about. As can be seen from the photographs after part machining the steam chest and its cover they were stuck together using shellac to finish the machining.

Perhaps it is worth mentioning how the cylinder was lined up with the piston rod. This was a little awkward to do as three screws from under its base hold the cylinder. A shouldered plug was made for the cylinder into which an over length piston rod could slide. Doing this allowed the cylinder to be clamped to its base and it was possible to check that the piston rod hadnt stuck and could still move while the holes in the cylinder were spotted from the underside.

All of the remaining work was straightforward the only deviance from the drawings being the replacement of soft packing on the piston with an 0 ring. A Stuart adjustable Dead Leg lubricator has been fitted along with commercially made oil pots. The following photographs of which I hope it isnt considered too many shows the machining and construction techniques used. I will add the photographs in batches over the next couple of days. With luck they will be in order!





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Chilled castings.



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Base checked before castings returned.




I'll stop now and do some more later.

Regards Tony.


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## don-tucker

You had bad luck with the castings tony ,Stuart castings used to be brilliant,I made one of these a couple of years ago to get myself back into model engineering .
Don


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## Tony Bird

Hi Don,

Yes the castings don't seem to be as good as when Stuart were at Henley-on-Thames. To continue with the photographs if there is something which isn't clear please ask.




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Well that's the eccentric, eccentric strap and fly crank machined.  SWBO requires transportation into the big city so I will continue later.

Regards Tony.


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## Tony Bird

Hi,

To continue.





New Castings.




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Taper turning using a adjustable tailstock centre.




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That's enough photographs for this post before PhotoBucket throws a wobbly on me.

Regards Tony.


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## Tony Bird

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More to come.

 Regards Tony.


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## Tony Bird

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Lining up plug fitted.



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 On the home straight now.

 Regards Tony.


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## Tony Bird

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The Video.





The steam on the video is leaking from a split silicon exhaust pipe not the engine. The S50 will be collected by its owner this coming Sunday. As said before if anything is not clear please ask.

Regards on the way to the shed which now should be warm enough to work in.

Tony.


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## mrussell09398

Dear Mr Bird

I am building my first engine and although I am progressing it is very hard, but equally rewarding (when the replacement castings arrive!).

Anyway I thought your tutorial was great, you shone a light on some of the bits I was stuck with!

I have a question, you see the lathe tool you used to machine the groove in the face of the cylinder cover? The one that looks like it has a hook?  What is it called?  I keep looking for a tool to do that task but I can't see how any of my existing tools would work.  see below...

thank you for sharing your expertise and knowledge, it really does help beginners you know!







Best Wishes
Mike


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## Tony Bird

Hi Mike,

The tool is a boring tool see attachment.  This one is an old carbon steel one which I have had for many years.  The tools you show have removable tips, you can get boring tools that use these tips.  I just used this tool as it would do this job, it produced a square corner on the inner edge of the groove and a tapered edge on the outer as shown in the photograph.  To square up the outer edge of the groove the tool was turner through 90 degrees into a similar position that would be used to bore a cylinder.  I hope this makes sense to you, if you have further queries that you think I can help with please ask.

Regards Tony.


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## Korben

Thank you for the great photos!  

I am very new to this hobby and machine work like you've done is way over my head.  It's fascinating to see what goes into making one of these engines.  I am fortunate to have acquired a pristine S-50 assembled in the 1960's from a factory-machined kit.  It seems perfect in every way.  My challenge is working through the piping and coordinating the various threads.  

I love your chuff pot!  It appears to be made from copper pipe and end caps.  I'm going to make one like it.  

Regards,
Korben


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## Tony Bird

Hi Korben,

*I love your chuff pot! It appears to be made from copper pipe and end caps. I'm going to make one like it.
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Yes quite correct, the oil separator is made from a 28mm copper pipe and a stop end, the chimney is a 15mm tube.  It is emptied by taking the top (stop end and chimney) off and tipping out the oil/water mix.

