* Real steam locos spin the drivers to get them hot, in turn creating friction/adhesion to the rails.* If we do this in the model, which actually does work much the time to get it over the crest of a grade, are we harming the model's wheel tread or maybe even softening the sometimes-plastic wheel within the tread ? Will it wear away the model tires ? Or, is it perfectly OK ? *
I think when steam locos spin the drivers it is because of lack of traction at startup, or opening the throttle too far for a given speed. Spinning the wheels won't do anything to the wheels on our models except if they have traction tires which could spin themselves off the wheels. Real wheels on real trains get very hot when running on steel rails and they cannot be touched until they cool down. Spinning the wheels on real locos will just damage the rails by making little dish spots. It doesn't take very long to carve out a dish spot.
Mark - When I was being trained to be a steam loco engr by an old pro, he was adamant NOT to spin the wheels. According to him ... the centrifugal forces created by spinning would put a great amount of damaging pressure on worn bearings and shims. But the most serious damage could be presented in the integrity of firebox components when a sudden rush of cold air is drawn in by the draft caused by the spinning wheels and the fireman is not able to boost the fire to meet the needed heat. (That's why whenever you see an engine spin its wheels there's almost always a large blast of black smoke from the stack as the fireman tries to compensate). Starting a train from a stop is always tricky ... there's 100% torque available as the loco sits, stopped. Whenever more traction is needed to start, engineers, as a rule, will apply sand to the rails.
First of all, real steam locomotives did not do this to gain traction. Spinning drivers damages the "tires" (replaceable wheel treads on the drivers) as well as the rail. I've been told that in certain conditions, this had been known to cause a backdraft of cold air in the boiler, damaging the flues. I don't think spinning drivers can built enough heat on a model to melt plastic, nor help traction. I don't know if it causes any physical damage, but I always avoid slippage as I still feel like I'm "tearing up my equipment ", but that's just my thought. Sent from my LG-P930 using Tapatalk 2
On a model, doing it a lot will eventually cause wear of the driver tires. If they are equipped with traction tires, will ruin those. On a prototype, it is not desirable for both rail and tire wear. I have been told of instances where the driver tire came loose from this type of abuse. As Pat noted about the draft, somewhere I have also either heard or read mention of something about this happening.
Except in extreme conditions or from poor skill development, steam locomotive engineers are loath to spin the drivers when they try to lift a train. If the locomotive is properly assigned to the trailing tonnage, and if the rails are not greasy, or wet, or covered with rotting soft leaves and other vegetable matter, a hogger who spins on start-up has made an error. A conscientious hogger IMMEDIATELY slams the throttle closed. That doesn't sound like trying to warm up the tires to me. For one thing, the tires on a freight locomotive have a linear dimension of about 12' if they are a mere 55" in diameter. With a thickness of about 3", and a mass of about 700 lbs, it would take a lot of spinning in place to warm those tires enough to change the friction appreciably, but meanwhile you are drawing steam away from the boiler (waste), using fuel to heat the now-wasted steam (more waste), using more fuel to heat the new water needed to keep the boiler level up (more waste because you're still madly spinning trying to get those tires hot)...and on and on, continuing down this nonsensical enterprise. Should we mention the unnecessary wear on the tire surfaces? It's bad enough it means a shopped locomotive every month or so in order to drop each of the 8-ton driver axles, move them to the foundry section, heat the tires, pull them, send them to the machine shop, have them milled to the proper contour, and then reverse all of those steps? Bill mentioned the problems spinning the running gear brings to the firebox. This was a severe problem in coal burning and wood burning engines, not so much in oil burning engines. Remember that, in order to keep the fire working well, the draft down those long horizontal flues is augmented by the exhaust steam emitting up the diagonal blast pipes, up into the petitcoat pipe, and out of the stack. If the drivers are allowed to speed suddenly into a spin, with the throttle open, the air replacing that being sucked rapidly out of the firebox must come from below the grating, under the firebox. That air also pulses with the pulsed draw down the flues as each exhaust chuff evacuates the smokebox. The rapid inrush, pulsing, lifts the coals and will actually fire a bunch of them down the flues. Now you have not only holes in the fire, meaning some flues are now cooling instead of staying warm because they are getting the much cooler air from those holes going down them toward the smokebox (means metal strain, broken welds, broken staybolts and the flue sheet and crown sheet cool differentially, leaky flues, steam getting past them and into the firebox...etc), but you have hot coals collecting in the smokebox, fouling the netting, impairing the chuff process, and maybe blowing hot coals out of the stack and onto adjacent straw-covered fields or into tinder dry bushes near the tracks. Sorry, but that's very bad information you got there.
