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[logoman]

I'm having difficulty restoring a Stevens' Model Dockyard engine and boiler.
The copper steam pipe from the boiler to the engine is threaded as it enters the steam chest.
I have not been able to measure the pipe properly but it is certainly an old size probably not produced any longer.
The closest i can find is 5/32 32, but this is too small, and (i need a vernier caliper) it looks about 11/64 (was there a standard between 5 /32 and 3/16?)
Is it likely that the tube may be an odd size but the thread is 3/16 Whitworth? Edit: the thread is definitely finer that 24tpi.

cheers.

[ooyah/2]

Hi Logoman,
There is no thread available as 5/32 x 32 tpi. there is a thread 5/32 x  40 and 3/16 x 40,  I would expect that Stevens would use 3/16 x 40.
The only other thread near that is 2 BA which is 31.34 tpi and you will find that the No of threads are never engraved on a B.A. tap or die.
There has never been a thread 11/64" and you are correct in that Whit is 24 tpi.
The copper steam pipe has probably worn  with age and will measure below 3/16 ( .187 " ) I strongly suspect that the thread is 3/16 x 40 tp.
Copper is not the best of materials to thread.
Hope this helps,
George.

[malcolmbeak]

You might also note that there is a BSF size of 3/16 x 32 tpi.

Malcolm

[ooyah/2]

Hi Malcolm,
Yes that's true but it's the only thread in BSF that has 32 tpi, and as the manufacturer like all others in the model trade use M.E. threads I never considered it as an option.
I  never use 40 tpi as it's so easy top get a cross thread so I stick to 32 tpi and only use 40 tpi below 1/4",
my bet for Logomans boiler it will be 3/16 x 40 M.E.
George.

[malcolmbeak]

Hi George
Stevens Model Dockyard date from the 1920's and before, and I believe the "model" series of threads were introduced much later than that. Also, if the tube were much below the nominal 3/16 diameter, there would be very little depth of thread formed using 40 tpi.
I would guess that the BSF, 2BA or even 3BA are the likely ones.

Malcolm

[gondolier88]

Not knowing the history of Stevens I ask the question; were they UK built?

Greg

[logoman]

5/32 x 32 screws into the threaded hole, but is a loose fit. The thread count is very close if not exactly 32. 3BA seems closest to me with an OD of 4.1mm.
5/32 or 4mm pipe is just a bit too small, so it seems I'm stuck. I can't turn down 3/16 pipe because the wall will be too thin.

yes Greg, uk built, this is the engine.
An alternative would be to drill, plug, drill and tap to a standard, and I could do that on the steam chest, but I'd be nervous of doing the same operation for the exhaust port on the cylinder.

[ooyah/2]

Hi Malcolm,
It looks as though you are spot on with your guess.
I don't have much knowledge of these old engines as I am fairly new to Steam engines, I have only been building them for the past 12 years and they have been mostly self designed Flash Steam  and Stuart engines.
I did at one time re-time an old engine and made a steam connection for a friends engine which had Stevenson  reverse with the valve gear to the inside and the thread on the steam chest was 1/4 x32 tpi, the maker of the engine is unknown, I shall open a thread and see if it can be identified.

Logoman from your picture of the engine can I suggest that you do as you have said , plug it and re -tap to a standard size and can you post a pic of the exhaust port and we may be able to suggest some thing.
George.

[Aeronut4]

If the thread is 3BA, then the easiest solution is to turn up a brass adaptor - one end 3BA to screw into the steam chest or cylinder the the other end bored  and threaded so that you can connect either a 5/32 or a 3/16 copper pipe.

[Bee]

There is no thread available as 5/32 x 32 tpi.

Oh dear. Go stand in the corner. Everyone should know 5/32BSW is the thread for Meccano. 

[ooyah/2]

Bee,
I will come out of the corner and give the dunces hat to you , we are talking about threads in steam engines which use M.E. threads and there is no 5/32 x 32 tpi M.E..
George.

P.S. I stopped playing with Meccano 60 years ago so I forgot.

[jviewing]

Your picture shows what I definitely thinks is a Stevens Model Dockyard engine and boiler. Any chance of a picture of the boat, I have a Stevens model dockyard launch from around 1891 (picture below)   I also have Model Dockyard catalogues from 1867, 1871 and 1919 which may provide more information on your model.
Best regards Jeremy

[ooyah/2]

Hi Jeremy,
As you seam to have a knowledge of Stevens Dockyard engines can you identify this engine which belongs to a friend,
So far we have had no luck in it's identity.
It was a devil to time as the valve gear is inside and difficult to get at.
I would appreciate your thoughts.
George.

[kno3]

Your picture shows what I definitely thinks is a Stevens Model Dockyard engine and boiler. Any chance of a picture of the boat, I have a Stevens model dockyard launch from around 1891 (picture below)   I also have Model Dockyard catalogues from 1867, 1871 and 1919 which may provide more information on your model.
Best regards Jeremy

Do you have more pictures of this beautiful boat?

[jviewing]

Hi George, what a beautiful engine.  It has similar supporting frames to my Steven's single, but does not have the telltale ridges in the cylinder casting that is common to Stevens engines. This on its own does not mean that it is not a Model Dockyard product.  There are a lot of other similarities Ie. steam pipe connection with central manifold.  I will do a bit of research and get back to you.
Jeremy

[jviewing]

I am conscious of not wanting to hijack someone else's thread take a look at http://www.modelboatmayhem.co.uk/forum/index.php?topic=8261.0 and post any question there. Jeremy

[ooyah/2]

Hi Jeremy,
That's a very fine old Edwardian launch and it pleases me to see somebody like yourself keeping them and restoring them.
Some time back LOGOMAN who is another collector of fine old boats and especially S.M.D. gave me an explanation that the engine was possibly one of their finer range and the owner/buyer didn't like the bands on the cylinder and had them removed.
This engine is very old and was purchased many years ago in a junk shop ( now called antique shops ) in Birmingham and he can't recall the cost but assures me that it wasn't a lot.
I had some fun timing it as the valve gear is all pinned with 1/16" taper pins which are all rusted in but even with the inside valve gear I eventually had it running very sweat in both directions.
The boiler feed pump is driven from an eccentric and after re seating and new balls it pumps away very well but unknown against boiler pressure.
many thank's for your input and any further info would be appreciated.
George.

[jviewing]

George, I think Logoman has a good point as the engine does look to be of a higher general standard, more model engineer than toy, although it keeps the spirit of model dockyard products. I cannot find evidence of a similar twin before 1911 in Steven's catologue. If it is Steven's it may be after the Model Dockyard company moved to 22 Aldgate from Fleet Street in London. I will get back to you.