BigJimDidn't I say that in my first post...hmmm?
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.
OvermodYour 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).
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
gmpullmanThe OP's questions originally were regarding a 1946 Victorian operating manual.
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.
OvermodThe point being, as Big Jim pointed out, that Greg's actual question involved understanding of current independent operation.
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
greg - Philadelphia & Reading / Reading
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.
OvermodI 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 ...
gmpullmanI used to run an engine equipped with #6 ET brakes. It responded as quickly as the air pressure could build up against the brake pistons (3 in this case) to about 45 pounds. Probably twenty to twenty-five seconds. Half that time in Quick Apply.
It responded as quickly as the air pressure could build up against the brake pistons (3 in this case) to about 45 pounds. Probably twenty to twenty-five seconds. Half that time in Quick Apply.
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?
gregci'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?
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:
https://heritagerailalliance.wildapricot.org/resources/Documents/AIR-BRAKE-WABCO-5046-13-14EL-BRAKE-EQUIPMENT-DIESEL-ELECTRIC.pdf
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?
gregcwhat are "AB" brakes?
https://ebs.co.uk/history-of-air-braking.aspx
(scroll down). This was standardized in American practice in the early 1930s and, as noted, the current ABDX (and the convertible ECP version) are just improvements on it.
If you take a look at NKP 765, what's that I see in there but a 26 brake valve.
https://tinyurl.com/y4fzvr9g
It didn't come from the factory that way!