Blind drivers vs. lateral motion devices?

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Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Fri Aug 22, 2014 2:29 pm

When did lateral motion devices on the driving axles of steam locomotives start to get used? "Blind" (flangeless) driving wheels on at least some axles seem to have been a common feature in early 20th C steam locomotive design (the Pennsylvania Railroad's I-1 Decapods famously had three axles with blind drivers when they were introduced, though later only the centre driving axle was so equipped), but some of their later steam designs with even longer "rigid" wheelbases had flanges on all drivers: I assume that lateral motion devices are what made the PRR's designers think this was reasonable. Followup with links to diagrams to follow up.

(Cross-posted to PRR forum.)
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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Fri Aug 22, 2014 2:53 pm

From a Web site devoted to the Altoona Works (past and present-- there are also drawings of the cabs used on current NS diesel rebuilds), here is the I1 as built: note the three blind driving axles:
http://www.altoonaworks.info/graphics/drawing_i1s.jpg
(From the format and, particularly, the style of the caption, I'm guessing that this drawing appeared in some edition of the "Locomotive Cyclopedia.")

The PRR's penchant for putting flangeless drivers on their locomotives wasn't limited to types with five driving axles-- here is the H6 Consolidation, with the second and third drivers blind:
http://www.altoonaworks.info/graphics/drawing_h6.jpg

Nor was the use of blind drivers on eight-coupled power limited to the very start of the 20th C-- here is the C1 switcher of 1925:
http://www.altoonaworks.info/graphics/drawing_c1.jpg
(Mind you, if Alvin Stauffer's "Pennsy Power" is to be trusted, the C1 wasn't one of the PRR's outstanding successes, being derailment prone…)

Indeed, sometimes the centre drivers of six-coupled locomotives were flangeless-- here is a well-known Pacific:
http://www.altoonaworks.info/graphics/drawing_k4.jpg
(Another drawing shows the experimental K5 Pacific of 1929… also with the centre driver blind.)

Indeed… Here is an 80-inch drivered Atlantic, apparently built for Atlantic City trains (where the Reading even used 4-2-2 power):
http://www.altoonaworks.info/graphics/drawing_e1.jpg
It LOOKS as if the first driver was blind-- can this really be so?

(Cross posted to PRR forum.)
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Re: Blind drivers vs. lateral motion devices?

Postby Pneudyne » Sat Aug 23, 2014 7:14 pm

According to A.W. Bruce (“The Steam Locomotive in America”) the lateral motion device was first developed in 1914. It went through a couple of phases before the definitive version with compressed coil springs arrived. Bruce does not give dates for the subsequent developments, but as I understand it, the final type was new at the time that the UP 4-12-2 was developed; the latter having had lateral motion devices on the 1st and 6th driving axles.

Somewhere I have read (it might have been in the Reed Locomotive Profile) that all North American 4-8-4s had at least one lateral motion device. Some had two, and a few had three such devices (e.g. D&H K-62 and UP FEF-2 & 3.) Its use on 4-6-4 types might have been rare, but I think that the Milwaukee F-7 was so-fitted. The D&H Challenger had one on each engine unit, the UP “big” Challengers had two on each unit, and the UP Big Boy three on each unit. The UP had evidently taken very much to heart the Alco/Blunt philosophy on both lateral and vertical compliance. The PRR T-1 had two devices, one each on the 1st and 3rd driving axles.

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Re: Blind drivers vs. lateral motion devices?

Postby Pneudyne » Sat Aug 23, 2014 7:26 pm

Allen Hazen wrote:Indeed… Here is an 80-inch drivered Atlantic, apparently built for Atlantic City trains (where the Reading even used 4-2-2 power):
http://www.altoonaworks.info/graphics/drawing_e1.jpg
It LOOKS as if the first driver was blind-- can this really be so?


