I wondered why there is no diesel-hydraulic loco in use in US RRs? Too maintenance-intensive? low hauling capacity? price? From another side, SRT have several diesel hydraulic switcher in use and some diesel-hydraulic road power in the southern route.
I certainly don't know why. The power of the hydraulic transmission is significant. IIRC, Amtrak tested a hydraulic (with cantenary?) about 10 years ago. It was much more powerful than what Amtrak was seeking. I believe this was attributed to the power transmission unit being hydraulic. OTOH, whn you have a bazillion diesel electrics in your country, all made by large US corporations, I guess it is hard to change. Espee and DRGW did have diesel hydraulics for a short period several years ago. Are the Thai engines hydraulic? I have been to Thailand many, many times and never noticed that. I'm not sure you could notice that externally? Thanks.
Hi Srt-fan. You ask about diesel-hydraulic locos. Both Southern Pacific and Denver & Rio Grand Western tried diesel-hydraulic powered locos from a German manufacturer, Kraus Maffaei, but were not successfull. The SP had 6 units and the D & RGW had 3 units. The SP bought D & RGW's units. The locos were more powerful than the other diesels that SP had, but they couldn't stand up to the rigours of mountain railroding. They also couldn't be mu'ed with other diesel locos, which limited their availability. I unfortunately don't have any dates at this time, as I'm writing purly from memory, but if you want, I'll look up the dates for you. Hope this is of use to you?
SRT Have several Henschel switcher in yard duty and some of Krupp 1500Hp Diesel hydralic road loco; the rest are diesel-electric. I'd hunt them down for you soon. Meanwhile, these are the pictures that our local railfan took. Enjoy. Henschel Krupp
US RR's don't like "new" or "different" technology. The KM locos didn't "cut it" as stated above, and at one time Alco had a hydraulic driven fan on their units. The RR's didn't like that either. Hydraulic oil is hot, and if a leak "pops up" in service, that can be a major problem. Hot leaks, reverse hose installation during service, all were/are a factor in RR's just saying "NO" to any type of hydraulics on their locos. MOW/track equipment is another story. A ton of hydraulics on these units.
Krauss-Maffei Engines in America The six Krauss-Maffei locomotives were first tested on the D&RGW in 1961. They were mounted on a pair of 3 axle trucks (C-C). According to Hollingsworth and Cook,On the D&RGW, the locomotives worked in duplicate or triplicate on trains of 4,000t to 7,000t on 1-in-50 (2 per cent) gradients. Although their work was satisfactory, the road decided not to continue with the experiment, and when the locomotives had covered 200,000 miles, they were sold to the Southern Pacific. The latter, by contrast, was sufficiently impressed to order 15 more, which were delivered in 1963. With a total of 21 of the German machines, SP was able to assess their economic and technical performance. The verdict came in 1968; the hydraulic transmission "could provide a reliable means of propulsion with competitive maintenance costs," but the engines suffered from "complexity of construction and inaccessibility for repairs." Air intake problems arose in tunnels, and the pneumatic controls were troublesome. Some modifications were made, but as the diesel-hydraulics came due for heavy repairs, they were withdrawn from service. SP also flirted with some Alco DH locomotives, but when Alco went belly-up, so did the idea of using DHs. My perception is that while DHs work, they don't show any real advantages over DEs to the point of justifying a change-over. Different parts and different tools and training make maintaining your power plant more complex and therefore more expensive. It just didn't make sense on paper back in the 1960's.
Electric traction requires no "transmission" to shift gears, as the rotational variation requirements of the wheels are much great than the crankshaft of the prime mover can accomodate. In other words, electric transmission is actually simpler and more efficient than a Diesel hydraulic transmission. It also provides greater tractive effort. Some very small Diesel hydraulic locomotives are still used for industrial switching. These were always an option with Plymouth Locomotive Works.
