4-10-2 VS 2-10-4

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4-10-2 VS 2-10-4
Posted by De Luxe on Wednesday, March 08, 2017 2:34 PM

What was the reason why only SP & UP (and a couple of railroads in Brazil) used 4-10-2 types while the 2-10-4 types have been used by 11 north american railroads?

What made the 2-10-4 more popular than the 4-10-2?

Obviously the 4-10-2´s were not bad engines since they were used for 30 (SP) and 29 (UP) years long.

Another thing I would like to know is why all 4-10-2 types (those in the USA as well those in Brazil) have been built as 3 cylinder locomotives, while no 2-10-4 was ever built as 3 cylinder locomotive. I don´t think that the additional weight of a 3rd cylinder could be the reason for 2-10-4 types not having a 3rd cylinder because of only one pilot axle, because in Germany there were many 3 cylinder 2-10-0 types operating highly successfull from the mid 20s till the late 70s!

I know that the UP 4-10-2 types were later converted to 2 cylinder locomotives, but why there were no 4-10-2 types built as 2 cylinder locomotives straight out of the factory?

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Posted by daveklepper on Wednesday, March 08, 2017 2:59 PM

Choice between a 4-wheel or 2-wheel leading (pilot) truck depends on desired boiler length as compared with overall drivers wheel-base, which is in-turn related to driver size.  This assumes the loocomotive is not designed for very high-speed service, when a four-wheel leading truck is generally preferred.  And possibliy the 4-10-2's were thought of, like most 4-8-2's, as dual-service passenger and freight locomotives.

4-wheel tdrailing-trucks came into general use in the super-power era, with larger fireboxes.   Passenger 4-6-4's grew from 4-6-2's, 4-8-4's from 4-8-2's; mostly freight -2-8-4's from 2-8-2's, and logically 2-10-4's from 2-10-2's.  The UP's and SP's 4-10-2's are an earlier design than any of the 2- 10 -4's.

Instead of going to 2-10-4's in later designs, both the UP and SP preferred to develop their own and different articulated locomotives.  Not before the UP bought some 4-12-2s, their 9000s.

The three cylinder concept means more even power application, less track wear, and greater efficieincy, but much higher maintenance cost and complexity.  This is an issue independent of wheel arrangement.

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Posted by De Luxe on Wednesday, March 08, 2017 7:24 PM

"This assumes the locomotive is not designed for very high-speed service, when a four-wheel leading truck is generally preferred" ---> Well, aren´t 4 wheel pilot truck designs more suited for high speed service? That phrase doesn´t seem logic to me. Because 2 wheel pilot truck designs (like the 2-10-4) are less suited for high speed service. But they were built in much larger numbers than the 4-10-2. And another intresting fact is, that those 2-10-4´s on the T&P and CP were regularily used in passenger service (Sunshine Special, Dominion) and in case of the T&P were able to run at 80 mph (!), while the 4-10-2´s never ran faster than 60 mph and were only regularily used as passenger train road engines on the SP in the 20s.

Both 2-10-4 and 4-10-2 appeard in 1925. So they´re both designs from the same year. The SP 4-10-2 arrived in April, the UP 4-10-2 in May and the T&P 2-10-4 in November. I wouldn´t say that these few months of difference would have such an impact. Especially given the fact that in 1926 and 1927, UP (26) and SP (26 & 27) continued purchasing 4-10-2´s.

Looks like the only reason for the 4-10-2´s not being produced in larger numbers was the fact that they only were offered as 3 cylinder designs and therefore were rejected by many roads simply because of too much maintenance costs. Still doesn´t answer my question why no 2 cylinder 4-10-2´s were ever produced. But maybe it´s because a 2 cylinder 4-10-2 would not be more powerful than a 2 cylinder 2-10-2 and therefore would be inferior to all 2-10-4´s because of the smaller firebox size. A good example is the UP 4-10-2 after conversion to a 2 cylinder design: they only had around 72.000 lbs of tractive effort, while B&O´s 2-10-2´s had around 86.000!

 

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Posted by NorthWest on Wednesday, March 08, 2017 8:50 PM

In the mid 1920s, locomotive manufacturers were faced with a question of what to do now, since the conventional model they had been using wasn't applicable to the quickening freight speed trends. Lima's solution was super power four-wheel trailing trucks, but Alco's was three-cylinder locomotives. Their design required a four wheel pony truck to support the weight and provide for room for the third cylinder. There was no reason to build a 4-10-2 without the third cylinder because a 2-10-2 with larger drivers like the B&O's Big Sixes would accomplish the same thing.

