Interesting engine question

[crueby]

Hey all,
Came across this engine on the National Archives website, its from the USS Monadnock, a twin turret monitor type warship. This engine was designed to rotate the gun turret. It has two cylinders, 90 degrees from each other, with a single crankpin. The part I've never seen before is the valve linkage, keys off the crankpin, with levers going out to either valve. Anyone ever see this before? Know who invented this type of linkage? I've attached a copy of the plan, scaled way down to fit - too small to read the dimensions, but you can still see the part outlines fine.
Chris

[Sanjay F]

No idea of the answer but am interested by what you say about the linkage and what it does; is that there to keep both cylinders synchronised with each other mechanically rather than timed 'by measurement or by eye'?

[crueby]

No idea of the answer but am interested by what you say about the linkage and what it does; is that there to keep both cylinders synchronised with each other mechanically rather than timed 'by measurement or by eye'?

The pistons themselves are connected to one crankpin, so that keeps them synchronized. Its the valve linkages that I've never seen before. They both work off the same crankpin as the pistons, which maybe could be adapted to a single cylinder engine?

[crueby]

Actually, I'm describing it wrong - the valves both get driven off the lower left crosshead movement, not directly from the crankpin.

[steamer]

Walschaert-ISH

[crueby]

Walschaert-ISH

    Don't think the patent office search engine has an '-ish' checkbox! 
 

[Charles Lamont]

Joy-ISH too. Each of the curved 'expansion' links is worked by the crosshead of the other cylinder. So each valve is phased at 90° to its piston. So there will be no lap and no expansive use of steam. Reversing both sets of gear is done by the bell-crank. Note that the die block for one valve is 'up' and the other 'down'. This cleverly provides the asymmetry necessary for coordination, just as with cross drive in duplex pumps.

[crueby]

Yeah, the use for the engine would have been for short stop/start runs moving the turret, so no need for changing cutoff, I'd say. It does seem to have elements of Joys and Walschaerts, but then so do any of the other 3 dozen railroad linkages. This one is a bit odd in that the cylinders are offset 90 degrees to each other, which would make sense for fitting in or around the perimeter of the turret.

Might CAD this one up to animate just to watch it go!

[Fj45]

 Hi Chris
   Not much for crime story "who dunnits", but love a good mechanical "what dunnit".
 It looks to me that the "lower left" crosshead only runs the "upper right" valve & the U.R crosshead runs L.L. valve.
 Starting at lower left crosshead there's a link parallel to conrod, pinned to a link with a tee shape. I assume the tee piece is the expansion link. It appears to simply pivot about a point dead center of its slot. Die block positioned in slot by links and arm from weigh shaft as usual. (weigh shaft sitting where camshaft would sit in .I.C. V8).
 Interesting setup l to have not seen before (doubt having studied half so many of these as you but).
 This one confirms my general opinion of US heavy engineering back in the day ..deceptively, ingeniously, simple.. once you get your head round it & (in my case) stop trying to solve imaginary complications that ain't there.
 edit .. couple of replies whist typing

[crueby]

Hi Chris
   Not much for crime story "who dunnits", but love a good mechanical "what dunnit".
 It looks to me that the "lower left" crosshead only runs the "upper right" valve & the U.R crosshead runs L.L. valve.
 Starting at lower left crosshead there's a link parallel to conrod, pinned to a link with a tee shape. I assume the tee piece is the expansion link. It appears to simply pivot about a point dead center of its slot. Die block positioned in slot by links and arm from weigh shaft as usual. (weigh shaft sitting where camshaft would sit in .I.C. V8).
 Interesting setup l to have not seen before (doubt having studied half so many of these as you but).
 This one confirms my general opinion of US heavy engineering back in the day ..deceptively, ingeniously, simple.. once you get your head round it & (in my case) stop trying to solve imaginary complications that ain't there.
 edit .. couple of replies whist typing

"What Dunnit" - great phrase!  I've had 'why-don-it-work' sometimes...

I love looking at old machinery and figuring out how it works. Often linkages got over-complex to get around someone else's patent, sometimes just since the designer didn't really understand the problem!   

[Fj45]

 "I've had 'why-don-it-work' sometimes"  yarrp..
 Thanks for an enjoyable hour, Chris, got any more?

[crueby]

"I've had 'why-don-it-work' sometimes"  yarrp..
 Thanks for an enjoyable hour, Chris, got any more?

No other ones at the moment since I  got that faulty dematerialization circuit  on my Tardis fixed...   




Might have one soon, am figuring out the paddlewheel engine from the Great Eastern. Last mechanism is  the  friction clutch setup for disengaging the  wheels.  Waiting on  some info from the science museum and an old book that may solve it...

[Fj45]

 Speaking of Tardis, I just realized what time it must be over there. I'll stop asking questions from New Zealand, where it's currently lunch time tomorrow.

[crueby]

Speaking of Tardis, I just realized what time it must be over there. I'll stop asking questions from New Zealand, where it's currently lunch time tomorrow.

Its only early evening yesterday here. Still time to buy a lottery ticket if you can tell me tomorrow's  numbers!   

[steamer]

Is there a title block with a name on that print?    Might be a good patent search if you have a name

Dave