I guess I forgot to address the model...sorry. The model's tires, unless milled from thick metal and not coated, are almost universally coated. That coating does wear in time. I have brass or bronze or something showing now on the tread of my first locomotive purchased when I entered the hobby, a BLI Paragon Hudson 4-6-4. Spinning will just accelerate this eventual problem. I use Bull Frog Not on some of them where they don't have traction tires. BTW, I just looked at a new BLI P2 Pennsy I1sa that I got about 18 months ago. It's installed traction tires are quite badly cracked, already. I attribute that to my layout's location in a loft above my garage. The roof is a hipped roof, making the building look more like a typical barn, if a small one. There is no attic. It gets quite hot in there, perhaps up to 100 deg F. It can't be good for the crappy compound that comprises those cheap traction tires. BLI says they include a spare set with each loco, but I haven't bothered to either look at them to compare or to install them just yet. A chore I'm not really looking forward to. Try NOT TO spin your steamer's drivers. It's a sign you have insufficient traction for your trailing tonnage.
excessive wheelslip can also cause damage to the rods and valve gear as they also carry momentum that must be changed on each stroke, wheelslip will wear down the bearings and on engines built before roller bearings, that's all friction based bearings, which will heat up and damage easily. This can also lead to failure of the drive rods and if the cab is close enough to the drive rods, the crew can get speared when the rods break off the bearings, this was one of the reasons that camelbacks were outlawed, as the crews sat right over the rods. We had a wheelslip at the museum that also resulted in a leaking cylinder head, never a good thing. There is a big difference between modern tourist railroads and the old working railroads when they ran steam. The engineers on the modern tourist railroads usually also have to maintain the engines and deal with the problems they cause, and thus are extremely adamant about not slipping the drivers. The crews back in the day did not have to maintain the engines and it was thus, not their problem. If you watch older videos or even look at old photos, engineers on engines back in the day would "hot dog" the engines on the way out which did produce a fair amount of wheelslip, however if anything broke, they would just punch the clock and be out while the guys in the shops were left to fix the damage. Do a google search on "Blue Peter", a Pacific in Britan that suffered runaway wheelslip due to boiler priming, this destroyed the valve motion, blew open both cylinders, and actually spun one driver out of quarter. Not an easy task to fix! As for the models, we don't carry near as much mass on the valve gear or assemblies to worry about. If you have traction tires and you spin the drivers, thats bad, as if the traction tires suddenly grab and get traction, you can throw a model out of quarter on that driver (don't ask how I know.....). On the drivers that are just polished metal, this isn't so much an issue, over time you'll wear the plating off, but I've never seen an engine in HO that wore its drivers down enough to cause a problem.
For the scale models, it usually doesn't happen. Except with many long years of use. But on tinplate, I've seen a few number of such as American Flyer, Lionel, Marx which wore enough to cup their drivers. I would suppose some of this could also be attributed to the material, plus arcing for many years.
