Stuart Sirus Engine

A special section just for steam engines and boilers, as without these you may as well fit a sail.
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fredrosse
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Stuart Sirus Engine

Post by fredrosse » Thu Jan 12, 2017 5:00 am

This type of engine is single acting, two cylinders, 1 inch bore and stroke, with an enclosed crankcase, and has been used for racing model boats, as well as the British WWII radio generator sets that are now rare collectors' items.

I have a Ritter Dental Air Compressor which can be converted to be almost exactly the same configuration as the Sirus engine, except it has 1-1/4 inch bore, 1-1/2 inch stroke. Have any of our forum members had experience with the Stuart Sirus engine, or something fairly equivalent?

I want to make a small (eleven feet long) steamboat with the Margaret S "little sister" hull, and this engine would fit very well. I do however have some concerns about lubrication. When I have converted IC engines to single acting steam engines, lower end crankcase oil becomes a white milky mix of oil and water, due to steam leaking past the piston rings. How does the Sirus engine (and its owner) deal with this condition, if indeed it does occur with the Sirus engine?
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RGSP
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Re: Stuart Sirus Engine

Post by RGSP » Thu Jan 12, 2017 8:37 am

Fred,
I have seen such things in action with hydroplanes - a long while ago! I think the answer to the lubrication issue is that the hydroplane runs were only a few minutes, and the oil got changed very regularly.

The Sirius is still a production item (as castings) from Stuarts, and I occasionally see references to people racing them in the UK. Somebody, somewhere, probably does in the US as well.
http://www.stuartmodels.com/item/59/stu ... unmachined
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Re: Stuart Sirus Engine

Post by Mike Rometer » Thu Jan 12, 2017 10:34 am

A possible solution to reduce the 'water in the oil' problem could be to fit two rings in the same groove. With the ring gaps opposed there should be a lot less leakage.
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Re: Stuart Sirus Engine

Post by cyberbadger » Fri Jan 13, 2017 12:35 am

Nice cutaway. This is on my list of engines to acquire. These can run so fast (for a steam engine) and they can be put to good use to make electricity.

-CB
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Re: Stuart Sirus Engine

Post by TahoeSteam » Fri Jan 13, 2017 6:04 am

Mike Rometer wrote:A possible solution to reduce the 'water in the oil' problem could be to fit two rings in the same groove. With the ring gaps opposed there should be a lot less leakage.
Total Seal does something similar to this with their "gapless" ring sets.. talking nearly 0% leakdown. I know a member on here put a set in his Stanley engine with great success... perhaps he'll chime in.
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Re: Stuart Sirus Engine

Post by TahoeSteam » Fri Jan 13, 2017 6:05 am

Oops double post
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Re: Stuart Sirus Engine

Post by Mike Rometer » Fri Jan 13, 2017 10:17 am

There are several 'ring' solutions to get rid of the gap, I suggested double rings as the most simple (you can make your own). Rings with stepped ends are available, or if you're made of money, Clupet rings. The only thing to be careful about is getting lube to both ends of the bore.
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Re: Stuart Sirus Engine

Post by Lopez Mike » Sat Jan 14, 2017 1:40 am

I think that Barts old compressor engine was set up that way.

Bart??
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Re: Stuart Sirus Engine

Post by barts » Mon Jan 16, 2017 10:14 pm

Lopez Mike wrote:I think that Barts old compressor engine was set up that way.

Bart??
Yup: old refrigeration compressor I converted into a steam engine: 2" x 2.5" bore and stroke. Ran
for many years (20+) until the bearings got too worn. I followed what the Westinghouse high speed engines
did - mostly water in the crank, with a splash of cylinder oil.

It was a really easy way to get steaming, and not expensive, and since we had little kids and a mortgage, that
was important.

Were I to build another, I'd use distance pieces and set up double acting cylinder above each original cylinder,
and use the original pistons as cross-heads. This would last about forever since there's be a sealed crankcase.

- Bart
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Bart Smaalders http://smaalders.net/barts Lopez Island, WA
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Re: Stuart Sirus Engine

Post by fredrosse » Tue Jan 17, 2017 2:09 am

Bart, I am assuming you had a 2 cylinder, 180 degree crank? Steam cylinder oil in the crankcase, or pure mineral oil (non-compounded)? Did you have a slide or piston valve, and did you inject oil into the steam?

For simplicity I plan on just adding a new head with a piston valve (very nearly), and an eccentric running a rocker, ala Westinghouse Junior Engines.
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