Dynamic Braking and Steam Engines

[Willy2]

When I watch Pentrex videos they say that they need diesel helpers on the trains primarily for dynamic braking, although somtimes for extra power. What did they do in the old days when they couldn't just stick a diesel on the steam trains? Just wondering.

Willy

[chad thomas]

I'm no expert but I believe they had to stop and set the retainer valves on the brake cylinders before decending the bigger hills. You would set a certain percentage of them not all of them.

[Modelcar]

....Yes....for hills such as Saluda down in North Carolina retainers would be set {even with diesels w/dynamics}, before decending that massive grade....But for most hills I imagine they simply relied on air brakes using the normal controls to do the retarding....

I always wondered why compression couldn't have been used in steam cylinders {of the engine}, for baking effort....by valve action...etc...

[martin.knoepfel]

Sort of dynamic breaking existed with some steam-engines. It was called counter-pressure-breaking.

[CShaveRR]

They used to set retainers on the C&O at Alleghany (yes, I spelled that correctly), Virginia, for the eastbound descent with loaded coal trains.  Not a significant grade by Saluda standards, but definitely an obstacle.  That's probably why there were four tracks at the summit and two nearly everywhere else on the line (of course, it's been cut back to a single track in many places now).  The brakemen would have poles with which they could reach up and set the retainers from ground level, thereby saving a bit of time (keep in mind that these were gons and hoppers, not box cars).

[tree68]

Sort of dynamic breaking existed with some steam-engines. It was called counter-pressure-breaking.

I don't remember the topic, but I think we discussed the counter-pressure braking thing a while back.  There apparently were issues with it having to do with cylinder lubrication... 

[Modelcar]

....I've seen it discussed on here several times...that is the act of "setting retainers" and I still wonder why it is necessary to trump the normal action of the brakes by mechanically setting them.

Don't quite understand what is deficient with normal air controls that the mechanical action is required in extreme cases....{steep hills}....?

Believe it is something in the process of using up the air supply somehow....??

[chad thomas]

 

I always wondered why compression couldn't have been used ade....But for most hills I imagine they simply relied on in steam cylinders {of the engine}, for baking effort....by valve action...etc...

Well what about dissipateing all that heat. If you turn the cylinders in to giant compressors that's got to produce huge amounts of heat. I suppose you could do it to for short periods of time to controll slack action but for sustained use on a long or steep grade doesn't seem feesable without a serious cooling aperatus. I don't know for sure that's just my take on it.

[tree68]

....I've seen it discussed on here several times...that is the act of "setting retainers" and I still wonder why it is necessary to trump the normal action of the brakes by mechanically setting them.

Don't quite understand what is deficient with normal air controls that the mechanical action is required in extreme cases....{steep hills}....?

Believe it is something in the process of using up the air supply somehow....??

Bingo - In order to apply the brakes you reduce the pressure in the train line, which is also where the reservoirs on the cars get their pressure.  When all is equal, the pressure in the reservoirs is the same as the train line.  The reduction on the brake pipe signals the triple valve (brake valve on the cars) to release pressure from the reservoir to the brake cylinders.  If you do a 10 pound set (from 90 to 80 on the train line) you end up with less pressure in the reservoirs for the next application - the reservoirs can't recharge any higher than 80 lbs.  If you do too many sets and releases without allowing the reservoirs to recharge, you have no brakes.

Setting up the retainers applies some brakes on the cars without losing your air reserve. 

There's more to it, but this might help you understand somewhat.

Brakes as I understand them (and I'm working hard on that).

[CopCarSS]

I asked about using the cylinders for braking once on the Georgetown Loop. The answer I received from them said something to the effect that it can be done, but it takes a really gentle touch on the Reverser and the Throttle to avoid slipping wheels (which would provide virtually no braking, along with being hard on equipment).

[dldance]

I asked about using the cylinders for braking once on the Georgetown Loop. The answer I received from them said something to the effect that it can be done, but it takes a really gentle touch on the Reverser and the Throttle to avoid slipping wheels (which would provide virtually no braking, along with being hard on equipment).