Regards Tony.


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## AndyWood

Dear Tony,

I have recently started building the S50 from the kit that Stuarts provided as my first attempt at building a model steam engine. I was interested to see your use of shellac to mount some of the parts for machining and hadn't come across this before but would be the answer to one or two tricky problems I foresee. Could you say some more about what form of shellac you use and how it is used in this way?

Many thanks for the article it has certainly been very helpful.

Best regards

Andrew


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## don-tucker

Well done Tony a lovely job as us usual an an inspiration to others.
I was wondering how you got on with your arduino rotary table,I am having a go,following chuck fellows example but not got very far yet
Don


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## Tony Bird

Hi Andrew,

*I have recently started building the S50 from the kit that Stuarts provided as my first attempt at building a model steam engine. I was interested to see your use of shellac to mount some of the parts for machining and hadn't come across this before but would be the answer to one or two tricky problems I foresee. Could you say some more about what form of shellac you use and how it is used in this way?*

The shellac I use comes in stick form and can be bought from Horological suppliers www.cousinsuk.com  in the UK.  It is in consumables and is the light brown one.

Shellac is a natural resin which is secreted by the Lac beetle and is one of the oldest types of glue.  When dissolved in wood alcohol (meths) it is the basis of French polish.

Shellac has a low melting point about 85C.  In use the chuck/mandrel is heated with a torch which a shellac stick is applied to and melts the work piece is then applied and also heated and positioned.  When cooled the work piece can be machined.  The work piece can be removed by heating by a torch or in water brought to the boil.  Any shellac left on the work piece can be removed by chipping or being dissolved in meths contained in a jar.

Do not heat the shellac until it boils, allow to cool naturally, use a sharp tool and take small cuts.  As far as I know other than for watchmakers lathes Shellac chucks sometimes known as wax chucks are not available for larger lathes so have to be made.  Mine are usually made from steel and the ones used on watchmakers lathes are brass, I suppose almost any metal could be used.  If the work piece is pushed down on to the chuck while the shellac is still mastic the thickness of the shellac between the two parts is usually about 0.20 mm which can be useful for measuring. 

Any further questions please ask.

Regards Tony.


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## Tony Bird

Hi Don,

I was wondering how you got on with your arduino rotary table,I am having a go,following chuck fellows example but not got very far yet.

I don't know what you are referring to?  Have I forgotten something? I have a small Chinese made rotary table for my milling machine but I am not making one.

Hope to see you soon.

Regards Tony.


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## Rudy

Thanks for the write up. I'm new to this and learning a lot.
Regarding the castings, I have bought a Stuart 10V kit and experiencing bad castings as well. Most of the casted parts are bad. Either glazed or very poorly casted. I got two of them replaced.
I encourage everyone getting bad castings to complain to Stuart. They have to straighten up their quality.


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## don-tucker

Hi Tony,what it is ,I was following an artical about fitting a stepper motor to a dividing head or rotary table and I'm sure I saw your name mentioned
Don


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## Tony Bird

Hi Rudy,

*Regarding the castings, I have bought a Stuart 10V kit and experiencing bad castings as well. Most of the cast parts are bad. Either glazed or very poorly cast. I got two of them replaced. I encourage everyone getting bad castings to complain to Stuart. They have to straighten up their quality.*

Yes I agree I have made several Stuart engines that required castings to be replaced.  I had part machined a cast iron steam chest that I had bought at a swap meet when I hit some hard spots.  I decided to try and get rid of them by annealing.  I lit a charcoal BBQ put the casting on top heated it until it was red with a torch and covered it with the burning charcoal.  When the BBQ had burnt out and cold the casting could be machined.  The casting was quite small, whether it would work for larger castings I don't know, I have only done it once. 

Hi Don,

Not me I think not much into stepping motors, though recently I fitted a three axis DRO to my lathe which I find very useful.

Regards Tony.


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