[darwins]

What are the different ways in which the reverser (cut-off) control can be operated on a steam locomotive?

I am not concerned here with how the machinery works, but simply with how the driver adjusts the controls in the cab.

So far as I know there are only three different ways to adjust the controls in a Simple Locomotive.


( 1 ) Lever Reverse
Lever Reverse(also known in USA as Johnson bar reverse) is used for:
(a) Manual lever reverse.
(B) Power assisted reverse (steam or air) with miniature Johnson bar control (USA)

Operation:

Reverser has discrete notches.
Driver moves lever forward or backward one notch at time.
The position of the lever corresponds to the cut off.

Represented in OR as for example

 Cutoff	( -0.75 0.75 0.0075 0
  NumNotches( 15
   Notch ( -0.75 0 Dummy )
   Notch ( -0.65 0 Dummy )
   Notch ( -0.55 0 Dummy )
   Notch ( -0.45 0 Dummy )
   Notch ( -0.35 0 Dummy )
   Notch ( -0.25 0 Dummy )
   Notch ( -0.15 0 Dummy )
   Notch ( 0.00  0 Dummy )
   Notch ( 0.15  0 Dummy )
   Notch ( 0.25  0 Dummy )
   Notch ( 0.35  0 Dummy )
   Notch ( 0.45  0 Dummy )
   Notch ( 0.55  0 Dummy )
   Notch ( 0.65  0 Dummy )
   Notch ( 0.75  0 Dummy ) ) )

This currently works correctly in Open Rails cab views using:

Lever (
 Type ( CUTOFF LEVER )

( 2 ) Screw Reverse
Screw reverse is used for:
(a) Manual screw reverse
(B) Power assisted reverse (steam or air) including examples such as "Precision Power Reverser".

Operation:

Reverser is continuously variable.
Driver rotates wheel left or right to adjust cut off.
The actual cut off is shown on a separate indicator scale.

Type ( REVERSER_PLATE GAUGE )

Represented in OR as for example

Cutoff	( -0.55 0.75 0.01 0
NumNotches( 0 ))

This currently works correctly in Open Rails cab views using:

Lever (
 Type ( CUTOFF LEVER )

( 3 ) Miniature Lever Reverse
Miniature Lever Reverse is used for steam reverse.

Operation:

Lever has three positions
When lever is in forward position cut off increases slowly.
When lever is in centre position cut off remains constant.
When lever is in backward position cut off reduces slowly.
The actual cut off is shown on a separate indicator scale.

Type ( REVERSER_PLATE GAUGE )

Operation of the lever is not currently possible in OR cab views.



A control called a "Norris Lever" is also mentioned but not explained clearly, this is possibly the same as the miniature Johnson bar mentioned above. Does anyone know more?



Reverser controls on Compounds may be more complex. Possibilities are:


( 4 ) Combined reverser control that gives identical cut off for both HP and LP cylinders.
Operation is the same as ( 1 ) or ( 2 ) above and can be represented in OR in the same way.
Used on Vauclain Compounds.


( 5 ) Separate or Partly separate control for HP and LP valve gear.

On many compounds including those built or modified by André Chapelon then separate controls were provided to operate the HP and LP valve gear.
In some locos both could be moved together to a particular relationship between HP and LP but then one could be adjusted to give some variation to the cut off.

More information and possibly cab views showing how this operated on real locomotives.

This is not currently possible in Open Rails either by cab view or keyboard.
Used on De Glehn / du Bosquet / Chapelon type compounds and also on the original Smith / Wordsell / Johnson compounds.
This arrangement of two seperate reverser controls can not currently be modelled in OR.



( 6 ) Fixed control that gives a pre-determined cut off ratio for HP and LP valve gear.

For example the Deeley rebuilds of the Johnson compounds, Deeley compounds, LMS compounds and GNRI compounds have a screw reverser.

