Thanks. It’s interesting that such a technology has been around for so long and so many people have toyed with it, yet it’s never made it into a production car.
Noise and efficiency problems. Especially efficiency–running a pump and a hydraulic motor, and the hydraulic flow pressure loss in the plumbing, sucks up a lot of energy. A conventional manual transmission, which is nothing but gears, is much more efficient.
I owned a Citroen Dyane (the posh version of the 2CV, with different bodywork but otherwise the same) with the 652cc engine, from 1975 to 1979.
It was superbly economical, practical, and fun to drive, but horribly lacking in acceleration. Overtaking was a chancy business, planned with a calendar and an up-to-date will. However, top speed was quite acceptable; hard to say what it was as the speedo only went up to 80mph and the needle would go past that and out of sight, so long as you were prepare to keep your foot flat on the floor for quite a while.
On the downside, the air-cooled engine was prone to overheat, accessibility was not good (it once took me all day to change the contact-breaker) and the corrugated cardboard tubes that piped hot air to the cabin tended to come lose and drape themselves over the exhaust manifold, leading to the stimulating experience of smoke & flames pouring from the heater vents.
I replaced it with a Renault 5 TS, which was twice as complicated, much faster, but still much more reliable. I did not look back.
Really? More efficient than a Prius is how one model is described.
I’ve seen hydrostatic drives designed for use in self-propelled aerial manlifts, telescopic fork trucks, and a variety of speciality ag and construction equipment; all of which, however, had a relatively high flow rate and low (max 10mph) speed. The pumps are noisy and cooling can be an issue if you don’t have a large enough hydraulic reservoir to cool the working fluid. (One one compact skid-steer loader we had to add fins to the inside and outside of the reservoir to get enough cooling under constant operation because the res was small.)
The main advantage of using hydrostatic drive in such equipment is that you don’t have to build around a mechanical transmission with straight shafts, differentials, couplings, et cetera; instead, you use rigid pipe and flexible hose to deliver power to motor hubs or hydraulic actuators, and since you usually have other hydraulic actuators (cylinders, rotators, et cetera) that you’re driving, it all becomes part of one powertrain. You can also use a much smaller motor than you would use in a mechanical system because instead of having to go through complicated gear reduction from a motor crankshaft to obtain enough torque to start moving, you can instead easily make use of mechanical advantage and the relative incompressibility of hydraulic fluid to trade flow rate for torque. The downside is you have to cope with leaky fittings, chafing hoses, flow resonance and back pressure, et cetera.
With an automobile. I’d have a hard time seeing how to get the high flow rate necessary without overheating the fluid. The hydrodynamic torque converter on a standard planetary gear transmission is bathed in open fluid and those tend to overheat if you put too much load through them.
They hydropneumatic suspension system pioneered by Citroen is more interesting and variants have been used on many automobiles, including the Mercedes 450SEL 6.9 and 500SEL. It’s a leap ahead of purely passive mechanical suspensions, but I suspect that magnetorheological or inductive (Bose-type) suspension active dampers will probably become the next widespread revolution in production suspesions.
Stranger
I used to work for an advertising agency where we did a lot of work for the manufacturer of an articulating dump truck. The firm has now been bought out by Caterpillar and I haven’t a clue if they still produce the same design but one of the features was that they used a derivative of the Citroen hydropneumatic suspension system. This was before I bought my first Citroen, a GS, and understood what all the fuss was about. Seems a sensible application.
One problem that CITROEN had in the USA was the lack of a fully-automatic transmission-instead, they had a clutchless manual, called “Citromatic”. As i recall, it worked fairly well, but had a few weak links-like the fact that the shift forks were actuated by hydraulic cylinders-which froze up, locking the transmission into gear (a bit of a problem if you have to stop). Did CITROEN develop a fully automatic transmission?
There are current Citroens with conventional automatic transmissions.
The main reason they died out in the US was the regulation concerning the bumper height above ground. When the engine wasn’t running the early ones ‘sank’ to their bump stops and infringed the regulation.
