Freight train stopping distance/brake force

[zaphr89]

I'm trying to improve the realism of wagons in the program Train Simulator 2020. I have quite a lot of knowledge (from a layman's perspective) of Swedish and German trains but very little when it comes to UK trains, freight trains in particular.
One aspect of the realism where TS2020 is lacking is brake physics, many freight trains have too high deceleration and stop unrealistically fast. In TS2020 each wagon has a maximum deceleration rate that is achieved with a full service application.

I've found some documents like the Railway Group Standards but they seem to only give minimum stopping distances rather than typical stopping distance and/or brake force values for particular rolling stock.

For mainland European wagons that use UIC brakes each wagon usually has a "brake weight" value that can be divided by the wagon weight and then converted in a table to get a nominal retardation rate, looking at pictures of UK wagons these values don't seem to be printed like the mainland counter-parts. Do these exist or does British trains use a completely different system?

Do brake force or deceleration values exist for British wagons (especially freight wagons) or is it more of a case of having to know the braking distance and then calculating the deceleration rate?

Does anyone know either the brake force/deceleration values (or if these are not typically known) stopping distances from some speed (doesn't matter which speed as long as it is known, then I can derive the deceleration) under normal conditions (little to no slope, good adhesion etc) for any (or all) of the following wagon types:

Tea tank wagons
Aggregate hoppers (JHA,JGA, HHA etc)
Merry-go-round wagons
flat wagons like FSA
older 2 axle wagons like the MTA,OTA etc

Since I'm approaching this from an enthusiast/non-professional angle the answers don't need to be exact or be "minimum exected" values. I'm grateful for any answers that I can use to improve the realism.

Extra question: On German and Swedish trains there are different air brake modes, R, P and G that give different brake application times and release times. For example, R- and P- brake will apply the brakes in 3-5s and release them in 15-20s while G-brake will apply the brakes in (if I recall correctly) 18-30s and release in 45-60s. I know many British locomotives have Passenger and Goods timings, I presume they exist for similar reasons to the R,P and G-brake timings. Does anyone know (if there is standardization between different locomotives) how fast the brakes on the locomotive apply and release for Pass/Goods timings?

Thanks!
William

 

[Dunfanaghy Rd]

A few wagon types for example:
Carknd Descde Length Brake force
TEA (TE015A)

Don't know what's happened here. Please ignore.

 

[Dunfanaghy Rd]

A few wagon types for example:
Carknd Descde Length Brake force Brake force Change GLW Typical
Tare GLW over number
TEA (TE015A) 60' 17t 58t 77t 102t CAIB87015
TEA (TE030C) 60' 18t 56t 65t 102t PR85300

JHA (JH005A) 45' 15t 52t 66t 102t ELC17501
JHA (JH014A) 48' 9t 39t 39t 102t OK19302
JHA (JH015B) 55' 11t 56t 54t 102t MAR17724

JGA (JG009A) 47' 13t 46t 60t 90t RMC13700
JGA (JG014A) 48' 26t 58t 46t 90t NACO19170

HHA (HH001K) 65' 18t 60t P 102t 370001
P=progressive
MGR (HA002K) 30' 10t 10t n/a 47t 356001

FSA (FS002A) 68' 15t 56t P 87t 608001
FTA (FT002A) 65' 15t 56t P 87t 607001

MTA (MT002B) 29' 7t 23t 22t 44t 395000
BEWARE: there are 39 different design codes for MTA!

OTA (OT001A) 38' 12t 27t P 46t 112067

HTH
Pat

 

[Ayrshire Roy]

Try posting this question over at railworksamerica.
A lot of guys over there have came up with solutions to your problem and made the game a lot better.
They aren't perfect but they are much better than release a couple of pounds and be put through the windscreen.

 

[zaphr89]

Thanks Roy, I have actually checked out railworksamerica and there is a lot of good information there, but the stuff I have found relates mostly to North American freight trains which behave quite differently (single pipe, different systems for calculating brake force "Net braking ratio" etc).

Pat, thank you so much for the data. I have two questions:

1. Could you perhaps explain each column (or the weights, wagon names and numbers I understand)? I presume the last number is the gross weight of a fully loaded wagon but the second number, is that the weight where the brake system has to change from tare setting to load? For the progressive-brake wagons, are the first two weights minimum and maximum brake force?

