Actually Terry, that is exactly what I said. The 38 is more slippery than the 36 is because of the additional torque available at standing or slow speed than the 36 type. Torque is what will make an engine slip and if you don't have enough under a certain condition, you won't slip. If you do have enough torque then slip will happen. You might also consider torque to be the drawbar pull of the loco. I'll also note that stupid engineers (which abound liberally) have an easy tmie of making a loco slip as they are the ones that leave the Johnson bar in the limit of its travel and open the throttle all the way to run along the track. For some reason, they are well hated by the firemen that have to work for them.
-- Bob May Losing weight is easy! If you ever want to lose weight, eat and drink less. Works evevery time it is tried!
If you had learnt some theory about firing locomotive you would not had had as much trouble keeping the fire going. As far as my experience, what has this to do with the design of steam locomotives and wheel slip? Nothing. The facts are what count's, not how much coal you or I may have shovelled on the locomotive footplate. You driving qualifications? Irrelevant to the fact the NSW 38 is less slippery overall compared to the lighter less powerful NSW 36. Facts you tried to cover up to push your story. We are all waiting for your qualifications, so far we have expert coal shoveler and expert cleaner. Did you get beyond these jobs and hold on to them? My steam experience involved testing boilers, turbines and stationary reciprocating engines. More knowledge and skill was required than to simply shovel coal or push a broom. Yes I have been on a number of locomotive footplates when in motion, but you do not have to be on the footplate to know the locomotive is slipping, an event I have witness many times on and off trains.
The engineers are correct, it does not have a dead centre overall, however there are a number of reasons why a 3 cylinder locomotive will stall. All piston engines have an uneven torque output. Your 3 cylinder locomotive has
6 positions of minimum torque, so if the locomotive is overloaded or low on steam these positions will be the most probable position to stall your locomotive. However the 3 cylinder locomotive has less overall torque variation compared to the 2 cylinder locomotive.
............................................................................ .................... My steam
A fireman's job on a steam loco is far more than to "Simply shovel coal". To state this shows an almost complete lack of knowledge in what a firing a steam locomotive is all about.. Firing is both a skill and an art. If you just hump coal into the firebox, like you almost can on a stationary boiler, then you'll soon be in deep trouble, with a dying fire, a rapidly dropping boiler water level and steam pressure that won't stop dropping. Not to mention the wrath of a very annoyed driver.
Not only do you have to know how to fire each class of locomotive, and some of them require very different firing methods from other classes and sometimes, individual locos within a class may require different firing techniques.
On top of this you have to know your route, both in daylight, and in the dark and bad weather when you can't see anything outside the cab. You have to know where the up grades are, where the down grades are, when to start firing to build up the fire and when to turn on the injectors to fill or top up the boiler ready for the upgrade and where, on the upgrade, to stop firing and to turn off the injectors so as not to overfill the boiler for the down grade otherwise you run the risk of priming the boiler or having the safety valves lift.
You have to know where tunnels are so that you don't fire while running through the tunnel and risk a dangerous blow back that can injure or kill either or both of the loco crew. You have to know when to stop firing ready for a station stop. How to manage the boiler so that when you do come to a stop, you still have room in the boiler to bang on the injectors to stop the safety valves from lifting all the while maintaining the boiler pressure just below the safety valve pressure. When nearing the end of the run, you have to know when you stop firing so that you can run the fire down ready for going on shed. After all, you don't want to go on shed with a roaring, deep fire that you, or the shed disposal crew if you're lucky, have to shovel out.
You also fire and maintain the boiler differently depend on what type of train you're working. Express passenger or freight with a few limited stops, a local passenger with frequent stops, a pick up good (way freight) with frequent stop and switching enroute, a "drag freight" with slow speed and long periods of waiting, or a yard shunter (switcher) all make different demands on the boiler and thus on the fireman.
And all of this is just the tip of the iceberg.
-- Cheers Roger T.
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of the Great Eastern Railway
Nope, a steam loco fireman isn't just a shoveller of coal.
You claim to have been involved in boiler testing, and yet you dismiss firing as being merely coal shovelling. I reckon that speaks volumes about how much actual knowledge and insight into the process you actually have. I'd be surprised if you're capable of boiling a jug to make tea.
