Air Conditioned Passenger Cars
By H.B. Bowen Chief of Motive Power and Rolling Stock
Many years ago Canadian Pacific published a series of ten books named the "Foundation
Library". One particular book in this collection, published in 1937, is named "Factors in Railway and Steamship Operation".
It contains many short stories and articles dealing with the company during that period. This month's article from that book, "Air
Conditioned Passenger Cars", written by H.B. Bowen, Chief of Motive Power and Rolling Stock, is reprinted here for your enlightenment
with the addition of some appropriate images.
Air conditioning has been experimented with since the
year 1930 by the railroads in the United States. We have followed this development since its inception and, in 1935, after examining all
the air conditioned cars that were then in service, it was decided to equip some of our cars.
We selected the ice activated system on account of its lower first cost and comparative simplicity as far as maintenance is concerned. A
recent A.A.R. test has confirmed this decision that the ice activated is the cheapest system to operate when the cooling season is short,
the condition we have in Canada.
In order to get some first-hand information with regard to the other systems, we have equipped one sleeper with a steam jet system, two
parlour cars with an electric compressor system, and several cars with the Waukesha compressor system, which does not take any power from
the engine but which obtains this power from the burning of propane. During the investigation period we were struck with the lack of
beauty in appearance of the outside duct system, similar to the first Pullman, where the distribution ducts are on the outside of the
cars, and, for this reason, we developed, and were the first to install in quantity, the inside duct which is merely a duct on the inside
of the car in the clerestorey, as against the ducts on the outside of the cars. This system has worked out well from the point of view of
the appearance on the inside and the outside, and we believe it is saving us considerable money in maintenance as well as a little in the
In general, all air conditioning systems work in practically the same manner, as far as the cooling and the distribution of the air are
concerned, that is, the air is taken in from the outside, filtered, and passed over coils or through water sprays to cool it to the
desired temperature, from which the air is distributed into the car, where it takes up the heat from the car and enters a re-circulation
filter, where it is again filtered and returns to the circulation duct to complete its cycle again.
One of the first things that impressed us in this survey was the objectionableness of the high velocity air jets, which several railroads
and sleeping car companies were putting into the car, and, for this reason, we decided at the outset to obtain a larger quantity of fresh
air than was then generally in service, and to distribute it into the car at a low velocity. This has worked out very well, as the
passengers receive all the comfort due to the cooling of the car without any of the objectionable draughts which are sometimes found in
other railroads' cars. This one thought gave rise to the design of the large area lower berth outlet which can be turned in any direction
and which has a manually operated damper, which the passengers can control at their own convenience. This lower berth outlet has caused a
great many very favourable comments from passengers and, to our mind, is one of the best types there is now on the market. Unfortunately,
on some cars of very old design this type cannot be applied, due to the construction of the car, but in general it is followed out as far
as it is possible to do so. As the amount of air that can be put into a car is largely dependent on the size of the ducts, we use three
20 x 20 fresh air grills, whereas the largest size used on foreign roads is three 16 x 20. Several other railroads do not use any
recirculation filter at all but, due to the amount of lint from the bedding and from the carpets, etc., we are still using two 20 x 20
recirculation filters, which ensure at all times properly conditioned air entering the car.
We have found from experience that 25 percent, fresh air, when heating or cooling, ensures the air being kept in a good condition if the
cars are thoroughly blown out before the passengers enter, with 100 percent fresh air by opening the end doors. In the winter time,
however, we have found that this 25 percent fresh air is a little too high for heating and we have accordingly reduced it to 16 percent in
zero temperatures. Another little refinement which we have developed in connection with conditioning the air, is a damper in the
smoke rooms, our porters having found that the amount of fresh air which was introduced into the smoke room during the night caused
discomfort. We have accordingly perfected a small damper in this distribution outlet, which enables the porter to turn off a large amount
of air during the night, and turn it on again in the morning when the passengers are dressing.
During 1936 we made an elaborate series of tests of our cars in conjunction with the A.A.R. Bureau of Research, and the final results of
this investigation have shown that our cars have probably the best coast-to-coast operation record of any trains on the continent. In
order to ensure that they are being kept in as nearly perfect condition as possible, we have sealed up the outer sash on all of our air
conditioned cars, leaving the inside sash in the majority of our cars so that they can be raised for cleaning. This one move has been
responsible, to a large extent, for the cleanliness of our cars, as it does not permit the dust to sift through the windows to the same
extent as it did in the past. This also applies equally as well in winter weather, when drifting snow has always been a source of
annoyance to the passengers who imagined they were cold when they saw snow between the two sashes.
The electric power load on an air conditioned car is considerably higher than the standard car, which has only generators and batteries
available for lighting and, for this reason, practically all of the cars which were air conditioned have had the size of the generator
increased and the capacity of the batteries increased in proportion. This required some changes in the wiring, and gave us an opportunity,
at the same time, materially to increase the lighting. The application of the inside ducts in a large number of cases meant the removal
and re-application of the ceilings. We have taken the opportunity at this time not only to improve the lighting from a light standpoint,
but also to improve the light distribution from the passenger's standpoint, by painting the upper decks a light colour instead of the old
sombre tones which were in use before air conditioning became the vogue.
