Was very curious about this and wonder if this is still done.
From what I understand; in the past freight and passenger trains often left terminals or stations with the brakes on the entire train partially engaged to control the slack. After getting to the desired speed as the engineer “feels” the slack running out he eventually releases the brakes 100%.
When I used to ride Amtrak in the early 80s the “Silver series” trains were 10 to 17 cars long at times ( I miss those days!). My friend Sam (conductor) would let me stand in a coach vestibule for a while with the upper half of the door open (Heritage Fleet). As the wind hit me at about 30 mph, I remember still smelling the brakes ( stinky!!) for a while after leaving the station. I wonder now if it was because Randall ( SCL engineer and my friend) had the brakes partially on.
Can you guys give some info on this, please? -----Thanks!
Rules for passenger trains require a running brake test after leaving the terminal so that’s what you were experiencing.
I’ve never left the terminal with the brakes applied, this is a practice that I’m not familiar with, although I understand that in mountainous territory something like this may be done, I’ve heard stories of running coal trains east down the mountain out of Bluefield, WV.
Stretch, or power braking is a practice that is actively discouraged because of fuel consumption, dynamic braking is the preferred method by the four large carriers now in the U. S. Sure was a lot more fun to stretch brake, though!
Big, big difference between powerslides and power braked trains. On the other hand, powerslides on locomotives are not much fun at all no matter which way they go…
I’d always heard of stretch braking being used to DECELERATE passenger trains into a terminal, not leave it (except when the departure is downgrade and the cars don’t have tightlock couplers). There’s a significant exception I’ll mention in a moment.
Now, I’ve always thought that in the steam era, the brakes were kept applied to reduce the effect of surges on starting, and then fully released once the rpm rate of the locomotive was up to the point the inertia of the cars would damp out the impulses. But that’s not what Antonio is talking about, I think.
The exception I noted above is related to electrical multiple-unit operation with only a small fixed number of contactors in the control box. I have observed the following method used to great effect on DC (older NYCTA subway trains, both IRT and IND) and AC (PRR/PC MP54 trains).
There is no ‘gradual’ way to apply starting power with these trains, as the first available position on the controller is one admitting substantial motor current, and with motors on all the cars the resulting ‘starting jolt’ is not damped out by much. So, instead, the brake release is modulated so that the brakes are just coming off as the motor torque comes up. The resulting start is smooth as silk, rather than giving a high initial acceleration.
In some cases, the brakes are left slightly applied as the controller is notched up further (I observed this to be typical in IRT subway operation where very high acceleration with loaded trains is utilized) and then completely released when a couple of cars have cleared the end of the platform. Of course, there’s some experience needed regarding the load of passengers, the type and length of train, etc. to figure out the best way to work the brakes to get the effect; I saw very few motormen who actually
Streach Braking is actively discouraged by the major carriers account of the fuel comsumption issue. However, like every rule there are exceptions to it. Many operating territories have specific physical characteristics the require the slack in a train to be accurately controled, otherwise the slack can run in an out within the train and develop enough draft and buff forces to break knuckles or pull draft gear out of cars. Those specific locations where strech braking is recommended are generally taught by the Road Foreman of Engines on the territory affected, and in some cases it may be mandated by a Timetable Special Instruction.
You guys have a great wealth of knowledge! Really appreciate the input. .
One outstanding point about the above information is that it very plainly shows how tough and challenging being a locomotive engineer is. [4:-)]
Quite humbling when you read the info and realize that just one mistake in slack control could potentially cause damge mounting to thousands of dollars, not to mention personal injury, damage to the track and the loss of revenue. [:0][B)]
With this info, its amazing that many in the public stll think that all an engineer does is sit quietly and push a button to make a train go and another to make it stop, and that’s it. I often talk about the railroading to my students and try to dispel the “myths” that they’ve heard.
On suburban passenger trains there is a definite advantage to starting the train with the brakes set. Despite the claims by some of the tightness of “locktite” couplers, there is still some slack in the coupling (otherwise, one would not be able to couple and uncouple the cars).
