Dodgy physics

[MikeK]

Nice! Is there anything that can be done about the fact that recharging the brake pipe after a brake release takes 3 seconds instead of several minutes?

[Kali]

If you mean the fact that the tail of the train shouldn't release for quite some time after the front, no I'm afraid not; all you can do is release the whole consist a bit slower. That part is easy enough, you can just play with the timings in the engine brakes. As far as brakes go, the whole train is one unit - I was hoping that was going to change in RW3, but not so far. If I did this it'd mean that a 10 car train would take as long to release as 100 cars, so it's not a fantastic solution...anyone with their fingers not in the RW code can only really work with scripts to add functions, and while I can think of a way to change the brake timings depending on the train length, it would need the script for every single piece of stock updated to make it work.

One day you'll get twin pipe airbrake systems :) but they're much less interesting to drive. Handle forward, brakes go on a few secs later... handle back, brakes go off again.

Having looked at the SD40 manual it does seem to have a minimum application ( and also an amazingly small range of lap ), so at this point I'd rather like some info from a driver :P like what actually is the minimum application and also what the suppression notch does.

The SD40 selector switch can be scripted somewhat - without the display to tell you what is selected unfortunately, so probably better saved for when someone does a suitable cab.

[TrainMaster1]

I am confused by a 3 second brake recharge....that happens only in games and is not close to prototype at all. Why would you need to recharge that quick anyway? If you are running properly you do what every crew since Westinghouse installed the first one does. Wait for the gauge to come back your way which differs from loco to loco.

Now in real life I can slide the reverser into neutral and grab a notch or two to encourage the compressor a little and this will speed up a recharge. But especially in switching ops or when someone fans the brakes (frequent applications and releases-never a good idea) then the pipe pressure drops and you have a much longer wait.

I prefer realistic physics as opposed to bending reality to the game. Yes, it makes it more challenging but it's worth it in many more miles of enjoyment.

Nick

[TrainMaster1]

Okay a minimum application is generally a 7 lb reduction if I remember my numbers right. This is used on long grades to keep speed under control. Sand Patch or Horseshoe would be excellent examples as well as any western mountain road as well. Done right in conjunction with dynamics you can control a nice long heavy train.

For example, to run down Track1 on Horseshoe correctly...here are the rules: Over 100 TOB (Tons per Operating Brake, any train) you have a mandatory brake test at AR. Then 8 mph speed from CP AR to SF (247.3) just before Bennington Curve. Then 15 mph all the way the way to Slope before you get track speed again.

Trains under 100 TOB have a 12 mph speed limit down from AR to SF, SF to MG it is 20 mph, then 23 mph MG to Slope. Note this is for Track One only. Track Two does not since it has an easier grade.

Suppression is the same as continuous service and is a setting you would use when you are ending your run as this is far in excess of a service application (around 20 lbs. known as first service in my day). Suppression is a far greater force than that and is close to placing the train in emergency (all air dumped) on the brake handle settings so be careful whenever using that.

Nick

[Kali]

OK, so the default min app is actually right ( sorry Tori! ). Suppression drops the pipe pressure below what would be required for a full service application - ie full cylinder pressure? so some sort of full-consist parking brake when you don't want to dump all the pipe pressure ( over here you just dump it all, but our trains are short ). I'd say "how much below full service" but I don't think it really matters. Is there some sort of detenté on the handle to stop you going that far by accident?

Also when we're talking 7 or so lbs for min app, is that in the pipe or the cylinders?( I'm assuming the pipe which gives 17lbs or so in the cylinders, but rather be sure than not ). I have just found a rather large issue in that if you make an application without releasing the previous one fully, you will get another minimum reduction on top and eventually if you keep doing that you'll make a full application without ever going over 4%. I also don't know why the pipe pressure goes instantly from 0 to minimum, I've never seen that before.

What we apparently can't do

* Have the brakes propogate from head to rear - actually how does that work with remote operated pushers? if you're going down a hill and they're coming up the back still, I presume you actually don't want them to start applying train brakes from the rear!. Regardless, RW seems to treat a whole consist as one unit.
* Bail off the engine brakes.

What I'm not sure of yet

* Multiple unit dynamic brakes.
* Run out of air. Perhaps if you set the engine reservoir up so it was the capacity of the entire train... but obviously that doesn't work for variable length trains. More poking around needed there I think.