2. How would these brake forces be converted into the deceleration of the wagon? German wagons usually give decelerations of around (brake force)/(wagon weight) x 0.8. So with this formula a fully loaded TE015A would brake with 77t/102t x 0.8 or 0.6 m/s^2. This would give a stopping distance from 60mph in goods timings (I read in an accident report that goods timings implies application times of between 18s and 30s) of around 850m if the lower (18s) number is used. If no scaling (0.8) is used then the stopping distance is around 750m (with this interpretation).

William

 

[Dunfanaghy Rd]

Thanks Roy, I have actually checked out railworksamerica and there is a lot of good information there, but the stuff I have found relates mostly to North American freight trains which behave quite differently (single pipe, different systems for calculating brake force "Net braking ratio" etc).

Pat, thank you so much for the data. I have two questions:

1. Could you perhaps explain each column (or the weights, wagon names and numbers I understand)? I presume the last number is the gross weight of a fully loaded wagon but the second number, is that the weight where the brake system has to change from tare setting to load? For the progressive-brake wagons, are the first two weights minimum and maximum brake force?

2. How would these brake forces be converted into the deceleration of the wagon? German wagons usually give decelerations of around (brake force)/(wagon weight) x 0.8. So with this formula a fully loaded TE015A would brake with 77t/102t x 0.8 or 0.6 m/s^2. This would give a stopping distance from 60mph in goods timings (I read in an accident report that goods timings implies application times of between 18s and 30s) of around 850m if the lower (18s) number is used. If no scaling (0.8) is used then the stopping distance is around 750m (with this interpretation).

William

OK. (It all looked so neat when I typed it!)
Re Q1 Length / Brake force in tare / Brake force at GLW / Wagon weight at changeover / GLW. Yes, P means a progressive brake force increase as wagon weight increases. Some wagons are not supposed to run part loaded (such as tanks and hoppers), and some will hardly ever run part loaded. So there is no point spending the extra money to get progressive brake force.
Re Q2 No idea, I'm afraid.
Pat

 

[zaphr89]

OK. (It all looked so neat when I typed it!)
Re Q1 Length / Brake force in tare / Brake force at GLW / Wagon weight at changeover / GLW. Yes, P means a progressive brake force increase as wagon weight increases. Some wagons are not supposed to run part loaded (such as tanks and hoppers), and some will hardly ever run part loaded. So there is no point spending the extra money to get progressive brake force.
Re Q2 No idea, I'm afraid.
Pat

Thanks, that makes sense regarding Q1. I was afraid you'd say that about Q2.

Do you (or anyone else for that matter) happen to know or remember an approximate stopping distance for a train consisting of any the listed wagons? Knowing both the stopping distance and the brake force values I could then solve (approximately at least) the relationship.

The way the brake forces were listed (with tare, loaded and changeover weight) it almost feels like the air brake system is the same or very close to the EU counterparts.

Question: Does anyone know if air-braked "conventional" passenger trains (like loco + wagons such as mk3,mk2 etc) have settings that give higher brake cylinder pressure (analogous to what R-brake is for EU) above a certain speed?
If I recall correctly the difference between R-brake and P-brake is that R-brake applies and releases slightly faster than P (and both are much faster than G-brake) but also increases the brake cylinder pressure above around 50km/h to counteract the way (I presume) clasp brakes get weaker at higher speeds.

If UK brakes for passenger trains behave the same way as EU passenger trains, then perhaps the two systems differ in name only.

EDIT: deleted a half-done sentence that I left by mistake.

EDIT2: I found an interesting document that might solve this conundrum. In Railway group standards GMRT2040 (unfortunately I can not find a link because the system has been updated and my copy is from before that change took place) there is a formula for converting the "Brake Retarding Force", F, to "Equivalent Brake Force", B.

B = F/(0.13 * 9.81) = F / 1.275

depending on if the numbers Pat posted are the equivalent brake force or brake retarding force the real deceleration would be increased by a factor of 1.275 or left as is.

My suspicion is that the brake force values are the "tonne force" (i.e mass * g or mass * 9.81) which the brake shoe pushes on the wheel/calipers push on the disc. Since they can only brake the wheel as much as friction allows that's where the factor 0.13 comes into play.

Does anyone have any input?

 

[zaphr89]

Not sure why but my last reply (invisible) that quoted Pat needed moderator approval.

If this message requires moderator approval as well, mods can delete it since it's a summarized repeat of my earlier post.

My question: Pat, are the brake force values you posted above referred to as "Brake Retarding Force" or "Equivalent Brake Force"? I found a formula to convert one to the other in document GMRT2040.

 

[Dunfanaghy Rd]

Not sure why but my last reply (invisible) that quoted Pat needed moderator approval.

If this message requires moderator approval as well, mods can delete it since it's a summarized repeat of my earlier post.