There is one point which I would like to bring out in connection with the cooling of the air with the ice activated system. I have heard
several people criticize ice activated cars, stating that the ice activated cars smell differently and are not generally as satisfactory
as the mechanically cooled cars. The only difference between a mechanically cooled car and an ice water cooled car is that the cooling
coils over which the air flows in one case are cooled with ice water and in the other case with mechanically cooled Freon. In no system
does the air come directly in contact with the cooling medium. The complaints which sometimes occur of stuffiness in an ice cooled car, in
general are due to high humidity, and have no connection whatever with the fact that ice is used instead of mechanically operated
compressor. The cooling system on an ice activated car consists of one or two ice boxes underneath the car, which carry from three to five
thousand pounds of ice. The cooling water is forced through the ice box around the ice and cooled to the proper temperature, where it is
pumped up by means of an electrically operated pump, through the cooling coils, and thence back to the pump or the ice box, depending on
the temperature that is required in the car.
With the mechanically operated system, there is an electrically operated compressor, which compresses Freon, which is forced into the
cooling coils over which the air passes, where it is expanded and again returns to the compressor for cooling and is again re-compressed,
to complete another cycle.
In the Waukesha System, the power for driving the compressor is secured from a gas engine which uses bottled propane for its fuel. This
system operates in exactly the same way as the electric system, except that it is independent of the locomotive power or steam from the
locomotive for its motivation.
There is another system, known as the steam jet system, where steam from the engine is piped back into the cooling machine, where it is
expanded, thus creating a vacuum which causes the water to boil at a very low temperature, which in turn cools the water down to
approximately 50 degrees F, whence it is pumped into the cooling coils in exactly the same way as an ice activated system.
All of these cooling agencies have their particular fields of use, and where the cooling season is very long, as on an American Railroad,
it is cheaper to use a mechanical cooling system of one of the kinds mentioned, but in Canada, where our cooling season is so short and
where the nights are in general cool, the ice activated system has proved to be the most efficient and economical.
In sleeping cars, where there is an attendant always present on the car, the controlling mechanism for keeping the car at the proper
temperature is handled manually by the porters or attendants, but, on coaches, etc., where the brakemen have other duties to perform,
there has been developed a new type of control known as the co-relative control, which keeps the inside temperature of the car within a
certain range relative to the outside temperature, the medical section of the A.A.R. having found that a person leaving a car and going
out into a temperature which is approximately 20 degrees F or more higher than the temperature in which he has been sitting in the car,
would be quite apt to receive a shock which, of course, might be more or less serious, depending on the physical condition of the
passenger. This co-relative control takes care of this condition, and we are one of the first railroads to adopt this system widely. If
further experimentation proves that it lives up to expectations, it probably will be generally used on all equipment.
In studying the comfort of passengers, besides having improved the lighting, appearance, ventilating, and heating of cars, we have secured
a sound level indicator which registers the noise levels of the cars. By establishing a noise level based on the type of cars previously
in service, we were able to establish a noise level for air conditioned cars which has been generally adhered to in the cars turned out
during the last year. As far as I am able to determine, we are the only railroad that has established, as yet, a noise level for cars.
The application of air conditioning to old and varied types of passenger cars is a matter that the layman very seldom appreciates. The
complicacy of the controls, tying in as they do with the regulations of the electric current, the thermostatic temperature control, and
the putting in of ducts into an old structure, without spoiling the appearance of the car, involves an enormous amount of detail work in
the Drawing Office. For instance, the application of the ice boxes underneath the car entails practically the entire revision of the
underneath parts of the car, and increases the weight of the car to such an extent that, in general, new, heavier axles have to be
applied. Because of the added weight, the braking power of the car has to be increased in proportion, in order that the car can be as
safely operated as before. In order to test the air conditioning apparatus, it was necessary for us to develop a Testing Laboratory with a
competent staff, at Angus Shops, so that each car, before being turned out into service, is put through the same tests that the car will
actually get in service, that is, in the shop the temperature is maintained at approximately 100 degrees F, with a very high humidity. We
were the first, and as far as we know, the only railway to install a Test Department of this kind. This Test Department has proved its
value in a great many ways in the last few months.
When we started, in 1935, to air condition 142 cars during 1936, the railroads of the United States and their car builders were very much
astonished and questioned whether or not we would be able to handle this number of cars. The work, however, was handled by Angus Shops and
the cars delivered approximately on time. This year we are air conditioning 152 cars, which means the ordering of a very large and varied
number of materials and the expenditure of considerable money.
Railroads in the United States, of course, have a somewhat different condition, inasmuch as their sleeping cars and parlour cars are
handled by the Pullman Company and they have only to take care of coaches and head end equipment. Due to the fact that we manage our own
sleeping car business, we have had to do the work which the ordinary railroads do for themselves, as well as the work which the Pullman
Company does for them before furnishing them with air conditioned rear end cars. This is a very unusual condition, and I think that our
shop forces at Angus should be highly commended for having accomplished this stupendous task in such a short time.
The general trend of air conditioning in the future appears to be one of simplifying the present cooling systems and medium of
distribution. As this development is still in its infancy, it has been surrounded by an enormous number of old standards and parts adapted
from commercial jobs. This condition is gradually being cleared up, and, in the future, I think we have every right to expect a much
lighter, simpler, and cheaper method of doing the work in a way probably more satisfactory to the travelling
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