Medical Society of the State of North Carolina. An.

Cyclopedia of automobile engineering; a general reference work on the construction, operation, and care of gasoline, steam, and electric automobiles, instruction in driving, commercial vehicles, motorcycles, motor boats aerial vehicles, self-propelled railway cars, etc online

. (page 10 of 27)
Online LibraryMedical Society of the State of North Carolina. AnCyclopedia of automobile engineering; a general reference work on the construction, operation, and care of gasoline, steam, and electric automobiles, instruction in driving, commercial vehicles, motorcycles, motor boats aerial vehicles, self-propelled railway cars, etc → online text (page 10 of 27)
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in an exhausted condition, as this is very detrimental to their con-
tinued usefuhiess. However, as most commercial vehicle batteries
are chained every twenty-four hours and the car's run is planned to
lie within its traveling radius on a single charge, with a factor of safety
allowed in addition, this is not a very onerous duty. The further
requirement of noting the current consumption on starting and
running, as indicated by the ammeter, in order that any defect in
the operation of the running gear of the car may be detected and
remedied, is abo a very simple one, so that an unskilled driver is
available at a correspondingly lower charge for labor cost in the
operation of the vehicle.

Power Efficiency. The amount of power available on a single
charge of the batteries without unduly increasing the weight is so
limited, that in the design of -the electric great care must be taken
to eliminate friction and other sources of power loss at every possible
point. Thb is further necessitated by the gradually decreasing
eflBciency of the batteries with age. Starting at 80 per cent eflBciency
when new, this may rapidly drop to 50 per cent or below, unless the
batteries are properly maintained, and this is likewise true of the
transmission efficiency of the running gear of the vehicle, so that
while unskilled labor may be employed for the operation of the
vehicles, this is not the case where their maintenance is concerned.
Power losses due to the tires are abo an important factor, and as
the pneumatic can very seldom be considered for commercial service,
the same degree of efficiency b not obtainable from the business
electric wagon as from the pleasure type employing the same motive
power. Road conditions must abo be considered, despite the fact
that electrics are employed almost exclusively for city or near by
suburban service, as mud, snow, and ice in winter, and poor pave-
ments at any time, cause an increase in the current consumption.

It is safe to say that if improvements in design had not been
effected as the result of experience, the electric vehicle would now
have been practically eliminated as a factor of importance in the
commercial vehicle situation, as the early types were extremely waste-
ful of power. One of the many reasons for thb was the employment
of two motors, which were at first considered necessary. It was
found that the substitution of a single unit of slightly less capacity
than the combined power of the pair previously employed was a



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long step in advance where power saving was concerned, and the
practice of using but one motor even on comparatively heavy vehicles
is now generally followed. This also served to cut down transmis-
sion losses, though it involved the use of a balance gear, or differ-
ential, to take the place of the independent drive to each rear wheel
that was in vogue when two motors were used. The abandonment
of a spur-gear drive in favor of chains was also a further improve-
ment in the same direction. This made possible the removal of the
motor from proximity with the driving wheels, to a point on the
chassis where its weight could be better supported by the springs,
thus effecting a step in advance on the score of maintenance as the
motive power was no longer subjected to the severe pounding.

BLBCTRIC DBLIVBRY WAQON

Whether considered from the point of view of design and con-
struction, or from that of operation, the electric delivery wagon is
without doubt the simplest vehicle in the commercial field. As
already mentioned, its operation may be mastered in a comparatively
short time, either by the ex-horse driver, or by a person who has
never had any experience in the control of a vehicle, so that the labor
cost — always an item of importance in this field — ^may be materially
reduced without fear of the equipment suffering in consequence.
* It will be noted under on "Electric Trucks," Page 22, that it is cus-
tomary with manufacturers of these vehicles to adopt a standard
form of design, which is employed throughout in every size listed by
the same maker, the only differences being those of dimension,
load capacity of the vehicle, and capacity of the battery to take care
of the increased weight.

This is likewise the case where electric delivery wagons are
concerned. For instance, all the Studebaker delivery wagons are
characterized by the same feature of design, except the one rated
at 500-pounds capacity which is intended for very light work. This
car is equipped with a single, high-speeii electric motor, placed for-
ward under the body and arranged to drive the rear wheels through
a countershaft and chains. All the others are equipped with two
motors which are placed near the rear wheels and drive the latter by
countershafts, roller chains, small sprockets on the ends of the
armature shafts and large ones bolted to the driving wheels.



