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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Thu Feb 13, 2020 7:04 pm 

Joined: Thu May 24, 2012 1:37 pm
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Sorry ... I did not read the initial post in this thread carefully enough.

The only thing that would connect a scalehouse with steam 'wheel balancing' is the fact that it uses balances. In a very different sense of the word.

Ignore what I said about other equipment. It would be unlikely to find it at Spencer, in a building of the type Dave describes.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Fri Feb 14, 2020 1:28 pm 

Joined: Thu Aug 26, 2004 2:50 pm
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Location: Northern Illinois
Overmod wrote:

The only thing that would connect a scalehouse with steam 'wheel balancing' is the fact that it uses balances. In a very different sense of the word.



I bet there was a model railroader involved in the interpretation of the site. Modelers are always talking about "balancing" brass models of steam locos, because the easy place to add weight to these models is in the smokebox, where the builder typically installs a large slug of lead. Problem is, this makes the model nose heavy, to the detriment of both adhesion and tracking of the rear drivers. The typical "balancing" operation involves placing the model on a straight edge laid over a dowel and adjusting the weight distribution until it will balance with the fulcrum at the center of the driver wheelbase. I can just imagine a modeler looking at this track scale with separate weighing segments, adding two and two, and coming up with five.

Somewhere there must be historic site plan drawings for the Spencer complex. It would be good if someone would check that source for what the building was called when it was in service, and return that name to common usage.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Sat Feb 15, 2020 3:11 am 

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Dave wrote:
Way back in my days at Spencer it was simply know as the "scale house." No idea where the new designation came from
Apparently it comes from the description of the building in the Historic American Buildings Survey of the historic shop complex.

From the PDF version of the text of this report is the following snip-it:
Attachment:
SpencerShops-Scale House.JPG
SpencerShops-Scale House.JPG [ 109.42 KiB | Viewed 603 times ]

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Sat Feb 15, 2020 9:06 am 

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Location: New Franklin, OH
Punctuation makes a difference - “scale-balancing pit”. I’d vote for car scale. After modification or repair you have to reweigh the car.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Sat Feb 15, 2020 3:09 pm 

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Location: Northern Illinois
jayrod wrote:
Punctuation makes a difference - “scale-balancing pit”. I’d vote for car scale. After modification or repair you have to reweigh the car.


But cars can be weighed on a simple single table track scale. What is special about this scale is separate beam balances for each driving wheel, which allows the determination of how wells the equalization is set up. The term "balancing" is, I suppose, appropriate, but confusing because people are assuming that it has something to do with the dynamic balance of rotating wheels.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Sun Feb 16, 2020 1:45 pm 

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This all makes sense to me about the equalization being tested or checked. Would think that would be important or an improved way of maintaining ones fleet. But for me it still poses a question about finding lead poured into a counter weight? Why and how did they guess on how much to add?

From what I have seen in major overhauls the companies such as Baldwin, Schenectady and Lima productions, did not go over every locomotive with a fine tooth comb looking for ways to improve things on production grade locomotives? Not an accusation, but I think today we think of silk purses and back then they thought about getting that order out the door. I know the larger RR and builders had their R & D depts who did look for refinements. Which leads me back to the question of the melted lead in one of the main drivers counter weights. I prefer not to mention the locomotive in question as I am not the owner/operator. It is running now and after the running gear overhaul is running square and sound. But still not my locomotive to ask about. So I ask about the practice if it was one? Or was this an "in house" attempt to to smooth things out? I also know nothing of British steam, would this be something they do or did back in the day? Maybe I will never find out, but the title of this thread got me started again on "who" and "when" this was done.

I used to work on a fleet of cars {Automobile type} years back and we balanced our own tires/wheels. One time we had a "General" tire brand new that we could not get to balance. It shook the whole car even on the rear axle. Took it to the General tire dealer who could not get it to balance either. It was a brand new tire. The only reason I mention this that if a tire is defect like the one I recall could jinx the whole car no matter where you put it. The long term effects of out of balance wheel or wheels could cause expensive and perplexing mechanical problems down the road. The mechanic would be chasing ghosts trying to figure out why things were wearing out prematurely. I know it is a poor comparison of "vehicles" but something grossly out balance could and usually will cause problems not easy to DX. How on earth you could balance a steam locomotive wheel is beyond my understanding with all the motion and forces involved. I know we tram locomotives and set the valves to specs as best we can, then tweak as necessary and hope for the best and maybe that is all we can do with the locomotive being what it is. Do not recall seeing pictures of anybody trying to balance wheel sets in old builders photos? Now I am wondering if this was just an attempt of some mechanic down the long road of history that "tried it" to correct problems of the day? Regards, John.


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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Sun Feb 16, 2020 4:09 pm 

Joined: Thu Aug 26, 2004 2:50 pm
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Location: Northern Illinois
John, I don't know of anybody who dynamically balanced railroad car wheels. If anybody should have, it would be my old employer, the Chicago Transit Authority, where they ran 28" wheels at 60 MPH in trucks with less than ideal suspension, but as far as I know they didn't, they just continually ground their railheads away trying to quiet the system by removing the "corrugations" the bouncing wheels beat in the rail. Everybody just assumes if you have a roll forged wheel, the circumference machined round and the axle bore accurately centered, it's going to be close enough to being dynamically balanced for the purpose at hand.

