Alco diesel hydraulic

[Pneudyne]

Pity the Class 21 and Class 22 differ inso MANY respects (though you suggest good reasons why they may have): it makes it harder to regard them as a "controlled experiment" to compare the two transmission types! (And thank you for the diagrams: the drawings in the Cooper book are exterior side views, not general arrangements diagrams!)

I suspect that had NBL endeavoured to make the 21 and 22 closer in equipment layout, it would have involved non-trivial compromise. They might be about as close as one could get, at least for single-engined locomotives. With two engines, the differences between a homologous pair might be smaller, although that would depend on the specific drive arrangements chosen for the diesel-hydraulic case.

Cooper does give a small bit of information about the Class 22 truck ("bogie" in British English) design:
"Mechanical construction was on similar lines to the D600 class [= BR Class 41], the bogies being a two-axle version of the Class D600 three-axle bogie."

Yes, the class 22 truck was a two-axle version of that used for the class 41/D600, which in turn was a modified version of the LMS Ivatt/Fox design used under LMS diesel-electric prototypes 10000/1, and which design in turn was said to have been inspired by the EMD/Blomberg A1A design used under the EMD E-series passenger locomotives. NBL couldn’t work out how to drive all three axles – the 41/D600 was originally intended to have a C-C wheel arrangement - so settled for A1A-A1A.

Given the remark on the Class 41,
"Mechanical construction of the locomotives was in the substantial style favoured by the BTC [= British Transport Commission, the gornment "parent" o the railways] and also in the tradition of a firm with a long and famous history of building steam locomotives,"
This doesn't inspire confidence!

In fact that form of construction was really NBL’s choice. For the D600, it had followed LMS 10000/1, which had used a “strength” underframe construction rather than conventional truss-sideframe cab unit construction for extraneous reasons. All of BTC’s own-design, own-production first generation diesel-electric cab units were of truss-sideframe construction, as were most, if not all of those acquired from the industry. NBL had lobbied the BTC to try some diesel-hydraulic locomotives; it had agreed (or perhaps there was some politicking and it was told to agree) and had actually ordered some from NBL ahead of the pilot-plan diesel locomotive orders. BTC decided that the Western region should have the diesel-hydraulics – which it may have regarded as being of passing interest, probably not foreseeing that by doing this it would create a monster. The BTC was probably unfairly blamed for the way the D600 turned out. It has been argued elsewhere that had it [the D600] been entrusted to a competent builder, the outcome could have been quite different. If the BTC was guilty of anything, it was probably of not caring enough about this sidebar issue to better direct and control NBL, although that could have been mission impossible anyway.

Returning to diesel-electric vs diesel-hydraulic locomotive equipment layouts, the Alco DH643 may be compared with the Alco C855: Allowing that the DH643 is roughly three-quarters of a C855, there are some similarities, perhaps more than in the BR 21, BR22 case.

Alco DH643.gif

Alco C855.gif

Cheers,

[Allen Hazen]

Pneudyne--
I've been meditating on a reply to your PREVIOUS post (the one with the very interesting article from the May 1966 "Railway Transportation" -- for which, thank you very much! -- on BR'scomparison of d.h. and d.e. express locomotives), and already you've written more for me to think about!
Will reply in time. Meanwhile, one comment on your latest post.
Re: "Yes, the class 22 truck was a two-axle version of that used for the class 41/D600, which in turn was a modified version of the LMS Ivatt/Fox design used under LMS diesel-electric prototypes 10000/1, and which design in turn was said to have been inspired by the EMD/Blomberg A1A design used under the EMD E-series passenger locomotives. NBL couldn’t work out how to drive all three axles – the 41/D600 was originally intended to have a C-C wheel arrangement - so settled for A1A-A1A."
--------------> !!!!!!!!!!! Just how bad WERE the designers at NBL? The LMS (= London Midland and Scottish, one of the pre nationalization railroad companies in Britain, which ordered prototype main-line diesels just before nationalization) 10000 and 10001 were CC models (CoCo in British parlance). So their designers were able to fit three traction motors in each truck. And NBL's designers couldn't figure out how to fit in the final set of gears, etc, to connect all three axles to the d.h. drive? IIIIIIIIIII

As for the connection with the EMD (Blomberg) truck used on E-units… Neither the drawing nor the photo of a Class 41 in the Cooper book is very good for truck details, but I have certainly long thought that the trucks on LMS 10000 and 10001 have an E-unit-ish look to them. What I take to have been the same engine and probably very similar internal electricals was used by English Electric on the 900 class for South Australian Railways (for American readers: Alco PA look-alikes, but only 1600 hp -- were among the first mainline diesel locomotives in Australia), which only had 4 motors (so: A1A - A1A). The trucks on these look even more E-unit-ish.

