Western Railroad Discussion > Air brakes: 24RL vs 26 L

OK gang, for the pros out there, what is the difference between these systems? Not a challenge, rather, a legit question. Thinking back to 1953 or so.

John Gezelius
Tustin, CA

26 air is more modern. You pull it to the right and it will set and maintain a brakepipe pressure determined by the position of the handle. This is called "self lapping"

24 air is older. You have to move the handle to the right to exhaust the air and watch the equalizing reservior level fall. When you reach the desired brake pipe pressure you have to stop the exhaust as in "lap" the handle and then the brake valve will maintain that pressure.

There are some other differences but this is the biggie. 6 type was not a pressure maintaining system nor a self lapping system though a number of modifications were tried to make them so.

Also, a variant is the 24RLMC1, the RL meaning "road locomotive", and MC meaning "maintaining conversion", which eliminates the need to manually "lap" or close off the air at the desired brake application setting. Quite a few BN SD-9's I ran that did not have the modernized control stand had this modification, and the ex-Alaska FP's on the WYCO, now on Verde Canyon Railroad in Arizona, have this modification. On the Wyoming/Colorado, this was very useful on the long, descending sustained mountain grades, especially with coal loads. --- --- - --- JLH



Edited 1 time(s). Last edit at 08/17/09 12:53 by highgreengraphics.

also 26L basically reduces the problem of overcharging the brake pipe

on the older system you can once you wish to release the train brakes move the handle back to the full release position and leave it there as long as you want but this will quickly put excessive air back into the train line hence causing the brakes to reapply

the techinque used was to move it from lap back to full release then back to running after a few seconds

then the brakes would recharge at a normal rate

the system i used to use was A6ET A7ET engine and tender also B7EL

the older system was great as you can hear the air escaping and recharging on the 26 system the sounds were noticably muffled



Edited 2 time(s). Last edit at 08/15/09 16:40 by bakersfielddave.

OH MY

This is truly part of the art of being an engineer.

John Gezelius
Tustin, CA

Most of the 6 automatic brake valves were modified with a stop welded in the "full release" position to keep the handle from being moved past "running" and overcharging the brake pipe.

Many times when dumping side dumps the extra pressure was desireable and one only needed to adjust the feed valve to accomplish what the "full release" did before it was blocked off.

The 26 system is a real improvement in that all of the pressure is maintained by "O Rings" rather than the lapped surfaces on the older 6 and 24 equuipment. The inspection period is also increased to basically 3 years as opposed to two years on the older equipment.

There are basically two different 26 systems (for switchers at least); the 26L for new installations and the 26NL which uses the existing 6 reservoirs. I'm not in front of my schematics or I could be more definate.

Dick Samuels
www.oregonpacificrr.com

Isn't that interesting? My experience with brake valves was with San Francisco's old streetcars. Just about all had simple valves that operated like a 24. To add air to the brake cylinder or reduce it, the motorman moved the brake handle back and forth frequently, moving small bits of air at a time. Late in the era I noticed that the MSR's 22 Fillmore line cars had valves that worked more like a 26. It looked much easier to run, just move the handle toward the right to bring up the brake pressure, etc. These cars were in an 800 series. I thought it ironic that the Market Street, with all its financial woes, would have this improved valve on some of its cars.

All the SPs 24s had gone through the shops and the "Full Release" feature was blocked. They also installed a "Maintaining" feature when you would put the valve over the hump after a set. They had brass tags with the "M" stamped on them and were riveted to the valve. In my opinion, they never worked very well at maintaining a set.

Nudge

spnudge Wrote:
-------------------------------------------------------
> In my opinion, they never
> worked very well at maintaining a set.
>
> Nudge

That is what the feed valve was for. You could even make a 6 valve maintian that way. It was wink, wink, not "approved" to do it that way, but it worked.

What I liked was when the DRGW put in "Frt" & "Pass" valves on the 26s. You had to keep track of what you were doing but it got away from the feed valve.

I knew some old heads that could "Bridge" the handle (between appl and lap) on an old 24 and get it to maintain.


Nudge

As a point of history, when I hired out with the SP in 1966, and worked the LA-Bakersfield district, (Tehachapi), most of the assigned power were SD-9's, SD-35,s, and a few SD-40's. All of the SD-9's had the 24RL, and the other two had the 26. Hell hath no fury like one of those old-head hogheads when he found out he had a 26 equipped unit on the point. The 26 was known as the "Mickey Mouse" brake valve. It was claimed that the recharge time wasn't as great as with the 24, along with a myriad of other shortcomings. It got to the point that the roundhouse foremen got tired of listening to the complaints, so a SD-9 was placed on the point whenever possible. Also, as I remember, there was an issue with the dynamic brakes if a SD-35 or a SD-40 was on the point with SD-9's trailing.

Brian B.

Back then a lot of the GP9s,SD7s,9s,Fs and old U-Boats had the field loop system for DB and a separate cable. There were set up switches in each unit for lead or trail. They mis-matched with the new extended DB and a lot of times you had the lead unit and that was it.

On the Zipper it was all old power, no new SDs, etc because of the DB. When they got enough of the new power the old stuff went to the locals or bone yard an the new power out on the road. (When possible)

Nudge

24. I just liked it cause I could let out what I wanted. Couldn't do that as precisely with a 26 valve

tehachcond Wrote:
-------------------------------------------------------
> As a point of history, when I hired out with the
> SP in 1966, and worked the LA-Bakersfield
> district, (Tehachapi), most of the assigned power
> were SD-9's, SD-35,s, and a few SD-40's. All of
> the SD-9's had the 24RL, and the other two had the
> 26. Hell hath no fury like one of those old-head
> hogheads when he found out he had a 26 equipped
> unit on the point. The 26 was known as the
> "Mickey Mouse" brake valve. It was claimed that
> the recharge time wasn't as great as with the 24,
> along with a myriad of other shortcomings. It got
> to the point that the roundhouse foremen got tired
> of listening to the complaints, so a SD-9 was
> placed on the point whenever possible. Also, as I
> remember, there was an issue with the dynamic
> brakes if a SD-35 or a SD-40 was on the point with
> SD-9's trailing.
>
> Brian B.


Oh yes the many nights we spent together on 365 , 375 and the rest of the drags...I remember hoping never to get an SD-9 on the point... for many reasons... the air gauges were really small and it was hard to get it just right on a set.. also the engines were equipped with the turret control stand.. the engines usually leaked cold air in the winter.. you could not see out of them with the big high nose.. I didn't mind them in the trailing position...

Oh yes the old field loop dynamic brake... think most it not all of these engines were changed whenever they went thru a major overhaul at Sacramento or Houston..

>>the older system was great as you can hear the air escaping and recharging on the 26 system the sounds were noticably muffled<<

As someone who used to ride GP7 powered trains to and from different stations as an agent-operator, I always thought that the noise from the brake pipe was way too loud and I quickly learned to either use ear plugs or ride a trailing unit instead.

Ted