Atomic Systems

Hi, so I am putting together the first part of my scenario from Bristol to Paignton and I am finding that with the load that the railtour had I have only just hit 80mph for the first time upon passing the junction to the south of Weston-Super-Mare. I have copied the default Class 47 TractiveEffortvsSpeed file in place of the one that comes with the Western as default already but it is just not getting up the speed - and if it doesn't speed up then the scenario will be a non-starter as I cannot replicate real life. Any help in this department would be greatly appreciated ASAP.

Just to note, I decided that as all the data was still available on Realtimetrains that as well as basing the scenario on the WTT, I am also actually running the services with whatever problems/delays they may have carried on the day in question too. So you can see why I need the player train to perform like D1015 did on the day as well.

Thanks.

deltic009 wrote:Hi, so I am putting together the first part of my scenario from Bristol to Paignton and I am finding that with the load that the railtour had I have only just hit 80mph for the first time upon passing the junction to the south of Weston-Super-Mare. I have copied the default Class 47 TractiveEffortvsSpeed file in place of the one that comes with the Western as default already but it is just not getting up the speed - and if it doesn't speed up then the scenario will be a non-starter as I cannot replicate real life. Any help in this department would be greatly appreciated ASAP.

Just to note, I decided that as all the data was still available on Realtimetrains that as well as basing the scenario on the WTT, I am also actually running the services with whatever problems/delays they may have carried on the day in question too. So you can see why I need the player train to perform like D1015 did on the day as well.

Thanks.

Hello Matthew,

I'm writing this post with the Diesel Electric model in mind, as I'm not too familiar with the Diesel Hydraulic one. I hope this can translate well to the DH model.

Usually using the TractiveEffortVsSpeed file to shape the performance of a diesel locomotive is a bad idea. First, the performance will still be limited by the MaxPower field of the simulation blueprint. Second, the sim will take whatever value is the lowest between the tractive effort limited by max power scaled by the regulator and the tractive effort limited by the TractiveEffortVsSpeed.dcsv file _not_ scaled by the regulator. The second reason is why the HST regulator has no effect from 40% to 100% above a 70Mph.

As for your Class 52 problem, I would first try to rise the MaxPower field in the simulation blueprint and see if helps. this value is in HP and should be the power at rail. If it does not change performance, then I'd try changing the TractiveEffortVsSpeed.dcsv file so that from 0 to 100 Mph the maximum published tractive effort (in kN !) is available in order to make sure that the MaxPower is effective without being hindered. If that still not works, then I seem to recall that there was some other DH specific dcsv files present that might be worth tweaking, but I'm affraid that's beyond my knowledge.

To be sure that your changes are taken into consideration by the game, I'd recommend always restarting the game from fresh after tweaking dcsv files or the simulation blueprint.

I hope all of this helps

Regards,

Thanks for the detailed response, I don't mind anything too serious as I always wanted to include the reskin with this scenario anyway (and may yet do one for the 47 as the dark green is nowhere near dark enough IMO).

I will continue to play in the hope that I should be able to improve, Class 52s were limited to 90mph but by extension probably capable of much more (see Class 37s on WR testing hitting 104mph and Deltic prototype doing 121mph). Thanks also for the bit about no effect on throttle for the HST, I believe this effects a lot of diesel locos, as hitting 108mph seems to be end game in a Celtic regardless of using 100% or 30% throttle.

Have you checked that the values for mass, drag coefficient and rolling resistance for the coaching stock you're using are correct?

Andy L

AndyUK wrote:Have you checked that the values for mass, drag coefficient and rolling resistance for the coaching stock you're using are correct?

Andy L

I haven't checked that actually, I have four different types of coaching stock on the railtour to get everything prototypically correct so I will also check those out.

They were cleared to 90mph, but had difficulty reaching it. Many of them seem to have had trouble getting above 85mph.

The main strength was on hills. They didnt slip much, and had a pretty good low down tractive effort. but speed wise they were not comparable in my view with a class 47.

The Class 52 page on Wiki suggests the transmission did not put the power on the rails and a single engine struggled to reach 90mph. The usual estimated draw-bar HP for a Western was around 1500 and the best, in recordings by Clough and Beckett, was 1775. A Class 50, with the same nominal power at the engine, produced 2115edbhp in the same series of recorded runs. I know this is Wiki and it's not always reliable but it does suggest that the Westerns were very much the inferiors of the diesel-electric classes. After all, the best recorded Western performance was only 84% of the Class 50's. Taking the lower figure it's only 71%.

Keith

Hi Matthew,

I have a couple of suggestions, firstly if you are unhappy with the pick up of the western try copying across the TractiveffortvsSpeed file from the RSC 50, this is better than using the same file from the 47 as the throttle is notched as in the western. If it is the top end that is the issue, open the Enginesimulation.bin and up the max speed line, this should help, if not move on to maxpower etc as has also been suggested. The way I suggest may not be best practice but certainly worked for me after making the first two adjustments.

Cheers,

Andy

nschichan's approach works well in my opinion too (again for D-E), and suggestions of checking rolling resistances and top speed are also good.

It's worth noting that the RW D-H model is believed to be rather broken...


