[beresford]

atsf37l, on 02 September 2014 - 10:58 PM, said:

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:
Engineer's View ATSF.jpg

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

Like it or not though, that is how they were driven (at least in Britain). If you look at any video of a crew of a steam loco at speed, the driver is not hanging out of the window. You would do it if you were shunting or backing on. One of my footplate instructors was a former railwayman whose colleague was killed when his 'head out' technique coincided with a bridge abutment.

One problem is that MSTS never considered providing a view for driving backwards, since the few engines in the base game weren't going to do much travel in that direction. In Britain, some engines have 'tender cabs' (a rearward-facing spectacle plate), some have tenders so low that you can see over them, and some have high flush-sided tenders where you DO have to drive 'head out'.

[copperpen]

In the case of Blue Peter, the wheelslip was the secondary cause of the priming, primary cause was an overfilled boiler. Once priming had occurred the throttle could not be closed, applying the brakes and opening the drain cocks could not have prevented the throttle runaway in this case.

[beresford]

copperpen, on 04 September 2014 - 08:32 AM, said:

In the case of Blue Peter, the wheelslip was the secondary cause of the priming, primary cause was an overfilled boiler. Once priming had occurred the throttle could not be closed, applying the brakes and opening the drain cocks could not have prevented the throttle runaway in this case.

My understanding is that by applying the ENGINE brakes you make the cylinders work against the brake and create a back pressure which will lessen the differential across the regulator. This should make it easier to close. You also reduce the angular velocity of the wheels which reduces the centrifugal force on the motion. This should make it easier to wind the reverser back.

[copperpen]

In theory yes. But with full steam pressure applied to the pistons and no wheel/rail resistance, rotation rate rapidly exceeds anything the brakes could hold or even begin to slow down. There is a lot of kinetic energy in a wheelset spinning at a rapid rate.

[captain_bazza]

There is likely to be an official report on the incident and it's probably available online.

Cheers Bazza.

[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.

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

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 mustered some enthusiasm and sustained it for a while. By dint of ignoring some defined constants I don't understand, adding a few undefined ones and altering some code I've achieved a very acceptable result. Vacuum braked trains up to 28 cars are now very controllable while retaining a propagation delay from front to back of the train. Whether my delay is prototypical I don't know but it can be varied.

I now have to test this in all the situations I can think of. I must also consider if I can justify the change in code and possibly refine it. I really don't know enough about the physics of compressed air. It may be considered by the more knowledgable to be a hack which has ruined the authenticity of the simulation.

More later (perhaps)

Dennis

[James Ross]

dennisat, on 08 September 2014 - 02:53 AM, said:

I now have to test this in all the situations I can think of. I must also consider if I can justify the change in code and possibly refine it. I really don't know enough about the physics of compressed air. It may be considered by the more knowledgable to be a hack which has ruined the authenticity of the simulation.

You can always share the changes as a patch (TortoiseSVN > Create Patch) if you're not confident of some aspects.

[beresford]

Vac brake systems don't compress air, quite the opposite :)

If it feels right, who cares about physics?

[dennisat]

beresford, on 08 September 2014 - 01:27 PM, said:

Vac brake systems don't compress air, quite the opposite :)

I'm sure the physics applies both ways.

beresford, on 08 September 2014 - 01:27 PM, said:

If it feels right, who cares about physics?

Since you seem to be quite interested in heritage steam, if I get a version that appears to me to work quite well would you mind testing it?
If so, do you have c# developer tools so that you could apply a source patch? If not we'll have to think of another way to get you a test version.

Dennis

[beresford]

dennisat, on 09 September 2014 - 08:03 AM, said:

I'm sure the physics applies both ways.



Since you seem to be quite interested in heritage steam, if I get a version that appears to me to work quite well would you mind testing it?
If so, do you have c# developer tools so that you could apply a source patch? If not we'll have to think of another way to get you a test version.

Dennis

No I have no developer tools and am not a software engineer. I thought about running the MSTS version so I could tell you if the brakes were realistic, to give you something to aim for.

As I said before, you shouldn't have to go below 10" to slow or stop a passenger train unless you are making an emergency stop. If you are travelling light engine or with fitted freight you do not have carriage brake cylinders and so you have to increase brake until you feel retardation rather than expecting certain readings on the gauge to work. As passenger trains got longer and heavier they found that the rear brakes weren't operating quickly enough in emergencies so they introduced a more complicated carriage brake cylinder which detects sharp applications and opens a valve to admit more air to the train pipe. Not sure we are modelling that level of detail though.