This might be represented as

Cutoff ( (-0.854HP -0.78LP) (0.8875HP 0.83LP) 0.01 0
NumNotches( 0 ))

"Notch" is shown on a separate indicator scale.

Type ( REVERSER_PLATE GAUGE )

The indicator scale has 12 forward and 12 reverse notches shown.

Some actual cut offs corresponding to these are:

Fore 12 HP 88.75% LP 83%
Fore 9 HP 82.1% LP 75%
Fore 6 HP 67% LP 55.5%
Fore 3 HP ? LP 35.5%
Mid F HP 10.6%
Mid LP 15.5%
Mid B HP 13.6%
Back 3 HP 35.4% LP 32%
Back 6 HP 62.7% LP 54.5%
Back 9 HP 77.6% LP 69.5%
Back 12 HP 85.4% LP 78%

This arrangement of different cut offs for HP and LP cylinders controlled by a single control is not currently possible in OR.

[Weter]

Hello, Darwin and all.
It seems to me, I might see screw reverse control (wheel-formed) with latch, fixing the wheel on one of notches, against creeping down, similar as Your example 1.
Certainly, due to screw mechanism, distinstions between adjacent notches were very small - the latch was used for securing / fixation of current cutoff, but not for separation of positions from each other.
Also note, that Assistance might be produced by springs (as on early NA engines, whose models Tim Muir made for ORTS), though that, as You have said is out of given discussion's focus.

[Traindude]

Here are some other possibilities. Steam- or air-operated power reverse gear, such as Franklin, Alco, or Barco. Here are two of the many examples found on North American locomotives.

Weter, on 04 March 2024 - 03:09 PM, said:

Do they distinct with control way?

I know the Franklin Precision gear uses a wheel while others, such as Barco, Alco and the Franklin "Raggonnet" style, all use quadrant levers.

Attached File(s)

•  Barco Dual Control Power Reverse Gear (M-1, M-2).pdf (355.44K)
  Number of downloads: 25
•  Precision Power Referse Gear, Type F, Instruction Book 4.pdf (1.65MB)
  Number of downloads: 20
•  Alco Reverse Gear.pdf (6.44MB)
  Number of downloads: 27

[darwins]

So we still seem to be more or less on three types. Though I am now wondering if there may be one or even two more to add.

The Franklin reverser with the wheel is Type 2 above (operation in OR the same as screw reverse) - and all those with 'Raggonet' style levers correspond to Type 1 above (operation in OR the same as Johnson bar or lever reverse).

There is a description of operation and photograph of a type 3 - miniature lever - reverser here: https://janfordsworl...rummond-t9.html

This was the type of reverser used by Dugald Drummond on the London and South Western Railway. I suspect the steam reversers used by his brother Peter on the Highland Railway were similar.

The more common type of power reverser in UK was invented by James Stirling of the Glasgow and South Western Railway in 1873. It worked on what was called a "steam and cataract" system. This was later widely used on the South Eastern Railway, South Eastern and Chatham Railway and Southern Railway. I am trying to find more information but it sounds as though the driver may have had to adjust two controls to change the cut off.

Also the Great Eastern Railway had a type of power reverser worked by compressed air. It could be operated either as a manual reverser or a power reverser and I am not sure if there was any difference in the method of operation.

[Weter]

Hello, Darwin.

Quote

This was later widely used on the South Eastern Railway, South Eastern and Chatham Railway and Southern Railway. I am trying to find more information but it sounds as though the driver may have had to adjust two controls to change the cut off.

As Tim Muir made his Tank Engine model - the significant research about power revercer with two rods were done.
https://www.elvastow...post__p__283566
Oh, You might remember that...
https://www.elvastow...post__p__283571

[darwins]

Thanks for the reminder Weter.

Tim's pictures clearly show two controls, a combination steam admission and oil by pass valve and the reverser handle.

