[steamer_ctn]

Some initial functionality has been added to OR to facilitate the operation of a diesel mechanical locomotive.

A diesel mechanical locomotive had a direct coupling between its engine and wheels so that engine speed could be impacted by wheel speed, and vicer versa.

If you want to see a more detailed description of a diesel mechanical transmission, then read from page 63 of this publication.

A demonstration model based upon a Hunslet 500hp diesel mechanical shunter is available from here.

The manual overview for this feature is as follows:

To indicate that the diesel is a mechanical transmission, ``ORTSDieselTransmissionType`` needs to be set to "Mechanic".

Two ORTS mechanical gearbox configurations can be set up.

These two gearboxes can be selected by the use of the following parameter:

ORTSGearBoxType ( A ) - represents a semi-automatic pre-selector gearbox that gives a continuous power output that is not interrupted when changing gears.

ORTSGearBoxType ( B ) - represents a semi-automatic pre-selector type gear box where although there is a break in tractive effort when changing from one gear to another, the engine speed is reduced by a shaft brake if needed, so that there is no need for the driver to adjust the throttle.

One of three possible types of main clutch are selectable for each of the above gear box types, as follows:

ORTSMainClutchType ( Friction ) - represents a mechanical friction clutch.

ORTSMainClutchType ( Fluid ) - represents a fluid coupling. Where a transmission includes both a friction clutch and a fluid coupling then ORTSMainClutchType ( “Fluid” ) should be used in the eng file.

ORTSMainClutchType ( Scoop ) - represents a fluid coupling that includes a scoop device to disconnect the engine from the transmission at idle speed.

ORTSGearBoxFreeWheel - indicates whether a freewheel mechanism is included in the transmission. ( 0 ) - should be used for transmissions that do not include a freewheel. This option will allow ‘engine braking’ to occur when appropriate. ( 1 ) - should be used for transmissions that include a freewheel. This option will allow the train to coast with the engine in gear.

GearBoxNumberOfGears - The number of gears available in the gear box.

Currently only a BASIC model configuration is available (ie no user defined traction curves or diesel engine curves are supported). OR calculates the tractive force curves for each gear based on the "inbuilt" torque curve of a typical diesel engine.

GearBoxMaxSpeedForGears - sets the maximum speed for each gear, corresponding to maximum engine rpm and maximum power . As an example, the values for a typical British Railways first generation dmu are:
GearBoxMaxSpeedForGears( 15.3 27 41 65.5 ) The default values are in mph, although other units can be entered. In the above case the maximum permitted speed of the train is 70 mph; a small amount of ‘overspeed’ being allowed in top gear. The fourth gear speed of 65.5 mph corresponds to the maximum engine rpm set in the eng file by ``DieselEngineMaxRPM``. The diesel engine may continue to ‘runaway’ above its normal ‘maximum speed’ until it reaches the maximum governed speed or ‘redline’ speed at which the engine governor will cut off the fuel supply until the engine speed is reduced. This speed can be set in basic Open Rails eng files using ORTSDieselEngineGovenorRpM.


In the case of the above train, then these would be

DieselEngineMaxRPM( 1800 )
ORTSDieselEngineGovenorRpM ( 2000 )

If under any circumstances the engine reaches ``ORTSDieselEngineGovenorRpM`` then the diesel engine will automatically be shut down.

ORTSGearBoxTractiveForceAtSpeed - The tractive force available in each gear at the speed indicated in GearBoxMaxSpeedForGears. Units by default are in N, however lbf, N or kN. Published values for tractive effort of geared locomotives and multiple units are generally those at the maximum speed for each gear.

Hence a typical gear configuration for a diesel mechanic locomotive might look like the following:

ORTSDieselTransmissionType ( Mechanic )

ORTSGearBoxType ( B )
ORTSMainClutchType ( "Friction" )
ORTSGearBoxFreeWheel ( 0 )

GearBoxOperation( Manual )
GearBoxNumberOfGears( 6 )
GearBoxMaxSpeedForGears( 4.5mph 6mph 9mph 14.5mph 21mph 33mph )
ORTSGearBoxTractiveForceatSpeed( 35400lbf 26600lbf 17700lbf 11200lbf 7600lbf 4830lbf )

[Laci1959]

Hello.

That sounds very nice. I will definitely try.
My biggest problem is that only the torque delivered on the engine crankshaft and the torque delivered on the towbar are given in the GANZ factory documentation. The speeds available in each gear are given, and from this and from the engine speed range I determine the gear ratio. I'll try to proportion that to the torque.
In addition, the internal combustion engine does not deliver the maximum torque at maximum speed, but below it. Exactly where it depends depends on the type of fuel.
The VI JAR 135/185 GANZ JENDRASIK diesel engine has an idle speed (Rpm) of 300Rpm, a minimum load speed of 400Rpm, a maximum torque speed of 800Rpm and a maximum speed of 1350Rpm.
When I obtained my professional license, the technical instructor explained that the diesel engine delivers the maximum torque at 2/3 of the maximum speed (Rpm). That was true for 44 years. Has the knowledge of the diesel engine changed in this direction since then? Because OR doesn't know that.