More anon.

[Pneudyne]

--------------> !!!!!!!!!!! Just how bad WERE the designers at NBL? The LMS (= London Midland and Scottish, one of the pre nationalization railroad companies in Britain, which ordered prototype main-line diesels just before nationalization) 10000 and 10001 were CC models (CoCo in British parlance). So their designers were able to fit three traction motors in each truck. And NBL's designers couldn't figure out how to fit in the final set of gears, etc, to connect all three axles to the d.h. drive? IIIIIIIIIII

I am inclined to say that the NBL designers were unbelievably bad, but they were probably a lot worse than that.

Still, three-axle drive in that case was certainly not an easy problem to solve, particularly with the constraint that the truck should still be of the double-swing bolster type. If nothing else, the D600 was excellent in the high-speed riding department.

BR Class 41.gif

As for the connection with the EMD (Blomberg) truck used on E-units… Neither the drawing nor the photo of a Class 41 in the Cooper book is very good for truck details, but I have certainly long thought that the trucks on LMS 10000 and 10001 have an E-unit-ish look to them.

LMS used fabricated box-frame rather than cast construction. Clearance considerations dictated inside rather than outside swing-hangers. And there was evidently not enough vertical room for fishbelly equalizing bars with coil springs between the bars and the truck frame. So overhung equalizing bars, within the boxframes, were used, with stirrup-mounted coil springs. The original design was for two motors per truck, with a conventional bolster. The change to three-motors per truck required the use of a thin and very light bolster frame that provided location and transmitted buff and drag forces, but did not transfer any weight, which was then handled by four loading pads at the bolster corners. This suited the NBL diesel-hydraulic design, in that a bolster with a large ring centre could be used, through which the transmission drop gears would fit.

What I take to have been the same engine and probably very similar internal electricals was used by English Electric on the 900 class for South Australian Railways (for American readers: Alco PA look-alikes, but only 1600 hp -- were among the first mainline diesel locomotives in Australia), which only had 4 motors (so: A1A - A1A). The trucks on these look even more E-unit-ish.

Yes, in this case those trucks were surely a direct copy of the EMD/Blomberg design. Detailed mechanical design of the locomotive was done by SAR itself, and the truck frames were cast by Bradford-Kendall.


Cheers,

[Allen Hazen]

Re: Pneudyne's THIRD most recent post. (I'm falling behind, though, given the quality of his posts, I'm not complaining!)

The article from the May 1966 "Railway Transportation" on BR's comparison of d.h. and d.e. locomotives is interesting reading.
A few comments:
---The types compared were the Class 52 (d.h.) and Class 47 (d.e.). They had been introduced about five (Cl. 52) and 3 1/2 (Cl. 47) before the date of the article: long enough for a pretty comprehensive series of tests, though maybe not enough to accumulate long-term maintenance data. (Ironically, given the concern about the high-speed engines used in d.h. locomotives, it was the Cl. 47 that was derated, starting in the mid 1960s, because of engine issues!)

---The article mentions intrinsic problems of large high-power DC (direct current) electrical gear, and mentions the possibility of a move to AC equipment in the future. British Rail had actually started a research program at that time into the use of AC induction motors, with variable-frequency current (the technology now standard on high horsepower locomotives in North America): test runs with the experimental locomotive "Hawk" (ex-10800) began in April 1965 (according to Cooper). … In the event, electrical technology of the day wasn't adequate, and the project was discontinued in 1968. I believe there was a German diesel electric prototype with AC traction motors in the late 1970s: in North America the idea was talked about in the early 1980s, but EMD and GE didn't start delivering production-model AC locomotives until 1993 and 1994.

---Some of the advantages of AC transmission, of course, are available with AC/DC units: locomotives with a traction alternator replacing the DC main generator, the current being rectified and fed to DC traction motors. This technology WAS available in the mid-1960s (EMD built its first GP40 prototype in 1964, with production models starting at the beginning of 1966. GE didn't field an alternator-equipped locomotive of its own until May 1966 (the test/demonstrator set 300-303), but GE's GTA-9 alternator was installed in a production Alco C-630 delivered before the end of 1965). British Rail did not adopt this technology at the time: they were in a mad rush to eliminate steam (steam use ended in 1968), installing new locomotives of existing DC technology as fast as they could be built. (For an American analogue: suppose, after being burned by unreliable F-M and Lima units, say, the American railroads had decided they wanted to complete dieselization in the period of BR's main dieselization drive, 1960 to 1968. One can imagine railroad managements asking for repeat orders of GP-30 until dieselization was completed rather than risking new and untried technology…) The only large locomotive introduced on BR between May 1966 and final dieselization was the Class 50, and it was based on a 1962 prototype. … After that it was a long time before BR made any further purchases of main-line locomotives: BR's equivalent of the GP-40 or C-630 (= their first big AC/DC freight locomotive) was the Class 56 of 1976.