Thanks for the replies. Though I believe all your facts, I see this being done in old movies on youtube. Real shots of main line steam spinning about 3 revs, then rolling, then slips, then rolls....Mostly I think I've seen it on early Americans (4-4-0 types). I have a modernized Richmond and a mogul (sound is broken so I stopped running her). Both Bachmann (HO), and an RS3, Bmann. So, neither have traction tires. I just finally began to enjoy pulling only 4-5 cars on this switchback branch line. Not only does this eliminate the slipping up 2,curved, 3% grades, but it just looks right at home at this length. Real bucolic ..Now that I'm happy with the entire RR's design I will have to demolish it in about 8-9 months due to my landlord employing the Ellis act (search Ellis and you'll know what's happening to me). And the way my money is, I doubt I'll have room in the next apartment for a layout (other than perhaps a 2x8 shelf, switching yard. Man, I was right at the beginning of serious hill and rock construction.. I can't believe it'll all be gone soon after 19 years here and 8 years on RR (open grid, NCE, point to point with wye and engine house on upper end of line on peninsula, interchange at lowest level ......I'm praying for a miracle.
Old movies.... that's just what they are. Spin 'em for the show, no one cares about locomotive maintenance in a movie set. Just because a prototype spins doesn't indicate the intent to spin. They dud slip on hard starts but care was taken to minimize wheel slip. Sent from my LG-P930 using Tapatalk 2
Movies are irrelevant. You will also see them doing such things as running extensively with cylinder cocks open, blasting out (wasting) precious steam. Or firing poorly so a huge plume is produced. All for effects, disregarding potential harm. You'd never see these actions done intentionally on a real railroad. It is purely for Hollywood show. Yes. On a real railroad, you may see a driver spin a very few revolutions, which is acceptible. It is not intentional, and is stopped as fast as humanly possible. If you've ever been in a steam loco cab when this happens, the engineer immediately slams the throttle closed to stop it, then starts working his throttle and using sand to try the start without spin. You'll never see a non-movie start where the drivers spin and spin. A 4-4-0 is a very light loco, and with their usually tall drivers can spin easily. Again, the engineer stops that as fast as he can. Railroads do not have movie stunt budgets, where they do not care if something breaks. Engineers who abused equipment didn't keep a job.
Recall the scenes in "Emperor of the North" where the 19's wheels are spun without care; and the scenes where the brakes were put in the big hole and slid to a stop! Geez! No wonder the old girl is so tired!
High drivered steamers with heavy trains are prone to slip when starting. Even in those "old movies" they only spin long enough for the hogger to close the throttle and stop it. Spinning drivers is never good.
Firstly, I wasn't referring to 'hollywood" movies. I was referring to those old black and white films from about 1920 on, made by the either the RR or the builder such as Baldwin/lima/Rogers, for promotional purposes/documentaries/newsreels in theater houses, et al. I always thought this was on purpose. But, being it's not, why then didn't engineer move out the throttle that much less, take up slack and continue very very VERY slowly ? I.E., If slipping is known to likely cup the rail head or worse, why then did he pull the throttle fast or far enough to cause slip in the first place ? If rain, ice, heavy load, or grade was present what happened to the sand ? Or does the sand drop on head inches ahead of the wheel treads so that there still is slip 'til he gets it directly on top of the sand ?! .....Anyway, I do sand corrected...
Those company type promo films, some were indeed filmed by Hollywood or similar commercial operations. The spinning was often done just for effect. A steam throttle is not always as smooth in operation as one might suspect. If you can get to a good site running steam, see about buying or begging a cab ride. Watch how the engineer works a throttle. It's usually not all that easy. You'll be surprised how much work is involved, especially when starting a heavy train. He manage more than just the throttle to get rolling.
Some place in my vast VHS collection I have a video on the Nickel Plate Berks. It shows them doing a wheel slippage test. Then it has an old-timer telling stories on how the big berks would slip and pound on the rails. He said after the testing was over, the section of rail was removed and the ends bent up like the rail was smiling. I guess this was footage from when the railroad was putting the first berk threw some trail testing. But it was an impressive video.