Ironically, with the engine running the bumper height was maintained regardless of whatever load was carried in the car. In this respect they were the only cars that actually complied with the regulation, although the ride height could be increased or decreased this was (is) only for limited applications
Apart from anything else, if you wanted something like a 2CV, by 1959 you could have a Mini, which was nearly as slow, and even more cramped, but actually went around corners without tipping over.
You didn’t get the natty full-length soft-top, but you also didn’t have to lean to one side to brace the car against crosswinds, either.
They’ll probably build a “2CV-inspired” model one of these days, a la the new Mini and new Beetle.
2CVs are actually quite hard to tip - they lean at lot - owing to the soft, high suspension, but there’s very little weight above the chassis, so although they look tall and wobbly, they’re actually very stable.
If they can recapture the fun of it, I’m all for it.
BTW, Nissan has a small van that is clearly 2CV-inspired - it’s called the S-Cargo (a play on Escargot - as it does look - and probably perform - like a snail)
http://images.google.co.uk/images?&q=nissan+s+cargo&btnG=Search+Images
The forklifts I’ve seen that have used that setup have all been relatively quiet. I’ve noticed, however, that noise and performance levels can vary greatly from manufacturer to manufacturer, so perhaps one or two has it figured out, but so locked down the various patents that nobody else has been able to work around them and is unwilling to shell out the money to license the technology. Details on the UPS system for their trucks can be found here.
I would say the C3 Pluriel is pretty much the successor to the CV2 – it even comes with the peel-back top. http://www.citroen.com/CWW/en-US/RANGE/PrivateCars/C3Pluriel/default/
Yeah, but it lacks the frog-eyed lunacy of the 2CV - which was my favourite part.
Not as hard as you might think. My brother had a Mini, then a 2CV, and you definitely couldn’t drive the 2CV the same way.
We lived in Dorset and he was saved twice by hedges bordering winding country lanes when he managed to make it fall over.
My Latin teacher in prep school had dozens of the things; he bought a new one every year or two from 1970 until about 1988. During the spring term the best player in the previous week’s Firsts cricket match got to drive it back to school from the practice fields. Much fun.
The transmission on a (top-line) DS is a marvel. You shift gears with a little wand that sticks out of the top of the steering column. No clutch pedal. The clutch is actuated, the engine is revved down and then up a little, the gears are shifted–all hydraulically, controlled by a module full of valves. My friend God of Citroens claims that Citroen had a program of steady improvements to the car and that later production ones are very reliable.
The 2CV’s transmission, by contrast, is a stone-simple three-speed.
If anyone here has seen the Irish thriller/drama Dead Man’s Shoes, which takes place in a small village, there’s a gang of local toughs whose badass leader drives a green 2CV, and the whole gang rides around with him in it. That’s, like, 6 or 7 guys all crammed into the 2CV. It’s funny because it totally undercuts any sense of intimidation that they might have been trying to project.
Reminds me of my Fiat 600. This was finger operated, but had disintegrated by the time I’d inherited it
My father, a European automotive writer, once saw 2CV’s raced. Described the sight as (iirc) “bellypans showing and spinnakers set”
Slight hijack. Manually pumped windshield washers -
I’m moderately curious if any other manufacturer did what the VW Beetle did to avoid having to pump the washer. Very early Beetles had a manual pump. Later ones (post '62) had the windshield washer hooked up to the spare tire. If the windshield washer stopped squirting, it could mean that you needed to put air in the spare, not washer fluid in the reservoir. The '72 I had supposedly had a pressure valve which prevented the spare from being deflated too much.
They’re still raced, such as at this event
My 1964 Rambler American (Americaine, for you Europeans 
) and my 1972 Plymouth Duster both had foot-operated squish-pumps for washing the windshield.
The Rambler had vacuum-operated windshield wipers, too–I always told my wife that anyone who would try to drive uphill in the rain deserved what was coming to him.