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Posted by daveklepper on Thursday, March 09, 2017 12:56 AM

My initial answwer was in error in one important respect.  Three cylinder aqpplications ARE related to wheel arrangement.  Because the four-wheel pilot truck is necessary due to the added distance between the cylinders and the first driver axle to provide space for the congigated valve motion, deriving its operation from rods connected to the valve motion of both side cylinders.  If the two 4-10-2 designs had been built initially as two-xcylinder locomotives, they would surely have been built as 2-10-2s.

And sure Berkshires and Texas Types couild go 80 if designed for it.  But Hudsons and Northerns and Juibelees were designed for 100 or 100+.  Thjat is what I meant for by high-speed.  But you are right, high speed was not the reasonfor the 4-wheel pilot truck on the 4-10-2s.  the space for the congigated valve-gear was the reason. 

As far as I know, the onliy three-cylinder locomotives that did not have a 4-wheel pilot truck were swichers withouit any pilot truck.  I think Union Railway, steel-company-owned, had some 0-10-0 three-cylinder switchers.

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Posted by BigJim on Thursday, March 09, 2017 7:59 AM

daveklepper
This assumes the loocomotive is not designed for very high-speed service, when a four-wheel leading truck is generally preferred.

So much for assuming! Witness the high speed N&W Class A 2-6-6-4.

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Posted by DS4-4-1000 on Thursday, March 09, 2017 8:14 AM

daveklepper
As far as I know, the onliy three-cylinder locomotives that did not have a 4-whjeel pilot truck were swichers withouit any pilot truck. I think Union Railway, steel-company-owned, had some 0-10-0 three-cylinder switchers.

Indianna Harbor Belt had 3 cylinder 0-8-0s.

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Posted by daveklepper on Thursday, March 09, 2017 8:19 AM

Was the A-2 a 100 mph locomotive?   None of the A-class were designed for more than 80 mph.  The only high-speed N&W locomtives were the Js.

A 4-wheel pilot truck is inherently stable in itself.  Its pivot can be anywhere between its center and its rear axle.   This combined with spring-and-damper controlled lateral motion can really help guide the locomotive smoothly into curves.   The two-wheel truck requires a long pivot arm stretching back toward the drivers and even then will have a tendency to not align perfectly with the rails on curves.

Many of the two-wheel pilot truck modern designs resulted from the simple fact that a locomotive of roughly the same design but with the four-wheel pilot truck would not fit on the railroad's turntables.  The L&N's are one example.

Mind you. I think that Berkshires and Texas Types are great machines.  Many of us think the Ripley AT&SF 2-10-4 is the best non-articulated freight locomotive ever built.  Others might choose the C&O's and PRR's.  But for realliy high speed, all designers chose 4-wheel pilot trucks, the Milwaukee's Atlantics and Hudsons, the Hudsons of other railroads, and the Northerns.  In Great Britain, the Pacifics remained the speed queens, with the exception of the Ten-wheelers of the Great Western, but again all with four-wheel pilot bogies.

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Posted by timz on Thursday, March 09, 2017 1:42 PM

daveklepper
As far as I know, the only three-cylinder locomotives that did not have a 4-wheel pilot truck were swichers withouit any pilot truck.

MP and L&N each got one 3-cyl 2-8-2, and it seems Wabash got five. Any other exceptions?

Offhand guess: no 3-cyl 0-10-0s or 0-10-2s in the US.

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Posted by daveklepper on Thursday, March 09, 2017 2:20 PM

How long did the exceptions you mentioin last as 3-cylinder locomotives?  Did they show any tendency to derail more often?  (Not that conversion to 2-cylinders would correc the problem.)

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Posted by BigJim on Thursday, March 09, 2017 3:00 PM

daveklepper
None of the A-class were designed for more than 80 mph. The only high-speed N&W locomtives were the Js.

And 80mph isn't high speed? Tell me what percentage of all of the track in the U.S. during the steam years was advertised for over 60 mph. Tell me what was the average speed of all trains back then or even today for that matter. 

A co-worker told me how back in the fifties he was traveling down Rt. 460 in eastern Virginia doing 80 on his motorcycle when an A on coal train passed him "like I was sitting still". The Class J had 70" drivers as did the Class A. I wouldn't put it past an A to go a lot faster than what you want to give it credit for.

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Posted by Firelock76 on Thursday, March 09, 2017 5:47 PM

Big Jim, I've heard the same from local railfans here in Virginia, that is trying to chase a Class A with a coal train down Route 460.  The A's ran away from them, and all they (the railfans) got out of the chase were speeding tickets!

