And the final Franklin page.

On CNR 6184 I wonder how much had to be done to the engine to convert it to the poppet valve gear. Did CN have to make a new cylinder saddle? Or were they able to make use of the existing casting, for example.

"Equipped with Poppet Valve Gear, applied to existing piston valve cylinder castings at Montréal Shops, 1949. One 14-in. piston valve in each steam chest replaced by two 7-in. diam. admission and four 7 in. diam. exhaust valves."

Joe,
It appears they used the existing castings and the photos confirm that.
Again, I wonder how much advantage this gave over the conventional Baker gear? That would be very interesting!
The locomotive was relatively new (1940) so they probably couldn't get too drastic a "re-do" past the "chief"! They went back to Baker gear and she ran out a few good years of service.

Former US Army locomotives photographed at Bill Miller Equipment Sales, Eckhart Mines, MD - January 18, 2013

Nice to see the orignal tender from WMSR #734 has been saved......

I believe Bill Miller (owner of the establishment) is a steam enthusiast who bought the locomotives.

Jeff, Alan Maples posted this, in this thread, on Mon Jun 29, 2009 8:51 pm :



This is why the engine is at Bill Miller's Equipment Sales.

Steve Hunter

Thanks, Steve for the "non-snarky" reply. I would not have thought to search the site for that bit of information since I have not been watching the RYPN Interchange long enough to have known about the saga of this locomotive.

No problem, Hamster, it's a long thread to go through. I was particularly interested due to the CNR content. Snarky's not my style, LOL.

:-)

Steve

Hopefully my postings on the CNR experiment have not upset this thread? I am new to the site and not certain of how things work or of the politics of things.
It was just that reading through the first pages about No.611, there was more information on poppet valve systems than I have ever seen before and myself and a friend had been discussing them in the spring.
I find it interesting to muse about the conversations that went on in the shops that led to these kinds of changes being tried. With No.611, one can see the need for an operating system that could be used by lesser trained personel and under less than perfect situations.
In the case of CNR No.6184, they had a full cohort of skilled operators. But were there really some good old steam men who hoped to find ways of keeping steam around a little bit longer? Again, it would be nice to find some reports on what they found.
Thank you.

One additional image showing some detail of the valve arrangement.

^ Nice photo; thanks for posting. As I said earlier, it would be really interesting to know how well this system (referring specifically to this "one-off" Franklin gear installed on USATC #611) worked from a thermodynamic standpoint. It would have certainly been a lot easier for a "non-steam" engineer to operate as the reverser only had 3 positions- forward, "neutral" and reverse.

I also wonder if it might have been beneficial from the standpoint of preventing runaway slippage.

I think that pure thermodynamic efficiency is somewhat deprecated in this design -- its inherent reliance on "wire-drawing" to achieve practical cutoff tells me that without further consideration. Note his reference to utility of the system for rapid forward-to-backward transition for switching in the patent, and how fleetingly he refers to multiple or continuous cam profiles there.

> I also wonder if it might have been beneficial
> from the standpoint of preventing runaway slippage.

In my estimation, clearly.

Quoting from the patent:

"Because of the above describ[e]d cam profile, different effective cut offs are provided at different speeds of the locomotive. Thus, at very speed operation or at start, the effective cutoff in the specific example given above will occur at 85% of the piston stroke, since, at start or at very low speed even a very small valve opening is adequate to admit the starting steam. As the speed of the engine increases, wire drawing occurs in the portion of the stroke corresponding to portion C of the cam, since at this time the opening is very small and insufficient to the volume of steam required to provide 85% effective cut-off. Similarly, at still higher speed, wire-drawing will even occur in the portion of the stroke corresponding to portion B of the cam, as a result of which the effective cut-off is again shortened, the progressive shortening of the cut-off being shown by the legends applied to Figure 9.

"From the foregoing it will be seen that by appropriate plotting of the cam profile a number effective cut-offs may be obtained with requiring any adjustment of the cam mechanism or of the valve gear. For this purpose the cam profile may either have a gradually inclined surface in the region from the main lobe down to point d or may have arcuate surfaces interconnected by inclines as in the form herein illustrated.
A similar action is obtainable by appropriate plotting of the exhaust cam profile. Preferably, according to the invention, the exhaust cams for forward and reverse operation (see cams 71 and 73 in Figure 5) are provided with at least one portion such as indicated at E, of substantially lower height than the main lobe 128, which portion (E) serves to delay the point of compression at start and at low engine speeds. At relatively high speed the effective compression point is advanced, since the extent of exhaust valve opening provided by cam surface E is not sufficient, at the higher speed, to fully exhaust the cylinder.

"The employment of cams of the type above described is of especial advantage in association with a control mechanism of the 2-position type, since notwithstanding the fact that the engineer's control has only one forward position and one reverse position, the mechanism itself automatically effects variation of cut-off (and also, if desired, of compression) according to the speed of operation of the engine."

Now, in a slip, even if the throttle is left in the same position, the wire-drawing effect will promptly decrease both the peak and mean effective pressures per stroke, which is exactly what is wanted for 'automatic' slip abatement. If at the same time the effect of increased rotational speed is to increase effective compression (as Kirchhof notes, by effectively throttling the exhaust flow) a fringe benefit will be increased counterpressure at the ends of the strokes, to help arrest any inertial component of an evolving spin.

Interesting analysis, Robert. All that makes perfect sense.

Regarding my reference to the gear's thermodynamic performance, I'd just be curious to see how it compared to conventional valve gear or "conventional" poppets for that matter. I wonder if it really gave up much operational efficiency compared to being able precisely regulate cutoff.

The problem is, absent actual indicated performance curves from the actual locomotive, complete with measured coal and water feed, it's not likely a fair assessment can be made.

The effect of the 'wire-drawing' will be similar to operating the engine with a partially-closed throttle, a bit like the sliding-pressure firing strategy I referred to a while back. This would be 'less efficient' thermodynamically to just about the same extent that 'driving on the regulator' would be vs. the conventional wisdom of working steam unthrottled (i.e. on cutoff only) as early as possible after a start.

The lack of continuously-fine-adjustable cutoff has been discussed with respect to a number of the 'old favorite' poppet valve gears, including those shifting-cam designs that feature (for practicality) only a small number of 'ahead' cams as opposed to continuous-contour with spherical roller followers. (Remember that Kirchhof IIRC was one of the bigwigs at Franklin/Balmar in the great age of the Franklin System). As you may note from the patent, the 'automatic cutoff' approach can be used either with multiple 'speeds' (cam profiles) or with the shifting-cam setup, and therefore aside from the 'wire-drawing' control feature should show about the same efficiencies -- pro and con -- of Franklin type B or Long Compression over a continuously-variable arrangement like type A. Fun to speculate on what the 'user interface' of a multiple-speed system would be: I personally hold out for the notch-style controller with visible indicator, but pushbuttons combined with the existing forward-back-neutral lever would be another approach with a bit more haptic "optimization" when running. I don't like the idea of the 'click-shift' approach (where, as on a bicycle or paddle-shift car system, the higher-speed option is reached by repeated presses on the same control) - but I'm open to all suggestions...

Anyone done, or know of, an analytic comparison of the PRR T1 equipped with type B against the original system? Even using only test plant results, this would give us something of a leg up on this, as I believe the valves and steam passages themselves were not fundamentally altered in the conversion...

If you are wondering why I'm advocating restoring the 611 to operation, it is precisely to answer some of these questions in proper detail. We're fortunate to have Mr. Miller as the owner, and what I believe is a careful and considerate team of people working on her.