"Hopping" steam engines

Hi All--
I have no memories of steam, even though I know that I saw a few in the early 50s. My brother, however, is 14 years older than I am, and can remember steam locos on the PRR Morrow secondary, in Ohio.

He said that he would watch them starting up, and that the engine would actually "hop" in place, as they were opening up the throttle. It would be slamming up and down on the rails, before it began to move forward. I said that I had seen steam engine drivers slipping as they began to move, (on film), but what's he describing is something I've never heard about.

So for those of you who either knew steam then, or work with it now--is this how some engines start up? All engines? Or was it something that couldn't be avoided under certain conditions?

IF it actually occured, it would likely be caused by VERY badly counter-weighted drivers... the reciprocating masses causing a vertical movement in the engine.

I've never seen a steam engine do it, but, I have been in a diesel when it occurs.. NOT a good thing to experience as this usually predates a ripped knuckle by about... 6 seconds or so.

I think it would be a bad idea to have this happen as a regular thing (a well-maintained locomotive ought to be well-enough balanced to keep it from "hopping" visibly), but it can happen. The new York Central, as a test, chained a Hudson in place and greased the rails so the drivers would slip freely, and did manage to get the locomotive to bounce visibly off the rails... when the drivers were rotating at a speed equivalent to running something like 150 mph.

jgallaway81 wrote:IF it actually occured, it would likely be caused by VERY badly counter-weighted drivers... the reciprocating masses causing a vertical movement in the engine.

I guess you mean the driver counterweights are too heavy-- but if that were the problem the effect would be proportional to speed. So unless the drivers were slipping at several revolutions per second...

How would counterweights get too heavy?

Thanks for the replies. This particular line was never a big revenue generator, and may have always had sub-standard track and/or rolling stock.

Allen Hazen wrote:The new York Central, as a test, chained a Hudson in place and greased the rails so the drivers would slip freely, and did manage to get the locomotive to bounce visibly off the rails... when the drivers were rotating at a speed equivalent to running something like 150 mph.

Why did they do this test?

The test was performed, if I recall what I read many years back correctly, during a time when bad PR in the trade papers about faulty counterbalancing in the NYNH&H I-5 class had brought balance on main line, high speed passenger locomotives to the forefront and both BLW and American Locomotive were forced to make some changes in their calculations for balancing. The I-5 locomotives were slipping when starting heavy trains under certain adverse conditions and the engines would in some cases actually lift their drivers, pounding and sometimes kinking the rail. Some have said the I-5's should have had boosters, but some have said properly counterbalanced (and cross-counterbalanced) engines shouldn't have done this in the first place. It would seem that American Locomotive had the calculations better on the NYC J-3a. I'm pretty sure the I-5's were modified to correct the problem.

-Will Davis

Will--
Thanks for that: I didn't know about the I-5 issues!
The New York Central seems to have had an active, on-going, research operation: tests could have been done in response to almost anything and might lead to operational changes or modification to equipment. My source was "New York Central Hudsons" by Brian Reed (Windsor, England (U.K.), no visible date: in the long-lamented "Locomotive Profiles" series). Two passages are relevant, the first to show that NY Central sometimes did make major after-purchase modifications to its locomotives:

"At first the J-1 engines were not cross-balanced for couples; this was effected later, around 1929-1931, after Kiefer had studied the British Bridge Stress Committee's voluminous report; and the smoother running obtained was said to permit shorter running cut-off and to give a reduction in track stresses. The latter was an important point on the N.Y.C., for one of the first thorough investigations into rail stress occasioned by impact loads had been carried out by one of the road's civil engineers."

As for the wheel-slipping tests, no specific motive is stated, but there are details I didn't remember off-hand when I posted before (5 posts back). After a paragraph describing the efforts to keep the weight down when the J-3 was designed, we have:

"Hammer blow at wheel-diameter speed (79 m.p.h.) was 5,900 lb. for front and rear coupled wheels and 4,400 lb. on the drivers, decreases of 50-51 per cent on J-1e values. ... Slipping tests on a length of greased rail with a J-3a in 1938 showed no wheel lift until an equivalent speed well above 130 m.p.h. was attained. Actual speed at which wheel-lift might begin was largely unknown, as it was not possible to simulate any particular speed, and the measurements and observations featured a big gap between 135 m.p.h. (no lift) and the next higher measurement of 164 m.p.h. (pronounced lift)."

Evidently a LOT of work went into refining the design to minimize "hammer blow" was done between 1931 (when the las J-1e were built) and 1937 (when the J-3 was introduced). I assume the detailed design was to some degree a collaborative effort between Alco's engineering staff and Kiefer and his staff at N.Y.C.: does anyone know how this worked, and how much of the input was from Supplier and Customer engineering personnel? (For comparison: according to something I was re-reading last night, the design of the Pennsylvania Railroad's GG-1 locomotive involved conferences, held at Baldwin, of engineers (& industrial designer) from Baldwin, Gibbs & Hill, Westinghouse, GE and PRR.)

http://www.steamlocomotive.com/northern/acl.shtml
I recall reading somewhere else that these engines would lift off the rails at speed. Since they were built in 1937, I expect they would also have been in the minds of those testing the J3.

What I find interesting is that both the NH I-5 4-6-4 and the ACL R-1 4-8-4 were built by Baldwin. I wonder if Baldwin's experience is what lead them to the Duplex concept?

Stuart

http://www.steamlocomotive.com/duplex/
Remember, the B&O built a 4-4-4-4 before the PRR/Baldwin engines. It was built around the time of these "hopping" engines, but I'd expect learning about the problem and designing a totally new engine to take longer. There was probably some earlier locomotive that had a similar problem.

I haven't found (in the few sources I've consulted) much about the chronology of Duplex-drive steam locomotive developments. Idea to outshopping a completed locomotive takes time, so I doubt the B&O's 1937 "George H. Emerson" could have been a response to problems specifically with the New Haven and ACL locomotives! But it could well have been inspired by consideration of the KIND of problem they later illustrated.

Baldwin had been trying to sell railroad managements on the Duplex idea for some time before PRR ordered the T-1 prototypes (& had even, I recall reading, been thinking of building a demonstrator). I ***think*** the Baldwin engineer behind the idea was named Johnson, but I don't know very much about his thinking...

I have found an old (September 1981) "Trains" article on the New Haven Railroad's I-5 4-6-4 which (like the ACL's R-1 4-8-4) had a bit of a "hopping" problem. I have posted a summary of the bits relevant to this topic on the "New Haven" forum ("Fallen Flags" section of the Board Index). There is more detail in the article than I have posted there, which I can provide if anyone is interested.

Alco and Baldwin seem to have had different takes on how to balance the drive wheels on high-speed steam locomotives, with the result that the New York Central's J-3 Hudson was less of a "hopper" than the New Haven's I-5.