Anyway, you can't dynamically balance a locomotive driving wheel, because the amount of weight in the counterbalance is a compromise. Yes, you can add weight to counterbalance the weight of the side rods, but what about piston thrust? When the piston thrusts rearward and the big end of the main rod goes down (assuming forward motion) part of that thrust is directed downward, where it acts like additional weight on that side of the driver. As the wheel continues around and the piston thrusts forward, part of that thrust is vectored upward, where it acts like negative weight as far as the balance of the wheel is concerned. Since this thrust component is variable and ever changing, there can only be a perfect counterbalance for one set of operating conditions, and everything else is a compromise.

To dynamically balance a locomotive running gear, one would have to run it on a test plant, like the PRR did with new designs. The results are worked into standard formulas that can be applied to other locomotive designs... and the driving wheel centers have pockets for additional lead weight to allow additional tweaking should someone think it's necessary.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Sun Feb 16, 2020 5:39 pm 

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Location: Strasburg, PA
John Risley wrote:
I am curious about balancing steam locomotive wheels ever since I saw some molten lead leak out of a main driver once upon a time. Had never given it a thought about balancing locomotive wheels? Does anybody do that now days when a set of tires are installed and wheels reworked?
#90 got the lead replaced in her main drivers during her latest running gear overhaul. Enough had leaked out that the chunk left could be heard clunking back and forth inside the wheel at slow speed. Being a low drivered freight engine, we added all the lead the driver could hold, confident from past experience that it still wouldn't be enough.

I recall seeing an EBT driver that would sit on the shop floor with one crankpin almost vertical and the other almost horizontal due to most if not all of the lead leaking out of one wheel.

The unpowered Thomas replicas we built have each wheel balanced within a couple of pounds to its rod so they wouldn't tend to hop around on the road due to the engine as a whole being so light weight. That was done by mounting each wheel on a stub axle, and adding weight to the crankpin until it balanced the counter weight. The amount to face off each counterweight was calculated from that. No lead needed.

Of course, with no reciprocating weight to deal with, virtually perfect rotational balance is theoretically possible.

Attachment:
small IMG_3877.jpg
small IMG_3877.jpg [ 221.72 KiB | Viewed 424 times ]
A T-1000 terminator is poured into #90's main driver counterweight.

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Last edited by Kelly Anderson on Tue Feb 18, 2020 11:00 am, edited 1 time in total.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Mon Feb 17, 2020 11:21 am 

Joined: Thu May 24, 2012 1:37 pm
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I think much of the discussion may become somewhat clearer if you look at this page (from the P2 replica effort in Britain):

https://www.p2steam.com/2016/10/31/getting-balance-right/

I had several pictures and documents regarding British dynamic balancing in the photos section of the steam_tech Yahoo group, but that is gone now. I believe there are online pictures of one of the Great Western balancing machines at speed, showing the linkage, but I can't find them so far.

Incidentally, the 'Wheelchex' referenced in the video is DeltaRail's version of a WILD, a wayside Wheel Impact Load Detector, not an onboard system. Among other things, the instrumented driver wheelsets for T1 5550 will be capable of assessing very precise balance (a couple of different ways) as a check to anything that would be communicated to the track.

With respect to the 'wheel balancing shed' part of the description, in addition to setting equalization correctly after shopping or modification, there is this consideration:

https://www.youtube.com/watch?v=-bO9LYkkpV8

(The actual rail content commences about 1:50)

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Mon Feb 17, 2020 7:20 pm 

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Thanks Kelly, Dennis and Overmod for your pictures and links. Being I am not a ME or rocket science master maniac I probably will never be able to use this info. I pretty much do trained monkey work most of the time. But the subject to me is very interesting even if over my head. The pictures of pouring lead at SRR on #90 is exactly what some one did to the above mentioned locomotive wheel and have been mystified ever since as you never hear of this or at least I never did. So thank you for not writing me off as the "Heretic" I sometimes am. After watching the link regarding balancing, I think I will go back and try to master walking and chewing gum simultaneously.

Regards, John {the heretic}.


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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Tue Feb 18, 2020 11:47 am 

Joined: Fri Jan 01, 2016 5:47 pm
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Brian Norden wrote:
Dave wrote:
Way back in my days at Spencer it was simply know as the "scale house." No idea where the new designation came from
Apparently it comes from the description of the building in the Historic American Buildings Survey of the historic shop complex.

Brian and Dave: thanks for figuring this out. That report provided the simple information I need, although I personally enjoyed the discussion by others about dynamic wheel balancing.


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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Tue Feb 18, 2020 12:07 pm 

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Incidentally, Kelly or others might want to comment -- at length, if possible -- on the specific alloying used for the "lead" used in this application.

