Diesel Hydraulics...why?

[Modelcar]

.....Where do the innovators stand in putting the hydraulic system to doing the equivalent of dynamic braking.....?

[trainfan1221]

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? 

[erikem]

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.

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. 

[M636C]

.....Where do the innovators stand in putting the hydraulic system to doing the equivalent of dynamic braking.....?

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

[Anonymous]

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.

 

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.  

The K-M was a mechanical-drive locomotive with a torque converter.  I think what you are suggesting is that there is opportunity to revisit such a concept (but not a hydrostatic concept).  But I can't see why; the same old disadvantages of the K-M transmission haven't gone away in the meantime.

RWM

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.  I was thinking of the hydrostatic principle, for example. 

So, my question is:  Did the KM experiment refute the diesel-hydraulic principle in engineering terms for the U.S. market for all time, or did it just prove that the KM product was not properly executed for the U.S. market at that time?

It seems like it must have been the latter because, as you point out, the KMs were diesel-mechanical, not diesel-hydraulic.

 

[Convicted One]

Back in the 60s and 70s...possibly earlier, several builders and carriers experiemented with diesel hydraulics. Why? What were they trying to accomplish...what advantage would a diesel hydraulic have over a diesel electric? 

 

According to published sources, the reasons "for" Diesel Hydraulic locomotive interest were:

1. 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

2.  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.

3. 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

[Modelcar]

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....

[carnej1]

 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....

[Allegheny1600]

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 proven machines & too sophisticated, requireing too high levels of maintenance from an unfamiliar workforce - also (putting aside British Railways Board politics!) quite similar reasons for the failure of the D-H concept in the UK. Note: by the time the workforce were familiar with the machines in the Western Region of British Rail - the remaining D-H's were racking up considerably better reliability figures than the D-E's drafted in to replace them!

Thanks y'all

John.

[SactoGuy188]

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.

[erikem]

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

Don't forget that the SP ordered an additional 15 KM units (with hood carbodies) about the same time as they ordered the Alco's.

One attractive factor for the SP with the potentially higher factor of adhesion and higher continuous tractive effort for a given weight of locomotive, is reducing the percentage of overall train weight taken up by the locomotive. I would guess that ca 1960, the locomotives ascending "The Hill" would represent between 15 to 20% of the weight of the train (assuming continuous tractive effort was equivalent to 13-14% coeficient of adhesion and a 2.2% grade). 

[CSSHEGEWISCH]

One of the things mentioned in the June 1976 TRAINS article was that coupled drive axles were a major factor in contributing to improved adhesion.  Perhaps the French were on the right track with the "monomoteur" truck in which one larger traction motor drives both axles.

[TH&B]

I did not know that the USA banned the Germans from developing the diesel electrics. Well as you say the Germans just developed DH's, there's always a way around that. The US Army used diesel electrics in W Germany, but as far as I know as soon as armys left the Germans stopped useing these DE's.

 

But labour was cheap because of the war and of good quality, wich helped in the manufacturing of the DH's I would think. As compared to "Flatwheel Jct" somewhere on the long route of the SP or mountain lines of the Rio Grand. Labour costs today are high for anything at all in Germany.

 

Check this stuff out;

http://www.greatwestern.org.uk/dieseltxt.htm

[Tulyar15]

Lots of interesting info on that site, however I should point out one minor mistake concerning one of the two preserved 'Warships'. D821 "Greyhound" was in the fact the last working member of the class and was bought by the Diesel Traction Group in January 1973 - the first main line diesel loco to be privately preserved in Britain. (For our purposes I am not including switchers/shunters).

The DTG ( http://www.westernchampion.co.uk/ ) had originally tried to acquire a D6300 class loco and in fact had paid the money to BR to buy D6319 the last survivor. But she was cut up at Swindon by mistake. After an angry phone call to the BR chairman they were offered D821 at the same price.

Subsequently the DTG have acquired the locos listed on their site. Except for "Western Champion" all their locos have run on the North Yorkshire Moors Railway but are no longer based there. D821 is based at the Severn Valley Railway ( www.svr-vlo.org.uk/floodline.htm ), D1015 and D7029 at the EWS depot at Old Oak Common and D8568 at the Chinnor and Princes Risborough railway.