I have seen it done once.  Very hard on the equipment - but the alternative was going to be much harder on the equipment.  Before moving again we had to visually inspect the rods and valve linkages to make sure nothing was damaged.  It also knocked loose enough crud in the bottom of the boiler that we had to manual clear the cylinder cocks and that with a boiler with only 10 days of use since the last boiler wash.  Definately not a replacement for dynamic braking.

dd

 

[Willy2]

It's a little more complicated/confusing than I thought it would be! But, I think I get the general idea that there was more than one way to keep train speed under control without the dynamic brakes and many of those ways were kind of difficult.

I also just noticed that in the subject line I used breaking, instead of braking and also didn't spell dynamic right.  I'll promptly change that. I guess it's just one of those days.

[broncoman]

 

I always wondered why compression couldn't have been used ade....But for most hills I imagine they simply relied on in steam cylinders {of the engine}, for baking effort....by valve action...etc...

Well what about dissipateing all that heat. If you turn the cylinders in to giant compressors that's got to produce huge amounts of heat. I suppose you could do it to for short periods of time to controll slack action but for sustained use on a long or steep grade doesn't seem feesable without a serious cooling aperatus. I don't know for sure that's just my take on it.

Couldn't they just limit the flow of the air out of a steam engine's cylinder (when the rod is plunging into the chamber).  It would be somewhat like an exhaust break on a diesel.  Not much negative effect for a pretty sizeable braking function.

[Modelcar]

....Thanks for all the comments on the braking functions and methods fellows...

I realize the air brake system on a working train is not simple and it must be handled with real knowledge of the situation, etc...If one goes about it with carelessness it will lead to disaster.

Even more wild yet...think of brakemen scrambling around across the old box car roofs setting hand brakes before Geo. Westinghouse even thought of his air brakes....!!

[tree68]

....Thanks for all the comments on the braking functions and methods fellows...

I realize the air brake system on a working train is not simple and it must be handled with real knowledge of the situation, etc...If one goes about it with carelessness it will lead to disaster.

Even more wild yet...think of brakemen scrambling around across the old box car roofs setting hand brakes before Geo. Westinghouse even thought of his air brakes....!!

What?  You propose to stop my trains with wind? - Commodore Vanderbilt

[Modelcar]

....You know...think of the engineer's possition of topping a hill {and before air brakes}, and having confidence the train would not run away decending the next down grade....and the only way to prevent that was the brakemen scrambling around and across his train setting hand brakes....and hoping they set enough or hoping they actually were back there on the job....actually doing the job...That would not have been a very nice position to be in starting down every hill.  Back then some of the original grades were in the 4 % range too....!!!

Or am I missing something....Was there a way to know "the train was properly braked before starting down"....???

[BR60103]

I don't remember exactly, but I think in The Great Locomotive Chase or The General movies, they had to make emergency stops by reversing the locomotives.

I read a story in a British magazine a while back. Britian was slow with adding what they called "continuous brakes" to freight cars -- hand brakes with a long lever were good enough. The was a rule on one grade that 33% of the brakes were to be pinned down before descending -- the lever would be pulled to apply the brake and a pin put in to hold it. There was another rule that brakes were not to be applied on tank cars.  So the train comes up and is all tank cars except the mandatory pair of wagons at each end.  Guess which rule was followed. 

 

[Anonymous]

There was a patented system, used widely in Europe, called the Le Chatelier Water Brake, which used the compression of the cylinders for braking effort.  As I understand its operation, going down the mountain the reverse lever would be placed in full back motion and the device squirted water into the exhaust chambers of the cylinders which vaporized, providing the retarding force for the pistons. 

AFAIK the D&RGW was the only US railroad that made wide use of this device.  Evidently, it was difficult to keep from sucking exhaust gases through the exhaust nozzles into the cylinders, and it must have been tough on valve gear and rod bushings.