A lot of speed traps down Route 460, so if you head down that way mind your "P's and Q's!"

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Posted by PRR8259 on Thursday, March 09, 2017 9:15 PM

First, during the steam to diesel transition era, speeds were higher than today.  For 4 years during the 50's, the ACL mainline was posted for 100 mph passenger running, then was reduced to only 90.  There are numerous tales of Illinois Central passenger trains going well above 100.

Before all the N&W fans get upset, I think Dave was trying to separate merely fast running from the elite speed engines and 80 mph seems like a reasonable figure.

Besides, even the "slow footed" UP 4-12-2 was capable of running 70 mph on freights...that just was hard on early, unimproved frames, track, and reputedly kidneys, as they were rough at high speed, excepting later improved ones, as documented by Mr. Kratville.  With all the final upgrades, they could roll.

John

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Posted by daveklepper on Friday, March 10, 2017 1:13 AM

 

OK.  YOU WIN.  

 A trwo-axle poney truck is OK for high speed.  But for VERY high speed you need a four axle.   The point is a J could go 100 mph even with 70-inch drivers, with modern disc wheels and very fine balancing, as well as a 4-wheel poney truck.  An A may have topped 80 mph, and I do not know the accuracy of the motercycle speedometer, but don't try to tell me an A could match a J in top speed.

After the Burlington and Sante Fe 2-6-2's of around 1900, name one locomotive designed expressly for fast passenger service that had a 2-wheel poney truck.

The CP Selklirks were designed for passenger service, but not for top speed,  instead for mountain climbing.

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Posted by RME on Tuesday, March 14, 2017 2:58 PM

daveklepper
The point is a J could go 100 mph even with 70-inch drivers, with modern disc wheels and very fine balancing, as well as a 4-wheel pony truck.

Ah, Mr. Klepper... can you show me a picture of a J with modern disc wheels?

It's much more 'to the point' that a 2-wheel lead truck would have more severe problems performing both the necessary high-speed guiding and the yaw control involved in Voyce Glaze's version of low overbalance.  The situation is stiff enough with the pin-guided four-wheel truck.

It's the "later" version of the N&W 2-wheel lead truck and its equalizing arrangement that is amenable to high speed; the 'catch' again is that even this truck will run into significant oscillation and probably mechanical coupling into a dangerous resonance if you were to push it into 100mph territory.  MUCH more 3-axis compliance and damping would be needed in a two-wheel lead-truck design, and it would be highly desirable to minimize yaw force (as on the German 19 1001, which was a nominal "Mikado" arrangement as far as its lead truck was concerned).

It is difficult to get a fully straight answer about the use of 2-wheel lead trucks in the period after 1900.  Haas and some others see a vicious conspiracy in the NYC-driven suppression of the LS&MS Prairies, and I am still wondering how objective the guiding instability in the original Wilgus S-class electrics actually was (the kludged 'fix' wedging Adams trucks into the limited space being part of the issue leading to Wilgus' resignation!) vs. massive overspeeding apparently on the general level of the Malbone Street Surprise.  However, by far the consensus is that a simple and cheap pin-guided truck works quite well far into the speed range where active control, variable geometry, and good shock absorption would become essential on a two-wheel Bissel.

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Posted by daveklepper on Wednesday, March 15, 2017 1:11 AM

I would define anything the N&W did for the J as modern, regardlesss of what type of actual driver wheels were used.  They apparently had the science of couinterbalancing down to a fine art on all their locomotives; otherwise we would not have the A class exceeding 70 wihtout problems.  

i appreciate your providing the real details of why a 4-wheel pilot truck is inherently better for really or very high-speed operation than a 2-wheel.   And, of course, neither the S or T or even the P motors ever got much above 70 mph ever.  

At the entrace to a ciurve, or at the transition of a reverse curve pair,  you would ideally like the pivot of the 2-wheel truck to be close to the truck axle, but in the curve itself all the way back to the center of the drivers' wheelbase.  No way of having it both ways and still keep the wheels from derailing.  So the interface of the wheels with the rail is more of a compromise than with a pinned fouir-wheel truck.  And complicated geomterical control is difficiult, hard-to-maintain, and seldom accurate under all conditions.

Was Wilgus connected with the BRT, as well as the Central?   (Malbone St. reference)

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Posted by RME on Wednesday, March 15, 2017 1:20 PM

daveklepper
At the entrance to a ciurve, or at the transition of a reverse curve pair, you would ideally like the pivot of the 2-wheel truck to be close to the truck axle, but in the curve itself all the way back to the center of the drivers' wheelbase.

