I did some thinking about acceleration model of the patch and how to imrpove it to include things such as locomotive gearing and technology differences.
The main difference between passanger and freight engine is the amount of force they can exhert on the coupler - freight engines sacriface max speed for force, passanger do the opposite. Universal locomotives are somewhere in between.
To catch that difference I suggest to alter the maximum TE formula of the patch.
TEmax = Wadh * mu
My proposition - allow graphic makers to preset TEmax instead calculating it - this value is static and does not require to be calculated on the fly - and if it was preset by human then it is human who would need to make all the calculations toward correct TEmax value - including getting historic data or knowing the difference between DC, AC, steam and diesel-electric traction.
Analysis of BR 05 - the recent freight revelation...
TEmax = Weight * 9.8 * mu.
typical european axleload is 22,5 tons (was less 50 years ago...). Since BR 05 had 3 driven axles then the maximum adhesive weight is 67,5 tons. Also - typical factor of adhesion for steam locomotives is 0,2 (due to the nonlinear power transfer)
To include that in the formula we need to add:
TEmax = AdhWeight * 9.8 * adhesion_factor
but BR 05 had drivers of 2000 mm which means that it had gearing at least 33% higher then BR 52 with 1500 mm drivers. So we need to lower its "TE" by 0.75 (and probably considerably less) to include that. So we get final value of:
TEmax = AdhWeight * 9.8 * adhesion_factor * 0.75 = 99.225 kN
TEmax according to Patch data = 346.92 kN.
almost 3.5 of the "proper" value - this is why it is used for freight or pretty much anything else...
For comparsion - BR 45 - patch value is 373.86 kN while more sensible value is 220,5 kN
Here is the difference why BR 45 is no better then BR 05 since there is minimal TE difference in the patch while it was a dramatic difference in reality...
Also - IORE freight engine:
Patch would calculate it's TE at 529,2 kN while the engine is rated at 600 kN continuus and over 700 kN hour which is possible thanks to the creep control electronics and sanding (it is possible to use 0,4 factor of adhesion then)
Now - what for.
This would allow to desingate engines toward freight or passanger service (assuming the industry production bump would happend). It would be possible to show differences between steam, diesel and electric technology, also it would be possible to simulate modern traction such as creep control (controlled wheel slippage to get maximum possible TE - 0,4% adhesive factor).
Realistic acceleration & express/freight locomotives
Moderator: TTDPatch Moderators
Re: Realistic acceleration & express/freight locomotives
It's a bit more complicated than that, due to multiheaded trains and powered wagons. Besides, TEmax doesn't really have that much influence on the train acceleration, because it's only used at very low speeds. At higher speeds, the TE is limited by the train power instead. TEmax would only influence the behaviour if you set it much lower or much higher than the current value, anything less than a factor of two difference won't be worth the trouble.uzurpator wrote:My proposition - allow graphic makers to preset TEmax instead calculating it - this value is static and does not require to be calculated on the fly
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No, I don't agree, because the freight train would accelerate too quickly to its maximum speed. Part of the thing with freight trains is that they accelerate slowly out of the blocks, and that's also why all-wheels-powered is such an advantage to passenger acceleration.
This is showing signs of going in the right direction, although I'm not yet sure where it will end up. I doubt that it is possible that a locomotive's entire performance envelope can be condensed down to two numbers, a "power" number of some kind and a maximum speed. Could it be done with three perhaps, those being: force (kNetwons I suppose), adhesion (max force that can be exerted per instant in time without slipping), and max speed? I'm not sure how they would interact though.
This is showing signs of going in the right direction, although I'm not yet sure where it will end up. I doubt that it is possible that a locomotive's entire performance envelope can be condensed down to two numbers, a "power" number of some kind and a maximum speed. Could it be done with three perhaps, those being: force (kNetwons I suppose), adhesion (max force that can be exerted per instant in time without slipping), and max speed? I'm not sure how they would interact though.
Development Projects Site:
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
The force is not constant, it depends on speed. Maybe engine torque would be better, but then that torque is equivalent to power, so that wouldn't change much. The only parameter that might make sense to introduce is the coefficient of adhesion (friction), the mu for TEmax = mu * adhesive weight. However, there isn't enough variability in that parameter and its effect would be very insignificant.
Last edited by Patchman on 17 Feb 2004 03:02, edited 1 time in total.
Umm. I vaguely remember from physics class, the ability to define an arc with a formula. Maybe it would be possible to pass in the definition of the arc which represents the power gradient at different speeds? Does this give anyone any ideas? Does anyone know what I'm talking about?
