I believe that the brake system that Greg is referring to is the A-6-ET, introduced in 1908, and is American as apple pie!
There is a figure of brake-valve handle positions, in my 1944 copy of the NZGR Air Brake Handbook, similar to the one Ed posted.
brake pedistal002 by Bear, on Flickr
brake pedistal001 by Bear, on Flickr
[2c] the Bear. [:)]
Thank you, Bear. I’ll show you MY pedestal (Yours looks like a No. 8, mine’s only a No. 6)
6_ET-pedestal by Edmund, on Flickr
The one I’m familiar with wasn’t pedestal mounted, though. It was a 1918, USRA locomotive.
Cheers, Ed
I can’t quickly find a photo for conslusive proof Ed, but I’m 99.7% that those pedestals would be found on the Ka and Ja steam locomotives locomotives that were still in operation in the late 60s, early 70s.
Cheers, the Bear.[:)]
yes, the green books says A-6-ET
~20 seconds, that’s helpful
thanks
I have operated this system on old electric engines.
Before we go round and round too much more, here is a link containing how familiar and reasonably modern 26-L independent brakes are controlled (p.15):
http://www.tcrc320.org/MEMBERS/2006_LET_complete_Workbook.pdf
Oh joy! I don’t need to post any long complicated technical stuff that drives some posters nuts. Here is technical information on 26-L from NYAB (don’t bother reading if this stuff doesn’t interest you):
http://www.nyab.com/media/nyab_1/documents_1/technical/instructionpamphletsip/ip_074.pdf
Zug or other real railroaders can tell you how long it takes for a control-valve change to be reflected in ‘shoes biting’ or measurable braking-effort change.
There’s a rule that when you start bailing off the independent, you wait at least 1 second for each MUed unit in the consist. (You see this mentioned in a number of contexts.) This is not the same thing as the ‘release speed’ I think you want.
Depends on the locomotives, hwo fast you are going, how good the brake shoes are, how they are adjusted, the weight you are trying to stop, grade, how slippery the rail is, and probably a few more I’m forgetting.
by 100% i mean max brake cylinder pressure
Most of our engines (GP-whatevers), if you slap the handle from release to full on, maybe a second to get max pressure? Then another second or two for the slack to run in and knock your coffee off the control stand. I never timed it. Widebodies may be a little longer?
Didn’t I say that in my first post…hmmm?
Yes, but you forgot the ‘magic woid’ – ya shoulda sed 26-L.
Your post promptly got buried in data downloads of 6ET (and nerd-style digressions about differences between 8 and 6 pedestals, which further confused the matter). At this point you might as well recap what you said to establish it free of any discussion of 6ET, FNL conversion to 24-series, or whatever might make poor Greg even more confused than I think he still is.
The modern independent brake is stepless, progressive, and self-lapping; it does not need metered ‘slow’ and ‘fast’ application and release speeds, or a dedicated center position. The bailoff control while present “on” the lever is unambiguously separate in action from moving the lever to select braking range.
In my opinion, this is (and always has been) superior to the older method of controlling an independent brake, similarity of operation to Westinghouse one-pipe brakes be damned.
Note that while I could bring in a discussion of the ‘transition era’ of brakes from 6ET through 24NL to 24FNL, I haven’t even mentioned the idea until now – and am as promptly dropping it. There are threads elsewhere on the Web that cover this in sometimes loving detail. But it does NOT belong in a thread asking about current independent-brake operation with improper starting assumptions.
Sorry.
The OP’s questions originally were regarding a 1946 Victorian operating manual.
I hesitated even replying to this thread, now I remember why.
Ed
No, the OP’s original questions were about understanding operation of current locomotive independent brakes – and his erroneous assumption was that they ran with five positions. It was then several posts until he provided the page from the Victoria Railways manual to substantiate where he got that assumption.
Then we got into the whole ‘where did this come from?’ discussion – in which, remember, I was participating fairly enthusiastically – and we tracked down that it was in fact a variant of 6-ET, and the discussion on older independent brakes was off to the races.