I have always looked at this a bit differently: the 'ideal' place to put that pivot would be the center of the rigid wheelbase, with good lateral motion on the first driver pair(s) doing some of the curve-shock attenuation.  Where the 'variability' is probably best applied is in the lateral compensation.  Stability is a very different thing for a lead truck using Voyce Glaze-style overbalance, as the truck has to control the yaw forces (including any momentum) in addition to its own curve-following and self-guiding tasks.

Perhaps interestingly, a pin-guided truck in the trailing position is nowhere near as dynamically stable as a good Bissel with angled rocker compensation, at least when the locomotive is running forward.  Reading discovered this and a couple of other things that should have been clear from good contemporary fabricated trailing-truck practice (and would become even more clear with the second Delta design) when they experimented with symmetrical pin-guided trucks on their 4-4-4s just before WW1.  (I do not know whether the two Baltics from just a couple of years earlier had similar issues with their pin-guided trucks -- this by the way is why a 4-6-4 with a Bissel rear truck is a Hudson, but one with a rear pin-guided truck, commuter double-ender or not, is a Baltic, except on Milwaukee).  The Germans didn't remember this when designing their high-speed tank engines in the '30s, and at least one of those had an air-activated mechanism that moved the pivot point to give stability in both directions... if I remember correctly, as-built the critical speed was no more than about 81mph so the air device was beneficial.

... complicated geometrical control is difficult, hard-to-maintain, and seldom accurate under all conditions.

The actual geometric accommodation needed for a 2-wheel lead truck to be reasonably stable when provided with appropriate lateral restoring force is not that difficult, and much of the actual curve-following physics is accommodated in the fixed wheelset in the same way it is according to Wickens.  Were the two wheels permitted to revolve at different speeds (e.g. on stub axles, as they would be if for example you wanted to implement some kind of Ackerman steering) the situation would become more difficult, and consequences of some comparatively likely system failures (including resonance effects) could quickly destroy any nominal advantage from that idea.

It may also 'pay' to remember that these trucks carry considerable engine weight, and some of the effective weight transfer that occurs in curving will need to be accommodated in the truck suspension and compliance effectively.  If this can be done in a way that aids nominal stability, I would think higher speeds than those predicted from static geometry might be achievable.

Was Wilgus connected with the BRT, as well as the Central? (Malbone St. reference)

Not that I know of.  It was just a bit of black humor: there was a terrible wreck just a couple of days after the GCT electric service started, which according to Staufer was caused by the same kind of wild overspeed observed in the Malbone St. wreck.  Very promptly -- and apparently without involving Mr. Wilgus, the engineer in charge -- the engines were sent to Harmon to be fitted with four-wheel trucks, something Wilgus thought highly unnecessary and a slur on his professional ability.

Staufer's account of all this was written half a century after the events, and it will be interesting to see what Mike comes up with, both in newspaper accounts of the situation (including Wilgus resigning right at the moment of his greatest triumph) and in engineering discussions of vehicle instability.

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Posted by selector on Wednesday, March 22, 2017 12:52 PM

Firelock76

Big Jim, I've heard the same from local railfans here in Virginia, that is trying to chase a Class A with a coal train down Route 460.  The A's ran away from them, and all they (the railfans) got out of the chase were speeding tickets!

A lot of speed traps down Route 460, so if you head down that way mind your "P's and Q's!"

 

...and A's.

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Posted by rcdrye on Wednesday, March 22, 2017 3:39 PM

While the term "Bissell Truck" is often used for a two-wheel lead truck, it properly refers to Levi Bissels's original 1857 design, with a trailing pin and inclined planes to center it.  The two-wheel truck that actually worked was designed by William S. Hudson of the Rogers Locomotive Company in 1864.  Hudson's design incorporated swing links (also used by others) and an equalizing lever connected to the main driver equalizers and was used right up to the last Berkshires.  NYC's original T-motors appear to have been equipped with either Bissell-type pony wheels or with non-equalized swinglink pony trucks. I haven't been able to verify that the LS&MS prairies had Hudson-style trucks, but it seems very likely to me. It's quite possible that the reputed instability of the LS&MS prairies had more to do with inadequate driver balancing than with poor equalization.  At high speed the transfer of weight from side to side as the drivers turned may have been too much for the truck design used on the Prairie.

It's not quite as necessary for four-wheel lead trucks to be equalized to the drivers. 

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Posted by daveklepper on Wednesday, March 22, 2017 3:53 PM

The AT&SF and CB&Q Praries seemed to outlast those on the Central.  Maybe you have the reason why.  But originally designed for passenger service, they ended up on local freights.

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