A few thoughts and questions. I believe this may have been stated here prior but the warping comes in following the closing of the throttle after the locomotive has been working. Someone mentioned "thermal momentum", a term I have utilized in training firemen for many years.... Along these lines, it is the heat being generated from a "road" fire which burns/warps the units once the throttle is shut. It takes a while for the fire to settle down. Whilst an oil fire locomotive is vulnerable to a lesser degree because the heat is "turned off" with the firing valve, it still as the "thermal momentum" in the form of the firebrick (potentially, depending upon the operation) glowing brightly such as at the canyon.

Case in point, for the first 10-15 minutes or so following the 29 or the 60 coming in one could almost not keep a low enough fire (for all intents). Following this period the fire would have to be gradually increased as the firebrick cooled down having released it's BTU's into the boiler.

Another point to keep in mind is that of preventing soot/cinders from entering the exhaust passages, abrasives in valves and cylinders= damage! Regardless of this, back to temperature related issues....it is easily possible for locomotives of necessary proportions to develop superheat temps above the flashpoint of the cylinder oil. The cylinder oil continues to do it's job because of an environment which is devoid of oxygen. Suck air in through the exhaust with the throttle shut, introduce oxidizer and FLASH.

Warping can and has occurred on locomotives with front end throttles as well. There may well be steam in the units at all times but if it does not flow then it does not cool. I have been told by several involved in the ORIGINAL rebuild of the 261 that a couple of the units were so badly warped they had to be cut apart and removed in pieces.

J.David,

As built, are the unites any shorter than on american locomotives? On US engines they stop about 1-1.5ft from the rear tube sheet. Chinese?

Cheers, Jason

There were locomotives that had a 1"(IIRC) line which would supply steam bypassing the throttle. As I have read it, one basically opened the valve wide open and just let the engine go. Anyone else?



Water is sucked into hot cylinders, flashes to steam, provides resistance. Honestly, I didn't know the D&RGW (and whomever else) put them on un-superheated locomotives. Would be interesting to find out how far that practice went back. While I was in colorado I had a discussion about this "brake" with a few lifetime narrow gaugers, they said that historically the failure rate on units was notable.

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I was in the cab more than once with Chuck when he refused to drift with the throttle open, keep an eye on him ;). As to practices being "better" than others, perhaps it was a matter of what was more practical for them regardless of mechanical repercussions. Or... the belief could have developed as a result from "I recon" decisions to "fix" symptoms rather than problems in the operating department. We have these type decisions being made today about mechanical and operating issues so why could such decisions not have been made historically based on myth, lore, legend and misinformation?

Cheers, Jason

Jason,
My 1905 AT&SF air brake manual discusses water brake operation.

Robby Peartree

Any chance you could scan or photograph and post?

Thanks, Jason

I have experience with both methods of drifting. On the D&RGW narrow gauge lines the practice, at least in the later years, was to drift with the throttle closed in full gear. This practice was passed on to crews on both the C&TS and D&S and, as far as I know, is still used on both operations. Having participated in several rebuilds of engines on the C&TS, I don't recall that we found appreciable warping or damage to the superheater units even after many years in service, certainly not anything like that in the photo Mr. Yuill posted.

Speed may be one determining factor in the method used. The narrow gauge freight operations were fairly slow, a maximum of 15 to 20 MPH generally. Passenger trains were run at higher speeds back in the day and may have used a different method for drifting.

Another consideration with the narrow gauge and, I believe, UP among others is the use of compression braking on long down grades for handling light engines returning from helper service. The narrow gauge engines have a valve that admits saturated steam directly into the piston valve chambers. These valves are referred to as "drifting throttles" although that may not be a completely accurate term. When running down grade light, the engineer opens the drifting throttle and runs the engine in reverse using the compression to control the speed. This develops high cylinder pressures and temperatures. We would intermittently drift with the engine in forward gear and use the engine brakes to allow the cylinders to cool and make sure they were getting enough lubrication. My point is, the narrow gauge practice allowed for drifting for many miles at a time with the throttle closed without severe detrimental effects.

On GCRY and other roads I have run on, the practice was to run the engine in full gear with the throttle cracked to allow just enough steam to follow the piston through its entire stroke. As Robby noted, this worked out to around 20 psi. steam chest pressure at 30 MPH. The method others have mentioned of using the cylinder cocks as a guide to set the throttle is tried and true.

Speed is one key, the faster you go the more volume of steam required. Cut off is another consideration. With long cutoffs it takes less pressure to get enough steam into the cylinder to follow the piston for the entire stroke. With shorter cutoffs a higher steam chest pressure is required.