Re: one line in Pneudyne's very informative latest post: "LMS used fabricated box-frame rather than cast construction" (about the Blomberg-inspired (?) trucks on 10000 and 10001) --- I think EMD's first application of the "E-unit-style" truck (on a streamlined-train power car for the Chicago, Burlington & Quincy before actual E-unit construction started) used a fabricated frame.

Thank you, once again, for posts from which I am learning a lot!

[tgibson]

I would assume that the lower efficiency was made up for by the increased adhesion since all axles in a truck were geared together?

[Pneudyne]

That would appear to be the case. For example the British Rail 52 class had the reputation of being able to start heavier freight trains than any of the comparable diesel-electric classes. But the downside was that when slipping did eventually occur, it could be of the rapid breakaway type, sometimes resulting in rail burn. I suspect that it was rather like what happened when six-coupled steam locomotives suddenly slipped.

Returning to the efficiency issue, the attached set of curves for the Voith L36r transmission are I think illustrative. The L36r was an early (mid-1950s) size 6 triple converter unit of generally similar form to the size 8 units used in the SP diesel-hydraulics.

Voith L36r Curves.gif

Both utilization factor and efficiency curves are shown. The former shows the extent to which the transmission can load (or overload) the engine. Where it drops below 100% utilization, it represents, as it were, power not taken from the engine, rather than power taken but lost in rejected heat from the transmission. Where overloading occurs, the engine speed droops, with consequent reduction of power output. In this case the engine concerned (a MAN 22/30 medium-speed unit) appears to have been fitted with an isochronous governor (and the Woodward PG was standard for this model), so that there is no engine run-up during underloading.

The net efficiency curve incorporates the utilization factor curve, and also clearly shows the characteristic torque converter parabolic efficiency curves for each of the three converter stages.

The diesel-electric curve shown for comparison assumes 100% utilization. This is reasonable if slightly generous, since it apparently ignores the effects of load control bandwidth. Still, for a hydraulically-driven load control rheostat controlled by a linkage-driven valve, the bandwidth is only ±1%. I’d expect even smaller numbers with governor-integral control valves and governor-integral rheostats.

Next are curves for the Alco DH643.

Alco DH643 Curves.gif

The torque converter effect is particularly apparent in the middle section of the curve, where the second stage is operating. One may visualize that the flattening is the result of adding a parabolic element to the underlying constant power rectangular hyperbola. Or to put it another way, the rectangular hyperbola that is tangential to the middle section of the curve represents a higher power output than that (or those) which intersects the ends of that section.

Turning to the hydrodynamic braking curve, the section above the peak approximates a rectangular hyperbola, over which braking power is constant, limited by the fluid cooling capacity. Over this range, braking coupling filling is progressively reduced as speed increases. Below the peak the actual curve deviates somewhat from the expected parabola. Here the coupling filling stays at maximum, with braking torque progressively reducing as speed decreases.


Cheers,

[Pneudyne]

There is an excellent book about the diesel-hydraulics available, Southern Pacific and the KM Hydraulics by Robert Zenk. It covers the development of the diesel-hydraulic program with the D&RGW and SP, the original six units, the 21 "production" units, the 3 "Alco-haulics", and the one surviving unit. Also covered are the diesel-hydraulics sold to Brazil (meter gauge), and proposed versions.

https://www.amazon.com/Southern-Pacific ... 0984624791" onclick="window.open(this.href);return false;

Thanks, Stuart. I wasn’t aware of that book; I have now ordered a copy.

The book has now arrived, and excellent it surely is, with much “new” information.

An aspect of the Alco DH643 that I don’t think was mentioned by either Strapac or Steinbrenner was that German locomotive builder MaK was a design partner. Apparently that was kept fairly quiet in the interests of presenting the DH643 as an American design. (MaK of course is now an engine-building Caterpillar subsidiary.)

