PRR K4s 5399

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PRR K4s 5399
Posted by daveklepper on Monday, September 14, 2020 8:15 AM

1.  Was this conversion by Lima in 1939 the only one?  2. Were others modernized by PRR itself.  3. How does a front-end throttle improve performance?

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Posted by CSSHEGEWISCH on Monday, September 14, 2020 10:15 AM

One advantage of a front-end throttle is that it reduces the response time of the locomotive to throttle changes.

The daily commute is part of everyday life but I get two rides a day out of it. Paul
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Posted by timz on Monday, September 14, 2020 10:59 AM

No other K4 got rebuilt the way 5399 did. One or two others got poppet valves.

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Posted by daveklepper on Tuesday, September 15, 2020 3:04 AM

What Type popet-valves were used?

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Posted by M636C on Wednesday, September 16, 2020 8:07 AM

daveklepper

What Type poppet-valves were used?

 

5399 was fitted with Franklin Type A valve gear.

This conversion is dealt with in detail in Vernon L Smith's "One Man's Locomotives".

The conversion to a front end throttle was part of a conversion to increase the steam flow area right through from the boiler to match the capability of the poppet valves. This involved changing the dry pipe, the throttle and the superheater. 5399 originally ran with the poppet valves and the original boiler and throttle, but was modified to increase its power. It could haul a train normally requiring two standard K4 locomotives.

Peter

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Posted by Overmod on Wednesday, September 16, 2020 9:17 AM

daveklepper
What Type poppet-valves were used?

On 5399, the Franklin System type A with oscillating-cam drive was used: this has two small admission valves and two larger exhaust valves per cylinder end (this is the layout on the 'heraldic shield' in contemporary Franklin advertising!)  This is the system adopted for the T1 construction, and in the rotary-valve T1 conversion (which used bridges to activate the paired valves from a single follower).

Oscillating cam poppet valves are something of a scam, because when operated from traditional valve gear the valve lift can be proportional to cam excursion, which is NOT productive of clean limited cutoff.  (This is not necessarily a 'bad' effect when running at lower speed, for the same reasons the 'type D' in the Vulcan conversions for Army 2-8-0s were).  It is interesting that the poppet-valve conversion was done before the large sine-wave superheater was put in.

3847, which was converted in 1945, uses a rotary-cam system, with the older very heavy Franklin outside drive frame similar to that on the C&O L-2 Hudsons with RC.  That engine's appearance can be studied here:

http://www.northeast.railfan.net/images/prr3847.jpg

In some ways this is a superior method, but only if fitted with continuous-contour cams (which are expensive to machine and difficult to maintain).  Most of the RC systems with discrete cam profiles (e.g. British Caprotti and some Reidinger) tended to have poor performance off the regime for which the cams were machined -- which was fairly often.  It might be interesting to see if modern hard coatings can solve some of the issues with spherical followers running on continuous-contour surfaces at the speeds and pressures involved with the heavier progressive spring pressures in practical 'debounced' Franklin-style poppet valves.

 

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Posted by gmpullman on Wednesday, September 16, 2020 2:10 PM

The Hagley Museum and Trust has several PRR negatives of the 5399 in their collection.

From the captions it would appear the testing was done in Fort Wayne.

Good Luck, Ed

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Posted by M636C on Wednesday, September 16, 2020 9:43 PM

Overmod

 

 
daveklepper
What Type poppet-valves were used?

 

On 5399, the Franklin System type A with oscillating-cam drive was used: this has two small admission valves and two larger exhaust valves per cylinder end (this is the layout on the 'heraldic shield' in contemporary Franklin advertising!)  This is the system adopted for the T1 construction, and in the rotary-valve T1 conversion (which used bridges to activate the paired valves from a single follower).

Oscillating cam poppet valves are something of a scam, because when operated from traditional valve gear the valve lift can be proportional to cam excursion, which is NOT productive of clean limited cutoff.  (This is not necessarily a 'bad' effect when running at lower speed, for the same reasons the 'type D' in the Vulcan conversions for Army 2-8-0s were).  It is interesting that the poppet-valve conversion was done before the large sine-wave superheater was put in.

3847, which was converted in 1945, uses a rotary-cam system, with the older very heavy Franklin outside drive frame similar to that on the C&O L-2 Hudsons with RC.  That engine's appearance can be studied here:

http://www.northeast.railfan.net/images/prr3847.jpg

In some ways this is a superior method, but only if fitted with continuous-contour cams (which are expensive to machine and difficult to maintain).  Most of the RC systems with discrete cam profiles (e.g. British Caprotti and some Reidinger) tended to have poor performance off the regime for which the cams were machined -- which was fairly often.  It might be interesting to see if modern hard coatings can solve some of the issues with spherical followers running on continuous-contour surfaces at the speeds and pressures involved with the heavier progressive spring pressures in practical 'debounced' Franklin-style poppet valves.

