The lengths people can go to in order to try new things is amazing, isn't it?
The complexity shown in this example is breath-taking, all in the name of saving a little money in the long run.
M636CMy recollection is that Voith use the term "Hydrodynamic" to differentiate their drives from the comparatively rare (in locomotives) "Hydrostatic" drive where hydraulic pressure is used in a hydraulic motor to rotate the axle.
I've always used the term "hydrokinetic" to distinguish torque converters and fluid flywheels from hydrostatic (e.g. vane-motor, positive-displacement) drives. Here is a PDF reference that describes some of the features and differences. Using that nomenclature avoids potential confusion with using 'hydrodynamic' in more common contexts such as tribology and naval architecture.
As a peripheral note: the method that is used on a large railroad locomotive to lock a torque converter (or fluid coupling) 'ought to' be a bit more complex than a simple Maybach or dog clutch, or similar mechanical device with positive engagement. Here is a reference that describes some of the concerns involved with locking a hydrokinetic device for direct drive; I think it is fairly clear how this idea would be adapted to optimize resistance braking without compromising the reliability or integrity of the transmission (and its fluid!)
Interestingly, the characteristics of torque converters of the kind found in normal 'automatic transmissions' are not at all favorable to fuel-efficient operation of many designs of road-vehicle diesel engines. I wonder whether at least part of the reported economy of the 'semi-automatic' bus transmissions relates to the absence of torque multiplication; were these transmissions also provided with some sort of 'slip lock' that could be engaged during steady-state running to eliminate the losses in the fluid coupling?
owlsroost RME Voith built an interesting 'take' on locomotives with multiple effective gear ratios: they had multiple TCs with different planetary or final-drive ratios, and "simply" by filling and draining these could vary the output torque without fixed clutches or mechanical moving parts and clearances in the drivetrain. Presumably these could be fairly easily locked up for direct in any of the selectable 'speeds'. Voith is still very much in the rail business with its triple-converter drives (and other types e.g. single converter plus multi-ratio gearbox for DMUs - ZF is active in that area as well). In Europe, those Voith 'hydraulic' drives (more accurately hydro-mechanical) are very popular for low to medium power switcher and road-switcher locomotives - combined with a high-speed diesel engine, it gets you a high power-to-weight ratio loco with naturally good wheelslip resistance, since in single prime-mover applications all of the axles are mechanically locked together via the final drives (it takes a lot of complex electronics to achieve the same effect in an electric AC drive loco!). As SP & K-M found in the 1960s, it's possibly not the best solution for high-tractive effort/low-speed lugging for long periods, but it's still a competitive drive system for general rail applications.
RME Voith built an interesting 'take' on locomotives with multiple effective gear ratios: they had multiple TCs with different planetary or final-drive ratios, and "simply" by filling and draining these could vary the output torque without fixed clutches or mechanical moving parts and clearances in the drivetrain. Presumably these could be fairly easily locked up for direct in any of the selectable 'speeds'.
Voith is still very much in the rail business with its triple-converter drives (and other types e.g. single converter plus multi-ratio gearbox for DMUs - ZF is active in that area as well).
In Europe, those Voith 'hydraulic' drives (more accurately hydro-mechanical) are very popular for low to medium power switcher and road-switcher locomotives - combined with a high-speed diesel engine, it gets you a high power-to-weight ratio loco with naturally good wheelslip resistance, since in single prime-mover applications all of the axles are mechanically locked together via the final drives (it takes a lot of complex electronics to achieve the same effect in an electric AC drive loco!).
As SP & K-M found in the 1960s, it's possibly not the best solution for high-tractive effort/low-speed lugging for long periods, but it's still a competitive drive system for general rail applications.
My recollection is that Voith use the term "Hydrodynamic" to differentiate their drives from the comparatively rare (in locomotoves) "Hydrostatic" drive where hydraulic pressure is used in a hydraulic motor to rotate the axle.
On my first visit to Mackay in Queensland in 1972, I climbed into the cab of a 250HP two feet gauge locomotive at a sugar mill and was amazed that it had an extensive set a of water manometers in the cab. Not realising what sort of transmission it used I assumed that these were attached to the engine cooling. And no, I didn't photograph it and I wish I had. And it is long gone, having picked up an Allison transmission some time later.
But Hydrodynamic is just as hydraulic as Hydrostatic. Other transmission builders, like Maybach (who built the RG and SP units) called their in house transmissions "Hydro-Mechanical" and their locomotives "Maybach-Mekydro" but these were big automatic gearboxes with a single torque converter, while Voith connected different ratios with the filling and emptying of converters connected to those ratios.
A type of locomotive not mentioned so far is the very common diesel mechanical switcher (called a shunter locally) in Britain. There were hundreds of these of about 150 to 300 HP using the Vulcan-Sinclair epicyclic gearbox with a hydraulic coupling. Since the coupling didn't involve a torque converter, these were regarded as mechanical rather than hydraulic transmissions.
