Those stiff short handle brakes were the worst. You really had to keep a eye on the guage and keep tapping on them to keep from putting too much on!!!
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zugmann BigJim . If the shop forces came and didn't have an O ring, they would swap out the Main Res. knob with the Eq. Res. knob and it would usually fix the leak. If not, the engine went to the house. Our local machinist had it all torn apart and couldn't get it fixed. Went to the bigger shop. Then you have the newer electronic airbrakes wtih a service zone about 2 microns wide. Not really made for switching with. They do realize there needs to be something between min and FS, right?
BigJim . If the shop forces came and didn't have an O ring, they would swap out the Main Res. knob with the Eq. Res. knob and it would usually fix the leak. If not, the engine went to the house.
Our local machinist had it all torn apart and couldn't get it fixed. Went to the bigger shop.
Then you have the newer electronic airbrakes wtih a service zone about 2 microns wide. Not really made for switching with. They do realize there needs to be something between min and FS, right?
Couple those short travel handles with one that's stiff. You end up setting way more air than you wanted. I've had a few where you have to really slam that handle back from the service zone to release, otherwise if you're not paying attention all you've done is moved it back to the minimum reduction position.
Jeff
BigJim. If the shop forces came and didn't have an O ring, they would swap out the Main Res. knob with the Eq. Res. knob and it would usually fix the leak. If not, the engine went to the house.
It's been fun. But it isn't much fun anymore. Signing off for now.
The opinions expressed here represent my own and not those of my employer, any other railroad, company, or person.t fun any
zugmann Then you get the worst of btoh worlds - a 26L that doesn't maintain. That is a miserable thing to use while working a local (yes, the engine got shopped...).
Then you get the worst of btoh worlds - a 26L that doesn't maintain. That is a miserable thing to use while working a local (yes, the engine got shopped...).
Oh yeah!
However, many times there was a very simple fix for that. I found that the problem, most of the time, was actually a bad O ring on the knurled knob of the gauge causing it to leak down. If the shop forces came and didn't have an O ring, they would swap out the Main Res. knob with the Eq. Res. knob and it would usually fix the leak. If not, the engine went to the house.
gregc wow! so it drops is a fixed amount and there is no need to return the handle to the LAP position to maintain a constant amount of braking once the brake line pressure has dropped to that level? looks like there are different types of equipment. from Westerm Pacific - Air Brake Principles and Specific Equipement from pg A-2 for 26L brake equipment Minimum Reduction The first position to the right of release is minimum reduction position. In this position equalizing reservoir will be reduced 6 to 8 lbs. and the corresponding reduction made in brake pipe pressure. When left in this position, the brake valve will maintain brake pipe pressure at 82 to 84 lbs., allowing air to flow into the brake pipe if necessary to compensate for leakage. from pg B-3 of for 24RL brake equipment 5. Service Position Next position to the right is service. In this position the equalizing reservoir pressure is reduced and brake pipe pressure reduced accordingly, at a service rate. This brake valve is not self-lapping in this position; that is, the reduction will not be limited by the valve. Equalizing reservoir pressure should be reduced the desired amount, and then handle should be moved to lap or pressure maintaining position, whichever is required.
wow!
so it drops is a fixed amount and there is no need to return the handle to the LAP position to maintain a constant amount of braking once the brake line pressure has dropped to that level?
looks like there are different types of equipment. from Westerm Pacific - Air Brake Principles and Specific Equipement
from pg A-2 for 26L brake equipment
Minimum Reduction The first position to the right of release is minimum reduction position. In this position equalizing reservoir will be reduced 6 to 8 lbs. and the corresponding reduction made in brake pipe pressure. When left in this position, the brake valve will maintain brake pipe pressure at 82 to 84 lbs., allowing air to flow into the brake pipe if necessary to compensate for leakage.
from pg B-3 of for 24RL brake equipment
5. Service Position Next position to the right is service. In this position the equalizing reservoir pressure is reduced and brake pipe pressure reduced accordingly, at a service rate. This brake valve is not self-lapping in this position; that is, the reduction will not be limited by the valve. Equalizing reservoir pressure should be reduced the desired amount, and then handle should be moved to lap or pressure maintaining position, whichever is required.
On the 24 valve, there is a position between running and lap called first service. This position could be modified and some railroads did so, to be used for pressure maintaining. When not so modified, first service would draw down the EQ reservoir by 6 to 8 psi using a reduction reservoir. This was not actually self-lapping in this position, but would allow air to continue to reduce pressure at a very small rate. The 26 and 30 schedule valves are self lapping and will hold the initial reduction at that amount.