Possibly, if it had a rigid-bolster rather than a swing bolster four-wheel leading truck. With a rigid-bolster truck, the rigid wheelbase is effectively the distance from the leading truck centre-pivot to the rear driving axle. When the truck enters a curve and moves laterally, so does the front end of the locomotive. So the leading drivers are laterally displaced, accommodation of this movement requiring either thin or no flanges. Another way of looking at is as if there were a phantom axle, part of the rigid wheelbase, positioned at the truck pivot centre, in which case the leading driving axle may be viewed as effectively being a cntre axle in the rigid wheelbase. Once lateral-motion swing-bolster trucks came along, then the situation changed and the leading driving wheels did require flanges.

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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Sat Aug 23, 2014 11:24 pm

Pneudyne--
Thank you for that account of things! … I suppose, if I really want to understand the history here, that I ought to look into when lateral-motion trucks began to be used! (I have a VERY small steam locomotive technical library… I'll look and report back if I find anything interesting.)
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Re: Blind drivers vs. lateral motion devices?

Postby Statkowski » Sun Jan 27, 2019 10:09 pm

Lateral-motion devices = more moving parts. More moving parts = more things to break or wear out.

Blind drivers were a simple fix for a known problem - sharp curves, mostly on branch lines. Imagine Pennsy I-1sa 2-10-0s operating on 10-degree curves (required a 10-mph speed restriction when operating in reverse).
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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Mon Jan 28, 2019 10:50 pm

Statkowski--
Words of wisdom, definitely!
So, if you were choosing, you might want to invest in lateral-motion devices on high-performance units intended for intense use and regular, daily, attention from maintenance staff: first-line passenger power, for example. And you might prefer the simpler, lower maintenance, solution if you were, say, buying a 598-unit fleet of drag freight engines (particularly, of course, if you were buying said fleet in the 1920s when l.m.d. were still under development as advanced technology... Grin!).
Note, however, that many railroads got l.m.d. on freight power: 4-6-6-4 and (non-passenger) 4-8-4. Do you think railroads making that choice were spending too much on their freight power? (Or maybe, with accelerated freight schedules, the relevant considerations for fast freight engines in the 1930s and 1940s were more like those relevant for passenger power earlier.)
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Re: Blind drivers vs. lateral motion devices?

Postby Pneudyne » Wed Jan 30, 2019 4:05 pm

Given how widespread was the application of the lateral motion device to American steam locomotives in the later era, a reasonable empirical inference is that the railroads viewed them not so much as a maintenance liability, but an asset whose benefits outweighed its initial and ongoing costs. The payback was in better tracking and riding, particularly at higher speeds, lower flange wear rates and probably lower railhead gauge surface wear as well.

As well as on higher-speed locomotives with driver sizes of 69 inches and upwards, it was also used on slower, 63-inch drivered locomotives, examples being the DTI 2-8-4 and the DMIR 2-8-8-4.

Something to bear in mind is that Alco referred to it as a lateral cushioning device. As well as safely allowing greater driving axle lateral freedom than had hitherto been used, it was also used in situations where previously small amounts (I’d guess up to around half an inch) of uncontrolled lateral freedom had been allowed, with the result that there could be some slamming action as laterally moving axleboxes hit the limits.

I should imagine that long wheelbase locomotives without lateral motion devices and which appeared to rely on the use of blind drivers on one or more axles also required small amounts of uncontrolled lateral motion some axles in order that they could get around sharp curves. So design may not have been straightforward choice between the simplicity of blind drivers or the greater complexity of lateral motion devices. Rather, once the lateral motion device was available, the question was whether the required lateral motion on some driver sets should be uncontrolled or controlled. If “controlled” was chosen, then as the lateral motion device allowed the safe realization of larger lateral movement than was hitherto the case, it introduced the possibility of eliminating blind drivers altogther.

The Pennsy 2-10-0 design might have predated the availability of the lateral motion device. But the Pennsy evidently appreciated its virtues – I understand that its Q-2 had one on each of the five driving axles.

Lateral motion devices were sometimes also used on the leading axle of four-wheel trailing trucks, I think those of the traditional longer wheelbase design with smaller diameter wheels on the front axles. The short-wheelbase type with equal wheel diameters probably would not have needed them.