One other aspect of the job is worth mentioning, Roger, and that's the ability to work co-operatively with your mate, to be part of a team. I can't quite see Terry managing that...
Terry, you seem to keep saying that it is one or the other which is quite wrong! Go calculate the possible torque that you can get out of the two locos - the basic specs of the two locos was given eariler - and figure out which loco has the higher available torque. You will see that the 38 type is going to have the higher torque available per ton on the driver and thus it will be the more slippery locol. With a certain rail/wheel adhesion factor, you won't have any slip up to a certain torque and then, at a certain point, the slip starts and the more excess torque that is available, the easier and faster the wheels start slipping. If you consider that the 36 type is right at the slip point then the 38 type will slip on certain occasions and will thus be considered a more slippery loco. If you don't understand that then you really don't understand the problem. PS. I will note that there is a lot more to being a Fireman on a loco than just shoveling coal, you are responsible for keeping the boiler filled properly with water and putting out the proper amount of steam fo rthe engineer to use along with all of the other maintenence chores that keep that boiler putting out the necessary steam. Shovel coal too long and the last thing that you will see in your life is the back end of that boiler lifting off of the loco!
-- There are more Democrats on the Calif. Special Election than Republicans! Go count if you don't believe me! Bob May
I would just use a DCC decoder with back EMF, then the fireman could kick back and pretent to be a static dummy, just like all the firemen on my railroad.
Just kidding. Your message was very informative. I didn't realize a fireman had to know so much.
Of course it does, but it also has a higher axle load.
But if you have a NSW 36 at maximum load, at slip point as you put it, then replace the NSW 36 with the NSW 38, the 38 on the same train is not at slip point due to its higher axle load, unless you deliberately decide to wheel slip using the extra torque available. I have been on numerous tours behind NSW 3801 and NSW 3642, both locomotives have often been brought to a stop on the Cowan bank, 1 in 40 grade when fully loaded. I do not recall the 36 was able to start more easily, plenty of wheel slip. However I do remember the Flying Scotsman 4472 and 3801 double heading up this grade, the train came to a halt, the Scotsman had allot of trouble with wheel slip, the 38 less so. The Scotsman is a powerful locomotive like the 38, with a slightly lighter axle load. So much for the 38 being a slippery Australian locomotive.
I am familiar with the difference between static friction and dynamic friction, which is what is being observed, however in the 36 V 38 case, the
38 is less slippery because of its heavier axle load, and is proven by maximum loads it can handle as I have identified in earlier posts.
Note I was referring to the skill level of Mark Newton the expert when talking about shoveling coal, not the general skill level of competent firemen.
As if you know anything about either. Perhaps when you pass the examination for your boiler ticket you'll be in a better position to comment. If you'd like any assistance studying for same, let me know.
Sigh! A higher axle load means that you can apply more torque to the axle before the wheel slips is correct. However, you have failed to check to see how much MORE torque is indeed applied to that axle to see if it is indeed more able to slip which is my argument.
-- There are more Democrats on the Calif. Special Election than Republicans! Go count if you don't believe me! Bob May
IOW you're comparing ratios of torque available/tractive weight - this is something that is entirely independant of wheel arrangement but probably increases with more modern designs.
Yep, more modern engines are more slippery than the earlier engines due to better boiler pressures amongst other things. The torque is maximum at low speeds because the flow of the steam through the pipes and valves is not impeded very much but is impeded at higher flow rates. Even despite this, some engines still have enough torque to be able to spin drivers at speed.
-- There are more Democrats on the Calif. Special Election than Republicans! Go count if you don't believe me! Bob May
Both the locomotives I have been comparing, NSW 38 and 36 have been tested over the years and the results published. Both are capable of wheel slip from a stand. Both use steel wheels on steel rail. The loss in adhesion for both locomotives after wheel slip is the same percentage of driver axle load. In other words for the worst case scenario for both locomotives the locomotive with the heavier axle load overall is less slippery. This is my argument. I have consistently agreed with you to an extent in earlier posts, stating the more powerful NSW 38 locomotive is easier to make the wheels slip compared to the NSW 36, If you want to do it.
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