[atsf37l]

Getting back to cabviews, this photo from the Yale Library of WPA photos (Yale University WPA Photos) shows why we have a headout view in MSTS and ORTS:


It also explains why the view ahead is not as important in a steam cabview. :)

[atsf37l]

copperpen, on 27 August 2014 - 09:07 AM, said:

A steam engine regulator is always working against boiler pressure and is not an easy thing to use, unlike an infernal combustion throttle. It is not possible to "slam" the throttle shut unless the pressure is low. It is possible to close it faster than normal if needed. That is why a steam locomotive throttle is such a big thing in the cab.

The problem however is that both opening and closing rate are controlled from within the eng file, so you can have if you want, an instant full on/full off throttle or anything in between.

You are correct in saying that the rates are encompassed in the .eng file and Derek has a good setup with 10% with each tap. I prefer 4% which is still pretty quick. But as to the slam shut/slam open question I would have to say you are right and you are wrong. Let me explain by quoting Earl Knoob, longtime Cumbres & Toltec Scenic Railroad loco engineer and now currently running trains on the Texas State Railroad. I remembered seeing a video of him working a K-36 up Cumbres on a rainy day, slamming the throttle in and out to catch wheelslips and I was going to link it but I couldn't find it but during the search I came across this conversation he was having about wheelslips:

"Does anyone out there know how the throttle valve in a British steam locomotive is set up? Do they use a "plug" valve like us Yankees? I'm getting the impression that British throttles are much more difficult to deal with and if wide open and the engine slips, the volume of steam roaring through the throttle make it impossible to close. I wonder if they use some sort of butterfly valve or some other unbalanced valve that the action of the steam through it makes it impossible to close."

Bottom line is that the throttles on this side of the pond are apparently not the same type as those on your side. Over here you can slam em shut and haul em open. Maybe having something to do with dual port (English) vs. single Port (US)? :)

[atsf37l]

markus_GE, on 02 September 2014 - 09:18 PM, said:

A simple yes for that one ;)

Cheers, Markus

Well yes and no. Sometimes used to keep the train stretched but also often used to keep the driver brakes from heating and slipping a tire. :)

[atsf37l]

OK, while we're talking about brakes let me paddle across the pond and speak a bit about non-self-lapping automatic air brakes on US trains. First, about the running and lap positions, on which dennisat is essentially correct, but neither of these positions, in real life or in MSTS, will release the brakes on the train. ORTS wrongly releases the train brakes when you move to "running"! Imagine my consternation when trying to get a proper set going down a 3% grade when the control slipped to "running" and I lost my air on the train!

Again, in the real world, there is a detent on the automatic brake valve that the brake handle comes up against when the handle is moved to "lap" so that the engineer doesn't accidentally slide right on past it to release and lose his set on the brakes. He has to force the handle past that little bump to go to "running" or "release." MSTS somehow programmed the brake valve on non-self-lapping brakes so that the "motion" (read: "values") of the valve when the ; key is pushed pauses when it gets to "lap," Preventing you from going into running or release. It isn't a hard pause that requires another tap to go to release but it should be. In both MSTS and ORTS the train brakes for either self-lapping or non-self-lapping have a positive "detent" at the top end of brake application preventing the valve from going into "emergency" unless you tap the ' key again. So the knowledge of how to put in such a stop is already present.

Would it be possible to build a similar "detent" on the bottom end of the sweep to stop the release action at "lap," requiring another tap to go past "lap" to "running" and "release?"

I have tested this functionality in both MSTS and ORTS using the same locomotive so I know it is not an .eng file setting. :)

PS, running 2439.

[dennisat]

beresford, on 01 September 2014 - 07:16 AM, said:

I HAVE to go back to the subject of brakes for a minute. I am driving the Pines Express with a 9F on Clive Heard's Somerset and Dorset route. The scenery is great with OR graphics, the vac brakes are ABYSMAL.

I have also noticed this and I think it is due to:

1. The control action rate set in the eng file is interpreted to be slower in OR than MSTS.
2. The (vacuum) brake pressure propagation rate (from watching the HUD) is slower in OR. This is probably due to a combination of eng file parameters and OR assumptions about brake system volumes.

The net result is that response to the brake is so slow that you cannot fine adjust it as you approach a stop. You either pull up hundreds of metres short or long. The only way to get through some acts is to save as you prepare to stop for any reason and if you miss, reload and have another go. Tedious.