The point being, as Big Jim pointed out, that Greg’s actual question involved understanding of current independent operation. Which is nothing like 6-ET. And we all confused him by haring off on an (admittedly splendidly documented!) exploration of systems obsolescent since the Sixties.
Don’t feel bad for contributing. I certainly don’t. But in retrospect it was (as Uncle Butch pointed out in a different thread) a mistake to fill the thread with posts and posts worth of something that actually had Greg looking in a very wrong direction for very mistaken understanding.
acutually trying to understand the behavior of older equipment which we presumably have the correct manual for and a live engine to evaluate. expecting to extrapolate this understanding to other steam locomotives
various manuals (e.g. Western Pacific) describe operation but not performance. they don’t provide any flow rates (cu.ft./min) for any brake line pressure or difference in pressure between main reservoir and brake line. I assume the flow rates differ on different locomotives, but i would expect the time to affect a change in braking % to be similar
since i’m trying to model this kind of behavior in a throttle, i’d like to know those flow rates or how long the brake needs to be in a particular position to achieve some % of max brake application
my understanding of independent brakes is a brake valve directly controls (no triple valve) air flow into and out of the brake cylinders on the engine and tender to increase/decrease brake force. my understanding is it takes time to increase/decrease the pressure in the cylinders.
whether there are two distinct steps, slow and quick, or a continuous range is not important. but i would like to know what the min/maximum rates or times are
as an example, using current flow values our model slows a 1 car passenger train from 10 mph to 0 mph (green) in ~30 with brakes set to SVC for 5 secs resulting in 22% braking (orange) before setting the brake to LAP. this is for air brakes (brake line PSI in cyan). yes it would take longer for a longer train to achieve the same % braking
I think the only real way to get meaningful numbers, rather than ranges, for a particular steam locomotive is going to be to model the physical layout of the brake gear on that locomotive – the lengths and characteristics of the piping, the size of the cylinders, the type of the foundation beams and rigging – and then working from the MRP and the orifices in the physical valve figure out how long it takes to various ranges of shoe pressure.
This will be essential for the ‘slow application and release’ as these are obviously jiggered to be far outside the response time of the equipment on the locomotive. So you’ll take the mass flow through the ‘slow’ orifice and figure out how long it takes for the particular gear to apply effectively, or release effectively, and you’ll need to know more than just pressure or flow at the valve to do that.
I am not an expert on 6-ET (or 24NL/FNL) but from what I know, railroads didn’t tinker with the ‘factory’ slow orifice to fine-tune it for particular services, although that would be technically possible between some limits. In a model or ‘simulated’ world you could just gin up a time delay to full application, and another one for effective slow release, and just imagineer the appropriate “orifice dimensions” that would produce that effect at the brakeshoes.
this is what i’m looking for – ~20 seconds to reach max pressure (45 psi) - thanks Ed
i’m being told the brake equipment described in the Western Pacific note: 26, 24RL, 14EL and 6BL, may only have been used on diesel locomotives, not steam. is this correct?
trying to determine a timeframe for various brake equipment.
what are “AB” brakes?
Depends on what you mean.
These brakes were introduced at particular times, and have some features – independent braking strongly among these! – that mattered far more to MUed consists than single or doubleheaded steam. As I recall, 24NL was a late-'50s and '60s thing, and FNL a '60s thing, so of course not installed on road steam. On the other hand these were meant to be compatible with ‘units’ using 6-ET control valves (see the 24-NL Altamont Press discussion) and at least theoretically that could be a steam locomotive with that style of valve…
For those of you who are ‘clueless’ about 14-ET, it was a variant of 6-ET intended for lighter diesel-electric locomotives. Interested people can read about it here:
If you have the money you can install 26-L or later brake valves on steam locomotives, and as I recall many have done exactly that. The modern version of independent control works just fine on big locomotives.
i can understand that steam locomotive brakes could be retrofitted
considering that the Reading T1 was one of the last steams engine designs, does anyone know what model brakes it has?
