Gas-powered Motorcycles

Gallery opened 2 Mar 2020

Updated 9 May 2020

Video of the gasbike in action

This idea for running motorcycles from coal gas (town gas) which contained hydrogen, carbon monoxide, methane, and ethylene, surfaced towards the end of WW1, when petrol shortages were starting to bite. It's clearly a very unwieldy set-up, and whether more than one example was made is uncertain.

Left: Motorcycle with a gas storage bag attached to the sidecar: 1917
The gasbag was made of fabric, presumably made gas-tight by some sort of coating, probably rubber. Its capacity was allegedly 600 cubic feet. The fabric was restrained by external cords and a conical plate on the front stopped the front of the bag being blown inwards at speed. What sort of speed would be possible with a large amount of asymmetric drag is hard to estimate.
Note the supply pipe running from the bottom of the gasbag to the engine. The drawing looks like it was derived from a photograph, so apparently at least one of these outfits was built.
Some gas-bikes are being made today, running off propane as conversions from petrol bikes. For example Greenfly.
A chap demonstrates his LPG motorbike on YouTube.
And there are instructions on how to convert your motorbike using the MagicGas equipment on YouTube.
Thanks to all those who sent me gas-powered motorbike links.
Image from Popular Mechanics for Nov 1917, p641

I have received this assessment of the idea from Mr J Kreutz, to whom thanks:

"The gas powered motorbike would be rather dangerous: I evaluate the area of the gas container at about 2 m². that means that with a lateral wind of 25 metre/s (not even 100 km/h) the drag might amount about 750 Newtons, the same force as the one exerted by gravity on a mean motorbike driver. Furthermore, the ratio of cantilever lengths of the center of the gas container, the hight of the motorbike seat, the length of the foot of the driver and so on let me suppose that this vehicle might have been rather dangerous and probably undrivable by bad weather conditions (wind gusts)... I consider here lengths by reference to the contact points of the tires with the road. I ride myself a motorbike (not methane powered!) and gusts with a speed of 100 km/h are still manageable, but require a lot of care of the driver... I can also suppose that speed above 30-40 km/h might have been problematic."

Having pondered the issue, I too have concluded that this machine would be uncontrollable in any sort of side-wind. There is also the buoyancy of the gasbag to be considered; it would tend to lift the side-car. More on this below.
However, there is now no doubt that the gasbike really did exist:

Left: Gasbike on the road: 1917
This is obviously the same machine as in the Popular Mechanics illustration. I had assumed the gasbike was an American invention, but it looks like it was British. The houses look British. The nose-cone carries the words 'CAM?? COAL GAS MOTORCYCLE'. A sidecar has been fitted to hold the wife and two kids.

Left: Youtube video of the gasbike: 1917
Remarkably, the Museum Staff have tracked down a film of the gasbike in operation. It is here. Towards the end the gasbike turns circles in the road, presumably to demonstrate that it did have some manoeuvrability.
Something interesting occurs at 5 seconds in; two men wrestle with some heavy object, possibly a box of bricks, and place it on the platform under the gasbag. I suspect that this was to counter-act the buoyancy of the gasbag, for as noted in the Museum gallery on coal-gas powered cars, coal-gas is lighter than air. The gasbag looks as if it is roughly a metre in diameter and two metres long, giving a volume of 1.6 cubic metres or 55.5 cubic feet. Compare gas-cars with bags containing 250 cu ft or more. Calculation of the uplift force should be do-able; the density of air at STP is 1.29 kg/m3 and that of coal-gas 0.58 kg/m3. So each cubic metre gives a lift of 1.29 - 0.58 = 0.71 kg so the total lift is 1.6 x 0.71 = 1.14 kg. That doesn't seem much; not enough to need a box of bricks to hold it down. Hmmm.
According to the commentary, the conversion was done by a Nottingham garage-owner.

Left: London bus with a gas storage bag on the roof: 1917
The American gas motorbike was inspired by the use of gasbags on London buses; Note the supply pipe running from the bag to the engine.
The placard on the front of the bus roof reads: "Eat Less Food" which does not sound as if it would help civilian morale; I suspect the artist may have made that up. The other placards are not legible. That there were food shortages is in doubt; see here, which a includes poster exhorting people not to waste bread. There is another good site on WW1 food shortages here. There were certainly posters saying "Eat Less Bread".
There is a site with more information on gasbag vehicles here.
Image from Popular Mechanics for Oct 1917