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.)
Allen Hazen
 
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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.

Cheers,
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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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