Development Projects Site:
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
Yes, I imagine so - it would be all but impossible for us to calculate the input.
Hmm, what other possibilities are there? I'm trying to figure out a workable approximation but it just seems very complicated no matter how I approach it. I keep coming back to keeping the train power calculations as they are; making the freight (but not the passengers, mail, or valuables) weigh more; and putting a speed-limit on certain freight-car types. That would approximate the desired effect.
Hmm, what other possibilities are there? I'm trying to figure out a workable approximation but it just seems very complicated no matter how I approach it. I keep coming back to keeping the train power calculations as they are; making the freight (but not the passengers, mail, or valuables) weigh more; and putting a speed-limit on certain freight-car types. That would approximate the desired effect.
Development Projects Site:
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
Patchman:
My inital concept was to steer the friction coefficent, not the whole TEmax but this would (i persume) require seperate calculations for each engine in multiheading - TEmax would not - simply add all TEmax.
This modification actually is 100% realistic for steam engines since up to certain speed (when boiler reaches its maximum steam output) they were constant force machines. For example Big Boy acheieved its full power at around 40 mph.
Also - for steam engines there is an error in the fact that they do not have all axles driven. BR 05 has maxTE of 132,3 kN when only adhesive weight is considered. Not whopping 350 that the current model assumes.
EDIT
Here was a calculation that considered many bizarre transtions which used locomotive gearing and stuff only for me to find the final result is...
Te = P/V
Which leads me to believe that the gearing is included with setting max speed of the vehicle...
EDIT
but this is illogical - it would assume that gearing is non important.
But i guess I know where does the error come from - we conclude everything from the side od the wheel and try to find motor speed while the motor speed is the constant here. It produces the torque that through gearing is transferred to rails.
Got to find a siutable model for this :/
My inital concept was to steer the friction coefficent, not the whole TEmax but this would (i persume) require seperate calculations for each engine in multiheading - TEmax would not - simply add all TEmax.
This modification actually is 100% realistic for steam engines since up to certain speed (when boiler reaches its maximum steam output) they were constant force machines. For example Big Boy acheieved its full power at around 40 mph.
Also - for steam engines there is an error in the fact that they do not have all axles driven. BR 05 has maxTE of 132,3 kN when only adhesive weight is considered. Not whopping 350 that the current model assumes.
EDIT
Here was a calculation that considered many bizarre transtions which used locomotive gearing and stuff only for me to find the final result is...
Te = P/V
Which leads me to believe that the gearing is included with setting max speed of the vehicle...
EDIT
but this is illogical - it would assume that gearing is non important.
But i guess I know where does the error come from - we conclude everything from the side od the wheel and try to find motor speed while the motor speed is the constant here. It produces the torque that through gearing is transferred to rails.
Got to find a siutable model for this :/
TTDPatch already uses TE = P/v, that's the most elementary formula for power. The problem with making TEmax a property of the vehicle and then adding them all up is that the vehicle weight can change, for example with powered wagons. That affects the TEmax as well, so just adding them up won't do.
Changing the fraction of Wadh that is used to calculate TEmax would be the most straightforward thing to do at this point. Then you could have different coefficients of friction, different numbers of powered axles etc. Still that's rather complicated.
Changing the fraction of Wadh that is used to calculate TEmax would be the most straightforward thing to do at this point. Then you could have different coefficients of friction, different numbers of powered axles etc. Still that's rather complicated.
OK - I did some research (mostly in my electric drive books 
)
While P = w*M
w - rotational speed
M - torque
this is true but due to the electrical and mechanical characteristic of the motor full power on low rotational speeds would simply destroy the motor (either torque would tear it apart or immense current would burn them). That is why sophisicated "turn-on" systems are used - to not overload the motors.
On low geared locomotives the peak power is achieved at lower vehicles speeds thanks to which they can pull more. However max speed is compromised then.
On high geared locomotives motors reach full power at higher vehicle speeds which allows for higher max, but compromised the weight the train can pull from standstill.
Locomotives are built with target starting TE and Max speed. Then electrical apparati on board controls that the motors will not produce more then starting TE until the TE=P/V kicks in.
For example
BR 103 has start TE of 314 kN
BR 151 has start TE of 441 kN
both are 6 axle locomotives, Br 151 however has max speed of 120 km/h and 6000 kW, while Br 103 is 7440 kW and 200 km/h
Also - for passanger locomotives only around 70%-80% of weight goes toward for adhesion (due to the way forces propagate through the engine body) and when high loads are expected extra linkage as seen below (on iore):
http://hem.passagen.se/ugj/illustration ... 19-500.jpg
is used to rise that to around 85-90% of the locomotive weight.