My question: Pat, are the brake force values you posted above referred to as "Brake Retarding Force" or "Equivalent Brake Force"? I found a formula to convert one to the other in document GMRT2040.

No idea on that, either, I'm afraid. They are simply the figures given when I did a TOPS enquiry (J6 ; 1) back in the day before retirement.
Pat

 

[zaphr89]

Thanks for your help so far Pat.

I did some checking and it seems the Class 66 has a "brake force tonnes" figure of 68 on the TOPS panel (that I could find at least). Looking up the brake weight for EU EMD 66 the figure is 66 or 66 tonnes in G-brake. Seeing as these are so similar it may just be that the brake forces are calculated similarly on both sides of the English Channel.

Do you happen to the brake force numbers for Class 66 (66/0 in particular but I doubt it differs that much between different versions)? If the value in your document is the same I think I know how to handle the other values you gave earlier.

I also have another request: Do you (or anyone else) happen to know similar brake force figures for the "gondola" style wagons like MJA, NJA, IOA etc (I think some are also called JXA or POA), and the open steel wagons such as BAA/BZA?

Thanks again for all the information!

 

[Dunfanaghy Rd]

I don't know what NJA is, I'm afraid. Here's what I did find.
HTH
Pat

Carknd	Descde	Length	Tare Wt	Tare BF	GLW	GLW BF	C/o	Number start
		(feet)	(tonnes)	(tonnes)	(tonnes)	(tonnes)	(tonnes)
MJA	MJ001A	46	23	17	102	61	P	502001
NJA	what’s		this?
IOA	IOE942	46	24.3	19	102	55	P	31.70.5892.001-5
JXA	JX029A	63	29	18	102	46	70	PR3100

 

[zaphr89]

Hi Pat, I don't know what NJA is either haha. I saw the name while looking at IOA and JXA wagons but I can't find the link again. In any case the combinations you posted should be enough for that type of wagon. Is BZA (or BAA or BLA, BCA) missing from your documents?

Last question: Do you either have similar data for locomotives (weight and brake force I mean, tare and load doesn't make much sense) or could you give your opinion on whether the printed brake force value on a locomotives TOPS panel is the same system as the figures in your documents (i.e TOPS)?

An interesting point I noticed is that the MGR (HAA etc) wagons have very low brake force. With either interpretation the deceleration for an MGR wagon should be less than 0.25m/s^2 so at 45mph the stopping distance will likely exceed the maximum stopping distance in the GMRT2044 document. Does anyone know if these minimums are simply for newly introduced wagons or if there is some other detail I'm missing?

 

[Dunfanaghy Rd]

No loco details, I'm afraid.
The braking of the MGR fleet was nothing special, and the Coalfish etc, built on their frames are no better. They used to carry a sticker informing all that the brake force in tare & under load was 10t. Don't know any more than that, except to mention that disc brakes are very different to tread brakes and can be useless until warmed up. [Sort of like putting racing linings on the brakes of a moped.]
Pat

 

[edwin_m]

The Group Standards catalogue is now off one of the dropdowns on rssb.co.uk.

 

[zaphr89]

I'm still not entirely convinced that the UIC method of converting brake forces to decelerations can be applied on UK trains (even though comparing the brake force on the Class 66 TOPS and the one printed on mainland EU EMD 66 are very similar) so I'd like to try a sanity check.

HHA hoppers are quite a common sight so I thought I'd take a train of a Class 66 dragging a consist of (loaded!) HHA hoppers.

With the GMRT2040 method, that I'm not convinced I understood correctly, the brake retarding force of a HHA wagon would be 1.275*60 or the retardation of a single wagon in full service brake would be around 0.75m/s^2.
If instead the mainland EU conversion is used the brake/mass percentage is 60/102 = 59% which converts to around 0.5m/s^2


Question: If this imagined, typical train of a Class 66 + (fully laden) HHA were to use a full service or emergency brake application from 60 mph, in normal adhesion conditions and no slope, it would take the following distances to stop:

0.5m/s^2 retardation: About 1000m (I've accounted for 18 seconds to apply the brakes)
0.75m/s^2 retardation: About 750m

Does anyone have an opinion on which of these stopping distances seem more realistic?

Maybe full service/emergency is used so rarely it's hard to get a feel for what's reasonable, lets take the example of 1 bar brake pipe reduction:

1bar reduction of 0.5m/s^2 maximum: 1350m
1bar reduction of 0.75m/s^2 maximum: 950m

Which one is more reasonable for a train of HHA hoppers?