[ATSF3751]

Many North American steam locomotives have more then one air compressor on them! Usually 2 of them of the same type.

Brandon

[Traindude]

steamer_ctn, on 01 February 2021 - 01:10 AM, said:

So how can this value be converted to a per second or per hour figure? The cu ft of air used will vary with the number of cars attached to the train (ie extra air pipe, reservoirs, etc). Hence the steam consumption will vary as the amount of air required varies (train length, etc). So how could this be accurately be modeled?

Currently OR uses the cyl dia, cyl stroke, and number of strokes to calculate a fixed steam consumption. To model cross-compound compressors would be more challenging.


Given the fact that the compressor doesn't run very much, and based upon the timing tests, it doesn't appear to be a heavy steam user. So having the ability to set different steam consumption may not be a huge advantage.

The entire book that I linked to you has almost everything you need--how it works, the results of testing the compressors, etc. Aside from this there's not much more data or info I can provide...what more are you looking for?

[steamer_ctn]

Traindude, on 01 February 2021 - 09:23 PM, said:

Aside from this there's not much more data or info I can provide...what more are you looking for?

The point that I was trying to make (see the first line of my comment) was that whilst it provided some steam consumption information, it was not in a form that can be easily implemented into a model for OR.

In regard to the fact that US locomotives had two compressors, were they always started and stopped together, or did they operate independently of each other?

[Traindude]

steamer_ctn, on 02 February 2021 - 08:42 PM, said:

The point that I was trying to make (see the first line of my comment) was that whilst it provided some steam consumption information, it was not in a form that can be easily implemented into a model for OR.

In regard to the fact that US locomotives had two compressors, were they always started and stopped together, or did they operate independently of each other?

Sorry, I misinterpreted your last post. Maybe since I only know "pseudo code" (AKA plain English), I need assistance from others to convert this into game code.

In regards to locos with two compressors, yes, they both start and stop in unison.

Another thing I wanna mention here, which I have already mentioned in the steam thread but will repeat it here as a reminder, is that steam air compressor governors did not always shut off the flow of steam to the compressor 100% when the main reservoir pressure reached max. Instead, the governor allowed a small "trickle" of steam to flow, which allowed the compressor pistons to slowly "creep". There were three main reasons for this function: 1) To ensure lubrication was still flowing to the compressor steam cylinders, 2) to prevent condensation from accumulating in the steam cylinders, and 3) to prevent the compressor pistons from seizing up. However, the speed of the compressor in this "idle" state is so low--no more than 12-15 strokes per minute--that it doesn't significantly increase main reservoir pressure. This is also why you sometimes hear an occasional "thump" from the compressor even though the main reservoir pressure is at max.

The following video (Fast-forward to 26:09-26:26 to see the clip I'm talking about) shows an example of a cross-compound compressor operating in the "idle" state I have described above.

[Laci1959]

Yes that is right. The compressor piston has a constant slow motion.

[Traindude]

Something I'd like to see in the visual FX department related to braking is brake shoe smoke emitters.

Especially in the days before dynamic braking was commonplace, the only way to keep a train in check on long downhill grades was by means of the automatic (train) brakes. Consequently, so much heat would be generated by the cars' brake shoes that a visible trail of bluish smoke emanated from the wheels of the cars. This action also heated up the wheels. It also wasn't unheard of for trains to have to frequently stop to allow their brake shoes and wheels to cool before continuing.

Here's an old film clip of a Big Boy descending Sherman Hill, with its freight cars trailed by a haze of brake shoe smoke.

On a related note, many older rolling stock in the 19th century had wooden brake shoes, which often caught fire if they got too hot. Not sure how this can be emulated in OR, but I'm sure there's something you guys can do in regards to that...

[Weter]

Hello. I have made a series of test-rides with passenger trains, trying to implement EP configuration, but didn't reach the desired behavior.
Hence, I would return to improvements discussion, counting on some success.

The passenger trains, I'm trying to configure, IRL have combined air brake system, corresponding to air-single-pipe with EP capability.
This means, that driver's valve handle have EP-only notch in addition to Apply sector. At this notch, EP system is actuated, but BP remains at Lap-with-feeding state. This causes fast BC feeling almost up to BP(AR) pressure (it is obviously higher, than equalized pressure at full-service of auto-brake)
Rising of BC pressure can be stopped at any moment by returning the handle to Lap/Lap-with-feeding notch.
And gradually release is possible, by short placing the handle to Release notch, with returning it to any of Lap notches then.
But, advancing the handle up to Apply notch causes regular application of air brakes -by BP discharge.

This is how it expected to be.

[Weter]

But now, let me tell, how it goes actually.

I wrote ("Air_Single_Pipe" "EP") at both, wagon and locomotive (for locomotive) sections.
EPOnly doesn't work atall,
EPApply offers application depth, corresponding to notch's position
(in given case-0,4 causes only up to 40% application, no more)
Apply (because FullService stops discharging at full service pressure of BP, while complete discharge possibility is needed) works, however, as expected, but returning handle to EPApply can sometimes (not every time) cause release of brakes.
HoldLappedStart causes momental brake release, due to minor BP pressure jump.
Two latter release events are nit prototypical.
Graduated release, as described above, which is needed - is impossible, only full release.

[darwins]

Hi Weter,

I know you are trying to model a brake system that is not currently available in OR. If I understand correctly in Russia there are single pipe trains, where instead of waiting for change in the brake pipe pressure, the Distributors automatically dump air in response to the electrical signal. I think a similar system is also used in USA where the brakes on push pull cab car trains are activated from the locomotive by electrical signals. Possibly someone from USA can explain further how the system works there.

First, to check that the wagon equipment is "Distributor" and not "Triple_Valve" if you are looking for graduated release.

Either this would need to be

(i) a new braking system in OR "EP_single_pipe" or

(ii) perhaps it could be made to work with "Air_single_pipe" if a new type of distributor were defined as "EP_Distributor" which would respond to EP signals without waiting for a change in brake pipe pressure.

Those who write the brake code would have to work out which would be better.


Please can you confirm if the operation of the wagons is as follows:

If the brake controller is in an EP apply position then the distributor moves to "Apply" (instantly) and air goes from auxiliary res to brake cylinder = Fast Application

If the brake controller is moved to a Running or Release position then the distributor moves to "Release" (instantly) - the brake cylinder is vented to air = Fast Release...

...but although the brakes are released, because it is a single pipe system the auxiliary reservoirs will only charge slowly as air from the train pipe reaches them. Thus it would not be possible to make a re-application directly after a release.


Could this possibly work in ORTS if you defined the brake type as ECP? (Just a random thought.)

[Weter]

Hello, Darwin.
Being at EP mode, they not dump air, but fill BCs from ARs, while BP works as feeder, trying to maintain normal pressure in itself and ARs.

(ii) matches better, but actually, there are two devices in one body:
- triple valve, for emergency and ordinary air brake application, and also for cases, when EP doesn't function due to any reason;
- and two EP valves, which fill or discharge BC (not BP, please note)

I confirm three of your statements, except the latter - which needs a MINOR correction: BP in EP mode (this can be switched off by driver, e.g. for testing or due to malfunction/short circuit of EP wires) works as MRP, maintaining AR's pressure near normal. It is in lap-with-feed mode, so driver's walve compensate all leaks/AR demands.

I thought about Distributor and ECP, but yet didn't try that.

BTW, pure EP variant of EMU handles partial release and instant application very well, though BP is being discharged too.