Robert A. Le Massena had an article in an issue of the late, lamented VINTAGE RAILS magazine about the Le Chatelier brake.

A couple of years back, TRAINS had a mountain railroading issue that covered downhill operations pretty well, including the use of dynamic brakes and retainers.

Ol' Ed

[jimrice4449]

To set air brakes (as mentioned above) you reduce train line pressure and the brake valve shunts air from the reservoir to the brake cylinder.   To release the brakes you bring train line pressure back up to the original pressure which causes the brake valve to exhaust the air in the brake cylinder.   A problem arises if you have to set the brakes again before the reservoir is fully charged.   The way the retarders work is by turing a lever at the end of the exhaust pipe from the cylinder (located adjacent to the hand brake) which turns one of three ports at the end of the pipe.   The normal posittion is an opening the size of the pipe which allows instant exhausting of the cylinder pressure.  The partial is a smaller orvice that retards the escape of air from the brake cylinder and the full retarder is a much smaller orvice which allows the brake cylinder to remain charged while the train line is being pumped up to full pressure.

[chad thomas]

....You know...think of the engineer's possition of topping a hill {and before air brakes}, and having confidence the train would not run away decending the next down grade....and the only way to prevent that was the brakemen scrambling around and across his train setting hand brakes....and hoping they set enough or hoping they actually were back there on the job....actually doing the job...That would not have been a very nice position to be in starting down every hill.  Back then some of the original grades were in the 4 % range too....!!!

Or am I missing something....Was there a way to know "the train was properly braked before starting down"....???

Think about the brakeman. Imagine being someplace in the middle of nowhere like Grass lake summit in the middle of the night in a snowstorm walking on frozen running boards and haveing to jump from car to car while moveing. Then as you crest the summit haveing to scramble from car to car to set brakes with your only light being the faint light of a lantern. There is no way I would have that job.

[Modelcar]

....Chad:

I really don't understand why almost every train say in wintertime and at night under severe conditions...didn't run away not having enough braking power set to control train speed....I simply don't know how it was done....How the stiuation was kept under control....I simply must be missing something in my scenario assuming the brakemen back on the train would "know" when to start to tighten brakes on "how many" cars.....??? 

Was the train possibly brought to a stop to "set" the brakes before starting down any important grade...??  Must be some answer different than brakemen running around on the top of box cars {and from car to car},  winding tight brakes...How would they have had time to get a train under control as it starts downgrade if it did not stop at the summit...??

Any thoughts out there...

[chad thomas]

They sure did have a tough job. As far as knowing when to brake they used whistle commands, not sure what they were though.

[dldance]

....Chad:

I really don't understand why almost every train say in wintertime and at night under severe conditions...didn't run away not having enough braking power set to control train speed....I simply don't know how it was done....How the stiuation was kept under control....I simply must be missing something in my scenario assuming the brakemen back on the train would "know" when to start to tighten brakes on "how many" cars.....??? 

Was the train possibly brought to a stop to "set" the brakes before starting down any important grade...??  Must be some answer different than brakemen running around on the top of box cars {and from car to car},  winding tight brakes...How would they have had time to get a train under control as it starts downgrade if it did not stop at the summit...??

Any thoughts out there...

RR rules for many grades stipulated the number and setting of retainers.  The train would be brought to a full stop -- ideally when balanced on the summit (summit point at midpoint of train) and the retainers would be set.  Many hills had a siding at the summit for that purpose.  Then if during the decent in pre-airbrake days, more braking effort was needed, the enigneer would whistle for brakes to be set -- I think it was 5 short blasts and brakemen would run along the top of the cars until their assigned number of cars had the brakes set.  Being a brakeman was a job with short life expectency - thus the rapid conversion to air brakes. 2 shorts was release brakes and move forward.  3 shorts was release brakes and move in reverse.

dd

[Modelcar]

....It is a miracle they made it over the division...and at what speed.  But then, the competition was not too swift in that era either.  Horse and buggy for some time and a bit later crude trucks with questionable roads.