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.
....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.
Quentin
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.
....Am I missing something. I'm hearing mention of torque converters in these diesel hydraulic units....?? I must not be understanding the system that were being used.
.....And the Powerglide and Turboglide....All had multiple turbine converters and were very inefficient.
I also don't think a torque converter can be modulated as rapidly as an electric motor. The DH's did get a boost in adhesion due to having all of the axles on one truck turning in unison compared to problems with slip control when the DC motors were operated in series at low speeds (to match the amp rating for the DC generators) - much the same way a locking differential gives better traction than an open differential. The disadvantage for the DH is that all the wheels on a truck need to be almost exactly the same diameter.
Another disadvantage to the hydrodynamic transmissions is that they almost require a separate engine for each truck - both the KM's and the Alco DH643's were dual engine.
I've heard stories about the Dynaflow - often referred to as the Dynaflush. Amusing to consider when I have a 5-speed Allison automatic in my pickup truck. Also interesting/amusing to consider is that many hybrid vehicles (e.g. Prius and GMC Yukon hybrid) use a combination of electric and mechanical means to get a continuously variable transmission.
Contemplating today's world, as contrasted to the then (and I recall basically the same thing about the KMs and Alcos -- maintenance issues, and a rather poor fit with US service).
Diesel hydraulics make, seems to me, good sense in a DMU type application (and indeed, they are used there): the power requirements are relatively small in relation to the size of the vehicle, and control (particularly slip) isn't a really big issue.
However... I would hate to see what hydrodyamic drives for a 6,000 hp diesel would look like! Further, the modern electronic controls for diesel electrics provide near-instantaneous variation of the torque going to the axles, and thus very very high adhesion factors. Maybe I'm missing something, but I doubt that one could modulate a torque converter as fast as one can modulate an electric motor -- and that's the one of the big secrets to the very high adhesions.
Anybody else out there remember the original Buick Dynaflow? The ultimate slushbox -- didn't shift at all; did it all with a very fancy torque converter. Worked fine, except the efficiency wan't much to write home about!
Bucyrus wrote:Can someone describe the power train between the engine and the wheels of the KM diesel-hydraulic locomotives tested in the U.S? Did the Alco diesel-hydraulic of the same era use the same power train as the KMs?
A good description of the operation of the power train is on pages 36-37 of the November 1962 issue of Trains. The Alco DH-643's also used Voith transmissions, presumably with the same operating mode as the Voith transmission used in the KM's if not exactly the same unit.
The engines were coupled to the transmissions by a Cardan shaft - essentially the same design as a typical driveshaft on a rear drive car. Another cardan shaft connects the tranny to a dropbox mounted in the bogie/truck of the locomotive, the lower part pf the dropbox is connected by driveshafts to gearboxes mounted on each axle, the gearbox contains a bevel gear to couple the longitudinal driveshafts with the axle.
The Voith L 830 RU transmissions used in the KM's had three torque converters optimized for maximum efficiency at 27, 41 and 59 MPH (85, 88 and 82.5% respectively), as I wrote earlier, 'shifting' is accomplished by draining one converter and filling another. The only time that gears are actually shifted is when reversing direction of the locomotive. The transmissions have provisions for hydrodynamic braking with a larger speed range than what was then available with electric transmissions. Also recall that torque converters can multiply torque when the impeller is turning faster than the turbine (which is why the Chevy PowerDive -er- PowerGlide transmission could get by with two forward gears).
The overall peak efficiency of the hydraulic drivetrain was about 86% (there were losses of about 2% involved with the truck's gearing and driveshafts), roughly comparable to the 85% efficiency figure quoted for electric transmissions of that era. AC transmissions are being quoted as having better than 90% efficiency.
My understanding is that the hydraulic transmissions used on RDC's and DMU's are essentially beefier versions of the automatic transmissions used in cars - though set up to have the same number of gear ratios in both directions. The advantage in this application is reduced size and weight compared to electric transmissions - but a lot of progress has been made recently on reducing the weight of the components used in electric transmissions.
Dan
They are still building and rebuilding a lot of diesel-hydraulics in Germany. Vosloh of Kiel, Germany under the brandname Mak, is the main diesel builder in Western Europe. They even supply quite a few locomotives to France See the website www.loks-aus.kiel.de. They may get competition at the high horsepower end from Voith, one of the hydraulic suppliers.
Alstom is rebuilding former East German V100's (very popular with private railroads!) and to a lesser extend West German V100's as well
Main competition is the EMD class 66.
greetings,
Marc Immeker
I undrestand that what doomed the Warships after all the mechanical issues were dealt with that 2000 hp was not realy enough for mainline passenger work when steam engines had delivered higher hp.
