Steam Engine back pressure braking?

[Modelcar]

Operating Steam engines on the downgrade...Was there any method that the engineer could set the valving to the steam cylinders to effect a braking effort..? Example: Jake Brake on modern Diesel truck engines.

QM

[nfmisso]

It is possible to put the a steam locomotive in reverse, but it was not designed for this and when done in an emergency would sometimes fail, and make matters worse. Not exactly like a Jake Brake.

Nigel

[Modelcar]

Wasn't there some way to allow some steam onto the opposite side of the piston as you would to make power, hence effect some braking action. I can imagine putting it into full reverse would really open the situation up for real trouble. Perhaps derailing.

QM

[BRAKIE]

Much like today the engineer would apply the train brake and move the Johnson bar to the next lower spot in order to obtain control..He would also close the throttle some in order to help cut speed.

[Modelcar]

Would moving the Johnson Bar down the one notch effect the piston / cylinder to have some braking power with the pressure of steam on the "back" side of the piston...?

QM

[sooblue]

Hi there,
If you put the reversing lever to the midrange or neutral possition when you were in motion, I belive that the engine would lock up and your wheels would slide on the track.
I think what your looking for would be applying enough back pressure to effect a braking effort.
To some degree that could be done but steam is non-compressable so I think you would be more likly to damage something. If steam would have continued in use I'm sure a reliable retarder would have been invented, such as air(which is compressable) pumped into the back side of the piston, Or steam with a pop valve so as not to blow out the cyl. cap??
The reason a Jake brake works is because it is dealing with compressable air.
mike

[Modelcar]

Great...we're getting lots of input into the subject of whether a steam engine had the ability to brake itself with the use of valving steam into the backside of the piston....etc. One comment....Are you sure steam is not compressable....For sure pure water is not, but steam is expanded water and wouldn't that be compressable...

QM

[alangj]

You're absolutely right. Water in the liquid form is virtually incompressible (under the non-exotic-laboratory conditions that exist inside a locomotive boiler), but water in the vapor form (a.k.a., steam) is quite compressible. After all, when the high-pressure steam is admitted to the proper side of the piston in the cylinder, it expands as its pressure drops as the piston is pushed toward the opposite end of the cylinder. That expansion of the steam is merely the opposite physical effect to the compression of the steam which was performed as it was generated in the fixed volume of the boiler initially. If steam couldn't be compressed, then it wouldn't be possible for it to later expand and provide any driving force to the piston.

Alan

[alangj]

I recall reading in Model Railroader many, many years (30+?) ago that another reader was asking about how to model the "LeChatelier Water Brake" which he had heard was used on some mountainous lines. The explanation given in the Q&A column at the time was that that braking system used a small pipe drawing liquid water from the lower portion of the boiler, controlling the water flow through a small, low-capacity valve, and timing things so that a bit of hot (but still liquid) water was injected into the "back" side of each piston/cylinder combination at the appropriate time of its cycle, in order to create a small amount of fairly dense, saturated steam for the piston to compress. Apparently, this also required the reverse lever to be set one notch to the "reverse" side of the "neutral" position, to allow the main valve gear to properly admit a tiny bit of high-pressure steam (to absorb the injected water and become denser), and then to exhaust the then saturated steam after the piston had done some work against it and created a braking force. The conclusion that the Q&A column came to was that it probably would only be visible to the truly "trained" eye if the appropriate pipe and valve were added to a scale model (especially in HO or smaller sizes.)

Alan

[Modelcar]

For sure Alan, steam expanding is a must for a locomotive to function....But thanks for all the interesting bits of info on this operation of steam in an engine. This question of braking has been on my mind for years in wondering if the steam engine did have any ability to do so such as the dynamic braking on modern diesels...One would think with valving and the cylinder / piston assy's they would have had a way to do braking with such. I often thought of that as steam engines [B&O],came clanking down the grade in my home area of Pennsylvania many years ago.

QM

[sooblue]

Thank you for correcting me.
back pressure was used to cushion the pistion at the end of each stroke so steam would have to be compressable. Maybe steam was used as a retarder by more savy engineers but it wasn't as effective as modern dynamic braking.

mike

[Modelcar]

The savy Engineers part, I have wondered about myself....Some may have learned how to "cheat" the system and live on the "edge" side a little to get something out of the locomotive that wasn't intended in the design.

QM

[Anonymous]

I remember reading a story in a 60 year old issue of Railroad magazine about using the cylinders for air compressors.A live steam engine was hauling a dead loco that didn't even have water in the boiler.The engineer on the dead loco wanted to put it on a siding the live engine couldn't get into without making a flying switch.So the engineer/salesman on the dead loco knew a way to use the cylinders as air compressors and filled the boiler with compressed air as the live engine was pulling.When they got to the siding,the engineer on dead engine suprized everyone by using the boiler of compressed air to propel the engine into the siding.Would opening the water drain cocks on a dead engine let air into cylinders?

[BRAKIE]

QM,According to my Dad and his brothers(all railroaders) my Grandfather lived on the edge and would get as much out of a engine that he could,in anyway that he could with out damage to the engine or anything else.My other Grandfather was just the opposite,he would run a engine with great care.Funny now,as I look back on it,both was friends,shared the same type of job,but different in engine handling..

[Modelcar]

Wow..., that is a new angle to it all. The theory sure sounds plausible. I'll bet some enginemen knew all kinds of tricks to their machines. If one had enough air pressure in the boiler I don't know why it wouldn't move the engine for at least a short distance.
Good old Railroad Magazine...That was a good one.