Many british buses of the period had the same transmissions that gave a relatively smooth operation compared to a straight manual transmission but were more economical on fuel than full automatic transimissions (because the drivers pushed the automatic buses harder).
M636C
RMEVoith built an interesting 'take' on locomotives with multiple effective gear ratios: they had multiple TCs with different planetary or final-drive ratios, and "simply" by filling and draining these could vary the output torque without fixed clutches or mechanical moving parts and clearances in the drivetrain. Presumably these could be fairly easily locked up for direct in any of the selectable 'speeds'.
shanelundStrange thing is I never even considered that there would be a fluid coupler for these monsters.
It ain't easy. Most of the vehicles with torque converter drive that could be locked up for "direct" were relatively light, and the amount of heat generated in normal use can be astounding (as can the damage to things like pump turbines if sudden loads are applied, as when slack runs in on a heavy consist). Voith built an interesting 'take' on locomotives with multiple effective gear ratios: they had multiple TCs with different planetary or final-drive ratios, and "simply" by filling and draining these could vary the output torque without fixed clutches or mechanical moving parts and clearances in the drivetrain. Presumably these could be fairly easily locked up for direct in any of the selectable 'speeds'.
We had a brilliant, but comparatively short period of experimentation with 'hydraulic' drive in the Sixties, first with the Krauss-Maffei 'Amerika-Loks' and then with the "Alco-Haulics". These appeared to founder more on maintenance considerations and general 'orphan' status than on any implicit unreliability in the torque-converter principle at 'locomotive' scale ... but I invite anyone's knowledge or distinctive competence that says otherwise.
You were thinking just what I was asking, a hard link. Strange thing is I never even considered that there would be a fluid coupler for these monsters.
Paul MilenkovicThe torque was not transmitted mechanically but rather through the magnetic field passing between the truck-frame bipolar armature and the axle-mounted motor armature. Maybe not very mechanically direct in its drive after all.
I wasn't going to say anything because the terms of the original question ruled out electric drive at all (other than for steam-electrics, and I know of no steam-electric that used jackshaft final drive as the Russian teploparavoz or the Swedish steam turbine did), but Batchelder drive does involve the 'closest thing to direct drive' that we have in the electric world. No gears, no shafts, no discs, no links. Of course, no reduction of unsprung mass or reduction of road shock to the armature, and reduction in working efficiency due to compromises with pole configuration and air gap ... but here is an interesting demonstration of the principle often quoted for reciprocating steam that operating simplicity and general reliability can trump better nominal performance or higher "thermodynamic efficiency".
The funny thing is that I distinctly remember one of the Heilmann locomotive style steam-electrics using Batchelder drive (in a four-axle truck) and went so far as to look to see if they might be mentioned in this thread, they were link 'quill' drive with armatures concentric with the axles.
Again, guys, electric power doesn't count in this thread. Even ultimate-simplicity arrangements. The 'transmission' is already implicit in the current control and possibility for interruption implicit in all the electrickery before the traction motors. In the thread we even ruled out locomotives with torque-converter drive that don't have full lockup, and locomotives with clutched transmissions.
On the other hand, my early understanding of the Bowes drive (which turned out to be incorrect on studying some of the preserved material) was that it acted as a self-energizing combination of generator and traction motor "in one casing", which could be locked once 'slip' or torque multiplication were no longer desired for acceleration, or useful for braking. At least nominally, a locomotive with such a setup (such as the postwar version of the PRR V1 turbine) would be using direct drive in lockup.
erikem Can't get much more direct than that!
Can't get much more direct than that!
I look up the class EP-2 "bipolar" electric on Wikipedia and found that maybe the drive was less direct than you think.
You see, the whole motor was not attached to the axle, only the armature. The axle shaft with its surrounding armature was allowed to bounce up and down in relation to the motor field windings, which were fixed to the truck frame.
The field winding was an older "bipolar" design where the poles were on the horizontal axis, allowing the armature that moved up and down with the flexing of the axle "primary suspension." You see, with the poles sideways, the armature could move up and down in relation to them without hitting anything.
Clever, huh? The torque was not transmitted mechanically but rather through the magnetic field passing between the truck-frame bipolar armature and the axle-mounted motor armature. Maybe not very mechanically direct in its drive after all.
If GM "killed the electric car", what am I doing standing next to an EV-1, a half a block from the WSOR tracks?
RME RDCs are direct drive (via torque-converter lockup) in their high-speed 'range'. I should know, but don't, if the K-M locomotives have this characteristic... but I suspect not, as slack run-in from a train at high speed might break gear teeth otherwise.
RDCs are direct drive (via torque-converter lockup) in their high-speed 'range'. I should know, but don't, if the K-M locomotives have this characteristic... but I suspect not, as slack run-in from a train at high speed might break gear teeth otherwise.
My understanding of the Voith transmissions was that they did not have a provision for locking up the torque converters. The tranny's had three torque converters, ech with a different gear ratio and "gear changes" were accomplished by draining the oil out of one torque converter and filling another - apparently very smooth process. Efficiency at optimum speeds was about 85% and it dropped off at higher or llower speeds - suspect optimum scaled somewhat with engine rpm.
