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Manual Gearbox in OR Rate Topic: -----

#1 User is offline   darwins 

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Posted 11 September 2021 - 02:28 AM

In testing out the OR manual gearbox, I am noticing a number of problems.
First of all variation in engine rpm was very erratic with large increases and decreases in rpm.
This can be partly solved by adding

GearBoxDownGearProportion ( 0.62 )

Although this should only be needed for automatic gearboxes it does calm down some of the variation in engine rpm.

Secondly behaviour in first gear is very strange

https://i.imgur.com/PwGRm0f.jpg

You can see from the above that for some reason unexplained, between 2 mph and 3.5 mph the engine rpm leaps up suddenly and then crashes down again. It is as if an imaginary extra gear had been added with a maximum speed of about 2.4 mph. I would expect to see something more like the dashed green line, depending on how much slippage the clutch will allow.

This erratic behaviour is also noticeable in the tractive force curves

https://i.imgur.com/hQVnC8N.jpg

Another issue is that the maximum speeds for the gears in OR do not correspond to the values entered in the eng file (at least for lower gears and lower speeds).


The eng file entry is

GearBoxMaxSpeedForGears( 4.5mph 6mph 9mph 14.5mph 21mph 33mph )

This is what happens

https://i.imgur.com/FhsO61A.jpg

Gear 1 has maximum speed of 4.8mph instead of 4.5mph, Gear 2 has maximum speed of 7.1mph instead of 6.0 mph, Gear 3 has 9.1mph rather than 9.0mph.
For higher gears and speeds above 10 mph or so, everything seems to work as it should.

#2 User is offline   darwins 

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Posted 18 October 2021 - 05:15 AM

I am now trying to find out some more information about mechanical transmissions.

Information about any gearboxes used on railways anywhere would be most welcome.

From what I have found out so far it seems that
( a ) gears were normally engaged anytime the gear/lever (or pre-selector clutch) was in gear, including when the engine was idling, some hydro-mechanical transmissions had a scoop controlled fluid coupling that only engaged above a certain rpm, but so far I have not found any example of this on a purely mechanical transmission;
( b ) there were very few fully automatic mechanical transmissions (as opposed to hydro-mechanical transmissions, most of which are fully automatic or hydraulic transmissions all of which are fully automatic);
( c ) for most mechanical transmissions power is interrupted when gears are changed, for some the driver must close the throttle to reduce the engine rpm when changing up gear, for others the input rpm is automatically braked when a new gear is selected.

Corrections and additions to the following list would be welcomed
https://i.imgur.com/PBI1YRR.jpg


#3 User is offline   scottb613 

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Posted 18 October 2021 - 07:05 AM

Hi Darwin,

While not my niche - your attention to detail is very impressive - you are quite the asset around here - IMHO.

Regards,
Scott

#4 User is offline   Laci1959 

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Posted 18 October 2021 - 11:35 AM

Quote

c ) for most mechanical transmissions power is interrupted when gears are changed, for some the driver must close the throttle to reduce the engine rpm when changing up gear, for others the input rpm is automatically braked when a new gear is selected.


Such was the gearbox developed by GANZ in the 1930s. There was also a 0 grade between each grade.
0, 1, 0, 2, 0, 3, 0, 4
Between the first gear and the second gear was zero gear, a single notch. He held it there a bit before moving the lever further to the next gear. When switching back, you gave a gas splash to make switching easier.

#5 User is offline   Hobo 

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Posted 18 October 2021 - 04:19 PM

That's what they called a " Double Clutch downshift " that was and still is used in commercial vehicles with " Straight cut " gears . Taught in WW 2 to be used on up and downshift by most drivers , especially the inexperenced . It saved a lot of transmission failures .

#6 User is offline   darwins 

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Posted 18 October 2021 - 09:26 PM

View PostLaci1959, on 18 October 2021 - 11:35 AM, said:

Such was the gearbox developed by GANZ in the 1930s. There was also a 0 grade between each grade.
0, 1, 0, 2, 0, 3, 0, 4
Between the first gear and the second gear was zero gear, a single notch. He held it there a bit before moving the lever further to the next gear. When switching back, you gave a gas splash to make switching easier.

Thanks for that. I will correct my description of the Ganz gearbox.

Another question is regarding freewheel. As far as I can tell all of the gearboxes that I have described include a freewheel, which allows the train to coast in gear with the engine idling. This is in contrast to the earlier Open Rails algorithm described here Manual gearbox observations

Were there in real life any gear boxes used on railway traction that did not have a freewheel? (That is transmissions where closing the throttle would not reduce the rpm but would instead result in engine braking, the same as a motor car.) Any technical information or links to technical information on such transmissions if they existed would be much appreciated.

[Possibly some simple road vehicle gear boxes were/are used in track inspection cars and maintenance vehicles. I would think it better for these to be a special type in OR rather the default.]


#7 User is offline   copperpen 

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Posted 19 October 2021 - 02:39 AM

View Postdarwins, on 18 October 2021 - 09:26 PM, said:

Thanks for that. I will correct my description of the Ganz gearbox.

Another question is regarding freewheel. As far as I can tell all of the gearboxes that I have described include a freewheel, which allows the train to coast in gear with the engine idling. This is in contrast to the earlier Open Rails algorithm described here Manual gearbox observations

Were there in real life any gear boxes used on railway traction that did not have a freewheel? (That is transmissions where closing the throttle would not reduce the rpm but would instead result in engine braking, the same as a motor car.) Any technical information or links to technical information on such transmissions if they existed would be much appreciated.

[Possibly some simple road vehicle gear boxes were/are used in track inspection cars and maintenance vehicles. I would think it better for these to be a special type in OR rather the default.]


Far as I can tell, all UK dmu drive systems incorporated a freewheel which prevented the railcar from driving the transmission when coasting. Mechanical drive locomotives used a fluid coupling between the engine and gearbox which served a similar purpose.

#8 User is offline   Laci1959 

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Posted 19 October 2021 - 06:51 AM

Quote

Thanks for that. I will correct my description of the Ganz gearbox.


I would rather supplement. I just added.


Quote

[Possibly some simple road vehicle gear boxes were/are used in track inspection cars and maintenance vehicles. I would think it better for these to be a special type in OR rather the default.]


This is still the case today. The engine and gearbox are for trucks. Due to the low number of pieces, it was more economical to use parts from a proven truck type.

#9 User is offline   Laci1959 

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Posted 19 October 2021 - 06:58 AM

Quote

That's what they called a " Double Clutch downshift " that was and still is used in commercial vehicles with " Straight cut " gears . Taught in WW 2 to be used on up and downshift by most drivers , especially the inexperenced


When I was a soldier, I was lucky enough to drive one. There was no synchronous ring in the transmission of the Csepel 344 D trucks.
The UAZ 469 also had such a gearbox. I learned to drive a car there.

#10 User is offline   darwins 

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Posted 15 November 2021 - 08:39 AM

Just found a nice picture of the Ganz gear control mentioned above.
https://upload.wikimedia.org/wikipedia/commons/8/8f/Arpad_railbus_dashboard.jpg
http://www.elvastower.com/forums/public/style_emoticons/default/smile.gif

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