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Odd feature on steamchest.
http://www.rypn.org/forums/viewtopic.php?f=1&t=44862		 Page 1 of 1
Author:  FeGua 200 [ Wed Sep 16, 2020 4:44 am ]
Post subject:  Odd feature on steamchest.
If you look at the steam chest you can see a rod that runs down from behind the valve stem and then by the means of a joint enters below the valve seat. I don't think it is connected to the motion. Does anyone have any guesses to what this might be? Would this be for water brakes or something of the like?
The image was taken from an Ebay posting that has now ended. I wish I'd remembered to bid on it...

Image

Thank you very much,
John

P.S. Is it just me or is the front pony truck wheel bigger than the rear?
Author:  nedsn3 [ Wed Sep 16, 2020 8:21 am ]
Post subject:  Re: Odd feature on steamchest.
I don't know the answer to your question, but I'd like to say that's a neat looking locomotive. Ned
Author:  filmteknik [ Wed Sep 16, 2020 9:30 am ]
Post subject:  Re: Odd feature on steamchest.
Indeed. Interesting application of Walschaerts on a slide valve engine.

I don't know if it's connect to the motion or not but is that an unusually tall valve? If it was connected could it be some technology that somehow involved two, stacked valves?

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Author:  Overmod [ Wed Sep 16, 2020 10:27 am ]
Post subject:  Re: Odd feature on steamchest.
Suspect this may involve Hobart-Alfree valves.

It can't be a device like riding cutoff or variable auxiliary exhaust valves because it is driven directly off the valve rod, not via separate adjustment.
Author:  Kelly Anderson [ Wed Sep 16, 2020 3:24 pm ]
Post subject:  Re: Odd feature on steamchest.
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It is operated from the cab into the same area where automatic drifting valves were often mounted in later years, so I'll bet that it is a manually operated predecessor of a drifting valve. It isn't connected to the valve gear, the valve crosshead guide was just a handy place to mount the trunnion for the linkage.

And yes, the second lead truck wheel measures about 12% smaller than the front one. Never saw that before on a new engine (at least I assume that it's a new engine from the photo).
Author:  Overmod [ Thu Sep 17, 2020 2:59 am ]
Post subject:  Re: Odd feature on steamchest.
I blew up the image in the original post and I think Kelly is precisely right: you can see the cross-shaft behind the trunnion, and the tightening bolt that holds the visible crank (which is a subtly different color from the bracket) tight on that cross-shaft, presumably with either a flat or key arrangement to lock it in alignment; it looks as if there is at least one universal or flexible joint (near the valve chest) on the rod connecting that crank to whatever is behind the cylinder jacketing...
Author:  joe6167 [ Thu Sep 17, 2020 1:34 pm ]
Post subject:  Re: Odd feature on steamchest.
When you start digging through photos of engines from that era you'll find so many mysterious experimental devices that only lasted a few years. So much from that era seems to have escaped documentation.
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