Given that Frisco 4018 & 1630 were on the PRR from 1919 to 1923 & 1918 to 1920 respectfully, has there been other USRA locomotives that were leased to the Pensy?

(30) B28s 0-6-0
(38) L2s light 2-8-2
(130) N2s heavy 2-10-2

I think that's all of them.

Where there any other Russian Decapods that were leased to the PRR besides 1630?

I'm not a PRR expert so take this with a grain if salt, but as far as I know, all of PRR's decapods were built by PRR and Baldwin to PRR's design. I don't think they had any others unless there was a very short term lease somewhere along the way or they borrowed one to test. Any oddballs would have had a different class designation above I1s, for example I2 or I2s but nothing like that shows up in any rosters. I could be wrong, though.

PRR and Baldwin built 598 of the I1s and I1sa Decapods. No Russians were wanted or needed.

Aren't the Russian's even lighter than PRR's previous "generation" of consols too?

In a fight, I'd pick a Pennsy H6 over one a Russian Deck any day.

But some Russian Decapods were on the PRR for a brief time

I did some more digging and learned that Frisco 1615, 1621 & 1632 were on the PRR for their lease before being sold to the Frisco

A gentle reminder that the "Russian Decapods" were NOT a USRA design, but rather an available surplus of extant steam locos requisitioned by the USRA during their nationwide "operation" or "seizure" of the mainline rail network. A number of Russians were put into service on the USRA "network" after the necessary regauging and other modifications by the builders, but they continued to have problems (such as wide wheel centers that fouled some switch frogs, a problem still extant today on IRM's 1630) that restricted their range and pressed most RRs to get rid of them as soon as they could.

Most of the "definitive" sources of PRR operational history I have looked at so far all but refuse to even acknowledge the existence of any USRA steamers operating on the PRR, or for that matter even that the USRA "nationalization" era even happened. I chalk this up to a combination of willful ignorance, PRR pride/parochialism (the "not invented here, so doesn't count" mentality--see the later J1 2-10-4's to C&O design during WW2 as the other example), and relatively low "intrusion" by USRA locos into PRR territory. I'm sure, given the "scholarship is inversely proportional to importance" aspect of RR history authorship ("White's Law," by John H. White Jr. of Smithsonian fame), that someone somewhere has penned some coverage of USRA locos on the PRR in the era (possibly some issue of the PRRT&HS Keystone or another newsletter), but I don't know where it is. And I'm wagering that the three Russian Decs mentioned may be all that ever got to the Pennsy--and it was "blink and you missed them."

The I1 class were low speed drag locos that weighed quite a bit more and had a lot more tractive effort than a russian. They started production in 1916 so I can see how PRR would say "no thanks".

I thought the PRR I1s were built with 50% limited cutoff and were good for PRR 50mph freight speed... if you could stand the bad ride out there at the back end of that overhanging chassis.

Probablly not wholly coincidental that the PRR experimented in the Twenties with low-mass aluminum rods on an I1s...

Here's one in retirement in Ulan Bator: /Users/billsmini/Desktop/IMGP3365 2.JPG

First, let me say that I'm not a steam expert so please feel free to correct me. My understanding was that the original 50% cutoff was for efficiency in steam consumption. I have no clue about the design top speed though I would imagine that the lack of adequate counterbalancing on small drivers would not only beat the crew at speed but also pound the heck out of the machinery. So my curious question would be did they ever run at a sustained speed approaching 50 mph?

When it comes to "The Standard Railroad of the World", never say never. The well known adage with the I1's was the question, "how does it ride?" and the answer is "it doesn't". Were they ever pushed to 50 MPH? Maybe, in a pinch, but I'll wager it was nowhere near commonplace.

The I-1 was tested on the Altoona test plant at maximum of 140 rpm which is 25 mph. In later years when the Pennsy needed to speed up their freight service, the engines had excessive compression issues. To eliminate this, they modified the valve gear to 78 percent maximum cutoff. The tractive effort went from 90,000 to 96,000 lbs.

According to William Withuhn, excessive compression was an issue for engines with limited maximum cutoff. He noted that when he tested the T&P 610 with Southern Railway's dynameter car, the recording showed a sawtooth profile of the drawbar pull.

Dave Wardale modified the SAR 3450 with a 65% limited cutoff, I don't think he had any issues. The Santa Fe equipped the 3765 and up 4-8-4's and their 2-10-4's with 60% limited cutoff. I don't recall reading about any issues with compression.

Tom Hamilton

It was my understanding that the PRR I1s was built with fixed 50% cutoff, which is far shorter than 78%. That is built into the ports, given a nominal valve travel, and any shortening of the valve motion would necessarily produce even less than 50% cutoff (compared to theoretical full stroke).

Excess compression would be a natural consequence of 50% fixed cutoff, as the exhaust release would be phased the same as inlet cutoff, leaving a considerable steam mass to be recompressed even if the front end were relatively 'free' to exhaust. One 'cure' for this would be to extend the counterpart of "cutoff" to allow release up to that stated 78%... but on a simple radial valve gear like Walschaerts, that necessarily means 78% rather than 50% limited cutoff on admission.

This is one area where Wardale's idea of paired piston valves would permit greatly longer-duration exhaust port opening, reducing the compression mass and effective compression stroke to match the 'inertia cushioning' requirements (and not incidentally allowing sufficient compression to bring the cylinder steam pressure just up to admission pressure in the port at the moment the valve starts unshrouding on the return stroke).

Incidentally going from 50% to 78% maximum cutoff would make starting torque far less 'peaky', which is a factor in practical stalling and slipping. The 'catch' is that to use that effectively without increasing steam mass flow, you also need to 'regulate' effective chest and mean effective pressure by carefully modulating the throttle, something a Wagner throttle would easily allow, buuuuuut NOT the typical throttle, or the typical engineman's way of working the throttle, provided on the I1s as built...

The riding qualities of the I1s are another question, which is certainly related to operating cutoff at relatively high developed horsepower at speed. You have a locomotive optunuzed for high adhesion after the manner of D&H and L&NE Consolidations, basically all drivers with the engine mass centered nearly over them, with a little afterthought Bissel lead truck to pull the long wheelbase into curves. This is not at all helped by the main rods that drive 'outboard' right on the center of the driver wheelbase, so both piston thrust and the horizontal resultant of augment forces are precisely positioned to cause maximal yaw forces (which that two-wheel truck is NOT designed to accommodate well!) Now consider the almost astounding rear overhang and the consequent effect on polar moment of inertia, which is a sort of Good Thing if out of phase, but just abjectly, face-palmingly bad if near a critical resonance...

There is actually a (partial) solution to the unrestrained yaw coupling: move the lead tender truck up from a pivot position near a 'quarter point' of the tender underframe as far forward as possible. A couple of European and Asian locomotives in fact moved this up under the drawbar pivot, so the truck bolster could actually be forward of the nominal tender body. Then couple the tender frame and rear of the chassis better so the lateral accommodation of the truck helps 'steer' the rear of the chassis the same way the outboard radial bearings at the rear of a Delta trailing truck do... (I leave it to the reader to start totting up where the problems with this approach on a coal-hauling PRR 2-10-0 might be...!)

Also in theory, the balancing method applied to the 9F 2-10-0s might have been applied to an I1s, with some interesting implications on how fast the result might 'spin' under power without inducing dangerous levels of augment. I doubt anyone sane would actually propose testing a 'hippo' to such speeds, even on the test plant, but just as with the N&W Y-class locomotives, there might have been very good reasons at certain times in operating history when the ability to run at higher track speed with loads would have been valuable...