What is up with these old french cars?
November 25, 2022 8:02 AM   Subscribe

I was watching Army of Shadows last night and in several scenes there are cars driving around with gas cylinders strapped to their roofs. Like the kind of cylinders you would find at a welding supply store. What is going on there? are they running on compressed gas? and which gas? For some context this movie takes place in occupied France during the second world war and these were seemingly just regular passenger vehicles.

I tried googling this and ended up finding a whole raft of other french cars with inflatable gas bags on their roofs, which was apparently a thing for running ones car on coal gas. But I don't that's what these were.
posted by selenized to Technology (12 answers total) 3 users marked this as a favorite
 
Best answer: Yes - same principal, here is an example with a bit of detail.
posted by Leud at 8:09 AM on November 25, 2022 [1 favorite]


The image under the compressed gas section of this blog post looks more similar than any of the gas bag designs, suggesting it might be compressed natural gas (though it sounds like that was more dangerous than coal gas or firewood fuel conversion). Given that pretty much all petroleum was diverted to the war effort, people got very creative with how to power their cars during the period.
posted by terretu at 8:10 AM on November 25, 2022


There's a mention here (towards the end of the article) that
"The only exception [to not compressing the gas] was the use of gas cylinders in France during World War Two (picture above), allowing for a smaller fuel tank or a better range. Natural gas was used in this case, which could be compressed without the drawbacks of compressing town gas. However, this configuration turned out to be more expensive and more dangerous."
posted by scorbet at 8:10 AM on November 25, 2022


Best answer: There is a page on Douglas Self's Museum of Retrotechnology site including photos of cars with gas bags and with cylinders, identifying both as a means of running on coal gas.
posted by automatronic at 8:11 AM on November 25, 2022


Response by poster: Oh that's super cool, I just assumed they were different because, well, one is a giant balloon on the roof (full of poisonous, heavier than air, carbon monoxide ..uh..) and the other were more conventional gas storage. The metal cylinders also seem to be more of a French thing.

(Just a note: Douglas Self's website only works with http, if your browser automatically switches to https, like mine does, it just gives a 404 error)

There's something of an alt-history of automobiles in this too. In some ways running one's car on town gas or natural gas is a "more obvious" way of going about things, for commuter vehicles, since you can fill your car up at home from the gas you already have supplied. No need to build out all the infrastructure needed to supply some alternative liquid fuel, such as filling stations &c. Interesting to think about how different the world would be if technology went that way before the widespread adoption of gasoline
posted by selenized at 9:20 AM on November 25, 2022 [1 favorite]


A lot of taxis in China run on CNG, though in that case the tank replaces the boot/trunk. (Which is always great when you're on the way to the airport with cases). Some of the petrol/gas stations there have CNG as an option, but not all.
posted by scorbet at 9:53 AM on November 25, 2022


CNG passenger cars are one of my favorite weird rabbit-holes—a few were made available in the US in the late 90s through the early 2010s (the last common one that wasn't a bus or a work truck was the Honda Civic GX), and until battery technology advanced enough to get us deep into the triple digits for range (which thankfully happened pretty fast) you can see how that might have been a more palatable way to wean people off gasoline. (Really makes me wish people'd tried it in the 70s and 80s.)

Until 2015 Honda would sell you the Civic GX (which looked exactly like a regular Civic and got 250 miles to a tank). There's some CNG filling station infrastructure out there that you could access that's mostly used by buses, garbage trucks, etc., but the exciting part was that you could buy a compressor called the "Phill" that would hook up to a 240v outlet and your gas line and fill the tank in your garage. (One awkward side-effect of CNG is that it adds a wear part, instead of replacing a bunch of them like a BEV does—you have to get the tank replaced every 10 years or so due to the stresses on it.)
posted by Polycarp at 10:33 AM on November 25, 2022


Natural gas powered vehicles are also very common in some parts of southern Asia, particularly Bangladesh and neighboring parts of India. CNG is significantly cheaper than gasoline, but the range per fill-up is much shorter, and you lose a lot of cargo capacity, so it's a trade-off.

I'm told that gasoline to CNG conversion is pretty straightforward, the kind of thing someone with basic tools can do in a garage in an afternoon if they are familiar with the car. It was probably even easier on carburetor-based designs; IIRC I think you just flow the gas through a pressure regulator and into the throttle body. (This is how my NG-powered generator seems to work.)

So it makes sense that people would have done it themselves during the war.

In the US, I have heard stories about people making methanol from farm waste during the war, and then cutting gasoline with it, in order to stretch the gas further. I've also heard that some people used peanut oil instead of petroleum oil in low-speed engines (tractors). I can't confirm either, but they are both not technically implausible.
posted by Kadin2048 at 10:40 AM on November 25, 2022 [2 favorites]


Pretty common in Argentina. My father-in-law had a pick up that ran on it - he reckoned that the truckers could go on strike and there would be no gasoline, but it was much less likely that natural gas pipelines would be shut down. We're in a pretty remote area, so I think the pain in the arseness of making sure he was always in range of a refill got old and he switched to gasoline.
15 years ago it seemed like most of the taxis in BA ran on it, not sure now.
posted by conifer at 1:08 PM on November 25, 2022


For some context this movie takes place in occupied France during the second world war and these were seemingly just regular passenger vehicles.

Focusing on this part, be aware that wood gas cars were a thing back then, due to rationing of regular fossil fuels: https://en.wikipedia.org/wiki/Wood_gas

Although the gasifier was usually mounted on the rear of the vehicle, not the roof. Google Images
posted by intermod at 2:47 PM on November 25, 2022 [1 favorite]


There was a period from the late 70s into the 90s where LPG and CNG conversions were common here in New Zealand, as a result of the 70s oil shocks. There was even targeted government support for conversions. (For distance reasons oil derivatives are fairly expensive in NZ, but natural gas is produced locally). If you got a taxi it would be a big old Ford Falcon or Holden Commodore with a gas cylinder in the boot. I think the economics were marginal for most people but for those who drove for a living it was worth it.
posted by i_am_joe's_spleen at 3:59 PM on November 25, 2022


wood gas cars were a thing back then

I've heard of people trying to duplicate this war-time technology and failing, it may be a lost art.

And since we're discussing CNG I want to note that it also powers all of the green&yellow tuk-tuk/auto rickshaw/taxis in Delhi.
posted by Rash at 11:56 AM on November 27, 2022


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