Thank you very much anyway.

Sincerely, Laci1959

[Weter]

Hello, Peter.
Thanks for Your new research and initial implementation.
I wonder, would it be extended to low-power vehicles, which have automobile-like manual gearbox with friction clutch and benzine engine?
And will it be included in testing versions?

There was mentioned parameter GearBoxOperation( Manual ), but without listing of possible variants. Which are available now?
Here is a variant of description, in some places more compact.

[darwins]

Laci1959, on 12 February 2022 - 11:50 PM, said:

the technical instructor explained that the diesel engine delivers the maximum torque at 2/3 of the maximum speed (Rpm). That was true for 44 years. Has the knowledge of the diesel engine changed in this direction since then?

That is still approximately true for most diesel engines. The built in default model torque curves agree with that.

There has always been some variation though. This is for an old naturally aspirated Maybach 6 cylinder engine from 1949 - the torque curve seems to be down all the way. (Though the 12 cylinder turbo charged version had a more typical torque curve.):

https://i.imgur.com/GAPlXPo.jpg

Similarly this is for two versions of the same Renault engine - the tops of the torque curves are clearly in different places:

https://i.imgur.com/x3sx73Z.jpg

For a modern Cummings dmu engine max torque is slightly above 2/3 max rpm, but the whole torque curve is fairly flat:

https://i.imgur.com/rFqhZrW.jpg

[Weter]

So, we see, that efficiency of engine descends from some point.

Is BHP British horse power?
And what is pre-selector? Indirect control for changing of gears?

[Laci1959]

Weter, on 13 February 2022 - 12:21 AM, said:

Hello, Peter.
Thanks for Your new research and initial implementation.
I wonder, would it be extended to low-power vehicles, which have automobile-like manual gearbox with friction clutch and benzine engine?
And will it be included in testing versions?

Hello.

I just singled out such a GANZ towing motor car for this purpose. The prototype motor car was put to work in 1925, still with a petrol engine, and I worked in public traffic until the late 1980s. As a working and nostalgia vehicle, some are still in circulation today. The latter is beautifully restored.

[darwins]

Weter, on 13 February 2022 - 12:21 AM, said:

Hello, Peter.
Thanks for Your new research and initial implementation.
I wonder, would it be extended to low-power vehicles, which have automobile-like manual gearbox with friction clutch and benzine engine?
And will it be included in testing versions?

There are three questions there.


1. The clutch - the good news is that we now have a working model of the friction clutch.


2. Gearbox type. In researching mechanical transmission, we divided gearbox behaviour into four types. The first two types have now been put into action by Peter. They were not very common, but have allowed the modelling of gear changing behaviour, different types of clutch and of the admission controlled throttle internal combustion engine model - all of which are new in OR. The two manual gearboxes so far possible are:

Type A - giving continuous uninterrupted power during gear changes - for example SSS Powerflow gearbox.

Type B - pre-selector gearbox where engine speed is matched to gear speed without the need to close the throttle - for example Hunslet gearbox.

All fully automatic gearboxes would also be either Type A or Type B. The other two gearboxes identified were

Type C - pre-selector gearbox where throttle must be closed before changing gear - for example the Wilson gear box used on British first generation dmu and most shunting locos.

Type D - fully manual gearbox where engine speed needs to be adjusted to gear speed - for example Renault and Ganz manual gearboxes.

The vehicle you are describing would probably have a Type D gearbox, so that is a future development.


3. Petrol engine

I do not know if there is any plan to add a "basic" model petrol engine to OR. Perhaps this could be put onto a Trello card. When an advanced model is possible then it should be a simple matter to model a petrol engine, by putting the appropriate torque curves into the ORTS diesel engine block. It is possible at the moment to make a Petrol-Electric railcar in this way. I would quite like to set up a model of an early Petrol-Electric car, but at the moment as far as I know there is no petrol engine sound set available for OR.

[darwins]

Weter, on 13 February 2022 - 12:34 AM, said:

And BHP is British horse power?
Hello, Darwin. :)
Hello, Laci :)
So, we see, that efficiency of engine descends from some point.

Hi Weter

bhp is brake horsepower - that is horsepower at the crankshaft

I believe that bkW is also used for the same purpose - though mostly people just say kW.

I am pleased to say though, that British horses were stronger than French and German horses.

Britain (and USA) - horsepower hp = 0.7457 kW

France - cheval vapeur cv and Germany - pferdestarke ps = 0.7355 kW
http://www.elvastower.com/forums/public/style_emoticons/default/sign_rockon.gif

[darwins]

Pre-selector means the driver chooses the gear before it is engaged. Not really relevant to driving in OR, but in some locos there were two different levers, a gear selector lever to choose the gear and a gear change lever that you pushed to move from the gear you are in now to the gear you had selected.

[Weter]

About horsepower-there
Post #3 updated