When drifting in full gear with about 20 psi of steam chest pressure, if the engine is then hooked up, you can see that the steam chest pressure rises to around 50 or 60 psi (if I recall correctly) and this will actually be enough to produce a little power. I used this to my advantage to get the train over small hog backs without having to adjust the throttle. This makes me wonder about Wardale's conclusion that drifting with the reverse centered and a light throttle is the best method. I am not disputing it, I have never tired it to see how well it works. I would think you would have to maintain a fairly high steam chest pressure when drifting with such a short cutoff.

As for the use of superheater dampers, they didn't seem to remain in widespread use. I suspect that the railroads determined that the cost of maintaining them was not justified. Either they found other methods of achieving the same results or they concoluded that the damage to the superheater units they were intended to prevent was not that severe.

Russ

On the subject of drifting throttles, I learned back in 1971 or so that this term can be used both as a verb and a noun. You can work a drifting throttle and can also use one on locomotives so equipped.

I used to ride out to River Bridge and back with Frank Cottle Sr. on the West Side & Cherry Valley. He could be pretty hard to get along with if you got sideways with him, but we got along pretty well. One morning, we were heading out of Tuolumne in Shay 12. After you crossed the county road at the old mill site, a grade started and continued past Baker Siding up to the Flume. We were barreling along and just before he shut off, Frank reached ahead and flipped this small valve 90 degrees.

He asked me what is was and I made the right guess when I said it was to protect the Superheater. Nifty little device.

We essentially did the same thing at the Power Plant that I worked in at Standard Oil. Before the last fire was pulled on one of our seven 830 lb. boilers, somebody would go upstairs to the outlet header and crack open the drain on the Superheater. The steam went to a funnel at floor level. Same thing, to protect the Superheater. I remember when one crew neglected to do this and sagged a bunch of elements. I got to work with the shutdown crew on the repair. All the operating crews got a big lecture on proper procedure and it never happened again.

Quite a few ATSF locomotives, including 3751 after the 1941 rebuilding, had the Wagner-style bypass valves. 3768 has them as preserved. 2903 has them. 2925 has them. Folks who work on those engines can tell you all the relevant technical details.

Some comments on the water brake are here:

http://www.trainweb.org/utahrails/drgw/waterbrake.html

Should be noted that this brake was fitted to some of the late articulateds -- if those 'aren't superheated' I'd be awful surprised.

There are a couple of flavors of water brake: the older kind, which used overcritical boiler water, rather obviously went out of favor with the advent of "proper" boiler-water treatment. The 'newer' kind, which uses a source of 'wet steam at low pressure' (for example from the turret) does not have a problem with TDS or, heaven help us, the brew that is Porta-McMahon treatment... There is also a European version, which uses air as the compression medium and meters the water to help cool the compressed air.

As a brief note, here is an excerpt from a handbook (circa 1900) describing operation of one of these systems:

The water brake should always be operated in a certain regular order, which is as follows: First, be sure that all the cylinder cocks are open and that the throttle valve is shut; next, open the water valve about one-quarter turn; then immediately place the reverse lever of the engine one or two notches back of the center and note the color of the steam issuing from the cylinder cocks. If dense white in color, the water valve is open sufficiently, but if the steam has a bluish color at the cylinder ****, which gradually changes to grayish white as its distance from the **** increases, the water valve should be opened a little wider until the steam has a dense white appearance from the moment it leaves the cylinder cocks. If the engine throws water from the stack, the valve is opened too wide and should be closed sufficiently to stop the trouble.

The amount of braking power exerted by the water brake depends on the position of the reverse lever. When it is in the first notch from the center, it exerts the least braking power, and the braking power is increased as the lever is moved towards the corner notch. the retardation of speed should therefore be regulated by placing the reverse lever in the notch required, and the water valve should not be changed after once being adjusted.

The water brake can be used when the engine is running either forward or backward, by simply placing the reverse lever so as to convert the cylinders into air compressors, observing the same rules of operation, regardless of the direction of running.

When it is desired to shut off the water brake, first close the water valve and then slowly move the reverse lever towards the center, to avoid throwing water from the stack.

The water brake, it must be remembered, acts to stop the rotation of the drivers, so that if the air driver brake [independent brake - RME] is used in conjunction with it , the braking force acting on the drivers will be too great, and they will be skidded. The water brake is simply an auxiliary braking device and should be used intelligently. It is most effective on a steady motion of from 3 to 12 miles per hour, is less effective at speeds greater than 12 miles per hour, and it should not be used at a greater speed than 18 miles per hour.

In double-heading on a grade, the engineer not operating the air-brake assists in retarding the speed of the train by using the water brake to whatever extent advisable.


I believe you will find that the Chinese superheater, as with many modern superheaters (since about 1930 if memory serves me right on the innovation) have bypass valves that allow steam to circulate in the elements when the (front-end) throttle is closed. I believe one of the selling points of this innovation was that it made movable elements like superheater dampers less important.