Another item is that at the SP’s request, K-M prepared a diesel-hydraulic design using a pair of GE 7FDL-12 engines, but it exceeded SP’s allowed maximum length. That’s probably more for the GE forum, suffice to note that GE’s German associate was Krupp (although perhaps that arrangement started later on) and generally, GE seemed not to release its FDL engine for use by other locomotive builders.

And evidently the DRGW and SP did separately and differently when it came to converting their K-M prototypes for AAR MU compatibility. From Zenk’s brief description, I’d say that DRGW developed an interface between the K-M and AAR systems without changing the K-M's control system itself. SP on the other hand converted its prototypes to use the same GE KC99 master controller (as used on the GE U25B) and electro-pneumatic control system that had been specified for the K-M production fleet. The German builders used variously all-electric, pneumatic and electro-pneumatic control systems for their 1950s and 1960s diesel-hydraulic locomotives. The Alco DH643 appeared to have had its own AAR-compatible control system, not using the GE KC99 master controller, perhaps a little surprising given that as far as I know, Alco did use the KC99 on its C855 twin-engined diesel-electric design.

Other Alco-MaK designs schemed out, but never built, included a 3300 hp B-B unit powered by a single Alco 16-251C engine. With one engine/transmission unit driving both trucks, that I think would have been a candidate for potential torsional vibration problems. Apparently quite a bit of work was required to eliminate such problems on the DB (German Railways) V160 prototypes before series production commenced. On the other hand, BR’s 35 class was not fully developed in this department, and evidently was quite troublesome.


Cheers,

[Chessie77]

I remember, years ago reading and article about the DH643 that talked about the fact that the Alco trimount trucks were reversed on these engines so that the hydraulic drive would fit. The article also said that the trucks rode better like this than in the standard configuration on the C628s and c630s.

[Allen Hazen]

Alco (unlike GE in the domestic U-series and Dash-7 eras) mounted the tucks symmetrically, so in operation a six-axle Alco would have one truck going frontwards and one backwards. So I would be surprised (not for the first time!) if reversing the trucks made a big difference to the ride. My own ***GUESS*** is that the final drive of the diesel-hydraulic was lighter in weight than a traction motor, so that the DH would have had less un-sprung mass in the trucks.
(But I'm a non-engineer. I've found that posting stupid remarks to this board gets them corrected by people who know more than I do, and I learn something!)

[Pneudyne]

As far as I can see, the “reversal” was in respect of the axle spacings. The usual Alco trimount truck had closer spacing between the outer and centre axles than between the centre and inner axles. The DH643 truck was the other way around, but it still had the rigid bolster and centre pivot placed between the outer and centre axles, with the “elephant’s feet” between the centre and inner axles, as per established Alco practice.

Like Allen, I suspect that lower unsprung mass would have had something to do with the reported better riding of the DH643, as well as perhaps lower rotational moment of inertia.

Centre pivots outboard and elephant’s feet inboard seems to have been the norm for trimount trucks generally, although relative axle spacings were variable. Widely spaced truck centres are I think generally regarded as an aid to good riding and tracking. Only one example comes immediately to mind where trimount trucks were fitted with the pivots inboard and the elephant’s feet outboard.


Cheers,

[Pneudyne]

Here is a line diagram of the Alco DH643 truck.

Alco DH643 Truck.gif

Cheers,

[Pneudyne]

The Alco DH643 appeared to have had its own AAR-compatible control system, not using the GE KC99 master controller, perhaps a little surprising given that as far as I know, Alco did use the KC99 on its C855 twin-engined diesel-electric design.

No, that was incorrect. The C855 had what appeared to be, from the photographic evidence (in Cockle’s “Giants of the West”) a KC92 control stand, which was a type then used by Alco in other models. But whereas the regular, or at least more familiar version of the KC92 had an 8-notch throttle, with continuously variable dynamic brake control via the selector handle, it was evidently modified for the C855 application to provide 16-step throttle and as well, 16-step dynamic brake control using the throttle handle. A reasonable deduction is that the underlying control scheme was functionally similar to that on the GE U25B (and U50).

In the case of the DH643, the underlying control scheme would have been different, in that on a diesel-hydraulic locomotive, 16 throttle notches meant 16 engine speeds (or 16 rack positions), or perhaps 15 if the 1st power notch was part converter fill at minimum engine speed. The Voith hydrodynamic brake was amendable to either continuously variable control, using a pneumatic operator, or stepped control, typically in 8 or 16 steps, using appropriate electropneumatic operators.

