E.M.U trains running in OR

[coolhand101]

After adjusting the Davis C parameter, i now get 608 ibf resistance at 90 mph. I have left the Davis A and B as your BR Stock curve. This allows the train to roll on a 0.3% grade. Infact, the rolling resistance for this stock is much better than the OR program friction. So again, thank you for your DAVIS figures.

Having adjusted my power curve, i now get my original timings for power vs speed.

I shall now attempt the 8 car resistance, adjusting the DAVIS C parameter.

Thanks

[baldwin]

Glad to have been able to help. Perhaps once you have finished you can publish the results for others to use.

[coolhand101]

Perhaps once you have finished you can publish the results for others to use.

Yes indeed. However this will have to wait as my PSU died on me. (hopefully a replacement by tomorrow).

Going back to rolling resistance. I found a chart, that for BR carriages, they have a high starting resistance.
For a 35 ton coach. that is 616 ibf. 542 ibf at 75 mph. 659ibf at 90 mph and 789 ibf at 100 mph.
Does that seem plausible. If so, what grade will the carriage begin to roll from rest.
I cannot access OR atm, but it does give the starting resistance for any stock. If my memory serves correctly, i believe it was around 600 ibf!

Thanks

[baldwin]

For my davis figures, I started with Fcalc2 4 axles and the data for a MK1 carriage. This was added to a wag file and tested against the published BR curve. Those figures were nowhere near a match, so I started to change then beginning with the A coefficient until I got a proper starting resistance using Roller bearings. Then it was a case of trial and error until I got a match from 0mph to 80mph with a single carriage. Then I cross checked by adding the final figures to a complete rake and testing again. So what you have are a true set of Davis figures arrived at empirically in the true manner.

Starting resistance is probably a bit low at 515, but that quickly rises to 735 then begins to fall as speed approaches 5mph. At around 5mph this has dropped to 658, and at 10 down to 580. This is with a slow acceleration rate. If the acceleration rate is increased the resistance also increases and this is what I based my results on.

[coolhand101]

Testing out the 4 car EMU in an activity, i'm noticing traction performance seems weaker, halfway through the 80 minute activity.

A quick search reports that if traction curves are being used, then OR will call this parameter "ORTSContinuousForceTimeFactor ( xxx )" and will apply the default of 1800 seconds. I am actually using "ORTSTractionCharacteristics".
Will this also call the "ORTSContinuousForceTimeFactor ( xxx )" ? If not, im at a loss for the weaker traction performance.


Thanks

[baldwin]

Way back in revision 2099 we have "ORTSTractionCharacteristics feature - a replacement of ORTSMaxTractiveEffortCurves". From this one can only assume things were changed, but exactly what I do not know right now. The only way you can be certain the performance is weaker is by plotting traction and train resistance to get a visual on performance. Unfortunately the main OR traction person is busy with real world projects right now.

[coolhand101]

Way back in revision 2099 we have "ORTSTractionCharacteristics feature - a replacement of ORTSMaxTractiveEffortCurves". From this one can only assume things were changed, but exactly what I do not know right now. The only way you can be certain the performance is weaker is by plotting traction and train resistance to get a visual on performance. Unfortunately the main OR traction person is busy with real world projects right now.

Will do, i will run a similar activity.

It normally takes my EMU, 50 seconds to get to 40mph on the level. It took between 60 and 65 seconds, when this performance oddity occurs!

Thanks

[baldwin]

Open Rails traction physics is not the same as MSTS. Unless you use the ORTSTractionCharacteristics Open Rails only uses the MaxForce, MaxPower and MaxVelocity to generate tractive effort. If you do use ORTSTractionCharacteristics Open Rails should match them if possible.

[coolhand101]

Open Rails traction physics is not the same as MSTS. Unless you use the ORTSTractionCharacteristics Open Rails only uses the MaxForce, MaxPower and MaxVelocity to generate tractive effort. If you do use ORTSTractionCharacteristics Open Rails should match them if possible.

I do use ORTSTractionCharacteristics for tractive effort. The above speed and different times happens with this parameter, after a certain length of time!

[baldwin]

Can you supply your ORTSTractionCharacteristics plus a plotted curve covering the period when this happens.

EDIT:- I have been trawling through the code and there is a section on motor temperature. An overheat would cause a reduction in power, but I am not sure if that has actually been implemented. If it has, I cannot find a corresponding blower for cooling.

[coolhand101]

Will do!

Having a look through my ENG file. I have these two parameters :-

MaxForce ( 85kN )
MaxContinuousForce ( 50kN )

I misread that OR will not read "MaxContinuousForce", however this only applies if no traction curves are present in the ENG file.
I'm wondering now if OR is reading "MaxContinuousForce" after a certain time? I've only notice this problem when in activity mode. I shall try the same path in explore mode.

Thanks

[baldwin]

The basic Open Rails Electric physics only uses MaxForce, MaxPower and MaxVelocity to generate the tractive force. This also applies to diesel-electric locomotives.

[coolhand101]

Yes I m aware of that . I have written down the tractive effort in ibf per speed, for normal running. I shall compare these figures, throughout the activity .

Thanks

[coolhand101]

Well this is very intresting.

Before starting an activity, i went into explore mode, full power and full brakes for 31 minutes. Here are the results :-

Test A

0 min Starting TE = 17.5kibf = 77.8kN
+31min Starting TE = 12.3kibf = 54.7kN

Test B

0 min Starting TE = 17.5kibf = 77.8kN
+31min Starting TE = 16.3kibf = 72.5kN

Test A was without "ORTSContinuousForceTimeFactor ( 7200 )"

Test B was with "ORTSContinuousForceTimeFactor ( 7200 )"


Could this explain the power loss ?

Thanks

Edit
Setting Max and Continuous force with the same power, the TE drop off, does not happen.

I do want to keep this feature as this does happen with DC electric motors, but it's finding the right time with the ORTSContinuousForceTimeFactor.

As most EMUs on surburban/outer surburban, 'power on' between one and three minutes. The power fall off should not be very noticable.

In Test B, 5kN was loss with continuous power for 31 mins with the 7200 entry. However the default of 1800 seconds, affects the motors too much, even on surburban runs.
I'm assuming the rate the motors cool down is slow, infact too slow, as im noticing reduce power on surburban activitys after 30 mins of starting!

Bit of a dilemma here!

Edit 2

What about setting Max Continuous force 10% from Max force, then setting the 'ORTSContinuousForceTimeFactor' at 3600 for a 1 hour rating. Does this seem plausible?

[baldwin]

It looks OK to me. It would be interesting to see how that would affect a fast or semifast from Southampton to Waterloo with the long uphill drag.

Is this with or without your ORTSTractionCharacteristics figures?. What happens if you Comment the MaxContinuousForce line?.