US Rolling Stock Physics, particularly brakes

[c44d9w]

Hello,

I have some questions about the physics updates for US Engines and Freight Cars by Bob Boudoin (aka plainsman) and Bill Prieger (aka Turbo Bill). This relates to standard US rolling stock, specifically the Dash9 and USGrainCar.

I am getting back into MSTS (after buying a new desktop). I installed following the instructions by steam4me, then applied the Physics changes by Bob Boudoin, and finally making the changes by Turbo Bill using RouteRiter and these instructions.

After either set of changes, I found the braking to be much worse than I would expect. Some specific observations:

• An engine alone brakes terribly, even with an emergency application. I would expect a single engine to stop on a dime at speeds below 25 mph.
• On a release, the brake cylinder pressure on the engine drops very slowly. On the MP Grain train, the last car released the brakes faster than the engine.

I had a look at the changes that each package made, and I noticed a few parameters that have very significant changes.

Dash9 engine, original value, Bob Boudoin's value, and Turbo Bill's value:

MaxReleaseRate         	40	0.49	0.93						
MaxApplicationRate    	40	0.93	0.45						
MaxAuxilaryChargingRate	35	0.28	0.842

US Grain Car, original value, Bob Boudoin's value, and Turbo Bill's value:

MaxBrakeForce          	50kN 	37.7kN	0.1674kN		
MaxHandbrakeForce	35kN 	58kN 	57.2kN						
MaxReleaseRate         	15    	0.93  	1.86			
MaxApplicationRate	25    	0.49  	0.9

Do these big changes seem reasonable? Where the original values really that wrong?

Anybody else feeling that the braking, particularly for light engines, isn't quite right?

Thanks...

Roger

[c44d9w]

I don't know if I did something wrong, but things do not make sense.

Based on the discussion here, the emergency stopping distance in feet is speed in mph squared. So at 40 mph, the stopping distance should be 1600 feet.

I used MSTS Route--Test Track to do some testing with emergency braking.

Basic Install (incl bin), but no physics changes:
* 2 x Dash9, 30 grain cars: 750 feet

With Bob's and Bill's physics:
* 2 x Dash9, 30 grain cars: 3500 feet

The original version stops way too fast, but with the modified physics the stopping distance is way too long.

I also tried the same tests in OR. With the original physics, the OR stopping distance is 1000 feet, better but still not close to 1600 feet. However, the modified physics takes more than 6000 feet to stop (in emergency!).

Roger

[geepster775]

I think OR physics hit the mark.

80 grain loads, 4 sd40s, mostly level track, 54 mph, throttle quick to 0, push button plugged it, stopped in 2823 ft, 54 squared is 2916 ft

[ragtimer]

As a retired train driver,I have played around with the braking characteristics to give something approaching reality when used in the sim.If the real brake force for locos and wagons is used,you get hopeless overbraking.First of all,you should see my recent posts,but I repeat here what I use for the "Brake_Train" section:

Brake_Train ( 0 1 0.05 0.25 )
NumNotches ( 5
Notch ( 0 0 TrainBrakesControllerReleaseStart )
Notch ( 0.2 0 " RunningStart )
Notch ( 0.25 0 " MinimumReductionStart )
Notch ( 0.3 1 " GraduatedSelfLapLimitedStart )
Notch ( 0.95 0 " EmergencyStart )

The important entry is the third.

I have also found that using a figure for the brake force in kN of approx double the mass of the vehicle gives a reasonable approximation to the real world,certainly to UK models.
For those in the UK,if you are travelling at line or train speed (whichever is appropriate)if you put the brake into "initial" at the double yellow (or single yellow in 3 aspect areas)which is what the "Minimal Reduction" gives you i.e brake pipe reduction of 0.4 bar giving 1 bar in the brake cylinders,you can put your feet up,read the paper,light a fag and you will stop your side of the red.The object is to pass (4 aspect areas) the single yellow at 30-35 mph.

[geepster775]

This is no longer strictly 'Bob & Bill's excellent MSTS physics adventure' anymore, where one set of WAG physics values tries to serve both MSTS and OR worlds.

Open rails uses a brake friction table in the wag file that the MSTS application cannot interpolate or understand.