SP and D&RGW Krauss-Maffei Diesel-Hydraulics

Is there any interest here in these old German-made diesels? I got interested in them when someone on an NYC group recalled when Central tested two of the Rio Grande K-Ms on the B&A back around 1962. They also tested on Delaware & Hudson briefly too. I believe at that time D&RGW bought three of the units and SP acquired seven, all carbody types, in 1961-62.

For their time, they were powerful locomotives. The most powerful on US rails, with twin Maybach MD870 prime movers per unit developing 4000 HP. The first batch were carbody units with odd 'close clearance' type cabs. Diesel-hydraulics, meaning no traction motors, direct drive.

It wasn't long before Rio Grande sold their three units to SP. SP went ahead and bought a second batch (hood-type units, not sure how many, one site says, variously, eight or fifteen) but none lasted more than six years.

Here's a link (might have to copy-and-paste) to a page named after the first K-M hood or road-switcher type unit delivered, SP 9010 in 1964. The only US-operated K-M still in existence, it is now owned by a group called the Pacific Locomotive Association which hopes to restore the unit:

http://sp9010.ncry.org/

[edited once for typo]

For more on diesel-hydraulics check the Alco forum.

For more information, see Southern Pacific Historic Diesels, Volume 2, Diesel-Hydraulic Locomotives by Joseph A. Strapac, published 1993 by Shade Tree Books, Bellflower, CA. ISBN 0-930742-15-X

Thanks for the sources. The link I posted has some good information too.

One interesting claim by the manufacturer, Krauss-Maffei, had to do with the engines' ability to resist wheel slip. The claim was based on two factors. First the characteristics of the direct drive system. Second, probably more important, was that the axles on the trucks were coupled together, instead of being separately mounted as on conventional diesels. Krauss-Maffei believed that wheel slips usually happened when one wheel set lost traction and by coupling all three axles on each truck together this problem would be eliminated.

In practice, this turned out not to be the case. In testing on the hilly Boston & Albany line, the two Denver & Rio Grande Western units experienced violent wheel slipping on grades. On the SP9010 site, former Southern Pacific enginemen likewise recount occasions when the units slipped (though it's generally agreed they were very powerful locomotives).

One example cited concerns the units grinding inches off the top of a rail as an SP crew experienced a prolonged wheel slip. The SP fireman relating this incident speculates the crew may've been trying to prove a point.

K-Ms slipped!

The website for the SP 9010 is very good not only for its history but also for its detail. All of the websites concerning the restoration efforts of the Pacific Locomotive Association are well done; they convey a sense of ownership taken by those undertaking such an effort. Anyone seriously contemplating such a restoration should look to this website as a benchmark. If you can convey your high level of interest and professionalism in your project others will respond.

As for high horsepower diesel-hydraulic locomotives, the concept is still quite fresh as embodied by the Voith Maxima.

The largest reason for the MK 4000's on the Rio Grande being retired and sold to the SP was the consistant overheating problem they had. If you look at the full body KM's like the Grande had, the intakes are up near the roof line. When the locomotives went through the tunnels, which the Grande had plenty, the locomotive would begin to overheat. The shops for the Grande tried to fix the problem by installing air-intake ducts that ran down towards the frame of the units to pull in cooler air that was closer to the ground. You can see in this some hard-to-find pictures where the ducts where actually on the outside of the locomotive body. A short time latter they were moved to the inside of the car body and can be seen in pictures by looking for two large horizontal vents that were down near the frame, where smooth sheet metal was in original delivery photgraphs. Supposedly even with this modifications the locomotives still overheated. Thus where promply sold to the SP.

If you think about it, that's a lot of work for a railroad to do to brand new lomotives, and shows the Rio Grande's williness to spend time and money in an attempt find a high horse-power solution to help tackle the severe grades they had to deal with on a regular basis.

I recall attending a meeting at the local NRHS chapter where a diesel expert talked about the KM Hydraulics among other things. I think he said these were actually fairly dangerous units to run (for the crews) in cases of hydraulic failure. I don't remember much else. Could anyone elaborate?