Well - could we set two values for weight? One for adhesion and Te calculations and one for train weight calculations? This would be an approximation, but much closer to reality then it is now.
)While P = w*M
w - rotational speed
M - torque
this is true but due to the electrical and mechanical characteristic of the motor full power on low rotational speeds would simply destroy the motor (either torque would tear it apart or immense current would burn them). That is why sophisicated "turn-on" systems are used - to not overload the motors.
On low geared locomotives the peak power is achieved at lower vehicles speeds thanks to which they can pull more. However max speed is compromised then.
On high geared locomotives motors reach full power at higher vehicle speeds which allows for higher max, but compromised the weight the train can pull from standstill.
Locomotives are built with target starting TE and Max speed. Then electrical apparati on board controls that the motors will not produce more then starting TE until the TE=P/V kicks in.
For example
BR 103 has start TE of 314 kN
BR 151 has start TE of 441 kN
both are 6 axle locomotives, Br 151 however has max speed of 120 km/h and 6000 kW, while Br 103 is 7440 kW and 200 km/h
Also - for passanger locomotives only around 70%-80% of weight goes toward for adhesion (due to the way forces propagate through the engine body) and when high loads are expected extra linkage as seen below (on iore):
http://hem.passagen.se/ugj/illustration ... 19-500.jpg
is used to rise that to around 85-90% of the locomotive weight.
Well - could we set two values for weight? One for adhesion and Te calculations and one for train weight calculations? This would be an approximation, but much closer to reality then it is now.
Setting adhesive weight separately would actually be the easiest proposition so far, as long as you don't mind the full weight of the cargo being added (i.e. total Wadh=Wadh of engine + Weight of cargo, not Wadh of cargo).
Certainly easier than simulating gear ratios, or changing either TEmax or the coefficient of friction directly.
Certainly easier than simulating gear ratios, or changing either TEmax or the coefficient of friction directly.
Sounds like a plan to me, assuming the weights of the trains are increased to something sensible.
Development Projects Site:
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
Here is a forumla that might be very useful. I found it here:
http://railwaymuseum.ab.ca/cnrprairie.html
---------
FYI-information gathered from an "Edel" series engineering hand
book I'd used for many years.
Tractive Force (effort) is the power which the pistons of the engine are capable of exerting through the drive-wheels, to move the engine and train. The efficiency of the engine's traction is dependent upon the adhesion of the wheels to the rails; for, where the adhesion is insufficient, the pistons will slip the wheels, and no useful effect will result. To prevent this, the weight resting on the drivers must be about five times the power exerted by the pistons An easy calculation...................
d2 Lp
T= D
Where:
T=Tractive force to the rails (%TE)
d=diameter of the cylinder in inches
L=length of piston stroke in inches
D=diameter of the driving whels in inches
p=effective pressure on the piston in psi
Horse-power is the measure of the rate at which work is performed, and is equal to 33,000 pounds lifted one foot in one minute, or one pound lifted 33,000 feet in one minute, or one pound lifted 550 feet in one second; therefore, one horse-power equals 550 foot-pounds per second.
Calculation is:
P x L x A x N
H.P= 33,000
P=effective pressure on the piston in psi
L=length of piston stroke in feet.
A=area of the piston in square inches.
N=number of strokes (four times the number of revolutions) per minute.
Or, by cancellation and substituting the diameter of the driving wheels,
the formula can be rearranged as:
C2 x S x P x (M.P.H.)
H.P= D x 375 (personaly, I never liked this
formula!!)
C=diameter of cylinder in inches.
P=mean effective pressure at given speed.
S=length of stroke in inches.
M. P. H.=miles per hour.
D=diameter of driving wheels in inches.
--------
And here's something else that is a whole lot simpler, but I'm not sure it makes sense, which I found here:
http://lists.twistedpair.ca/pipermail/g ... 11601.html
----------
Torque x RPM = Horsepower
In consistent units. If you're using ft-lbs for torque and RPM for rotational
speed you need the proper conversion factor. But, the relationship is the
same. For example an engine making 200 ft-lbs of torque at 2000 RPM is
producing the same HP as one making 100 ft-lbs at 4000 RPM.
The "straight line" analog is:
Tractive force x speed = HP
This is why it's easier to break the wheels loose at lower speeds. As speed
goes up, the tractive force goes down.