I have been meaning to tinker with the OR code in this area. However, most of my simming is "modern image" so I don't drive (vacuum braked) steam very often and soon lose the enthusiasm!

I have noticed, however, that the MEP route has railcars with vacuum brakes that are controllable. The effect is basically brake full off or on with nothing in between but the reaction is quick enough to pull up accurately. The virtual passengers probably don't appreciate the jerky stops and the virtual wheels must be rather prone to developing flats.

Dennis

[atsf37l]

:sign_sorry: I have a great sound for flatwheels if you need it Dennis!

[cjakeman]

atsf37l, on 02 September 2014 - 11:20 PM, said:

"Does anyone out there know how the throttle valve in a British steam locomotive is set up? Do they use a "plug" valve like us Yankees? I'm getting the impression that British throttles are much more difficult to deal with and if wide open and the engine slips, the volume of steam roaring through the throttle make it impossible to close. I wonder if they use some sort of butterfly valve or some other unbalanced valve that the action of the steam through it makes it impossible to close."

Certainly seems so.

Semmens' detailed book "How Steam Locomotives Really Work" compares the sensitivity of some US throttles which give much better control than the typical UK regulator. One reason might be that the UK steam valve is usually located in the "dome" and actuated by a rotating rod that passes into the boiler. The gland must be steam-proof and therefore adds a lot of friction. Slide valves were mostly used, it seems. There is a diagram and a good description of the problems here.

[atsf37l]

I was reading in that same wheelslip post about a restored locomotive over there that was destroyed by an uncontrolled wheelslip taking the drivers on the nearly stationary locomotive to a spinning speed of about 140 MPH before the cylinder heads blew off, stripping the rods and severely injuring the inexperienced crew. Seems the loco was prone to priming (lifting water into the throttle valve) and the water forced the throttle open so the driver couldn't close it. He attempted to adjust the cutoff but the screw wheel jumped to full forward injuring his hands and arms with the crank handle, rendering him incapable of further action. High pressure engines can be unpredictable and dangerous in less than capable hands. :sign_sorry:

[beresford]

dennisat, on 03 September 2014 - 12:56 AM, said:

I have also noticed this and I think it is due to:

1. The control action rate set in the eng file is interpreted to be slower in OR than MSTS.
2. The (vacuum) brake pressure propagation rate (from watching the HUD) is slower in OR. This is probably due to a combination of eng file parameters and OR assumptions about brake system volumes.

The net result is that response to the brake is so slow that you cannot fine adjust it as you approach a stop. You either pull up hundreds of metres short or long. The only way to get through some acts is to save as you prepare to stop for any reason and if you miss, reload and have another go. Tedious.

Dennis

One of the points I made was that the braking action of a vacuum brake on a fitted train is mainly not a function of the engine and should not therefore be solely determined by an ENG file, unless you are travelling light engine. Of course some engines cannot blow the brakes OFF if we are modelling that.

I found a way of getting the train to stop, after shutting off I switch the lever to reverse American style and then stop the train with the regulator. Not prototypical but at least it stops you on the platform.

[beresford]

atsf37l, on 03 September 2014 - 03:09 PM, said:

I was reading in that same wheelslip post about a restored locomotive over there that was destroyed by an uncontrolled wheelslip taking the drivers on the nearly stationary locomotive to a spinning speed of about 140 MPH before the cylinder heads blew off, stripping the rods and severely injuring the inexperienced crew. Seems the loco was prone to priming (lifting water into the throttle valve) and the water forced the throttle open so the driver couldn't close it. He attempted to adjust the cutoff but the screw wheel jumped to full forward injuring his hands and arms with the crank handle, rendering him incapable of further action. High pressure engines can be unpredictable and dangerous in less than capable hands. :sign_sorry:

Are we talking about the 'Blue Peter' incident at Durham? The engine wasn't 'destroyed' (we have the technology, we can rebuild it) but required considerable repair as the valve gear was scrap and the tyres had slipped on the wheels. It returned to service but has now been awaiting overhaul for a long period due to lack of resources. It isn't particularly 'high pressure' by British standards, look at the 'County' class (280lbs, but the new one being built will regrettably use a lower pressure boiler from a donor engine).

If an engine is priming, the first thing to do is make a full brake application and then open the drain cocks. The guy wasted time wrestling with the other controls.