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Re: Blind drivers vs. lateral motion devices?

Postby Statkowski » Wed Jan 30, 2019 8:53 pm

Meanwhile, on the numerous low-speed, sharp-curved branches in coal country, the older, pre-LMD steamers kept doing what they did.
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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Thu Jan 31, 2019 1:31 am

Re the PRR Q2--
The PRR diagram at
http://prr.railfan.net/diagrams/PRRdiag ... z=sm&fr=ge
(which I accessed through the "Fallen Flags" site) specifies amount of lateral play on each of the five driving axles. Not conclusive, I suppose, since in some or all cases it may have been uncontrolled lateral motion, but at that late stage in steam development, I'd bet on controlled.
(Statkowski-- yes, and we know the I-1 outlasted the Q-2 in service by several years! But -- though it pains me, as a long-time I-1 fan, to say this -- a railroad has to use the power it HAS, and the continued use of non-LMD power in the late 1940s and early 1950s would have made good economic sense even if it was not TECHNICALLY ideal. In judging the comparative advantages of LMD and non-LMD locomotives, we have to consider a counterfactual: if railroads had been buying new steam locomotives for service on the low-speed sharp-curved branches in coal country instead of replacing them as fast as they could with diesels, would they have gone for traditional, non-LMD, designs or modernized, LMD, designs?)
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Re: Blind drivers vs. lateral motion devices?

Postby Statkowski » Thu Jan 31, 2019 9:52 am

If LMDs provided no appreciable advantage in 25 mph territory, and the engine design was unsuitable for Main Line service, then I'd assume they'd get new steamers without LMDs, if there was a price differential. Every now and then you've got to listen to the bean counters.
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Re: Blind drivers vs. lateral motion devices?

Postby Pneudyne » Wed Feb 06, 2019 3:55 pm

Re the PRR Q-2, the RME 1946 January article as reprinted in Train Shed Cyclopedia (TSC) #49 confirms that it had LMDs on all five driving axles. Additionally, the #3 drivers were blind. The allowed lateral motions, from 1st to 5th driver sets, were 2¼”, ½”, ½”, 13/8”, ½”. Total wheelbase was quoted as 26’4½”, and rigid wheelbase as 20’4”. I’d guess that the rigid part excluded the 1st set of drivers. One may see that the 3rd set would need more freedom than the ½” lateral allowed, hence the use of blind tyres. Possibly flange thickness varied amongst the drivers, as well.

The Q-2 is the only example that I have found that had LMDs on all of the driving axles. It is also the only example that combined an LMD and blind tyres on the same axle. One has the impression that the PRR wanted to avoid any lateral shocks and binding, perhaps not just to ensure good tracking and riding, but also to avoid events that might incite slipping.

Pneudyne wrote:Lateral motion devices were sometimes also used on the leading axle of four-wheel trailing trucks, I think those of the traditional longer wheelbase design with smaller diameter wheels on the front axles. The short-wheelbase type with equal wheel diameters probably would not have needed them.


Not so. The short (54-inch) wheelbase trailing truck of the B&O 2-8-8-4 had a Timken LMD on its leading axle. It had Alco LMDs on its 1st and 5th driver sets. (That from RME 1944 June via TSC #47).

Re the modern branch line locomotive case, apparently CN did map out a couple of such designs, one 2-6-2 and one 2-8-2, although none were built.. Whether enough information has survived to determine whether either – but particularly the 2-8-2 - used an LMD and/or blind tyres I do not know. The C&O reverted to a pre-WWI 2-6-6-2 design for its final (1949) batch of coal branch locomotives. It did undertake some modernization, though, in that these used a latter-day single-plane, single-pivot articulation joint in place of the traditional two-plane type. That was gleaned from observation of the example at the Baltimore museum a long time ago. I didn’t notice whether it used LMDs, but with a short-wheelbase six-coupled driver set, neither that nor blind tyres were likely to have been needed.