Regarding prototypical performance, I'd be interested to know how the power at rail varied with speed. I'd heard that they were known for their good starting ability, but that the '3rd gear' torque converter was poorly matched and didn't allow the engine to produce its maximum power at higher speeds (as mentioned in Wikipedia, now that I check).

Rockdoc2174 wrote:The Class 52 page on Wiki suggests the transmission did not put the power on the rails and a single engine struggled to reach 90mph. The usual estimated draw-bar HP for a Western was around 1500 and the best, in recordings by Clough and Beckett, was 1775. A Class 50, with the same nominal power at the engine, produced 2115edbhp in the same series of recorded runs. I know this is Wiki and it's not always reliable but it does suggest that the Westerns were very much the inferiors of the diesel-electric classes. After all, the best recorded Western performance was only 84% of the Class 50's. Taking the lower figure it's only 71%.

Keith

You are indeed correct, a diesel hydraulic like a Class 52 doesn't have traction motors producing power to the wheels instead the wheels are driven from a transmission mounted in the loco(in a Western one in each end behind the cabs) these transmissions are driven by carden shafts from the power unit and from the transmission the wheels are driven by final drive shafts(quite like road vehicles) which is where one issue comes in where if wheelslip occurs all the wheels slip at the same time due to them all being driven at the same time so hydraulics in bad whether can't put their power down as well as diesel-electrics also the drivers of hydraulics are trained not to exceed a certain RPM below a certain speed when pulling away from a standstill so to prevent the transmission from getting wrecked by the torque of the engine as it powers up, which is something you don't have to worry about with diesel electrics as the traction motors would get overloaded and cause the loco to lose power...

faedundee2 wrote: You are indeed correct, a diesel hydraulic like a Class 52 doesn't have traction motors producing power to the wheels instead the wheels are driven from a transmission mounted in the loco(in a Western one in each end behind the cabs) these transmissions are driven by carden shafts from the power unit and from the transmission the wheels are driven by final drive shafts(quite like road vehicles) which is where one issue comes in where if wheelslip occurs all the wheels slip at the same time due to them all being driven at the same time so hydraulics in bad whether can't put their power down as well as diesel-electrics also the drivers of hydraulics are trained not to exceed a certain RPM below a certain speed when pulling away from a standstill so to prevent the transmission from getting wrecked by the torque of the engine as it powers up, which is something you don't have to worry about with diesel electrics as the traction motors would get overloaded and cause the loco to lose power...

I'd take an opposite view on both those points!

Firstly, having coupled axles should mean better adhesion. With a Co-Co, as weight transfers off the leading axle it becomes more likely to slip. Without advanced control systems (e.g. SEPEX, EMD Creep Control or Class 70 inverter-per-axle) the only way to stop the leading axle slipping is to reduce power to all axles. With a C-C, the available tractive effort is reacted by all the axles together so the one with the greatest weight on it takes the greatest share of the TE.

I've read numerous sources describing the Westerns as "surefooted" and very capable on heavy stone trains, for example.

Secondly, I'm given to understand that over-loaded traction motors and generators are far more serious than an overloaded torque converter - plenty of Youtube videos of Westerns doing notch-10 standing starts suggest that it's not a problem, while Deltics I believe need a gentle touch on pulling away to avoid flashover.

Not quite the same thing, but one of the selling points of hydraulic transmission for the Western Region was that the transmissions could stand long periods of full power dragging heavy trains uphill at low speed, whereas 1960s electric transmissions would have overheated or even suffered catastrophic failure under the same conditions.

Hydraulic torque-converters have to handle the power put into them and if some of the energy is not going through to the drive and useful work then it has to go somewhere else - heat. That's basic thermodynamics but a hydraulic system definitely has an advantage over a traction motor because excess heat is unlikely to cause total failure - as quickly at any rate. They should be forgiving of situations where slippage between the input and output elements is occurring but it's bound to cause the oil to thin and then slippage will worsen to some degree. That may have been a factor in the class being unable to reach their full output. If the top gear was too high for the torque-converter to synchronise then the oil would be thinning all the time it was under load and the efficiency of the torque-converter would fall continuously.

C-C or Co-Co? C-C will the advantage that one axle can't slip while its compatriots grip so it should, as the class' reputation suggests, give it a surer footing at low speeds. Once the speed is high enough that wheel-slip is unlikely then neither design has a particular advantage as far as I can see.

Keith

True about the heat needing to go somewhere, but as you say hydraulics are likely to be more tolerant than electrics!

I'm not sure about the oil thinning being an issue - torque converters work on kinetic energy / momentum transfer, not viscosity - in fact they were first developed to work with water! They should get more efficient with thinning oil...

My take on the matching thing is that effectively top gear was too tall, thus 'bogging down' the engine and preventing it from reaching its full power speed - particularly with a free-floating turbo (as I assume they had), any reduction in speed is likely to produce a larger reduction in power.

This is my supposition, but it fits with my background powertrain knowledge as well as certain things I've read.

ttjph wrote: ....... while Deltics I believe need a gentle touch on pulling away to avoid flashover.

And also because their high power to weight ratio makes them prone to wheel slip when pulling away at low speed. Seen and heard many a time when they were in active service

Regards,

Len

Hi Matthew,

I was just wondering if you got it sorted?

Cheers,

Andy