Triple Expansion Steam Engine Cylinder Cocks
by John
Some further progress on the triple.
I bought cylinder cocks from Reeves UK, and the picture shows them fitted. In case I eventually install a mechanism to open all of the cocks simultaneously, they are in straight line, which necessitated making extension peices for the high pressure cylinder cocks.
The handles required bending to clear the pipework.
The cocks look a bit strange to me. Too big, and the handles are wrong. I am thinking about making a set from scratch. But that can wait.
Drain pipes from the cocks will be installed at some stage. Still deciding where to run them. And whether to join them into a common trunk.
The engine turns over by hand, but it is still a bit stiff. There was a tight spot which took many hours to locate. It turned out to be a valve rod thread which was about 0.5mm too long, touching the inside of the high pressure valve chest. Fixed in a jiffy.
I hooked up the engine to a small compressor at 30psi, but general stiffness prevented the engine from rotating. So I gave it an hour being rotated in the lathe at 200 rpm. It is noticeably more free, and getting very close to working. The valve timing is approximately correct (checked by my expert friends Thomas L, and Rudi V), but will need fine tuning at some stage.
johnsmachines 
Gday John,
I though that the design uses automatic drain valves on the cylinder covers. Do you need drain cocks as well?
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Hi Russ, No drain valves at all on the OB Bolton plans, or that I have seen in the Bertinat articles. Most photos on the net show drain cocks similar to these. John.
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On the cilinder covers there are safety valves with a spring tension. The drain cocks are for heating up the machine from a cold situation.
The steam in a cold machine can cool down so fast that it become water again,
For that purpose you open up the drain cocks to let the piston push out the steam with wather, After a little time you can close the drain cocks wenn the machine is heating up.
On YouTube you can see on the OLD STEAM POWERED MACHINE SHOP by David Richards, that’s when David is starting his steam engine to the shop working, after a few turns of the machine he close the drain cocks, on the cilinder, in one action. You can see it in different episodes.
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wow that is very impressive did you build all the parts for it to?
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Hi Doug, the cocks were purchased then modified. I am not satisfied with them, and I have ordered some more with a different shape and size.
The rest of the engine was built by me from castings and bar stock. Plans by OB Bolton. If you search the blog, including older posts, you can see most of the stages of construction if you wish. John.
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