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Offline freddyhayward

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Tram brake forces
« on: November 24, 2020, 05:57:35 AM »
I have noticed that all trams in pak128.Britain-ex have a brake force at least as great as their weight. Were these temporary values, and is there any relevant data available?
« Last Edit: November 24, 2020, 10:14:39 AM by jamespetts »

Offline jamespetts

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Re: Tram brake forces
« Reply #1 on: November 24, 2020, 10:04:21 AM »
I have noticed that all trams in pak128.Britain-ex have a brake force at least as great as their weight. Were these temporary values, and is there any relevant data available?

The trams do not have any brake forces set in the .dat files, so the defaults are used. I do not think that I have any data on tram brake forces; if you or anyone else have/has some data, then that would be very useful.
« Last Edit: November 24, 2020, 10:14:44 AM by jamespetts »

Offline Vladki

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Re: Tram brake forces
« Reply #2 on: November 24, 2020, 10:12:57 AM »
I have found nice data from brake tests of czech trams T3, T3M and KT8D5. - Braking from various speeds, empty and loaded, normal and emergency brakes.
I can post the spreadsheet somewhere if you think it is useful. I have no idea how Czech trams would differ from other contemporary trams. Especially, if there were no trams produced in UK at that time :)
« Last Edit: November 24, 2020, 10:15:04 AM by jamespetts »

Offline jamespetts

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Re: Tram brake forces
« Reply #3 on: November 24, 2020, 10:16:37 AM »
I have split this from the discussion about a drive by sight tram speed.

It would be useful to have tram brake force data for UK trams; I am not sure how one would extrapolate from Czech trams without a very large amount of work in calibrating. Is there a discernible pattern from the brake force data from Czech trams that is sufficiently clear to be usefully applicable to UK trams by extrapolation?

Offline Vladki

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Re: Tram brake forces
« Reply #4 on: November 24, 2020, 10:31:04 AM »
It is only 2.5 trams (T3M is just upgrade of T3), so one cannot extrapolate too much. But in general, I think the limiting factor would not be the braking system itself, but the friction between rail and wheel. (Especially in wet conditions). Unfortunately I have not written down the source. I'll put the spreadsheet up to google so you can see for yourself. I think it can be used to judge at least if the automatic values are not complete nonsense.

Edit source is probably here: http://tram.webzdarma.cz/vozidla/z-t3.htm

Offline jamespetts

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Re: Tram brake forces
« Reply #5 on: November 24, 2020, 10:35:20 AM »
If the limiting system is the adhesion, this would suggest that the default values are probably adequate until we can find more specific data.

Offline Lieven

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Re: Tram brake forces
« Reply #6 on: November 24, 2020, 10:40:34 AM »
Brake force is only for Simutrans-Extented right ?
There no brake force data that can be set for a Simutrans-standard addon ?

Offline jamespetts

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Re: Tram brake forces
« Reply #7 on: November 24, 2020, 10:44:49 AM »
Brake force is only for Simutrans-Extented right ?
There no brake force data that can be set for a Simutrans-standard addon ?

I believe that this is correct, unless this has changed in Standard recently.

Offline Lieven

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Re: Tram brake forces
« Reply #8 on: November 24, 2020, 10:53:18 AM »
Ok, that's regrettable, because to see trains anticipating there stops a little bit earlier should be nice ^^

Offline freddyhayward

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Re: Tram brake forces
« Reply #9 on: November 24, 2020, 11:02:17 AM »
The reason I brought this up was that I was experimenting with sighting distances for trams. I successfully implemented a system where sighting (but not travel) over light rails is blocked by road vehicles as they currently are with bridges and corners. This worked, but had no real effect because all trams were able to brake within <125m at 50km/h and did not need to slow down.