The empirical evidence is that, pari passu, diesel-hydraulic locomotives seem to have required more power control steps than their diesel-electric counterparts, and that requirement was learned fairly early on in the development of diesel-hydraulic locomotives. Perhaps the fact that often they were lighter for a given power output had something to do with it. But also, the torque spikes from upward notch changes may have been sharper in the diesel-hydraulic case. In Germany, the DB V200 class had 6 notch all-electric throttle control, but later derivatives went to 15 notches. The later V100 and V160 classes had 15-notch electropneumatic control based upon a Westinghouse 4-piston actuator that could provide 16 output positions (and which could also be used for hydrodynamic brake control). In the UK, BR started out with 6- or 7-notch control for its early diesel-hydraulic designs, which was found to be far from ideal, and went over to continuously variable pneumatic throttles for its classes 35 and 52. That said, it may be noted that BR had found that the 8-notch control fitted to its very early diesel-electric designs was too coarse for typical UK operating conditions, and specified continuously variable pneumatic throttles for most of its first generation diesel-electric fleet.

Cheers,

[Typewriters]

Still no! I think you've misinterpreted the photos in Giants of the West.

For those who don't have the book, in the C-855 section on pages 102-103 there are a number of in-cab shots provided to Cockle by the Union Pacific.

Now, of all of these, the photo on the center left of page 102 is simply the cab control photo from a contemporary ALCO Century operator's manual, which is identical to that in my later TP-447C. All the rest of the photos are actually of UP 61, and most are labeled as such on the photos.

The shape of the control stand is a function of the locomotive manufacturer's design, not of the manufacturer of the controller itself. So the same general configuration of control stand will fit the 8 notch KC-92 controller with dynamic brake control on the selector lever, or the 16 notch KC-99 controller with only a B position on the selector and both throttle and dynamic brake control on the throttle lever. In the photos, you can make out the fact that 1. The selector lever on the UP 61 only has five positions and 2. There are no indicator windows over the selector and throttle to indicate their position, but rather decals on the control stand itself. This is exactly what you see on the KC-99.

Also look closely at the throttle lever on the UP 61 photos and you'll see that it's exactly the same as provided on early U25 units. Different from the lever on a KC-92. Finally, there is no 16 notch version of the KC-92 that I am aware of.

Hope this clears things up a bit!

Now, as for the DH-643. The controller appearance with the handle sticking out below a semicircular ring of jeweled sort of position indicators is something I've only ever seen on the Reading ALCO Century units that had the "duplex controller." On this the controller was buried inside a box that stretched across the cab and had remote operating levers on both sides, which moved at the same time as each other. Maybe the C-415 had this too. However my point here is that it seems to show that the controller is not right behind the lever, and I suspect (owning an operating manual for the DH-643 but not an electrical maintenance manual) that there's a linkage from that lever to a controller up near the cab front wall. No way to be positive on this without a maintenance manual. There is of course always that chance that what ALCO has used is NOT a GE controller at all but something from Germany, in which case any guess is as good as mine!

-Will Davis

[Pneudyne]

Thanks for the clarification, Will! I should have looked more closely at the pictures in “Giants of the West” and also should not have second-guessed myself.

With the DH643, as you say, it’s anyone’s guess, but one could make a mild circumstantial case that the mechanism remote from the throttle handle was the KC99 type. Evidently SP had specified the KC99 for its production K-M diesel-hydraulic fleet, and had also used for the retrofit of its K-M prototypes. So SP could well have specified it, or at least indicated a preference for it, for the Alco DH643 fleet, in the interests of standardization. And given that Alco was also planning to use it for the C855, it was already an Alco part and so logical to use also for the DH643.

That’s not to say that MaK or another of the German builders would not have provided a bespoke master controller if requested to do so. But left to their own devices, the German builders appeared to have preferred a combined throttle and dynamic brake handle (or wheel) in which dynamic braking was obtained by moving it in the opposite direction to that required for power control, as was the case for the SP and DRGW K-M prototypes. Swiss electric locomotive practice post-WWII (and perhaps earlier) might have been influential here. An apparent outcome of the tragic Waderswil crash of the late 1940s, which involved an older electric locomotive in which the power handle doubled as the electric brake handle according to the position of the master switch, and which was in the power mode when the engineer thought it was in braking mode, was to ensure that master controllers be arranged to avoid any possible confusion between motoring and braking. This kind of combined throttle and dynamic brake control was also used by English Electric (UK) and Alsthom (France).

Cheers,

[jr]

Perhaps of interest - The June 1976 Trains magazine has a story on two of the Rio Grande KM's testing on the New York Central. Several pages, many photos, and a lot of operational details on various test runs. I found it to be very informative.

JR