Driving the s282

[numbat]

Hi All,

just finished restoring the s282 and have done my first job. That was intense.

I have a couple of questions. Firstly, I don't really understand the reverser/cutoff. How do you decide what setting. I've watched squirrel's video, and he says start with it in full then pull it back, but how do you decide when/where to run it? I ended up just using full for takeoff, then all the way back almost to centre.

Secondly, how long do you need to have the cylinder-♥♥♥♥ open when you start off. I'm not really sure if I'm hearing water in the cylinders or not, but how long would it take to clear it? And do you need to do this every time you stop?

Cheers,
Chris.

[Knsgf]

Originally posted by numbat:

I have a couple of questions. Firstly, I don't really understand the reverser/cutoff. How do you decide what setting. I've watched squirrel's video, and he says start with it in full then pull it back, but how do you decide when/where to run it? I ended up just using full for takeoff, then all the way back almost to centre.

When the reverser is all the way forward, steam is admitted for almost entire duration of a piston stroke. This makes torque as uniform as possible, which is important when starting a train or in rainy weather, when the performance of the locomotive is limited by adhesion - but it is also inefficient. Keep an eye on steam chest gauge and note a pressure when wheels begin to slip, then adjust the regulator as necessary to keep chest below slip threshold to avoid losing traction.

Once the regulator is fully open, you can start pulling back on the cut-off to run the engine more efficiently. Again, watch chest pressure - 12-13 bar gives maximum efficiency but reduces power, while 8-9 bar lets you use full boiler steaming capacity and accelerate faster if there is an uphill route coming up. Because shorter cut-offs lead to less uniform torque, S282 tends to become very slippery when reverser is around 25-40 %, so watch out for that.

If you're running with a light consist, you can centre the reverser as soon as the train gets moving and simply use regulator to control speed.

Originally posted by numbat:

Secondly, how long do you need to have the cylinder-♥♥♥♥ open when you start off. I'm not really sure if I'm hearing water in the cylinders or not, but how long would it take to clear it? And do you need to do this every time you stop?

Yes, draincocks must be opened after every stop. Count 4-8 chuffs, then you can close the drains.

[ling.speed]

Cutoff is kind of an efficiency wheel. The further it is open (away from center) the later more steam is introduced to the cylinder during a cycle. This increases max torque to some extent - as full pressure is in the cylinder in more optimal positions of the crank, but the later new steam is introduced the less work it can do, and at full cutoff you are using steam to top off the cylinder thats just about to blow the steam out for return stroke. At lower regulator positions, full cutout will consume so much steam, the chest pressure will drop further reducing efficiency of the motor. It can be beneficial at times of limited traction, but otherwise its not good.

- For light loads staying between neutral and first notch is good. Its also safe position when in dry - as even max boiler pressure should not cause wheelspin.

- At the middle notch between neutral and max you reach the peak torque of single (important for traction considerations) its also still decently efficient. Useful for heavy loads uphill. But at speed you will consume A LOT of steam so you will need to run full damper, shovel coal constantly and have at least half injector open to keep up.

Going even faster or using even higher cutout will reach limit on the steam flow through a fully open regulator and your chest pressure will drop.
Chest pressure is "work pressure" - the higher value the more torque and steam/coal efficiency. So as long as traction permits running full regulator is good, regardless of speed and load. Less regulator is useful for starts.

- Second to last cutout notch is for slow speed, heaviest of pulls (you can pull as much as DE6 at 14bar and with max sand usage). We'll be traction limited at that point, and going past that notch will not increase pulling power because of worsening torque curve shape.

- Max cutout is only useful when using reduced chest/boiler pressure and needing to move precisely during service/shunting or accelerating from stanstill with very heavy loads.




As for cylinder-kocks, the temperature of cylinders is tracked, so depending on how cold they are it can take a while. How often new steam is entering the cylinders is also important here.
Generally if you dont run too fast while there is water inside, cylinders wont get damaged much, so you can leran by experimentation. The worst is to have them closed when wheelspin happens - that might blow a cylinder in a second.

Freshly used loco will barely need one cycle to clean water out (listen to hisses, and close them with interval of 4 - as there are 4 work chambers to clear of water).
Loco that was going downhill for the last half an hour or was cold started could take even 10-15 minutes to heat up and clear all water if its not hauling much load and steam is used efficiently.

Note that cutout position also changes how much water is expelled, so you can speed up the process by throwing a lot of steam through the cylinder.

[ling.speed]

Originally posted by Knsgf:

Again, watch chest pressure - 12-13 bar gives maximum efficiency but reduces power, while 8-9 bar lets you use full boiler steaming capacity and accelerate faster if there is an uphill route coming up.

Great advice overall! I would note that running below 12-13 bar is not going to give more power. The firebox will produce more power yes, but it will not be transfered to the wheels because 8-9 bar creates less torque and power is torque times speed, so we are spending more coal to do less. It is however easier to manage traction with less pressure.

Because shorter cut-offs lead to less uniform torque, S282 tends to become very slippery when reverser is around 25-40 %, so watch out for that.

Shorter and longer cut-offs produce more spiky torque (all cylinders combined) the flattest torque curve comes at around ~50% cutout.

Ideally it would be exactly 50% but range of cutout isnt from top dead center to bottom dead center of the cylinder (ends earlier), so it's a bit more than 50% (maybe 60%, hard to say). At speed the steam does not enter the cylinder "instantly" also skewing the results further down.

And a random trivia for another steam enthusiast: the 282 in game has such spiky torque that when traction limited, running with loco brakes on and more cutout can produce enough extra average torque (through effect similar to cars ESP) to overcome braking of the tender for a small net gain in pulling and more safety vs runaway wheelspin. But its tricky to do anyways, so trivia only, not reccomending using brakes beyond starts in unknown rail slip states.

[numbat]

Thanks for those detailed responses folks. I shall give those ideas a try and keep a watch on that chest pressure gauge.

Cheers,
Chris.