The only "hydraulic failure" that I could think of that could immediately impact crews would be failure of the hydraulic lines that drove the radiator fans - although I've never heard of that being singled out as particularly likely or dangerous before, and would only apply to the original six units.

-Will Davis

Yes, but these were called Diesel Hydraulics not Diesel Mechanicals. To me (and I know nothing about these units) this implies that the power train from the prime mover to the wheels was literally via hydraulic fluid or pressure, in which case a failure could be catastrophic (I may be out to lunch). I'm groping to remember the Trains mag articles on these units and the NRHS presentation which was years ago. Can anybody explain to me how these units worked?

Diesel-Hydaulic works just like your car with an automatic transmission. There is a motor that turns a torque converter full of hydraulic fluid, that turns an impeller that is connected to a transmission that turns the whells on the truck. It is almost like a mechanical diesel but with the fluid connection at the one point between the motor and the transmission. This allows the locomotive to be stopped with the engine still idling. Just like when you have your foot on the brake but the engine idles at a stop light.

The torque converter also allows more torque to be applied to the impeller which is then applied to the wheels, so it helps in that aspect too.

So really there wouldn't be anymore of a safety issue with desiel-hydraulic then there would be from the garbage truck that runs down your street that also has a torque convert between it's engine and transmission.

Kudos to the one person that said that they reason the KM4000's where Anti-slip was just beacuse they had all of the wheel linked together. I never was able to find out what system they used to be considered anti-wheel-slip.

Wikipedia has a very good description on it if you go there and look at the article "desiel locomoties" there is a good 4 paragraph section on just desiel hydraulics.

Look here, on my site, to read about hydraulic transmissions and diesel-hydraulic locomotives.

http://www.geocities.com/wbd641/HydraulicLocoTrans.html

Be sure to follow on to the second page to see Steve Palmano's great discussion of hydraulic drive.

-Will Davis

I recall reading that the K-Ms had a system where they could cold spray water over the radiators to increase heat transfer. I know a cold water mist on the air conditioning condenser coils helps my workplace cooler in the summer.

Right you are, EDM5970! The 1963 Krauss-Maffei units (the road switchers for SP) had such a system, as did the Alco DH-643 locomotives.

-Will Davis

Re. safety, drgw-sd45 is correct in what he says; the 'hydraulic' part of the transmission is a torque converter (1) in a transmission casing, NOT a system where high-pressure hydraulic fluid is transmitting the drive through hoses (which I think is what the poster who mentioned safety was concerned about).

The one potential safety issue that I have heard caused some concern about crew impact was the possibility of a failure to the cardan shafts, which took the drive from the engine to the transmission, and from the transmission to the wheels; at least one of those ran under the cab floor, and in the event of a failure you could conceivably have a big shaft carrying a huge amount of power come flailing through the cab floor... or at least it was speculated this might be possible.

(1) in fact a series of torque converters of different size for different speed ranges, exactly analogous to field divert or field weakening on a diesel-electric locomotive, was used in the transmission; this was standard for a Voith transmission. The other major diesel-hydraulic locomotive transmission maker, Mekydro - not used in the USA on large-scale locomotives at least - used a system with a single torque converter and a self-changing 3 or 4 speed gearbox, exactly like an automatic car transmission!

Mike

The Maybach Mekydro did get some use here, in the sense that B-L-H's entries into the "Train X" lightweight Talgo craze that briefly flared up in the mid-50's used this transmission with the 1000 BHP V-12 Maybach MD-655 engine. Built only for NYC and NYNH&H. All the Krauss-Maffei and ALCO diesel-hydraulic freight locomotives used Voith pattern three-converter (three true torque converters, no fluid clutches as was coming into vogue in Europe) transmissions with hydrodynamic brake.

My locomotive site went down, but you can see the archived info on diesel-hydraulics here:

http://web.archive.org/web/200910280227 ... ives1.html

-Will Davis