Before the F40PH, the CNW used F7’s and E8’s for suburban service. The locomotives had a switch that controlled the position of the load regulators; unfortunately, it was only a two-position switch (minimum or maximum field). In the minimum position, the unit would load way too slow to keep a suburban schedule, but in the maximun field the unit would load up to 1500 amps with the first notch of the throttle.
If the train was stopped such that the slack was in (against the loco), we would keep a five-to-ten pound reduction on the train to ease the jolt of starting (the independent was set to 30psi, and was insufficient to hold back a unit instantly loading 1500 amps). This way, the loco would pull on the first car and some of the momentum would be absorbed by the resistance of the first coach (which would get a bit more of a jolt than the last coach), and so on with the rest of the train. So by the combined effort of the engine and train brakes, we could affect a smooth start. If the slack was out, the brakes on the train were allowed to completely release.
When operating from the cab-control car, managing slack was both easier and harder. Easier, because the cab-cars did not have an ‘independent’ brake (they had a 'parking brake, but that was not used much due to the incredible noise it made when releasing). It was just easier to leave the brakes set on the train when stopped. The bad thing about leaving the train brakes on was that the brakes were not charging while they were set, and the stations were so close together that sometimes the trainline would not be fully charged for the next station stop, especially with a longer train.
"Occasionally, before Drawbar Slack was removed from Freight Rolling Stock in the Seventies, an Engineer would Apply and Release the Train Brake to Start a Heavy Train on an Uphill Grade.
On Stopping a Long Freight Train on an Upgrade, the Train would be Stretched Out to the Caboose account the Grade.
When he wished to Lift the Train he knew the Power from the Diesels could Tear the Drawbars out on the First Cars, as the WHOLE Weight of the Train was on the Lead Cars because the Train was Stretched Out.
He would Set the Brake on the Train so it would not Roll Back, THEN Back into the Train with the Locomotives, Bunching the Slack on the First twenty or so Cars, Depending on Grade and Tonnage, Then Release the Train Brake.
As the Brakes Released from the Front back, he would start to Pull Gently, while the First Cars Releasing and Slack being taken Up One Car at a time.
He would then have SOME of the Tonnage Moving and the Momentum would help lift the Standing Cars.
This took skill, and when the Slack Ran out to the Standing Portion you could see everything come to a Stop, then Start again".
I don’t think slack has been removed from freight equipment. This method is still used to start trains on grades.
I think your explanation is ingenious… but is that what he’s saying? I think paragraph 3 is describing what happens with locomotive leading, and paragraph 4 with the locomotive trailing.
If the train was stopped such that the slack was in (against the loco), we would keep a
five-to-ten pound reduction on the train to ease the jolt of starting (the independent was
set to 30psi, and was insufficient to hold back a unit instantly loading 1500 amps).
With the slack in, and 30psi “insufficient”, there isn’t going to be any relative ‘kicking’ of intermediate cars in the train, is there? I don’t know of anything providing extensive sprung recoil between commuter cars, which is the only thing that would give the kind of surging physics described. That means that the locomotive would be substantially accelerating the whole train at once, and light train-brake application would only provide additional resistance to make the initial acceleration (up to the point that available hp at early notches balances resistance) less ‘coffee-spilling’. More support for this:
This way, the loco would pull on the first car…
Doesn’t sound like locomotive trailing to me; that would be loco pushing on the last car, or pulling on the last car in the previous scenario…
… and some of the momentum would be absorbed by the resistance of the first coach
(which would get a bit more of a jolt than the last coach), and so on with the rest of the
train. …
Again, with the slack bunched and assuming (not biblically ;-}) that “first is last and last is first” you wouldn’t be seeing progressively greater jolting on acceleration. That only makes sense in traction.
So by the combined effort of the engine and train brakes, we could affect a smooth start.
Independent holding down the full acceleration of 1500A on what is (for the first few inches or feet) little more th
If the train was stopped such that the slack was in (against the loco), we would keep a five-to-ten pound reduction on the train to ease the jolt of starting (the independent was set to 30psi, and was insufficient to hold back a unit instantly loading 1500 amps).
This part refered to when operating from the locomotive, and the train was stopped on a downhill grade.