D832 "Onslaught" was used by BR's research department for several years after its withdrawal until eventually bought and restored by the East Lancs. Railway.

[Former Car Maintainer]

Was wondering how speed control was accomplished? Was the engine speed brought up to a fixed rpm and then the speed controlled by shifting valving in the auto tranny? Or was the speed controlled by linearly controlling engine speed? How was the speed control compatible with the Diesel Electric Notches?

[Overmod]

If I remember this correctly there are 3 torque converters optimized for different speeds, and they are actually emptied and filled sequentially to change the speed range.

The 'r' in their designation indicates a hydrodynamic 'retarder' which takes the form of two fluid couplings.

As one of these transmissions has been rebuilt to operating condition I expect there are detail pictures somewhere here:

http://sp9010.ncry.org/

[Erik_Mag]

Overmod

If I remember this correctly there are 3 torque converters optimized for different speeds, and they are actually emptied and filled sequentially to change the speed range.

That's what I remember as well. At optimum engine/track speed ratios, the Voith transmissions were about 85% efficient, which was about the same as a contemporary diesel electric with DC traction generator and DC motors.

[blue streak 1]

This is different but can be compared.  I drive a hydraulic powered Deere.  The performance is great over all speeds with the "prime"  mover running at top speed. Can maintain speeds to 1/2 MPH and suspect probably 1/10 MPH. Speed control is very precise although no way to compare to electric drive. 

Absolutely no unplanned maintenance on hydraulic drive with over 1000 hours.

BTW the pulling power is much greater than a Craftsman I own of the same HP.

Hydraulic and electric drives both have improved greatly from the D-H that SP bought.

[Former Car Maintainer]

Overmod

If I remember this correctly there are 3 torque converters optimized for different speeds, and they are actually emptied and filled sequentially to change the speed range.

The 'r' in their designation indicates a hydrodynamic 'retarder' which takes the form of two fluid couplings.

As one of these transmissions has been rebuilt to operating condition I expect there are detail pictures somewhere here:

http://sp9010.ncry.org/

 

The 9010 has currently restored one engine. The other engine was beyond repair and the second transmission missing. It appears the first transmission was serviceable and not rebuilt. Little information on theory of the voith transmission operation is mentioned. Supposedly, the KMs were able to get more horsepower to the bogies through the use of a double turbocharged, DOHC, 5 valve per cylinder compact power plants and an 85% efficient fluid drive system.

Back to the speed control question. The transmission supposedly had three torque converters and a torque retarder. The three torque converters, were likely controlled by actuators, and switched in or out through speed ranges. This would imply each converter had some type of gearing effect. But I read that each converter was actually designed for specific efficiency at a specific speed range. This would imply that speed was not controlled through converter shift, just efficiency. Perhaps the retarder was modulated throughout the acceleration process to control speed as well as during the braking process. The retarder did have a 5 valve modulator. Wonder if it worked like a vacuum modulator on a car tranny?

[Paul P]

I worked on 821 in heavy stone train service in it's last months before retirement. The loco covered 1.1 million miles in its 12 years of service.

[Former Car Maintainer]

Found the theory behind the hydrodynamic braking in the voith unit..

https://video.search.yahoo.com/search/video?fr=yfp-t&ei=UTF-8&p=Voith+aquatarder#id=1&vid=8fe74ec08c3fdc6f2fa52057cc2ef3fb&action=click

[Overmod]

Erik_Mag

At optimum engine/track speed ratios, the Voith transmissions were about 85% efficient

The astounding thing to me when I first read about these is that they have no positive engagement at all, either via some kind of progressive TCC or a lockup as on RDCs.

There are efficiency data for Allisons with no clutches, a couple of clutches, and clutches on all speeds. I have not made a rigorous study of the efficiencies but my overwhelming impression of these things in diesel pushers (Cummins C-range motors, about 833cid if I remember correctly, so larger than an 8-92TA as found in 'half an SPV2000') and fuel economy with actively-engaging lockup on all speeds is supposed to be considerably improved.

As I've noted with regard to duplex steam locomotive conjugation, a TCC or any other locking clutch on a large locomotive would need to include Ferguson-like functionality against various kinds of road shocks (and to save damage to the universals and gearing) but this would not be difficult for Voith engineers...