That the 24 will continue to reduce at a very small amount isn't a problem when you consider train handling. Good practice when slowing or stopping is using a split reduction application. That is, making the initial reduction (first service/minimum reduction) of 6 to 8 psi, allowing it to take effect and then making further reduction(s) as needed.
The initial reduction is to help control slack. Remember the brakes on a conventional train apply from head end to rear end. Too heavy and the brakes will start to set up hard on the head end of a long train allowing the rear end to run in to the front. With the right combination of train make up (position of loads.empties) and terrain, a light car might be "popped" out of the train. Even if that doesn't happen, severe slack action can cause damage to loads. (I saw the result of load damage many years ago when I worked for a meat packer on the load out dock. A truck returned with a 53' trailer that had been loaded all the way to the door. The driver had to make a very hard stop and the load had crushed itself forward so now it physically occupied only 1/3 of floor space.)
On 24 valves that have been modified to use pressure maintaining, the first service position no longer makes a set amount reduction. In that case the application needs to be made by moving the handle into the service zone, drawing off the desired amount and then moving the handle to pressure maintaining or lap position. I think equipment with 24 valves at the WP museum may be set up for pressure maintaining. If so, they wouldn't have the first service reduction capability.
greg - Philadelphia & Reading / Reading
If the question is:
"Does moving the automatic brake handle from the release position to the minimum reduction position result in a fixed amount of pressure drop in the equalizing reservoir?"
The answer is YES!
i thought the simple answer is ... "no, the valve doesn't drop the pressure a fixed amount?"
but based on your response, i wonder if it is possible
Greg,
You are wrong, wrong, wrong, and you are making this much harder than it really is. And, I am sorry, I just don't have the time to type out 40+ years of air brake artistry.
BigJimNot sure what you are trying to say.
gregci'm being told that service 1 reduces the brake line pressure until it has decreased by 10 psi from the starting pressure when the service 1 state was first applied. no need to move the brake to LAP to prevent a further reduction in brake line pressure.
first, i don't believe this to be accurate
for example. brake line pressure is currently at 82 psi. set the brake to SVC 1. brake line pressure drops to 72 psi and remains at 72 psi without the brake handle move from SVC 1.
if you then momentarily move the brake to Release and the pressure rose to 75 and then move the brake handle back to SVC 1, the pressure would drop to 65.
gregc BigJim Look at the PDF from this web site: WP Air Brake Principles that was helpful it seems no "air" brake valve drops the pressure by a fixed amount. maybe an independent brake the closest to that behavior is reducing the equalizing reservoir pressure to a desired amount and making no further reduction. and then allowing the relay value to control the brake line pressure.
BigJim Look at the PDF from this web site: WP Air Brake Principles
that was helpful
it seems no "air" brake valve drops the pressure by a fixed amount. maybe an independent brake
the closest to that behavior is reducing the equalizing reservoir pressure to a desired amount and making no further reduction. and then allowing the relay value to control the brake line pressure.
Not sure what you are trying to say. The independent brake works in a completely different way (opposite) than the automatic brake!
BigJimLook at the PDF from this web site: WP Air Brake Principles
gregc what is an "equalizing reservoir"? and "self-lapping"?
what is an "equalizing reservoir"?
and "self-lapping"?
Look at the PDF from this web site:
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.wplives.org/forms_and_documents/Air_Brake_Principles.pdf&ved=2ahUKEwi0hujkmvnsAhVBw1kKHQd9DbAQFjADegQIIRAB&usg=AOvVaw3-9X2H86J8UK4R2eDy-6Lw
There was an interesting discussion of some of the 'finer points' of 24NL and FNL on the Altamont Press board a few years ago (these were versions that upgraded locomotives built with 6ET brakes at "minimum cost" which sometimes wasn't low enough to suit particular railroads' mechanics... )
I was looking at this while posting on RyPN a couple of days ago, and can probably find the reference there if he needs it (if the current moderation permits posting an URL to the content directly under the TOS). Searching on 24FNL will probably pull it up within a page or three of results...
The brake valve reduces pressure in the equalizing reservoir, the brake pipe will drop to the pressure of the eq reservoir.