QM

[sooblue]

I talked with a steam engine operating crew
over this week end. I asked them about using the reverser to help slow down. I was told that it can be done to a degree but it was frowned upon because while the steam is compressable the water that drops out of the steam isn't and a slug of water going into the back side of the piston with the steam will blow off the head or bend or break a rod. The Savy engineers kept their jobs.
If steam would have continued to be developed and refined maybe something would have been invented to be a dynamic brake we'll never know though.
Mike

[Modelcar]

Mike....Thanks for adding more info on the subject. Surely if steam would have carried over into the new development stage we surely would have had new arrangements to the hardware where the steam pressure could have been put to work on the downgrade...Perhaps within a geared Turbine that could have been charged with the pressure to effect hold back energy. I was part of a team developing automatic transmissions for trucks some years ago and we had a chamber and impeller [splined to output shaft], with minimum clearances and when retarding forces were called for we pressurised that chamber and it was rather effective down a few gears from high range. Different for sure from steam but still using an avail. force for braking action...

[Modelcar]

...Forgot to sign above entry...QM

[sooblue]

Not to change the subject but a few decades back the gas turbine was experimented with in autos and trucks but was dropped because there was no retarding when the foot pedal was released(that's what I read at the time)
could your transmission work have been applied to the turbine ?
mike

[Krokodil]

In Europe, there was a system developed by Riggenbach.
The pressurized air (generated in the cylinders) was collected in an extra air tank (not to mix with the fresh steam in the boiler).
The steamengine had extra valves for this brake operation. Also the airtank had extra valves for too high pressure.

This kind of brake system was mainly used on Cog-railroads.

[Modelcar]

Mike...I remember the turbine cars you speak of and in fact I had the opportunity to be in one of them at a business place in Pennsylvania in the mid 60's. I believe at the time [if I am remembering correctly], Chrysler had made 50 of them and put them out to selected people to evaluate them for a certian period of time and then the vehicle was moved on to another selected person, etc...I was about to get a ride in that vehicle when the operator of it was called and could not take the time to do it...I remember it was sitting there idling and the tach was reading about 18,000 RPM...but to attempt to answer your question. I believe if there would have been room to install the hyd. retarder someplace between the engine and the drive train it surely would have had to "brake" the vehicle when it was ingaged. The retarder required hyd. pressure and very ample cooling to cool the oil as it exited the retarder and then recirculate back through the system...

QM

[Modelcar]

Yesterday I mentioned our work developing a hyd. retarder for Truck Automatic Transmissions...and I stated of the impeller being splined to the output shaft. I should have said "splined to the input shaft"], as that way we could take advantage of gear ratio in the transmission if needed.

QM

[sooblue]

Thanks, QM
Your invention could have worked on a steam engine and been cooled by the water in the tender.

[Modelcar]

Oh no....It was not my invention...I was just part of the Exp. team that was involved. Experimental routine and testing.

QM

[sooblue]

In my book that makes it yours too. It was a team effort and that team should be listed on the pat.
maybe not practical, still, you deserve to have the recognition.
My father had several inventions that the company he worked for took credit for. He got nothing because that was the way it was done back then.
he should of at least got some credit for the work he did. It changed how a lot of things are done in manufacturing today.
when he retired they gave him a silver pin with the company logo on it. He used to use it to mark his ball on the green lol.
mike

[Modelcar]

Mike...In the time frame I'm talking about it was a written agreement of employment in such and such departments that creations and such were a company property not the individuals...I'm sure agreements were different many places. The situation I'm talking about, we did a full test cycle on such but it did not make it to production. It surely did work, but that specific transmission and retarder did not go into production. It surely did hold your speed in check decending the mountain grades.

QM

QM

[sooblue]

I've opperated some motorized equipment that had hydrolic accessories ie. a forklift.
if you are in gear and moving and use the hydrolics it can be like putting on the brakes especialy if a cylinder gets bottomed out.
You would get a great heat build up but if you could keep that in check it would be a great retarder. It would have worked great on steam with the water tender providing cooling.
I know I'll get laughed at here,but, I think it's possable that some time in the near future this nation will go back to coal( our greatest fuel reserve ) and water for power. Oil is an endangered animal. It wouldn't take much to use up all we have access to.

mike

[Modelcar]

The hyd. retarder did procuce a LOT of heat when in use...but with the size of a truck radiator and of course not being used too much on the downgrade it has lots of capacity to remove heat from the Transmission / Retarder oil. In our application, we had a large heat exchanger connected in series with the bottom of the radiator back into the intake of the water pump on the engine and it removed heat produced in the retarder oil [out], of the retarder.

QM

[sooblue]

How much did it raise the temp. of the water cooling the engine?
The reason I ask is that I have always wondered about placing a big heat producer like an air conditioner condenser in front of the cooling radiator. Some times you can't touch that coil it's so hot.
You would think that the efficiency of the radiator would be cut.

Mike

[Modelcar]

I don't think I can remember precise figures for you Mike but with the truck size radiator the engine cooling coolant temp. was never any problem as it stayed within acceptable range. Remember now, the only time one calls on this system to cool is when the engine is NOT working, [Down hill]. The heat exchanger type we used was water to oil...It was connected in series at the water outlet at the botttom of the radiator to the water pump at the engine. Using the retarder did raise the [trans.], oil temp somewhat over 100 degrees, don't remember exact amount but the cooler did the job of cooling it as it came out of the retarder. Being experimental the oil was changed quite often [for inspection], so don't know what long term usage the heat would have had on the transmission oil...But can say this...We did testing for thousands of miles on the system with good results.

QM

QM