FWIW, gears were a significant source of inefficiency on early electric locomotives, especially when going faster than the speed at which continuous tractive effort was produced. Efficiency at maximum running speed for the geared locomotives was on the order of 70% vs nearly 90% on the gearless bipolar locomotive built for NYC and the Milw.
I also highly recommend Douglas Self's website for both the loco locomotives and retrotechnology. The articles on audio are interesting as well.
Thanks to ALL of you for the help. Each of you has given me plenty to ponder. The Russian units are the wildest in my mind combining steam and diesel.
Thanks
I am know about the Voith Drive Technology in the marine side of industry, never knew they designed systems for the rail.
Thanks for the note back. This is right on point for what I was wundering about, the complexity of the drive system is amazing.
The problems with direct diesel drive to wheels are many, some of which characterize the Thermolokomotive ... the most important difficulty is that a typical diesel has a minimum effective speed, so you either need a clutch (and probably jackshaft) or compressed air assist (as on the Thermolokomotive) to start the train and get it up to "combustion" speed. (With the exhaust expansion cooling while on air drive cooling down the cylinder head at just the time you want compression heating to ignition temperature...)
The interesting exception to this is the 'combination' steam/diesel locomotive, best exemplified by the Kitson-Still or ... something like this:
The basic idea is to use typical locomotive-pressure steam on one side of double-acting pistons (usually the 'end' with the piston rod) and compression-ignition cycle on the other, with the combustion exhaust passing through a HRSG stage which ... theoretically ... recovers some of its waste heat to the Rankine cycle. As it turned out in practice, there is precious little recoverable heat compared to the additional complexity involved in using it, and there are some consequences for emissions that didn't factor into the design process 'back then'.
There are Russian enthusiast sites for those things. I can see why.
I'm guessing when the guy asked about "direct drive" diesels he meant direct drive, like a reciprocating steam locomotive. Did any exist, aside from the ancient Sulzer?
There are some good direct-drive steam turbine designs (the Swedish 2-8-0s, the Turbomotive, and the PRR S2 being examples). An unbuilt but approved-for-production locomotive, the PRR class V1, would have had mechanical drive to eight axles (and even more problems than a Centipede with keeping wheel treads in shape!)
I suggest a perusal of Doug Self's site for most of the 'other' direct-drive versions, with careful attention to the rocking-lever Russian OR class (and perhaps the Teploparovoz!) and the Paget locomotive. There are a couple of interesting early 'rotary' engined locomotives (think of a reciprocating piston that produces rotating motion directly -- better seen than described) that have still not quite been 'explained' enough even by the Newcomen Society pundits.
The whole class of 'motor locomotives' probably count as direct-drive for purposes of this discussion -- there were a number of famous European types, one of which came to the USA after WWII and was shamefully scrapped (after the Germans didn't want to pay to get it shipped back!) in the Korean War scrap frenzy, and the partially-built B&O W-1 ... I leave it to the reader's ingenuity to give an appropriate Whyte code. In my opinion, some version of the motor-locomotive principle would have been a logical 'replacement' for many classes of orthodox reciprocating steam if diesel-electric development had progressed more slowly or been financially less successful.
CSSHEGEWISCH The 21 torque-converter locomotives sold to D&RGW and SP by Krauss-Maffei in 1961 and 1964 plus the three Alco C643H's sold to SP could be considered direct-drive locomotives.
The 21 torque-converter locomotives sold to D&RGW and SP by Krauss-Maffei in 1961 and 1964 plus the three Alco C643H's sold to SP could be considered direct-drive locomotives.
Depending exactly on what is meant by "direct drive". Most stringest case is a pure connection by gears or jackshafts, but a looser definition would include torque converters.
A lot of the early early internal combustion rail cars and small locomotives were gas mechanical (e.g. McKeen cars).
There were others too. One German company built a diesel locomotive for the Russians that had a three speed gearbox to a jackshaft drive. It must have been fun to shift a locomotive at speed.
Also the Russians developed several Steam-Diesel locomotives that looked like normal steam locomotives but with two sets of cylinders. One set of cylinders was normal steam cylinders while the other set was double acting diesel cylinders. The locomotive would start on steam and at some speed the diesel cylinders would be cut in for fuel economy. You can read about them here
http://www.douglas-self.com/MUSEUM/LOCOLOCO/russ/russrefr.htm
Think the Sulzer diesel was the first diesel locomotive-- before 1920, wasn't it?
And the drive doesn't get any directer than that. Used compressed air to start from a standstill.
Here is one direct drive diesel
It was built by Sulzer and ran in Germany between the wars.
Probably not quite what you are thinking about, but the Fell diesel mechanical locomotive from 1952 might be of interest - https://en.wikipedia.org/wiki/British_Rail_10100
It's about the closest I can think of to a large diesel loco with purely mechanical transmission.
Understanding steam locomotives are direct drive, has there been any other power units that were direct drive? Has there ever been a diesel engine that was direct drive?
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