What I know I can do

* Adjust the brake timings so application and especially release take a *lot* longer. I've already done this for UK freight which takes 30-40s to release, and while it's not perfect - that is the whole train releasing at the same rate - it's much better than instant.

[GaryG]

Hi

I like where this is heading - definitely will make the train handling more realistic.

The seven pound minimum setting is the trainline pressure drop so you are setting that correctly. There is a problem though, the brakes on the rolling stock are far too efficient and that seven pound drop is applying too much braking effort in the sim (MSTS was also too high).

An example - on the Cajon grade keeping a train's speed checked probably would require a 15-20 pound train brake application as well as a fairly high DB setting. As we currently sit, a minimum trainline application and minimum DB setting can hold the speed under control even needing a bit of power in a couple spots.

I guess what's needed is to look at the overall train braking rather than just the loco braking. When I first bought this sim, I looked at the braking and didn't like the way car braking was defined as a simple percentage of the total weight. In the real world with current cars, there are (simplified explanation) two maximum levels of braking that a car can apply - the empty/light load setting and the loaded setting. The empty/light load setting is much less that the other setting to minimize the chance of sliding the wheels. A web search for "freight car braking ratios" will point to some info about this aspect of rolling stock brakes with recent equipment.

GaryG

[Kali]

I tested the last patch myself a little, it looks like the last patch I did *does* turn the dyna brakes on on trailing engines. This does mean stock has to be able to pass consist messages, which is something I've been pushing for for some time... but not something that is universal yet.

Agreed on the stock; one issue is it uses unladen weight only, I think, rather than adding the vehicle load and using the percentage again ( which would allow for the way wagons auto-adjust - at least european stock automatically adjusts anyway ). There are horrible logistical issues with adjusting brakes on rollingstock; you would have to change every single blueprint you have which might easily run to 200+ for wagons. We did it already for UK stock in the UKTS freeware wagon pack so it's not impossible, but the logistics might kill any attempt at doing that.

I run my tests starting halfway down the steeper part of Cajon; with three SD40s and a reasonable train ( they will pull it up at about 20mph ) full dyna alone will hold it at about 9mph if they're all braking, and minimum app of about 7psi in the brake pipe will bring that down to walking pace. I assume that's too much?

[arizonachris]

I was running a scenario yesterday, created by "footeforward", it's to test the braking on a set of 3 Sd70ACe's and a loaded consist going over Cajon. About 1/3rd thru, you have to test the dynamics. OK, so I'm at 48% on the train brakes, about 33% locomotives, holding 40mph steady, nice. I hit the dynamics, and the train surged ahead to 50mph! I thought WTF! Before I could even think to look at pressures, etc, I derailed because the cars were tilting too much.

I'll run it again tonight (maybe) but should applying the dynamics bail off the train and cab brakes? That was just too strange. Before last night, I guess I really haven't used the dynamics, come to think of it. Something else to learn (I know which keys they are now at least)

[Kali]

No, it shouldn't bail off the train brake... what does happen though is that it bunches the train up more ( and actually holding it just on the train brake will stretch the couplers out ); you think you're slowing down and all the couplers finally compress and you get a kick in the backside - eventually you'll slow down again with them compressed and braking will be steady again. I guess tweaking the couplers is also something that needs looking at, especially seeing as it's quite easy to kick the train head into surging it's speed above the train's original speed.

Thankfully there are only a few US couplers and adjusting those adjusts all of the stock.

[TrainMaster1]

Independent brakes (the locos) should be used sparingly in switching or low speed situations only if you are trying to simulate prototype. 48% on train line is not the number to look at unless your gauges in the cab do not accurately display brake pressure. If they do, then you should look to see what gives you your minimum and first service applications. That is a much more important number provided the game translate those physics right.

Glad to see that DB applies to all locos in RW too so that part of our training class will stay the same. Could someone let me know if the independent brake does as well? I know in MSTS it only applies to the first loco which is not a good thing.

The biggest concern I generally have with people writing scenarios is they frequently have no basis in reality and do not take into consideration what actually happens on a particular line or what the rule books and SSI covers for special situations.

The heavy westbounds travel 1 and 2 for the most part on Cajon because on three that earns them a 10 mph restriction all the way to the bottom. We have run this in session earlier and I can tell you that the actual DS 14 who governs this territory gets fined if a Z train (high priority intermodal) gets slowed or held up anywhere on BNSF.