 

 

5399 had the cams driven from the crosshead, the Walschearts valve gear having been removed.

Even before the boiler improvements, 5399 could haul a 1000 ton train at 94.7 mph under AAR test conditions. I seem to recall that this was about the same as the original UP 800 when tested.

It was allocated to heavy trains which would normally have required two K4s. On 5 Nov 1939, it worked The General  weighing 940 tons, saving 21 minutes on the schedule at an average overall speed of 65 mph.

After the boiler improvements, it was tested against a standard K4 5341.

At 40 mph, it was 16.2% more powerful in indicated horsepower.

At 60 mph,17.1%

At 80 mph, 22.9%

At 100mph, 46.8% (4070 ihp against 2770 ihp)

Of course, if 5341 had had the boiler improvements and had the piston valves been enlarged, the difference might not have been as great.

In France, although many locomotives were rebuilt up to the standard of the Paris Orleans 3700, it was found that dramatic increases in power and economy could be obtained simply by applying improved Low Pressure piston valves, along with improving the steam flow from the boiler to the HP cylinders and between HP and LP cylinders. This was much cheaper than the full Chapelon treatment.

Peter

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Posted by Overmod on Wednesday, September 16, 2020 11:55 PM

M636C
5399 had the cams driven from the crosshead, the Walschaerts valve gear having been removed.

This was essentially the same design adopted for the T1 (remembering that one side was driven from the opposite crosshead, a design I believe Wil  Woodard had a hand in developing),  What you forget is that the crosshead drive did not move the cams directly: there are two additional pieces of equipment in there.  One of these in essence contained a stunted little set of link valve gear, which is what imparted the swing to the oscillating cams.  There have been subsequent plans to give more of a 'Corliss' effect to the poppet-valve excursion (a couple being to use a mechanism tripped by valve gear position to move the valve desmodromically, analogous to the spring action that physically moves the Corliss valve from lock to lock).  At least in principle this gets around some of the shrouding that results from very short cutoff, but introduces some problems of wear and inertial effect of its own.  

RC gear, of course, has neither a substantial shrouding of valve openings or a periodic reversal of momentum of the cam to accommodate.

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Posted by daveklepper on Thursday, September 17, 2020 3:36 AM

Why were not more K4s improved?  It would seem like reduction in crew costs would have made the investment worthwhile.  Or were savings eaten up in additional maintenance costs?

How did these improved K4s compare with the two K5s?

 

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Posted by M636C on Thursday, September 17, 2020 5:11 AM

 What you forget is that the crosshead drive did not move the cams directly: there are two additional pieces of equipment in there. 

I didn't forget it. I checked the drive from one of the photos in the Hagley group linked earlier.

 

This is in principle the same drive as the Young gear used on the UP 7000 4-8-2, which was replaced by Walschearts gear, most memorably on the streamlined 7002. Whatever the theoretical disadvantages, 5399 actually worked rather well. It had the advantage that the gear was readily accessible in that application. Smith commented that the subsequent application on the T1s resulted in poor accessibility, not only in the rear cylinders, but due to the streamlined boiler casing extending over the forward gear.

As Dave no doubt recalls, one of the K5s had Caprotti gear which did not show the advantages that 5399 demonstrated.

Peter

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Posted by Overmod on Thursday, September 17, 2020 7:37 AM

This goes to show the evils of assumption, where references talk about the crosshead drive being similar, and I look at photos just enough to conclude the crosshead was driving mechanical lubrication.  Upon review I believe this is the system shown in Woodard's patent 2234614 of March 11, 1941. 

This raises something else interesting: the substantial cylindrical device on the lower rear cylinder head visible in the picture.  I don't know if this is a typical compression-relief device but it is considerably longer than any I (admittedly, again, not very carefully) have seen in late practice.  Good secondary compression relief (and I agree with Jay Carter that having it reversible, like an extension of 'cushioning' compression volume in the endspace up to the valves, would be a great advantage.

Interestingly, the nightmare-box part of the T1 gear (the thing that was on end and crammed between cylinders for the rear engine) was apparently not the thing that needed serious maintenance attention -- it could be sealed and given oil changes and according to a couple of notes in the T1 Trust engineering committee discussions very few of them seem to have required working on.  It was the other piece, the little radial gear in a box, that seems to have been involved in many problems.  I don't remember any definitive answer on how much of this was related to increasing the spring pressure to 'debounce' the poppet valves.  (Better control of the valves was one of the projects for 1948 that were not 'proceeded with'.)

