Steam Tug Alva B - Engine Question

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PatJ
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Steam Tug Alva B - Engine Question

Post by PatJ » Sat Dec 25, 2021 9:42 pm

Can someone explain the rocking valves on the Alva B single cylinder tug engine.

Appears to be two valves, and multiple eccentrics.
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Re: Steam Tug Alva B - Engine Question

Post by PatJ » Sat Dec 25, 2021 9:43 pm

Specs on the engine:


22" bore x 24" stroke, 425 hp @ 120 rpm, HPNC (High Pressure Non-Condensing) engine built by Whitman Co., Buffalo, NY


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Re: Steam Tug Alva B - Engine Question

Post by TahoeSteam » Sun Dec 26, 2021 8:23 am

I have seen some unsusal launch-sized engines with rocking/sleeve valves.. but never something that big, and usually just one valve not what appears to be two.
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Re: Steam Tug Alva B - Engine Question

Post by DetroiTug » Sun Dec 26, 2021 2:34 pm

The big Corliss engines used rotary valves like that on each end of the cylinder, and I think one for inlet and one for exhaust to combat the temperature fluctuations encountered when using one valve for both. That may explain the extra valve gear.

Incidentally I've read that that was one of the issues with rotary valves, if fitted tight enough to not leak, they could seize when warmed up due to different expansion rates of the valve and body.

Ron

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Re: Steam Tug Alva B - Engine Question

Post by PatJ » Sun Dec 26, 2021 4:46 pm

Thanks for the responses.
I have been searching the net for rocking valve info, and while plenty can be found regarding the Corliss engines, I have been unable to find anything of significance with a rocking valve engine that is not in a Corliss configuration.

One of the only engines I can recall seeing with a rocking valve was a small bottle engine (photo attached).

I assumed that there would be more rocking valve info online, but I am pretty much coming up empty handed.
I also assumed that rocking valves were simple, and self-explanatory, but that does not seem to be the case either.

The double rocking valve arrangement on the Alva B has me stumped.

From a purely practical standpoint, it would seem that a rocking valve would essentially need to be a D-valve that is stretched/morphed into a round shape, maintaining the same relative port openings.
This is just a guess.

When I first looked at the drawing for the Alva B, I assumed that one valve was for steam, and one was for exhaust, but I can't make that work out at all, and so I am starting to think both valves were for steam and exhaust, and the valves could be operated independently, which would improve efficiency.

I always assume that I have sort of seen it all as far as steam valve and valve gear types, having read numerous steam books, but I always stumble across "that engine" that has some strange configuration that defies logic.
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Re: Steam Tug Alva B - Engine Question

Post by DetroiTug » Sun Dec 26, 2021 11:12 pm

"The double rocking valve arrangement on the Alva B has me stumped.''

What we may be looking at is rotary valves that are actually two valves in one, an inlet on one end and an exhaust on the other. Another thing to keep in mind is that is a drawing and often times details are not accurate, many old patent drawings are that way. Drawn in such a way to protect intellectual property but still convey the idea.

Ron
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Re: Steam Tug Alva B - Engine Question

Post by cyberbadger » Mon Dec 27, 2021 1:33 am

Here is an example of a single rotary valve steam engine:
https://www.youtube.com/watch?v=Sn2NsUXNJAg

Ron is probably correct that the drawing may be partially representative, some of the linkages in the drawing look quite skinny.

Oddball steam engines sure are interesting!

-CB
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