You can imagine the whack at the cab-car end this would produce if you did this with a fast-loading engine… accelerating downhill (which is presumably the way you get ‘slack out’ condition on a push-pull consist braking into a station, then releasing brakes completely before loading the engine as this sentence implies).[/brown]
With the F7 & E8’s, when making a stop, we shut the throttle off (to take the locomotive out of paralell), apply the train brakes, then as the train was coming to a stop (around 20mph) we would put the locomotive in the first notch. So if the station stop was being done correctly, at just the right time we would release about 10-15psi of the full application, that way the train did not do a “stand-it-on-its-nose” type of stop (which results in the passengers being thrown back into their seats at the complete stop). So with the reduction of braking effort, the loco in the first notch would gently bunch the slack when stopping. We then left the entire train’s brakes applied, and when it was time to depart, we could go to power immediately while releasing the brakes, and the train would start smoothly as one piece.
With the F40PH’s, the units had “blended braking”, so use of the throttle of course defeated the dynamic brake, so this method was not used. In fact, it was prohibited by the Metra, as there were some problems with the locomotive wheels overheating due to the friction braking effort.
As a passenger train engineer,I have worked with old head engineers, one from the Rock Island RR, one from the C&NW, and one from the CB&Q. All three of them will start the train with the air set. I’ve done and seen it done many other ways, all of which seem to work equally well as long as the engineer knows what he’s doing.
As far as stopping, unless it is downgrade, the best is to keep the slack stretched. And power braking is the best way to do this. Also, we run locomotives at both ends of the train, so powerbraking is a must to keep the locomotives on the rear of the train from running in when the brakes are released. This can normally be accomplished by just placeing the throttle in 1 a few seconds before you release the brakes.
By the way Zardoz, we happen to run two former C&NW F7-A’s, numbers 402, and 403. Both of which ran commuter service at some point in there career, and both are still geared for 90
Powerbraking, stretchbraking, and cyclebraking are all the same. The terms vary from region to region. All of the replys I have read have merrit however, this form of braking is mostly used on frieght to control start and stops and controlling slack on multiple hills. The main problems with this as mentioned, are the skill and timing of doing this. If not done right you would pull drawbars out or break knuckles. This form of braking causes excessive wear on brake shoes and, the biggest danger is depletion of air in the aux. reseviors on each car without adequate charging time. I was taught by the old heads to use this methd over undulating hills to help control slack in heavy and mixed trains. Also, it worked well to stabalize the ride over a rough spot in the roadbed. We did not use this form of braking in passenger service often except for the latter reason as there was not as much slack to control. This is generally a dangerous practice and is prohibited in most places except by timetable special instruction.[2c]
After finding this thread again after many years (and a new account!) I sort of wanted to explain powerbraking for anyone who is starting to train for an engineer position and runs older equipment. I personally run a GP10 on a class 3 shortline with no dynamic braking, and was taught how to powerbrake by two former steam locomotive engineers. I’ll keep this simple, short, and sweet. When leaving a station you never want to leave your brakes applied. Starting our passenger train I’ll fully release my independent and my train brake, put it up to notch 1 and progressively notch up and down as I feel the slack run out car by car. As you feel your slack run out notch up. notch down, repeat until you feel your slack run all the way out. It’s a feeling that’s hard to explain to someone when you first start training, but in a little bit you will get the feel for it. After that, I’ll do my rolling brake test, and when you do so, never let the locomotive go to idle with the brakes applied, this will have your slack bunch right up and at least keep it in notch 1. On the shortline I run on, out of the yard it’s a pretty steep grade downhill, and to ultimately keep passengers comfortable and not have slack running in and out, I will set about an 8 pound reduction (varies day to day), and I keep that reduction set for the most part until the downhill grade ends, always leaving the train in notch 1 at a minimum if the brakes are applied, and traditonally around curves and etc I’ll notch up to keep a rolling speed and the slack stretched out. It takes about 15 seconds for the brakes to release, so still keep your locomotive in notch 1 until you feel the brakes released. I hope this helps anyone who has found information on powerbraking to be rather vague online.