The Caprotti gear was on there largely because Baldwin made an agreement in the late '20s, thinking Caprotti poppet-valve gear was going to be the wave of the future, and succeeded in flogging it to a large number of railroads.  They even featured logging and narrow-gauge export locomotives with it.  To my knowledge it was successful nowhere Baldwin tried it, and eventually had to be removed; to my knowledge none of them were subsequently converted to Franklin System so the issues were more than in the cambox and general frailty of the actuation system.

The K5s were unfortunately timed: they came just after the massive orders for K4s in the late '20s, and had to sit out the capital dedication to mainline electrification, by which point the frenzy over duplex augment reduction on large passenger power (and perhaps the bad taste of the ACL R1 fiasco) was in full cry.  By the time the results of Timken lightweight rods on eight-coupled heavy engines were becoming evident PRR had already committed to something larger and smaller at the same time!

Since the K5s were orphans they weren't used as testbeds for much of anything, being stuck on the Northern Central where high speed was unimportant and relatively low FA already a concern.  It literally took an act of Congress to get stokers put on them, which perhaps shows up mistaken design priority better than any other thing.  It would be highly interesting to see what a K5 modified as 5399 was would have been able to do ... just that it would neither be used to advantage or serve as an example for service conversion or new practice any more than a K4 conversion would.

Now, I still don't quite understand why PRR didn't do any poppet/lightweight rod conversions on the M1 chassis: that would promise to be groundbreaking.  

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Posted by daveklepper on Thursday, September 17, 2020 8:45 AM

I agree that a modernized  M-1 fleet would have been a better investment than just about anything in steam PRR could have done, T-1s. Q-2s, or even modernized K4s.

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Posted by timz on Thursday, September 17, 2020 10:20 AM

M636C
After the boiler improvements, it was tested against a standard K4 5341. At 40 mph, it was 16.2% more powerful in indicated horsepower. At 60 mph,17.1% At 80 mph, 22.9%

By the way-- those are test-plant results. PRR said in the 1939 road tests, before the boiler improvements, 5399 did 2800 dbhp at 80 mph, compared to 2000 for a standard K4.

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Posted by gmpullman on Thursday, September 17, 2020 4:22 PM

Franklin rotary poppet [valve] gear drive, probably located on #1 axle.

 Poppet_drive by Edmund, on Flickr

PRR 5399. PRR Photo E12275, Hagley Trust.

This view better illustrates the levers that communicated the cam box with the combination lever as discussed above:

 Franklin by Edmund, on Flickr

Regards, Ed

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Posted by M636C on Thursday, September 17, 2020 10:15 PM

gmpullman

Franklin rotary poppet [valve] gear drive, probably located on #1 axle.

 Poppet_drive by Edmund, on Flickr

PRR 5399. PRR Photo E12275, Hagley Trust.

This view better illustrates the levers that communicated the cam box with the combination lever as discussed above:

 Franklin by Edmund, on Flickr

Regards, Ed

 

I think the rotary drive on the locomotive axle would be for a lubricating oil pump. Vernon Smith, who was involved in the design of the gear on 5399, says "the cams to operate (the poppet valves) were placed in a double deck cam box that required an oil pump to lubricate the upper cam and rollers".

He also said "since the drive for the gears came from the locomotive crossheads only, it was neccesary to cross the drive over inside the box to get the motion in the correct phase to drive the respective links."

Peter

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Posted by Overmod on Friday, September 18, 2020 1:25 AM

M636C
He also said "since the drive for the gears came from the locomotive crossheads only, it was neccesary to cross the drive over inside the box to get the motion in the correct phase to drive the respective links."

I believe that is a necessity for any crosshead drive, going back to the earliest examples which are I believe in British practice.

See also the Berry accelerator gear (on Dr. Richard Leonard's site) for a different application of the principle.

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Posted by gmpullman on Friday, September 18, 2020 4:10 AM

M636C
I think the rotary drive on the locomotive axle would be for a lubricating oil pump.

I must be getting my Franklin Type A & B confused. I know that on some installations the "rotary" drive is quite obvious, linked to the crank pin the way it is. Seeing the photo of the right-angle axle gear reducer mounted on the axle that the PRR 5399 simply had the rotational drive shaft between the drivers, essentially hidden from view.

This patent drawing shows the Type B if I'm not mistaken.

 Franklin Rotary by Edmund, on Flickr

Solid documentation is certainly hard to come by! Looking at the arrangement for the Type A, I can not see where the right-angle drive as shown in the Hagley photo series would have been applied.