The first service/minimum service reduces pressure by 6 to 8 psi. That's so the brake pipe drops low enough that the pressure wave "bouncing" back forward doesn't cause some brakes to go to release.
The minimum/first service position is self lapping on the 24RL. The 26 and 30 brake valves are automatically pressure maintaing and self lapping in all positions and don't have a lap position. On the older (24RL) valves, when more braking was desired, the handle is moved to the service zone and then back to the pressure maintaining or lap position after the desired pressure reduction. The further reduction on the 24RL wasn't self lapping.
The lap position closes off the brake valve and doesn't allow air to go into or out of the brake system. Pressure maintaining allows enough air to enter the system to compensate for brake pipe leakage. 24RL valve was the first to incorporate pressure maintaining although there is a way on the older valves under the right conditions to set up an ersatz pressure maintaining. Of course that practice wasn't 'legal."
What was once called first service is now called "Minimum Reduction". It is the first detent away from "release". Move the brake handle from release to M/R and you get a reduction on the equalizing reservoir of 6-8 lbs. Further movements around are "service" applications until you get to the next detent which is "Full Service". Once you get to F/S, that is all of the brake you can put on the train without going to emergency. Any further reduction is wasting air.
never mind svc 1, 2 3, then
does svc drop the brake line pressure to a fixed amount without setting the brake to LAP (valve closed)?
I've never heard of second or third service. There isn't one. I believe the term first service, although some may still call it that, was used with the 24RL brake valves. On today's brake valves it's properly called minimum reduction.
It's supposed to reduce the equalizing reservoir by 6 to 8 psi. Today's brake valves are self-lapping, there is no lap position.
When making an application on the 24RL with pressure maintaining, moving the brake valve to first service reduces the eq reservoir by the prescribed amount. When you want to increase the application you move the valve to the right into the service zone, beyond the pressure maintaining and lap positions, to reduce pressure by the desired amount and then back to either the pressure maintaining or lap position. Pressure maintaining would be used in most cases, lap more for making brake tests when you don't want air flowing through the valve.
Brake valves before 24RL didn't have a first service and pressure maintaining feature. To make an application you moved the valve from running position past lap to the service zone, drawed off the desired first set - at least 5 psi - and returned the valve to lap. When more reduction was desired, the valve is moved from lap to the service zone. When the desired amount is drawn off, the valve is moved back to lap.
I've worked with the older systems years ago at a museum and the current valves at my day job. The museum received an engine with a 24RL valve, but it was after I left to go to work for a class one.
The WPRR Museum has a pdf on the brake operations of it's fleet.
https://www.wplives.org/forms_and_documents/Air_Brake_Principles.pdf
It may help to recognize what "LAP" means -- it is the same thing as with long-lap valves in steam design practice.
Lap means the valve is blocked from exhausting. In that position no more brake-pipe reduction or pneumatic signaling will be made from the valve, although other parts of the system may have valves in different positions. All Al is saying in the sentence you quote is that he started a 10-pound set at 90#, wants to stop releasing line pressure when he gets to 80# (without releasing the brakes any, and remember he doesn't have graduated release), and needs something that promptly stops venting the brakeline pressure when he sees the gauge reach close to 80#. Since LAP is quickly reached with a twist of the wrist, and stops venting promptly (there may be some weasel exceptions to this, but ignore them for now) he uses that position to hold the system at 80# line pressure with "whatever is happening back in the train" executing however it is intended to.
Brake systems have changed over the years. I'm going to go out on a limb (a very sturdy one) and say the description of the SVC1, SVC2, SVC3 settings is for one fo the more modern systems, while Krug was describing operation of an older brake stand.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
how do service brake setting work and what is the difference between service 1, 2 and 3 settings?
i'm being told that service 1 reduces the brake line pressure until it has decreased by 10 psi from the starting pressure when the service 1 state was first applied. no need to move the brake to LAP to prevent a further reduction in brake line pressure.
if the brake are moved from SVC1 to LAP and back to SVC1, the brake line pressure is allowed to drop an additional 10 psi
and serivce 2 drops the pressure by 20 psi.
this appears inconsistent with what AA Krug wrote:
Meanwhile, up in the cab, the engineer watches his gauges. When he gets the brake pipe pressure lowered to where he wants it he puts the brake valve handle in the neutral, or LAP, position.
Let’s say he "makes a 10 pound set". This means he reduces the brake pipe air pressure from 90 psi to 80 psi then "laps" his brake valve.