Modelcar,
The KM’s and Alco DH643’s used hydrodynamic, not hydrostatic, transmissions. The KM’s did use hydrostatic drives for the fans. I’m not sure if I want to be anywhere near a hydrostatic transmission capable of handling 2,000HP. OTOH, locomotives with a few hundred horsepower may likely be hydrostatic.
…I need to stop and see schematics of drive train components so I really understand what is being discussed here.
Diesel Hydraulics and or Diesel Hydrodynamics…
There are “Powerwheel” units driven by hydraulics with pretty high horse power into running them and that application doesn’t have torque convertors, and now this railroad application of hydraulics is something in a different direction, so must see what we’re talking about.
Modelcar,
The article in the November 1962 Trains specifically mentioned hydraulic torque converters and specifically mentioned impellers, guide wheels (reaction members) and turbine runners. The “hydraulic” presumably comes from the reaction fluid being a liquid as opposed to a gas (i.e. pneumatic). Without the torque converters, the KM’s (and Alco DH’s) would be diesel-mechanical as power transfer between the engine and transmission, the transmission and truck (bogie), the truck gearbox and axles were all handled by Cardan shafts (shafts with U-joints at each end). The “hydraulics” were only used to provide for a variable ratio between engine speed and axle speed. One huge advantage of a torque converter over a staright mechanical transmission is to allow a running engine to supply torque to a stalled load.
Hope this clears things up a bit.
There’s a nice cutaway drawing of the KM in the October 1961 Trains which shows the locations of the engine, transmission and the numerous Cardan shafts.
Voith is coming out with a competitor to the Vossloh/EMD Euro 4000 (European SD70M-2), called the Maxima 40C it will be a 4000hp Diesel-Hydraulic powered with a ABC 16-cyl. medium speed diesel. Voith decided to get into building their own complete locomotives when they saw the inroads EMD was making into the European market causing them a loss of sales. Vossloh has been kind of ambivilent about building locomotives, they own the former MaK factory in Kiel and bought the former Alstom (ex-Macosa) factory in Valencia, Spain. But the CEO who engineered these moves was forced out. The locomotive business is cyclical, and dissident shareholders want the company to sell the locomotive business and concentrated on building components for passenger equipment and track components. Vossloh has good sized subsidiaries in the US in these business lines. Because of this uncertainty, especially at the Kiel factory, some of the Engin
…Erik: Thanks for your comments. I simply need to eyeball the power train components. Guess I really haven’t looked at the layout of such a powertrain or if I have it’s been too long ago.
I probably have those TRAIN’s mag. and articles you mention, but you might know how it is with them stored in boxes, etc…
It sounds like you are saying mechanical power was brought to the truck area via the double cardan shafts and into an arrangement of torque convertors and then into a mechanical gear box and on to the axles…
If that is the case, those must have been some stout T C’s to handle that job. Of course if that was the set up, the T C’s assisted in starting the load by their capability of multiplying the engine torque into the gear set and into the axles…and on grades where the speed would get down to a point where the load and power would dip into the T C’s uncoupling and start to once again multiply torque.
Thanks Erik. So the KM transmission used three separate torque converters. I assume that they each produced a different speed/torque multiplication. So then shifting from one torque converter to another was equivalent to shifting gears in a mechanical transmission. I can understand the problem of the wheels needing to be the exact same diameter.
My understanding is that a hydrostatic transmission uses a variable displacement, engine-driven pump, which pumps oil to a fixed displacement motor. So by mechanically controlling the rate of output flow from the pump, the motor speed can be changed. I have heard that the motor can also be variable displacement, thus adding to the speed change capability of the pump.
This type of drive would seem to be quite analogous to the diesel-electric drive of locomotives if the hydraulic motors were hung on the axles like electric traction motors, and the hydraulic pump were directly coupled to the engine. Is there any fundamental engineering reason why this hydrostatic drive cannot be applied to a locomotive? One problem I can see is the need for hoses connecting to the motors in order to accommodate the movement of the axles relative to the rest of the locomotive.
An electric traction motor requires flexible leads for the same reason. Anything that routinely flexes is heading for eventual breakage. It may not be an issue with electric leads as they may be easy enough to monitor and replace if necessary. But the flexing of hydraulic hoses occurs when the hoses are already under the physical pressure loading of operation. Whereas, with electric leads there is no physical aspect to the electric load (I guess). The consequence of a broken hose would not only be locomotive failure, but also a serious oil spill. Perhaps, however, a 100% reliable hose connection could be developed for such a hydraulic traction motor application.
Quentin,
Glad I was able clear things up. I can understand your confusion as “hydraulic” is usually associated with high pressure and relatively low flow.
