[N&W] Re: I'm a damn old eccentric crank
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nw-mailing-list at nwhs.org
Thu May 6 22:07:04 EDT 2004
>[Kurt S. Kramke wrote:]
>To answer the question posed by Ben Blevins on the eccentric crank, on a
>steam locomotive it is connected to the pin of the driver where the main
>rod(the one from the cylinders) and is used to operate the valve gear.
>The crank is offset either forward or backward between 15 and 25
>degrees, as near as I have been able to determine from photos, so that
>the drivers will move when steam is applied to the cylinders. When
>moving the crank end traces an elliptical path, look closely at steam
>videos to see what it looks like. With the exception of some S and O
>scale models, I have not seen a brass locomotive come in with the crank
>set right(which I immediately correct).
[Ed King steams a reply:]
Kurt - you can't set the cranks "either forward or backward", your choice.
Not if you want the engine's valve motion to look like that of the real
thing. That's the problem with the P2K engine now. The cranks on the right
side of the model lean backward, which is wrong. The ones on the left side
of the model lean forward, which is correct. This is why, if it was a real
engine, the two sides of the engine would try to run in opposite directions.
AGAIN: FOR AN INSIDE ADMISSION ENGINE WITH DIRECT VALVE GEAR OF EITHER
WALSCHAERTS, BAKER OR SOUTHERN, THE CRANK CONNECTION WITH THE ECCENTRIC ROD
MUST FOLLOW THE MAIN PIN BY 90 DEGREES. HENCE, THEY MUST LEAN TOWARD THE
CYLINDERS (NO MATTER WHICH SIDE OF THE ENGINE THEY'RE ON), AND NOT AWAY FROM
THEM, IF YOU'RE SETTING THEM ACCORDING TO KURT'S LAW. THE Y-3 HAS INSIDE
ADMISSION CYLINDERS WITH DIRECT BAKER VALVE GEAR. IF YOU SET THE CRANKS
LEANING BACKWARD, WHEN THE ENGINEER PUTS THE REVERSE LEVER IN FORWARD
POSITION, THE ENGINE WILL MOVE BACKWARD!
FOR OUTSIDE ADMISSION CYLINDERS WITH DIRECT VALVE GEAR OR INSIDE ADMISSION
CYLINDERS WITH INDIRECT VALVE GEAR, THE CRANKS WILL LEAN AWAY FROM THE
CYLINDERS. THE Y-3 DOES NOT HAVE OUTSIDE ADMISSION CYLINDERS, NOR DOES IT
HAVE INDIRECT VALVE GEAR.
I still cannot understand why modelers can get the damn whistle linkage
right and can't set the damn cranks. The real thing would run without a
damn whistle, and 90 percent of the other stuff they attach to the boilers.
But the real thing would NOT run if the cranks weren't set correctly.
Oh, and don't knock the old Mantuas. Or Varneys. Same reasons. If they were
full size they wouldn't look like the old Tenshodos and Crown Uniteds
everybody went ape over, but if they had steam up they had valve gear good
enough to run. And the Tennies and CrUds didn't.
I'll repeat the offer. If anyone who is interested enough will send me a
SASE (put two stamps on it, please) to 10265 Ulmerton Road, #197, Largo, Fl.
33771, I'll send him a copy of a story that appeared in the May 1984 issue
of TRAINS which explains all this stuff in words of two syllables or less.
I mean, it's eight pages you have to read, but I've been told it's a good
read . . .
I'd send a copy to the folks who make the P2Ks, but I'm afraid I'd just piss
Thanks to Ed for explaining that! I will confess it
is hard for me to comprehend all the aspects of steam
locomotives, considering all the N&W steam I ever saw
was 611, I always had to work when 1218 came through
here. I haven't seen 1218 since I was 5 when my
father took me to Roanoke to see her in 1976. It
broke my heart when I didn't get to see her at the
convention, I wish they could have let us in to see
her, even in her current condition.
I don't go see 611 much, it breaks my heart when I do.
She just sets quietly, no hissing, or pumps running,
no occasional chug of the stoker, she just sets there
lifeless, AND IT HURTS! Just some of my thoughts...
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