Whether anyone would have contemplated a light 2-10-0 for branchline service in the late steam era is a moot point, but the CN example suggests that trailing trucks might have been preferred to make for easier backing-up. But in the case that a light 2-10-0 was considered to be desirable, then fitting the rearmost driving axle with an LMD and allowing a reasonable lateral excursion, say 2 inches or so, could be beneficial from the viewpoint of backup moves.

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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Thu Feb 07, 2019 1:02 am

That the Q-2 had l.m.d. on all five driving axles, with the third drivers blind, is also reported in "Pennsy Q Class: Classic Power 5" (published by N.J. Intrnational: neither the author nor the publication date is given on the title page (!), but the an interior page suggests that E.T. Harley wrote at least part of it, and the Library of Congress number, 82-081755, suggests publication in the early 1980s). The 1946 "Railway Mechanical Engineer" article is listed in the bibliography, though, so this is probably not an independent source.
It does present a further, minor, mystery. L.m.d. on five axles means a total of ten l.m. devices. On page 20, in the paragraph describing the l.m.d. arrangements of the Q-2, it is said that 7 of the devices were from Alco, with three made by P.R.R. So at least one driving axle must have had an Alco device on one side and a (presumably cheaper?) home-made one on the other!

My impression is that Alco did a lot of the earlier development work on l.m.d., but evidently it didn't have a monopoly on their manufacture in the 1940s.

(I have somewhere seen drawings of at least one of the late CN proposed steam designs, so there is information on them... somewhere. I'll report back if I find anything.)
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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Fri Feb 08, 2019 12:36 am

About that Q-2 book mentioned in my previous post...
(1) There is a paragraph about the author on p. 87. E.T. Harley, born 1927, was a railfan (started taking photos of trains while in junior high school) and a mechanical engineer: joined the P.R.R. in 1949 on graduating from Northwestern University, ultimately became "P Company's" last (before the PennCentral merger) Assistant Chief Mechanical Officer - Locomotive. (Started his Pennsy career early enough to have ridden in the cab of a Q-2 on a Fort Wayne - Chicago freight.)
(2) The book contains a reprint of the 1949 "Railway Mechanical Engineer" article that Pneudyne mentioned. Also very detailed (HO scale) drawings of a Q-2, and a 1943 P.R.R. engineering dept. drawing of a "Q-1.5": an early proposed Q-2 design, later revised, with "cosmetic" features taken over from the Q-1.
(3). Also included, some internal documents, including a letter from a P.R.R. purchasing agent to Alco, enquiring about the royalties Alco would want for seven lateral motion devices. (That one surprised me: I had assumed that the devices themselves were manufactured by Alco, and that any patent royalties would have been included in the price...) Explaining that "Because of some design details, only 7 of the American Locomotive Company devices will be used; the remaining 3 will be a Pennsylvania Railroad design."
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Re: Blind drivers vs. lateral motion devices?

Postby Allen Hazen » Fri Feb 08, 2019 1:13 am

Yet more information I don't know how to interpret!
The Q-2 book also has a P.R.R. locomotive diagram for the Q-1, also available at the "Fallen Flags" rail image site at
http://prr.railfan.net/diagrams/PRRdiag ... z=sm&fr=ge

The Q-2 diagram (also at "Fallen Flags," but not in the book) gives "total lateral" figures for each driving axle. The Q-1 diagram in addition gives a "Tire Setting" for each driving axle: 53 inches for the first three, 53 1/4 for the last two. ("Total lateral" being 2 1/4 inches, 3/8 inch, 2 1/4 inches, 3/8 inch, and 3/8 inch for first through fifth driving axles.)

"Tire setting" is also shown on the diagrams (at "Fallen Flags") for the T-1 (slightly different values in three diagrams) and for the J-1.

I know some railroads used thinner flanges on the tire of some drivers. Is setting the tires in different positions -- closer to the centre-line of the locomotive on some, further on others -- an alternative means of getting the same effect with tires of uniform profile?
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