One description I have of operation is this:

"Both steam and water cylinder valves have a rotary movement and are directly connected by rods, as is also the reversing lever to an arm centred on the crosshead. Any movement of the reversing lever will therefore rotate the valve in the steam cylinder, thereby opening one end to steam and the other to exhaust. Simultaneously the water valve of the cataract cylinder is opened and allows water to pass from one side of the piston to the other, thus releasing the gear, which is moved in accordance with the position of the reversing lever. The movement of the piston rod is transmitted to the bell-crank levers shown, and the links are therefore raised or lowered accordingly. When the reversing lever has been moved and locked by the trigger in the notch on the sector, a new fixed centre is given to the crosshead arm, which, however, is returned to its normal vertical position by the movement of the piston rod, thus again closing the valves and locking the gear in the required position."

That makes it sound like you adjust the reversing lever, just like type 2 (lever reverse) but not clear about the other control.

Although another description posted by a driver that used this long ago says:

"If my memory serves,you had to move a little brass pointer to the desired cut off marked on a scale,then twist a valve alongside the mechanism and it was notched up."

Suggesting that perhaps nothing happened until you used the "combination steam admission and oil by pass valve".

I am wondering if I can get to the bottom of this without finding one of these locos (there are about 20 preserved, many in working order) and going to watch, not so easy to get a footplate pass in many places!

[Weter]

Well, the process, You described, looks like "booster of follow type" (don't know the english term) action.
So, operator refers the desired (end) position of mechanism, while some "servo motor" will actually move gear and stop there.
The moving part will act counter control part and "equalize" it's position, once have reached the state, defined by operator.
That's negative feedback - result decreases input. Mechanism can be heavy, remote, danger or demanding some side-correction.

Also, indirect controller on electric stock works: driver refers the notch, on which controller's shaft should stop turning, and servo-motor (electric motor, or pneumatic cylinder of any design) rotates shaft in stepped way until defined step will be reached, then stops there.
That's just the case, where mechanism is multiple, distant, danger, heavy and needs correction according to maximal allowed current.

I can only guess, that said cataract cylinder allowed to discharge working (steam) piston of revercer gear's weight, while gear is being fixed on desired position.
If so - no need to maintain steam pressure in power cylinder, no need to allow steam leaks, cooling/condensation, unavoidable during long "idle" periods of mechanism's work. If that's right guess - steam was admitted to valve's camera only while movement was needed (change of cutoff/direction), while all the rest time, admission cock was closed and cut reverser's cylinder valve chamber from boiler.

Steam cooling would lower pressure in cylinder and cause gear's down movement, excessive steam admission which is useless steam waste. Not saying about condensation

Also, if bypass valve of cataract cylinder provided only small (adjustable) opening - it could smoothen movement and neutralize jerks, coming from rotating eccentrics of mechanism, while locomotive rolled, plus equalize up (counter weight - heavier) and down (following weight - eeasier) mechanism's movement speeds.

[Laci1959]

https://kephost.net/p/MTE0NzkxNw.jpg

Hello.

The vertical arm is the direction change arm with the locking latch. This also regulated cylinder charging through the control unit. Small locomotives and very old locomotives had this. Later-designed locomotives already had the previously mentioned screw-spindle solution, supplemented by a directional lever. GANZ MÁVAG's first locomotives designed with screw-spindle direction changers did not yet have a direction-change lever, the spindle had to be wound a lot.
The image is from the Internet.

Sincerely, Laci1959

[Traindude]

Here another oddball power reverse gear. Apparently, it was installed on several NYC 2-6-6-2 Mallet locomotives in the 1910's and used an "air over hydraulic" principle. I don't suppose this type of gear is worth committing to modelling in ORTS with the other types...is it?

[Laci1959]

https://kephost.net/p/MTE1NDMwNg.png

Hello.

A solution from Hungary. The rotatable spindle controlled the cylinder filling ( Cutoff ), above it was the lever continuing downwards in the fork, the reverse lever. You could quickly change direction by moving the lever. In principle, it was also possible to change direction by turning the spindle, but I am not sure about that.

Sincerely, Laci1959