 Franklin-Type-A by Edmund, on Flickr

There certainly must have been a great deal of head-scratching and perhaps a grumble or two from the Lima engineers tasked with mounting that cam box ahead of the steam chest. From what I've read, Franklin (Lima) covered the cost of the installation in hopes of selling the PRR on the idea.

Regards, Ed

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Posted by M636C on Friday, September 18, 2020 6:30 AM

Overmod

 

 
M636C
He also said "since the drive for the gears came from the locomotive crossheads only, it was neccesary to cross the drive over inside the box to get the motion in the correct phase to drive the respective links."

 

I believe that is a necessity for any crosshead drive, going back to the earliest examples which are I believe in British practice.

 

See also the Berry accelerator gear (on Dr. Richard Leonard's site) for a different application of the principle.

 

 

The two designs that come to mind are G.J Churchward's first "Star", no 40, later 4000 and Deeley's 999 class 4-4-0.  It was not widely used apart from these eleven locomotives in total. Both these locomotive types had inside cylinders and valve gear, although No 4000 also had outside cylinders with the valves operated by rocking arms.

Inside rotary drive to poppet valve gear was quite common with British applications of Caprotti gear, including export locomotives. A number of LMS "Black 5" locomotives were built in 1947-48 with rotary drive from the second (driving) coupled axle.

Peter

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Posted by Overmod on Friday, September 18, 2020 11:53 AM

M636C
A number of LMS "Black 5" locomotives were built in 1947-48 with rotary drive from the second (driving) coupled axle.

Can you, once and for all, resolve the difference between British Caprotti and 'Reidinger'?  From what I know, Reidinger had the driveshaft only on one side, driving both cams (and I don't think they had the flexible coupling in the center that the shaft in an FM 38D OP engine does) whereas British Caprotti, like Franklin type B, has a separate shaft for each side.  Differences in the actual cam follower and valve operation I couldn't make out from the small drawings I had.

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Posted by M636C on Saturday, September 19, 2020 8:25 PM

Overmod

 

 
M636C
A number of LMS "Black 5" locomotives were built in 1947-48 with rotary drive from the second (driving) coupled axle.

 

Can you, once and for all, resolve the difference between British Caprotti and 'Reidinger'?  From what I know, Reidinger had the driveshaft only on one side, driving both cams (and I don't think they had the flexible coupling in the center that the shaft in an FM 38D OP engine does) whereas British Caprotti, like Franklin type B, has a separate shaft for each side.  Differences in the actual cam follower and valve operation I couldn't make out from the small drawings I had.

 

 

The whole thing is more complicated than you suggest...

Reidinger gear was applied to a total of seven locomotives (but one set was successively applied to two locomotives, so there were only six sets of valve gear).

Your description applied to the one set that was moved, first applied to LNER D49 4-4-0 365 and later moved to sister 361 (BR 62764).

All locomotives with Reidinger gear were built with rotary cam Lentz gear with stepped cams with limited fixed cutoff sttings.The Reidinger patent covered continuously variable cams to give variable cutoff settings.

I don't know to what extent the original Lentz valves and layout were maintained, but the external appearance of the Reidinger modified locomotives was not significantly changed. 

The LNER locomotives, both RC Lentz and Reidinger were driven by a shaft from a bevel gearbox on the right hand side only. The Reidinger unit had the bevel gearbox at the cylinders mounted outside the cylinder casing while the Lentz engines had it (just?) inside the casing. These were three cylinder locomotives with 120 degree cranks.

The other five locomotives were LMS Fowler Class 5 2-6-0s which were two cylinder locomotives with bevel gear drive on each side.

LNER 365 was built with RC Lentz gear in 1934 and was converted to Reidinger (with steam actuated valves) in 1939. 365 gave trouble in service and after the bevel gear drive was damaged in 1941 it was taken out of service. Edward Thompson rebuilt it with two inside cylinders with piston valves.

The valve gear was retained and fitted to 62764 in 1949, but in this case the original valves with spring actuation were retained. the locomotive was extensively tested on the Rugby static test plant, and it returned to service and retained the Reidinger gear until withdrawal in the 1960s.

The five Fowler 2-6-0s built in 1931, were rebuilt with Reidinger gear in 1953, possibly as a result of the tests on 62764, and they also kept the Reidinger gear until withdrawal.

Since it was based on RC Lentz conversions, I assume that Reidinger valve gear had the poppet valves arranged horizontally above the cylinders while British Caprotti had the valves arranged vertically above the cylinders.

The BR standard Caprotti locomotives had steam actuated valves, and I assume the last two LMS Class 5s with outside rotary drive also had steam actuated valves. I can't say about the earlier LMS Class 5s with the inside rotary drive that I mentioned earlier.

Peter

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