Proper train handling indicates DB and Automatics to handle a train downgrade. The real trick knowing how to bunch slack and start a train on an upgrade. That is something you will need to know in case you ever get stopped by opposing traffic coming downgrade that has priority over your train. That is just one of many train handling topics we cover when we add new road crews to our operating sessions.

I am very glad to see people interested in learning more about prototype running. Our final Intro Event where we teach prototype operations, train handling and more is coming up on November 3rd and 6th and shortly after that we will be holding our first RW mini sessions and full sessions in November as well. So if running with live dispatchers, yardmasters, MOW and more interests you, check out our next live session on 10/29 and sign up for the Intro Events on 11/3 and 11/6 so that when we start RW sessions you will be ready to go and up to speed on everything you need to know to run in a prototype session. All details and answers to your questions are just a short PM away.

Thanks,

Nick

[Kali]

Glad to see that DB applies to all locos in RW too so that part of our training class will stay the same. Could someone let me know if the independent brake does as well? I know in MSTS it only applies to the first loco which is not a good thing.

DB certainly doesn't get applied to all locos at the moment, it needs scripting to change that - thankfully it's actually possible to solve easily unlike some of the other problems. No idea if the independent brake is propogated ( it certainly wouldn't be for a UK diesel, so I have doubts ). Might be able to script that also.

"First service" applies to non-lapped brakes? from what I can see it's an application *rate* rather than an application *state*. As an example the SD40 manual linked shows a self-lapping brake controller which is a different beast to the L-8-PA I've just found info on.

Incidentally I've just randomly chosen an item of US stock which appears to be permanently loaded as far as weight goes, and has 70% of vehicle weight for brake force. That's not bad if it had disk brakes(!) but what, 3x what it ought to be?

[TrainMaster1]

Ooops...misunderstood you on the DB applying to all locos without a little assistance on adjusting the programming. That changes how to handle a train and how much weight you can safely handle too especially on mountainous routes.

Think of riding a bicycle and jamming your front brakes on but applying none to rear wheel. An excellent way to end up with a face full of handlebar and Lord knows what else.

A first service application when I was running was a 20 lb pipe reduction. Most engines were either using 24 or 26 brake so they were self lapping with a few older museum pieces still retaining their #6 systems. I have operated older traction equipment as well where you had to set the brakes to lap manually but to be honest most of them leaked air so badly you could get them to sit down without spilling a drop just by going to lap and sitting there. Used to drive the road foreman nuts doing that as he did not want other crews learning that maneuver.

Sounds like there is a ways to go in the programming to get DB and Independent brakes to do what they should do for an engineer. That would be a nice advance to have all three systems (Independent, Automatics and Dynamics) closer to the real world so that you could get an actual feel for how the 1:1 does it.

Nick

[Kali]

Okay, another SD40 attached; depending on tests it does or doesn't seem to propagate DB, so can someone else test? I attempted to do the same for the independent loco brakes but that doesn't look like it's going to work at all. The scripting is in there, it just doesn't seem to do anything.

I have also stuck some european freight brake timings in, which means a full brake application will now take about 45s to release fully - while this isn't enough, it's better than it was and also means you won't inadvertantly start concertina-ing the consist. The handle settings are mostly back where they are on the default, because it was actually sensibly set up.

The modified engine is SD40 Black Dynamod again.

[arizonachris]

what does happen though is that it bunches the train up more ( and actually holding it just on the train brake will stretch the couplers out ); you think you're slowing down and all the couplers finally compress and you get a kick in the backside - eventually you'll slow down again with them compressed and braking will be steady again. I guess tweaking the couplers is also something that needs looking at, especially seeing as it's quite easy to kick the train head into surging it's speed above the train's original speed.

I think we've also had a dialog about stretching and bunching. When this speed increase happened, it was, BAM, instantanious. From 40 to 50 in a split second. And would setting the dynamic to just 20 do that much braking? Throttle was at idle going downhill. Like I said I'm gonna run it again. No independent, just train brakes at first, then when they say test the dynamic, I'll take it slow.

[Kali]

Well if it's instant, then other than some really strange coupling physics I don't know at all - does seem similar to the wierdness you get when you couple up on a gradient and the whole consist warps to 15mph or whatever though. If it's reproduceable and default stock, I'd send it to RSC support. I don't think there's anything we can do about it except try and drive round it.