As I recall, elements like antimony are included to harden the alloy, but they also add a key characteristic that answers one of Mr. Risley's implicit questions: they cause a change in the metal structure as it hardens that makes the material expand and 'key' itself into the pockets. This keeps subsequent augment or suspension pounding, tread overheating, etc. from helping the lead mass work loose and start banging around and pulverizing itself.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Tue Feb 18, 2020 12:28 pm 

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Quote:
"Yes, you can add weight to counterbalance the weight of the side rods, but what about piston thrust? When the piston thrusts rearward and the big end of the main rod goes down (assuming forward motion) part of that thrust is directed downward, where it acts like additional weight on that side of the driver. As the wheel continues around and the piston thrusts forward, part of that thrust is vectored upward, where it acts like negative weight as far as the balance of the wheel is concerned. "


Not to hijack the subject, but relevant to the 'title of the thread as amended' for anyone reading later:

Vertical component of piston thrust is NOT the thing that causes most of the augment. In fact you see it compensated for in Voyce Glaze's balancing method for the N&W J, where the only overbalance kept in the main driver is for the approximately 80lb of peak thrust component that Glaze thought needed to be compensated. Note that the net magnitude of this does not materially change with speed, although the characteristic plot of thrust at different degrees of rotation may ... we can presume that as with almost any other class of high-speed-enabled steam power that highest cyclic (and hence top achieved speed) will come at right around 40% cutoff -- and this with steam pressure at the chests, achievable mass flow, and a good indicator diagram will give you a very good idea of the 'resultant'.

What causes the augment problem is the inertial force from the mass of the rods and pins, which adds up geometrically and dramatically with higher rotational speed. There is a substantial mass of main rod which cannot be rotationally balanced (due to the linkage from rotating motion at the main pin to sliding longitudinal motion at the crosshead) and Johnson (for one) goes into great detail about using the center of percussion to find the effective point where 'compromise' between the rotating end and the sliding end masses should be calculated. But the 'overbalanced' mass in the mains is one of the things that causes that wheel to dance ... and the problem is compounded because the acting counterweights in the wheel structure are of necessity inboard from the center of mass of the rods they are supposed to 'counterbalance', so there is a lateral couple building up that rocks the axle laterally, something that tends to complicate implementation of workable lateral-motion devices. As you may already have anticipated, the valve gear is still further outboard, and its inertial action may provide even more lateral unbalance... a reason behind adoption of Woodard's crosshead conjugated valve-gear drive on the PRR T1s.

The Australian late practice on a couple of classes was to try eliminating overbalance entirely (!) as the locomotives concerned were running on very light rail with uncertain-at-best maintenance and couldn't tolerate any balance hammer blow 'at all'. Naturally this led to much more pronounced nosing/hunting tendency, and greater surge felt at and behind the tender. The Langer balancer, when it can be fitted, will relieve the surge, but only better controlled lateral 'steering' will help resolve the former ... if you're wondering why the N&W J has such stiff lateral on lead and trailing truck centering, eliminating tendency for resonant hunting couples (which might emerge suddenly and quickly at high speed!) is one of the most significant reasons. (Note the implications for shock absorption laterally into the track, and the effect of high center of gravity as in the PRR DD1 electrics and some other early power...

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Tue Feb 18, 2020 1:14 pm 

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Location: Philadelphia, PA
There's another type of balancing here. The Reading used its M-1 2-8-2's on troop trains to and from Indiantown Gap where many WWII European Theatre Veterans were discharged.

One M-1 powered troop train derailed and the analysis was there was too little weight on the lead truck causing instability at passenger train speed (the same problem P&R 2-4-2's had had in the 1890's) and the solution was to move the air pumps to the pilot beam, plus a lead weight, to make the engines more stable.

Thus the engine needed balanced fore and aft, not the rotating machinery. A scale such as the one in Spencer would be the tool for this job.

The true solution came with equipping the 1947 group of T-1 4-8-4's (2120-2129) with steam and signal lines, relieving the M-1's of this duty.

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 Post subject: Re: Steam locomotive wheel balancing
PostPosted: Tue Feb 18, 2020 1:51 pm 

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I propose going forward that we distinguish the term 'balancing', with is normally applied to rotating machinery on locomotives, from 'balance' which is the calculation to assure correct weight distribution on the wheels.

Some idea of the care with which a company like Baldwin calculated these weights can be seen in Larry Brashear Jr's book on ATSF modern steam power. (There he's disparaging of the Baldwin stick-in-the-muds for raising things like the issue of different weight and distribution for a riveted 325psi boiler ... you may have a very different view on who was right and wrong after reading!) As a 'first pass' the weights would be calculated in ~10' increments, very tediously with effective moments, and these then applied as resultants to the suspension geometry. Of course in practice the engine would be physically weighed (with the appropriate balances and fixed-height reference fulcrum points) and fine-tuning done as necessary.

When this principle was ignored -- as it most certainly was on the T&P 'Silver Slipper' motorcar's lead truck -- "Hell followed with it..."

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