Offline jamespetts

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Re: Tram brake forces
« Reply #10 on: November 24, 2020, 11:13:03 AM »
The reason I brought this up was that I was experimenting with sighting distances for trams. I successfully implemented a system where sighting (but not travel) over light rails is blocked by road vehicles as they currently are with bridges and corners. This worked, but had no real effect because all trams were able to brake within <125m at 50km/h and did not need to slow down.

Interesting. As I indicated, if anyone has any real life data on tram brake force, that would be very useful.

Offline Vladki

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Re: Tram brake forces
« Reply #11 on: November 24, 2020, 11:16:57 AM »
The reason I brought this up was that I was experimenting with sighting distances for trams. I successfully implemented a system where sighting (but not travel) over light rails is blocked by road vehicles as they currently are with bridges and corners. This worked, but had no real effect because all trams were able to brake within <125m at 50km/h and did not need to slow down.

As is pointed in the link above. Loaded trams were able to break from 55 km/h in 105/130/150 m (using the standard non-emergency brakes)
I'll post the full spreadsheet later in the evening

Offline jamespetts

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Re: Tram brake forces
« Reply #12 on: November 24, 2020, 11:48:44 AM »
As is pointed in the link above. Loaded trams were able to break from 55 km/h in 105/130/150 m (using the standard non-emergency brakes)
I'll post the full spreadsheet later in the evening

Does this give us any idea of the brake force to weight ratio? It is brake force that we need to enter in the .dat files rather than braking time.

Offline Ranran

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Re: Tram brake forces
« Reply #13 on: November 24, 2020, 12:13:28 PM »
Japanese trams have a deceleration of 5km/h/s, but they do not always use that braking force. The passenger collapses. It's an emergency braking force. American PCC  have a deceleration of 13km/h/s.
In simutrans extended, the driver does not brake properly, only it depends on the weight. Therefore, if you set an excessive braking force, it will usually make a sudden stop. I think it's enough to set the standard braking force.

Online prissi

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Re: Tram brake forces
« Reply #14 on: November 24, 2020, 12:34:41 PM »
For all that is worth: the then new Berlin Trams could stop from 50 km/h within 80m using magnet brakes (which greatly increase friction). However, those are not used in normal operation, same as Ranran mentioned.

Offline jamespetts

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Re: Tram brake forces
« Reply #15 on: November 24, 2020, 12:39:36 PM »
Thank you both - yes, the brake force needs to represent the maximum ordinary service brake force application, not the emergency braking capability (if better).

Offline Vladki

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Re: Tram brake forces
« Reply #16 on: November 24, 2020, 12:51:40 PM »
here is the spreadsheet. It includes data from http://tram.webzdarma.cz/vozidla/z-t3.htm
- speed, braking distance, weight (according to specs http://tram.webzdarma.cz/vozidla/t-t3.htm).
All other values (brake force, decceleration) are calculated - claculation is simplified - ignoring air and rolling friction, and assuming constant decceleration.

https://docs.google.com/spreadsheets/d/1jRQweLu8IlUdoIBkijuZxcEoFdIj-DqkKQzIQW-KmBk/edit?usp=sharing

Offline Lieven

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Re: Tram brake forces
« Reply #17 on: November 24, 2020, 01:32:18 PM »
if anyone has any real life data on tram brake force, that would be very useful.

The Nantes's tram company communicated about that : https://www.youtube.com/watch?v=piaPjIjxtlE

The Besançon tram (Caf Urbo3, 29 tons configuration) need 40 meters to stop at 20kph. (press information)

Traduction of a press acticle relating an accident in Angers : On August 3, he (the tram) was traveling at 38 kph. When the driver realized that the pedestrian was continuing to cross the platform, he engaged the emergency braking. But the tram was only four meters away. Not enough to avoid the shock, which occurred at 35 kph. The tram stopped 12m further on.
The Angers's tram is an Alstom Citadis 302, 5 elements, 32 meters long, 40/60 tons (empty/full)

I found this one too. This it's about norms, they are tables about maximum stop distance with different cases (emergency brake, failing brakes etc...)
It starts on page 41, and they're some graphics on the next ones. It can be a nice definition for the minimal performance of the brakes.
They're almost some informations about the normal brake distance in commercial service. Pages 41 / 42 / 44 / 46.