----------
Does this mean that we can do a rough-and-ready conversion of the tractive force of a steam locomotive into HP for the game, by multiplying the tractive force times the top speed? This seems too easy, and I'm not sure it makes sense.
http://railwaymuseum.ab.ca/cnrprairie.html
---------
FYI-information gathered from an "Edel" series engineering hand
book I'd used for many years.
Tractive Force (effort) is the power which the pistons of the engine are capable of exerting through the drive-wheels, to move the engine and train. The efficiency of the engine's traction is dependent upon the adhesion of the wheels to the rails; for, where the adhesion is insufficient, the pistons will slip the wheels, and no useful effect will result. To prevent this, the weight resting on the drivers must be about five times the power exerted by the pistons An easy calculation...................
d2 Lp
T= D
Where:
T=Tractive force to the rails (%TE)
d=diameter of the cylinder in inches
L=length of piston stroke in inches
D=diameter of the driving whels in inches
p=effective pressure on the piston in psi
Horse-power is the measure of the rate at which work is performed, and is equal to 33,000 pounds lifted one foot in one minute, or one pound lifted 33,000 feet in one minute, or one pound lifted 550 feet in one second; therefore, one horse-power equals 550 foot-pounds per second.
Calculation is:
P x L x A x N
H.P= 33,000
P=effective pressure on the piston in psi
L=length of piston stroke in feet.
A=area of the piston in square inches.
N=number of strokes (four times the number of revolutions) per minute.
Or, by cancellation and substituting the diameter of the driving wheels,
the formula can be rearranged as:
C2 x S x P x (M.P.H.)
H.P= D x 375 (personaly, I never liked this
formula!!)
C=diameter of cylinder in inches.
P=mean effective pressure at given speed.
S=length of stroke in inches.
M. P. H.=miles per hour.
D=diameter of driving wheels in inches.
--------
And here's something else that is a whole lot simpler, but I'm not sure it makes sense, which I found here:
http://lists.twistedpair.ca/pipermail/g ... 11601.html
----------
Torque x RPM = Horsepower
In consistent units. If you're using ft-lbs for torque and RPM for rotational
speed you need the proper conversion factor. But, the relationship is the
same. For example an engine making 200 ft-lbs of torque at 2000 RPM is
producing the same HP as one making 100 ft-lbs at 4000 RPM.
The "straight line" analog is:
Tractive force x speed = HP
This is why it's easier to break the wheels loose at lower speeds. As speed
goes up, the tractive force goes down.
----------
Does this mean that we can do a rough-and-ready conversion of the tractive force of a steam locomotive into HP for the game, by multiplying the tractive force times the top speed? This seems too easy, and I'm not sure it makes sense.
Development Projects Site:
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
Well, kinda, in that the Patch doesn't know the cylinder sizes of the steam locos or the diameters of the driving wheels, all it knows is the HP. I was trying to calculate the HP of the steam locos from the given TF, but that didn't work so well. So I just researched as best I could and took the numbers I found that seemed to make sense.
Development Projects Site:
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
http://www.as-st.com/ttd
Japan, American Transition, Planeset, and Project Generic Stations available there
krtaylor - afaict - patch uses the most basic formula TE = P/v
I did a complex power analysis for the electric motor (from torque side) only to get the basic formula at the end.
Currently patch uses two simplifications:
1. Uses full locomotive weight instead of adhesive weight
2. Steam specific - steam power is dependant on speed while patch uses max value no matter what.
The first one is relatively (in relativity to the second one ) easy to do. The second one can be aproximated by using lower adhesive weight for steam. The full model of the second one would require to include extra value (max hp speed) and engine specific calculations. This will require engine specific calculations in multiheading = this is a bad thing
I did a complex power analysis for the electric motor (from torque side) only to get the basic formula at the end.
Currently patch uses two simplifications:
1. Uses full locomotive weight instead of adhesive weight
2. Steam specific - steam power is dependant on speed while patch uses max value no matter what.
The first one is relatively (in relativity to the second one
) easy to do. The second one can be aproximated by using lower adhesive weight for steam. The full model of the second one would require to include extra value (max hp speed) and engine specific calculations. This will require engine specific calculations in multiheading = this is a bad thing Patchaman - anything from 5 to 60 mph. But Id say that 35 was typical. Ofc there is also an upper limit - when pistons reprociate so fast that steam has no chance to leave the cylinder before new steam was admitted. This was happening around 20-80 mph and reduced power of a steam locomotive from the top. I'd say that 55 mph was typical. However it is difficult to say since without a massive statistical data it is all more or less a work for an oracle
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