Bucyrus,
Making a long lasting flexible electrical connection is relatively easy, just use lots of very fine strands of wire in the cable, the key issue in fatigue is the ratio of overall bend radius to the individual strand radius. Making a high pressure hose that can take a lot of flexing is a ‘bit’ more of a challenge. I think you’re on the right track with the comment about electrical connections not needing physical strength compared to high pressure hose.
There’s some really interesting discussion above (thanks for the info on Vossloh, beaulieu) but to return to the original question.
I assume you are talking about the U.S. only. The only significant experiment with hydraulic transmission took place 1960-63 with the design, construction, and commissioning of Krauss-Maffei A.G. locomotives for Southern Pacific and Rio Grande, followed by a valiant but ultimately futile effort to obtain value by moving freight. The rationale of the railroads in question was to have a locomotive that could:
deliver full prime-mover horsepower to the rail at very low speeds in drag-freight, heavy-grade service – diesel-electrics with D.C. transmissions cannot deliver full horsepower to the rail for more than a few minutes below their minimum continuous speed (typically 11-12 mph) without experiencing permanent damage to the traction motors.
obtain higher horsepower in a single unit than what was then currently available from EMD – nominally 2500 hp for EMD vs. 4,000 hp for the K-M, thereby obtaining unit reductions for the equivalent drawbar tonnage.
dispense with traction motors, a high-maintenance component and the least-reliable major item on the locomotive.
a general dissatisfaction with the lack of innovation at EMD, and desire for the viable strong competitor to EMD that Alco wasn’t. Recall that in 1959-60, when this idea had genesis, that EMD had 85% or better market share (testimony to Alco’s weakness), and for 10 years had been upgrading the GP7 only incrementally. Granted the GP9 was a much better iteration of the GP7, but from an operating department point of view there wasn’t any meaningful difference, and the GP18/GP20,
I wonder if the hydraulic transmission might some day become victorious; as the ground shifts with respect to fuel efficiency, the use of copper, etc. I don’t see any fundamental reason why fluid drive should take a back seat to electric drive. One reason we are doing it the electric way is that we have done it that way for so long.
It is interesting that the hydraulic transmission has evolved as the preferred method for the high power drive trains in bulldozers, yet one of the major pioneers in that area was R.J. Letourneau, advocating what he called the “electric-wheel,” as he called the principle.
Letourneau coupled a diesel engine to a generator, and used the electricity to power traction motors. He was an electric drive advocate swimming upstream with those who were more enamored with the idea of replacing gears with hydraulics.
Hydraulic transmissions for future locomotives? I am deeply doubtful.
Earthmoving machinery is quite a different application and only weakly comparable to locomotives. Machinery drive types have proliferated in order to optimize the machine’s suitability for the the type of use, periodicity of use, and initial and operating costs. Three basic types are offered: diesel-electric, where the prime mover drives a main generator that supplies electricity to traction motors geared to each driven axle or wheel; hydrostatic, where the prime mover drives a hydraulic pump that supplies hydraulic fluid to hydraulic motors powering each driven wheel or axle; and mechanical drive, where the prime mover is directly geared to each driven wheel or axle via an intervening geared transmission connected to the prime mover via either a clutch or torque converter.
Earthmoving machines that have intermittent use with lots of idling time and are “entry level” such as loader-backhoes are mostly mechanical drive. Mid-size machines where flexibilit
…Where do the innovators stand in putting the hydraulic system to doing the equivalent of dynamic braking…?
They were an interesting concept and I have read some positive stuff about them, but they just weren’t normal in these parts. I don’t know if that has anything to do with it.
What I read at one point is that the hydraulic turbine or whatever it was simply drove a dynamo and the rest was normal motor drive. That made no sense to me since why would you bother?
Fuel efficiency aleady favors the electric drive over the hydraulic and there is still room for progress in electric drives. The improvement in efficiency isn’t so much driven by reducing fuel costs as by cooling costs. A motor with 96% efficiency will put out 20% less heat than a motor with 95% efficiency. Overall efficiencies of AC drives exceed 90%.
Copper costs are another story, although replacing induction motors with synchronous motors may reduce the amount of copper needed. The iron in the rotor can reduce the reluctance in the magnetic path of the stator windings, which reduces the amount of current needed to generate a given torque which reduces the amount of copper needed to carry the current.
Voith offer hydrodynamic braking with most of their transmissions. They call it a “retarder”, and it is indicated by the suffix letter “r” at the end of the transmission model number.
For example, a very common diesel railcar transmission is the model T311r which is often paired with the Cummins QSK 19R engine of 750 HP. The “3” indicates that there are three converters or fluid couplings used in the design.
The energy from the dynamic braking is absorbed from the “retarder” converter into the hydraulic fluid which is passed through heat exchangers located with the radiators, cooled and returned to the transmission.
The same principle is applied in locomotive transmissions.