Like mentioned above the Warships were not suitable for freights because of their low weight to horse power, but I heard it wasn't because of pulling power, it was more about braking power. Diesel hydrolics don't slip as easy as the contemerary diesel electrics but you wouln't want to lock the wheels when braking. Freight trains had no brakes exept a hand brake in the brake van and what the locomotive and tender has. No bakes on freight cars?! I guess the technoligy of the Warship was foiled by outdated technoligy and operations for freight traffic.
The German equivilant was the V200, wich were used on heavy coal and freight trains for a long time, wich were heavier then British freights at the time.
To go back to the question WHY, British Railways' Western Region's reason for opting for Diesel Hydraulics for main line power was the significant weight saving on the then equivalent Diesel Electrics available.
The difference in the weight of the D800 class and its variants and the D200 class (later Class 40) offered by English Electric was the equivalent to around a carriage and a half (perhaps someone with a better personal library can quote the exact weights).
Their thinking was that either less fuel would be used to haul similar trains, or the popular trains could accommodate rather more fare paying customers.
The downside was that being lighter, the D800s would be totally unsuited and highly unpopular for anything other than passenger and parcel trains and the fully braked freights of that time. So no chance of seeing them on a typical South Wales Valleys coal train.
Hwyl,
Martin.
As mentioned there would be some efficiency advantages with diesel hydrolic locomotives, if you can make them reliable that is.
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.
So when skilled labour is more plentifull then fuel oils, then go hydrolic. When properly maintained they should work great.
Western England used Diesel hydrolics extensively for a while too, but suffered from lack of skilled mechanics.
As I recall, erikem hit the main reason - we ask different tasks of locomotives here than they do in Europe (where the design was, and may still be, popular). I believe trains there are generally shorter, and the runs are definitely shorter. Plenty of opportunity for tweaking.
On of the K-M's ended up as a camera platform for SP - pushed by Diesels.
Aside - one nickname of the ALCo DH's was "Alcohaulics."
Larry Resident Microferroequinologist (at least at my house) Everyone goes home; Safety begins with you My Opinion. Standard Disclaimers Apply. No Expiration Date Come ride the rails with me! There's one thing about humility - the moment you think you've got it, you've lost it...
Pop-off-valves would be hard to control so the pressure would get lower as the spring got weeker. Thus the horsepower from the engine would drop. It took a mechanic that knew his job at seting the pressure. To high and the oil lines would blow.
If you blew a line then the oil would be all over and one heck of a mess to clean up. Hot oil in an engine compartment set the stage for a fire. Nothing like stoping a train like an oil fire.
....Wonder if price might have been a factor....Example: Our last automobile had 2 hydraulic motor driven radiator fans and now our current automoblle {same brand}, has in the same place...2 electric motors to do that job. My guess is simply the electric motors are less expensive and it was a cost cutting move. Perhaps same reason in the locomotive. {At least as one of the reasons}.
JT22CW wrote:Another advantage that they may have (someone please confirm this) is one that was lost when US railroads converted from steam to diesel-electric, that being the ability to run through flooded sections of track that would be under relatively deep water. (Diesel-electrics cannot do this; their traction motors would short out.)
Another advantage that they may have (someone please confirm this) is one that was lost when US railroads converted from steam to diesel-electric, that being the ability to run through flooded sections of track that would be under relatively deep water. (Diesel-electrics cannot do this; their traction motors would short out.)
The main reason that the D&RGW and SP werelooking at hydraulics was to get more continuous tractive effort fom a single carbody. The hydraulic transmission was supposed be happier running at low speeds than the current DC traction motors and the fact that all three axles on a truck were turning in unison helped with adhesion. Nowadays, those advantages are provided by AC traction motors plus improved slip control (e.g. EMD's super series technology).
Reasons why the hydraulics didn't catch on is that the engine reliability on the KM's was poor, and the Alco's weren't hugely better. Seem to recall that the hydraulic transmissions weren't as rugged as expected from European service - there's noting in Europe quite like "The Hill" (Donner Pass route).
Added note: The hydraulic transmissions used torque converters (not hydrostatic) obviously on a larger scale than the ones used in automotive tranny's. The KM's were equipped with three torque converters per engine/truck each with a different gear ratio, transitions were accomplished by draining one converter and filling another.
Yet another advantage of the DH's were that hydrodynamic braking was effective at lower speeds than with the then available dynamic braking on diesel electrics.
Believe it or not, they are often more efficient than diesel-electric. Most DMUs are diesel-hydraulic, to boot, due to this. Pay Google a visit if you really want to learn more about them.
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