best fuel for a gauge one gas fired locomotive is the one that is safe to use,
performs best over a wide range of temperatures, and is available at the lowest
cost. I have arbitrarily decided not to consider propane (Pn) as a fuel
for gauge one locomotives because of its dangerously high container pressure at
any reasonable temperature. All manufacturers of gauge one locomotives
specifically caution against the use of propane as a fuel in their locomotives.
I am fully aware that some model engineers have had great success with propane
as a locomotive fuel, but that has been in locomotives specifically engineered
to accept the very high pressures inherent in the use of propane as a gauge one
model locomotive fuel.
performance is important because the liquid gasses that are used in gauge one
locomotives are dependent on temperature in order to vaporize properly at a
pressure high enough to be useful in the locomotive's burner. If the
temperature drops too low, vaporization slows down and the pressure at the
burner's nozzle drops. In the case of butane (Bn) this drop can be so
great that the burner refuses to burn much below 60 F without additional heat in
the form of a hot water bath in the tender or a cab mounted gas tank that
absorbs heat from the locomotive's backhead. Even if the outdoor
temperature is above 60 F the vaporization of the liquid gas in its storage tank
will cause it to lose heat energy. If the storage tank is too well
protected from the outside air, and little additional heat energy can reach the
tank, the gas pressure will drop until some steady state of reduced temperature
vs. pressure is reached. This condition explains why many locomotives
start off their running pulling strongly only to slow down or struggle by the
end of the run. It has nothing to do with the supply of liquid gas in the
container, but it has everything to do with the temperature of the container as
it affects the gas pressure at the nozzle.
of the liquid gas containers that are used to fuel gas one locomotives are
really designed to fuel camping stoves, illuminating devices and heaters for
campers, backpackers, hunters, and other outdoor users. The manufacturers
who cater to this market have a problem similar to the one that plagues gauge
one locomotives - outdoor temperature. Liquid gas evaporation is just as important
to the proper operation of their appliances at it is to the burner jet in gauge
one locomotives. As the out door temperature drops, the efficiency of
their products fall off and, in days past, the cold weather outdoorsman turned
to gasoline and kerosene fuels when the weather turned frosty.
gas appliance manufacturers look for a gas that would perform better at lower
temperatures, and the petroleum industry responded by developing isobutane (Bi) liquefied
gas to replace the butane liquefied gas then in service. Isobutane is an
isomer of butane. That means that it is has the same number of hydrogen
and carbon atoms, but that they are rearranged in a different order within the
molecule. This change results in a product that exerts more pressure
within its container at any given outdoor temperature than regular butane.
Although isobutane boosts the performance of outdoor appliances it has one
drawback and that is price. The petrochemical industry changes more for
isobutane than for butane because of the cost involved in juggling the atoms of
hydrogen and carbon.
had been long known in the petrochemical industry that it was possible to mix
two related gasses together (such as butane and propane) and to produce a hybrid
gas having a container pressure somewhere between the two, depending on the
ratio of one gas to another. This approach had a problem insofar as the
combined liquid gasses would not remain in a homogeneous state, but would
disassociate themselves over a short period of time. In effect what
remained was a container half full of propane and half full of butane.
This meant that instead of having a container of liquid gas at some median
pressure it would revert to the pressure of the propane for the first portion of
the use and drop to the pressure of butane for the remainder of the use.
told that the push in the United States to free the atmosphere of of Freon
products used as propellants in aerosol containers convinced the petrochemical
industry to revisit the blending of various liquid gas products. They saw
a potential market for these products as a replacement for the soon-to-be-banned
fluorocarbons, but the problem of disassociation still loomed.
this point the science of cryogenics entered the equation. Cryogenics is
the study of the behavior of substances at super low temperatures - somewhere
down around absolute zero. It was found that if two liquid gasses were
blended at a very low temperatures, somewhere around their freezing point, that
when they were allowed to heat up to room temperature they would remain stable
and exhibit pressure characteristics proportionate to the ration in which they
result of the work was a new family of aerosol propellants and the first of the
propane and butane liquid gas products for the cold weather outdoorsman.
There is one caveat. Cryogenically blended liquid gasses will, over time,
disassociate them selves in the container storing them is subjected to
temperatures below 20 F for extended periods of time.
blended products are now available for use in gauge one locomotives, but they
tend to come in containers that do not accept the standard screw-on decanting
valve that is used on the butane or isobutane containers. There are
exceptions, regional in nature, such as the imported containers from
England. I have been told of mixtures as high as 40% propane to 60%
butane, but I have never seen them. I suppose that their performance is
superior to isobutane, but I suspect that their cost is higher per unit of
Hadden, who regularly steams all winter in Utah, has been using a liquid gas
product sold under the brand name Gaz™, which consists of a 20% propane and
80% butane mix. I started using it last winter here in Sacramento.
The advantage of using Gaz over isobutane is two fold; it works better in cold
temperatures because of its higher container pressure (see figure one) and it is
far less expensive to purchase per unit of measure.
I pay 1 cent per gram
for Gaz (1# container) vs. 1.5 cents per gram for isobutane in my local outdoor
supply store. Unfortunately, the Gaz container is one that has now screw
threads and it will not accept the standard decanting valve. Both Jim and
I were using a Rube Goldberg setup to milk the Gaz container, but we felt that
the process was too dangerous (frozen fingers) for publication. There is
now a decanting valve available for the Gaz container.
hope is that this discussion of liquid gas fuels for gauge one locomotives sheds
some light on the folklore that seems to surround them in conversation at