M636C
I was just wondering if the diesel-hydraulic transmission principle was potentially applicable to locomotives in a variation that is different from the KM or Alco prototypes.&n
According to published sources, the reasons “for” Diesel Hydraulic locomotive interest were:
Higher horsepower per unit weight of the locomotive. Looking at the Krauss-Maffei units first sampled in the very early 1960’s, each unit had 4000 gross horsepower, with 3540 net after losses in the transmission. Compare those figures with what the contemporary diesel electrics were offering in a single unit
Results in German everyday use showed greater adhesion with hydraulic drive, meaning the power mentioned in item #1 above, could effectively be put to work.
USA experience was that electrical transmission drive systems were the biggest repair item for diesel locomotives at that time, accounting for up to 2/3 of ALL road failures
So, it just made sense to explore D/H as an alternative.
Why did they fail? Well, the Maybach engines employed were not proven in everyday service. The engines put in the units imported by SP and DRGW were scaled up for the us customer’s needs, while the Maybach engines that had previously been proven in German everyday use were not used. Further, the pneumatic controls employed by the units were a constant problem. And on long heavy hauls up steep inclines, the hydraulic fluid would overheat.
Why the latter attempts? the thinking was that maybe Alco engines would avoid the problems of the Maybach engines in the K-M units, but Alco’s closure in 1969 put and end to that idea forever
M636C…Thanks for your input.
Interesting subject. I’m wondering if when you mention of the “3” indicating of three convertors, you might really mean a convertor with 3 turbine components…{sorry if I’m thinking wrong}…
And the “retarder”…used with hydraulics I am a bit familiar. 45 years ago we {BWA}, ran tests in Pennsylvania with trucks out of our test station. Using automatic transmissions {experimental}, and a feature of them was a hydraulic retarder. It was a chamber fitted with an impeller running freely and connected to the imput shaft. When braking was needed we filled that restricted chamber it ran in, with oil under pressure and the massive friction braked the drive train of the truck and was very effective. Since the gearsets were “back” of the retarder, one could select a lower gear and make it more effective yet…But oh boy did it create the HEAT…Required a large heat exchanger to remove excessive heat but one had the use of the whole radiator since the vehicle was on down grade and not being heated by the enigne, and so on…
Just a slight correction on the KM Diesel Hydraulic units, although they were touted as “4,000 HP” they actually produced about 3,500 HP at the rail (my source is the original DIESEL SPOTTERS GUIDE). Being built in Europe they followed the standard European practice of using Gross Engine HP, rather than net HP as is common in North America.
I’ve often wondered whether Diesel Hydraulic units would be useful in flooded track situations in North America (lines along the Missisippi river for instance). In the days of Steam some railroads did run through flodded track sections but I realize that freight cars where much lighter back then. I suspect that the weight of modern cars makes running through flood outs a dangerous proposition even if you didn’t have to worry about traction motors, etc…
TH&B wrote:
West Germany was the biggest successfull use of diesel hydrolics. My theory is that Germany in the post war period had plenty of cheap and skillfull labour to tap from. So the cost of low tolerance regular maintance wasn’t so high as compared to most everywhere else including the US. Now the cost of skilled labour in Germany is astronomical and not as readily available and this has reduced the use of diesel hydrolic locomtives in mainline service. More diesel electrics.
I’m afraid that I simply have to take issue with this statement!
Yes, West Germany was the biggest succesful user of Diesel Hydraulic locomotives not particularly because of “Plenty of cheap & skillful labour” - far from it. Do not forget that when the first V200’s came out in 1954 was a mere 9 years after Germany had suffered the most resounding and devastating defeat (largely at the hands of the Russians!). Indeed before the war, Germany had been building diesel electric locomotives although no-where near as succesfully as in the States.
What sent W. Germany off on the path of the diesel hydraulic locomotive was none other than the victorious USA itself, who would not allow W. Germany to develop the diesel electric concept (thinking to capture the entire European continent as an export market). The ever efficient and resourceful Germans however developed the D-H concept and are indeed still developing it today - the latest machines from Voith are not 4000 Hp but 4000 Kw!!! Do the math & see how much more powerful that is!
As to why the D-H concept was such a failure in the USA seems to have been very well covered in other posts, but to recap: Not well enough built or
I think what doomed the diesel-hydraulics was a combination of poor reliability and the fact both GE and EMD came out with vastly better diesel-electric locomotives by the middle to late 1960’s that offered way more power per locomotive. However, the promise of more power and tractive effort per locomotive offered by the Kraus-Maffei locomotives was still a major enticement to railroads, and that’s why really spurred on better and better diesel-electrics to today’s highly advanced EMD SD70ACe and GE ES44AC locomotives with their 4,300 bhp prime movers, AC traction motors that could operate from essentially dead stop without frying the traction motors, and very clean exhaust emissions. That’s why the SD70ACe and ES44AC are being bought in large numbers for heavy unit train service and for operations in mountainous territory.