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjCvfqQppvtAhVHrxoKHdcZDywQFjATegQIEBAC&url=https%3A%2F%2Fec.europa.eu%2Fgrowth%2Ftools-databases%2Ftris%2Fro%2Findex.cfm%2Fsearch%2F%3Ftrisaction%3Dsearch.detail%26year%3D2015%26num%3D205%26dLang%3DFR&usg=AOvVaw3hYxsUDR2PgpnXsqtPONz7
« Last Edit: November 24, 2020, 01:52:11 PM by Lieven »

Offline Freahk

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Re: Tram brake forces
« Reply #18 on: November 24, 2020, 02:53:40 PM »
Modern trams braking capabilities are not due to technical restrictions but due to operational rules to maintain a specific level of comfort and security.
Standing passengers should not be thrown around the tram in normal operation.

The exact limits will very likely vary depending on the country, as any kind of law or guideline.

In Germany, according to BOStrab, braking must not be dangerous to standing passengers and must be within a comfortable range. ( BOStrab §36, 1. (1) )
https://www.gesetze-im-internet.de/strabbo_1987/__36.html
What exactly that means is not preciesely defined in the BOStrab, but the VDV defines that an operational braking must not exceed 2.0 m/s²
https://www.vdv.de/technische-regeln-bremsen.pdfx#page=27

In emergency cases, this limit can be exeeded and in fact decelecations of at least 2.73 m/s² at 70 km/h is requested in BOStrab.
https://www.gesetze-im-internet.de/strabbo_1987/anlage_2.html
Note that the first table is about minimum brake forces if one brake system fails.

It's difficult to find anything preciese about tram laws in the UK.
« Last Edit: November 24, 2020, 03:04:07 PM by Freahk »

Offline jamespetts

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Re: Tram brake forces
« Reply #19 on: November 24, 2020, 03:41:30 PM »
If any of you can find information on the actual brake force in normal service that I can put into the .dat files, that would be very helpful.

Offline Vladki

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Re: Tram brake forces
« Reply #20 on: November 24, 2020, 04:45:09 PM »
If any of you can find information on the actual brake force in normal service that I can put into the .dat files, that would be very helpful.
Look at the google spreadsheet I posted above. It is calculated there (from the weight, speed and braking distance). Of course it is not very precise, but gives rough idea what are reasonable values.

Offline Lieven

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Re: Tram brake forces
« Reply #21 on: November 24, 2020, 06:56:36 PM »
If any of you can find information on the actual brake force in normal service that I can put into the .dat files, that would be very helpful.
In the document I shared in my precedent post, I found that :

[FR]
2.4.3   Décélération moyenne par freinage
Correspond à la décélération a en m/s2 qui s’obtient à partir du chemin parcouru "s" en mètres par le véhicule du déclenchement du freinage jusqu’à l’arrêt par rapport à la vitesse "v" en km/h lors du déclenchement du freinage correspondant à la formule
a=(v²) / 3.6²*2s
Remarque:
La décélération moyenne par freinage est une grandeur de calcul. La vitesse initiale doit être indiquée pour une calcul précis.

[EN]
2.4.3 Average deceleration by braking
Corresponds to the deceleration a in m/s2 which is obtained from the distance traveled "s" in meters by the vehicle from the beginning of the braking to the complete stop with respect to the speed "v" in kph when the corresponding braking is initiated to the formula
a=(v²) / 3,6² * 2s
Note:
The average deceleration by braking is a calculation unit. The muzzle velocity should be given for a precise calcul.

That's in german, here is the traduction

Braking detail (v / s representation with a↓mid, a↓max)


Braking detail (v / t representation with data from standard EN 13452 and a↓time)