RME

Some quotes from an American Multiple Throttle manual:



On CNR 6167, the steam supply for the blower comes from the whistle, which is in turn routed from the throttle. When she was built she did have a pipe running from the throttle, along the running boards up to the turret to provide a supply of superheated steam for the auxiliaries, but this was removed, likely within her first decade of service.



From a 1925 Elesco Superheater Book:

Pages 230 and 231 of the book.

Page 232

Jason

The AT&SF air brake book’ age is a guess by the person who gave it to me based upon their knowledge of the Santa Fe Motive power. I am sorry about the quality of the scan.

Mr. Fisher

Running at speed with 18 or 4960 with the exhaust nozzles of the time the ratio 50 psi steam chest to 2 psi back pressure usually gave you a good setting for drifting at 20 psi in the steam chest. As you describe as speed of the machinery increases the flow rates from the boiler must increase to maintain the same pressures. Mr. Paul King's charts were very helpful for me. I do not know how much you and your wife assisted with those?

A thought for everyone,

It is important to remember that the tensile strength of any metal is a function of temperature. Therefore a metal that can handle certain forces in one environmental condition may not be able to in another due to the change in temperature.

Robby Peartree

This has been a very interesting thread.

I realize that Trofimov valves are of little relevance to the US, but since Paul Woodring and J. David have both mentioned them, I do have a question.

Paul's description of how the Ol49's in Poland drifted with the throttle closed matched my recollection from 20 years ago. The driver would open the throttle wide, lift the latch on the screw reverser and allow it to run forward into full forward gear. He would then close the throttle.

In a cab ride on the Ji-Tong, we took siding at Liudigou and when we got the start signal, the driver merely released the brakes, and without touching the throttle, the train slowly began to roll. The rest of the way to Linxi we rolled along with throttle closed at 50 mph, a bit faster than I had been told QJ's were supposed to run. I don't remember the position of the reverser, but J. David said that Trofimov valves were supposed to be in mid gear for drifting.

Any idea what the reason would be for the two different methods of drifting, since both locomotive types were equipped with Trofimov valves? In the case of the Ol49's, the trains were light 3 car passenger trains on relatively level ground, while on the Ji-Tong they were 2,400 ton freights on a descending 1% grade.

Thanks.

Michael Allen

Trofimoff (which was the spelling years ago when I first came across them; it may well be -mov in common use now) valves are described in Ransome-Wallis' Encyclopedia of World Railway Locomotives. As I noted, there is a similar device, attributed to Wagner (probably RFP Wagner, Chief of Design of the Deutsche Reichsbahn). I believe placement relative to the valve and power cylinder is the principal difference.

This device was described to me as having an internal spindle with two moving piston heads on it. When steam pressure in the chest is below a certain level, the heads slide to allow steam to move from one end of the cylinder to the other freely; when steam pressure increases to 'power' levels, the heads move out and seat and the engine then runs normally. An advantage of this is that the action is automatic and proportional; another potential advantage is that 'drifting steam' requirement is limited to what is necessary for lubrication -- which as pointed out will be minimal when mechanical lubricators are in use for the cylinders.

The big problem with them is that carbonization, from whatever cause, on the spindle will cause one or more of the heads to stick, which causes all sorts of problems that may not be easy or even possible to fix on the road. I do not have a good arrangement drawing or picture.

Here is a discussion of how the ATSF Wagner bypass valve works (from Trainorders.com): [Note: quoted here only for reference]

The arrangement is fairly simple. A long cylinder with free floating pistons at each end of it is placed at the top of the valve chest. The pistons are held apart by a long coil spring and not attached by any rods or links. At rest when the throttle is closed the pistons are at their furthest point away from each other and covering the steam admission ports. This then allows the bypass ports to be uncovered which in tern balances the pressure in the valve chest and piston cylinder. The lubricated steam/hot air then travels back and forth between the cylinder ends through the bypass ports maintaining lubrication. The engine could then drift downgrade with a closed throttle without fear of loss of lubrication or sucking flue gasses into the valve chest. When the throttle is again cracked open the steam pushes the pistons back over the bypass ports uncovering the admission ports. Now the engine can be operated normally. One thing, when you are setting and open the throttle you can hear the bypass pistons opening as they are pushed up against their stops in the cylinder. Another thing is that when the throttle is opened the engine acts as if it has a blow. This is because the pistons have the bypass ports open. When the pistons slam shut then the blow immediately stops. There is not any secondary admission of steam to the cylinders at any time.


RME

Another problem with Trofimoff valves noted by Wardale is they are HEAVY, not a good thing when you are trying to maximize valve size and travel for optimum steam distribution.

It sounds like the Wagner valvs are parallel to the main valves, so do not affect their size and weight, but the Trofimov system is built into the piston valve on the same stem?

Michael Allen