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Author Topic: Steam test of Scotch Yoke Steam Engine  (Read 437 times)

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  • Tony Bird
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Steam test of Scotch Yoke Steam Engine
« on: February 18, 2023, 11:15:46 am »
Hi,

I have just downloaded a video on YouTube of a steam test of a model steam engine with a Scotch yoke drive which I help a friend a few months ago and he has since run it on steam.



Take care Tony.
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Re: Steam test of Scotch Yoke Steam Engine
« Reply #1 on: March 08, 2023, 07:44:07 pm »
nice job
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Re: Steam test of Scotch Yoke Steam Engine
« Reply #2 on: March 09, 2023, 04:35:46 am »
Bonjour Tony,
Great job for this quite original steam machine, I had never seen such model before.
Could you please remind us its bore and stroke ?
As it seems to be fast, which was your working steam pressure during this test ?
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Raphaël, Membre du Modèle Yacht Club de Paris : http://mycparis.fr/
Membre de l'Offshore Club de Paris: http://site-ocparis.wifeo.com/
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Re: Steam test of Scotch Yoke Steam Engine
« Reply #3 on: March 10, 2023, 02:47:25 am »
Hi Raphael,

The engine has a 3/4" (19 mm) bore and stroke and when in steam the boiler was at 20 psi. It does now tick over on air at about 2 psi.

The full size engines are often horizontal, the other size of the scotch yoke being connected to a pump. Also the full size ones tend to use a die block in the scotch yoke rather than just the crank pin. What is a bit unusual is the use of the yoke on the eccentric. Using a Scotch yoke rather than a connecting rod does make a very compact engine, good for use in a boat?

Take care Tony.
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Re: Steam test of Scotch Yoke Steam Engine
« Reply #4 on: April 27, 2023, 02:24:40 pm »
Tony:

Any insight into the advantages of the Scotch Yoke design?

Where were these engines commonly used?

Thanks for sharing the video.

Charlie
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Re: Steam test of Scotch Yoke Steam Engine
« Reply #5 on: April 28, 2023, 02:05:57 am »
Hi Charlie,

The only advantage of using the Scotch yoke design I can think of is that it makes a shorter more compact engine because no connecting rod is required. I think the full size engines were mostly used as pumps, the ram of the pump being on the opposite side of the yoke to the piston rod, a Weir type pump with Stephenson valve gear, if that makes sense?

Take care Tony.
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Re: Steam test of Scotch Yoke Steam Engine
« Reply #6 on: April 28, 2023, 01:24:21 pm »
Makes sense.

Thanks Tony!
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