Edinburgh's Transport

Gas-powered Buses

Technical Comments


Alex Dow

Thank you to Alex Dow, Fife, Scotland, who wrote:

Liquid to Gas

"Gases typically are around 800 times the volume of their liquid version, ie one cu foot of most liquid forms of a gas will occupy about 800 cubic feet.  For example, the steam from a litre of boiling water occupies about 800 litres.

LPG or Liquified Petroleum Gas as mooted for motor vehicles today, for any given liquid volume has only about 55% of the energy content of the same volume of conventional petrol."


"That is for every litre or gallon of petrol used in a car, it would need almost 2 litres or 2 gallons of LPG in liquid form to cover the same distance.  Hence one litre of LPG costing roughly 50% of one litre of petrol.  So the gases produced in those Producer Gas Trailers during WW2, provided relatively little energy compared to petrol or diesel.

Gas also does not have the natural lubricating properties of petrol and more-so diesel, so with the need to keep the buses in low gear even more than usual, there would be a lot of friction and wear - not what you want during a war particularly."


"This resulted in the buses being grossly underpowered; and therefore not successful in a hilly town such as Edinburgh, especially as there is the additional weight and friction of the trailer and solid fuel to trail around. It is also why very few commercial vehicles run on LPG today.

They were of more use on flat routes; and some of the SMT country runs may have been suitable, such as along the coast to Port Seton, although I don't recollect actually seeing any SMT buses with those trailers."

Alex Dow, Fife, Scotland, December 5+6, 2006


More comments from Alex Dow

Thank you to Alex Dow for also sending me his comments on:

gas-powered buses in WW1 and WW2, and

- gas trailers at Central Garage, Annandale Street in WW2


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