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Discussion Starter · #1 ·
Did the K-27 prototype have 2 or 4 chuffs per revolution?  
 

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Depends on whether or not the engineer instructs the fireman to run the coal retaing boards up and remove the jumper.

I can see it now.
 

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Take a look at this:

http://www.kesr-operating.org.uk/walschaert animation.htm

Steam locomotives with the usual standard type cylinder on each side with the usually found valves and gear will produce four chuffs per revolution of the wheels. That's because the piston is double acting, meaning it's driven in one direction by steam, and then exhausts that steam while being driven back the other way while the other side is being driven by steam. The valves choose which side is getting the steam and which side is the exhaust.

(You folks from the live steam section will please pardon the oversimplification here.... )

The point is, and you'll see it if you watch the above, that you have two exhaust strokes per cylinder per revolution, for a total of four. At some point early in the locomotive's history, the exhaust steam was routed into the bottom of the smokebox and up the stack which acts as a sort of muffler, and also provides draft on the fire. Thus, each time the locomotive's wheels turn, there are four times that the valve opens, and the exhaust steam is blown out, and up the stack. Because the two sides of the locomotive are 90 degrees different (when the main rod is at the very top on one side, it will be halfway down on the other...) you have four (nearly) evenly spaced beats from the exhaust instead of the two large ones you'd get if they were the same, or 180 degrees apart.

With a shay, you often have three cylinders, and thus six exhaust beats per turn of the CRANKSHAFT .... which will translate to turn of the wheels depending on what gearing the crankshaft has to the gear on the wheels, which varied from model to model.

Make sense?

Matthew (OV)
 

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Matthew, thanks. Neat site. Wish it had sound though. I had to add my own (orally). /DesktopModules/NTForums/themes/mls/emoticons/tongue.gif
 

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Discussion Starter · #7 ·
Thanks for the explanation Matthew, and the link!

One question, on a 3 cylinder Shay I've heard that 12 chuffs per revolution is normal, so from your explanation that would mean 2 turns of the crankshaft per revolution? Probably because they were typically geared so low for heavy loads? In particular I have the WSL #15 Shay, which I have set for 12 chuffs per revolution.
 

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Hmmm.
Kind of.

Two chuff exhausts per cylinder per revolution.
Two chuffs times three cylnders is 12 chuffs.


EDIT:
Actually, I should have added 12 to a wheel rotation.
It's about a 2:1 reductiion at the wheels.
It's 6 per rotation of the crank, and depending on gear ratio, about 12 to a rotation of the drivers.
I counted the teeth once, think that's what it was.
Over about 6MPH it's just a roar.
 

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Guys, for a 3 cylinder shay it's 6 chuffs per revolution of the DRIVE SHAFT.  The wheels are gear driven. Who knows how many chuffs it takes to make one revolution of the wheel.  It maybe 12 or it may be 24.................thimk.  depends on the gear ratio.
 

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Discussion Starter · #11 ·
Nice video, thanks Matt! It was a little difficult to see the counterweights rotating except for just the end of the clip, but looks like 4 chuffs is correct.
 

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And just to add proof that live steam is where it's at;) :

GS-4 Link
Aster mikado with four on the floor, err rails (timed square, all 4 beats hitting at the proper time):

For reasons stated above, most two cylinder engines (save for those badly out of time) had 4 exhaust beats per revolution.  On an engine that is perfectly square, you can time the beats with positions on the drivers {12:00, 3:00, 6:00, 9:00, and repeat}.  3 cylinder dos engines had 6 beats per rev and 4 cylinder simple steam engines had eight.  The chuffs tended to blend together at higher speeds, creating the whirr effect that you hear from mainline steam. 
 

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Just so's nobody thinks the geared guys corner the market on "buzzing sounds" ..... note that the "Volcano Effect" is big and scary enough to all but drown out the WHISTLE:

http://www.youtube.com/watch?v=3HgvqSaDEoY

Though... in proper Soo fashion, it's hooked up high enough that you can still hear something of a cadence.

Ok, but folks wanted to count beats..... so try this instead:

http://www.youtube.com/watch?v=Xv4Qz-O95xQ

I know at least one fellow who's now cheering for his favorite steam engine! I was gonna use my alma mater with these two clips, but unfortunately the engine isn't working too hard, and the rod knock drowns a lot of it out....

http://www.youtube.com/watch?v=QIFHyM8I06M

http://www.youtube.com/watch?v=Lp79vO3k90U

(Please give full credit to the insanity in the second clip. Since the passenger is doing the filming out his window, the second clip is filmed with the chase vehicle travelling in REVERSE! Do not, however, ask anything about who that posessed driver might be....)

Matthew (OV)
 

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Discussion Starter · #14 ·
Nice videos Ryan and Matt.

Matt, I do have a question regarding the "chase" clips. How fast would said driver have been going to keep up with the loco? In particular the one where said driver was actually driving forward :)
 
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