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10 COMMERCIAL VEHICLES

Package delivery wagons and express wagons of the electric
type have a useful load capacity rangmg from 500 to 2,000 pounds,
though very few of less than 1,000-pqunds capacity are now built
or employed. They are designed for maximum speeds of 10 to 15
miles an hour under favorable conditions on the level, and are fitted
with batteries permitting of a maximum traveling radius of 40 to
50 miles on a single charge. The 40-mile run is standard and is
based on an average speed of 10 to 12 miles an hour, including stops,
as the necessity for frequently stopping and restarting the car in de-
livery service has an important bearing on the mileage of which the
car is capable on a single charge. The latter is naturally figured
on the maximum eflBciency of the car as a whole, so that in practice
this is seldom fully realized, due to the deterioration of the batteries
in service. Consequently, while there are numerous instances on
record of vehicles doing 40 miles a day or better, 25 to 30 miles will
more nearly represent an average figure.

Design. The design of many of the early electric vehicles fol-
lowed very closely the lines laid down and adhered to for so many
years by the wagon builder. That is, the entire vehicle was a unit.
Then, the practice of making the power-plant and nmning-gear, or
chassis, entirely independent of the body, which obtained in the
gasoline field, was followed and is representative of the usual electric
vehicle construction today. This permits of fitting any style of body
desired by the user. As a matter of fact, as soon as engineering
practice became fairly well standardized, as applied to the design
of the gasoline-driven car, that of the electric vehicle followed it more
or less closely, except as necessarily modified by the difference in
the motive power. Thus, it will be ^ noted that the electric has
progressed through the stages represented by the angle-iron frame,
armored wood frame, and modifications of the two as employed on
gasoline cars, to the now generally current type of pressed steel frame.
This has the advantage of being extremely strong for its weight.
It is composed of side and transverse members produced in hydraulic
presses direcdy from steel plates of about yV'^^ch thickness, these
members being riveted together and further reinforced by gussets
at the comers. On account of the height of the vehicle, the frames
are made perfectly rectangular and without either a drop or narrow-
ing forward.



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The types of suspension employed also show the same variations
as are to be fomid in the gasoline-driven cars, some of the smaller
electrics having full elliptic springs as ordinarily employed on wagons,
while intennediate and heavy vehicles have either straight semi-
elliptic springs front and rear, or a half-platform type of suspension
in the rear. A study of the Studebaker and General Vehicle types
of delivery wagons and trucks will show how closely they approach
to what is considered general practice in the automobile field as a
whole. The latest Lansden vehicles are distinguished by a novel
form of suspension employing groups of helical springs, and rep-
resent about the only departure of note.

Where the axles are concerned, the electric still bears traces of
its predecessor, the horse-drawn wagon, as these are usually straight
forgings of square section, though tubular axles are employed in
some of the lighter cars. The steering spindles on the front axles
and the wheel spindles on both front and rear follow conventional
practice, as ball or roller bearings are generally employed. Because
of the heavy loads carried and the fact that solid tires are used, the
entire running gear has to be planned on a very liberal scale. This
is likewise true of the springs. While it is desirable that the latter
afford as much protection to the mechanism as possible, sufficient
stability to carry the load is of more importance than flexibility, as
the comparatively slow speeds do not occasion either the rapid
oscillations or the violent shocks that are met with in the pleasure
car with its light load and high speed.

Motive Power. As already mentioned, the motive power of
the majority of smaller electric vehicles consists of a single motor,
and in some makes, such as the General Vehicle, this practice is
extended into quite heavy units with a corresponding increase in the
efficiency of the vehicle as a whole. In order to keep down the
weight as well as the space occupied, these motors are very small
for their power output and consequently have to be wound for high
rotative speeds. They are usually of the series type, of General
Electric or Westinghouse make, and are designed to carry heavy
overloads for short periods to enable the car to pull out of a bad place,
to start with full load on a heavy grade, or to meet similar emergen-
cies, the motor, under such conditions, delivering an amount of power
totally disproportionate to its size, and particularly to its normal



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12 COMMERCIAL VEHICLES

rating. This brings up a question that has proved very puzzling to
the layman, and frequently to the engineer not familiar with elec-
trical practice. If at least 20 to 25 horse-power are necessary for the
average small gasoline car, how is it possible to run a delivery wagon
with a 2J-horse-power electric motor, and a truck of no mean pro-
portions with but 5 horse-power? The overrating of the amount
of power necessary in the first case, and the undervaluation of the
actual amount of power available in the second go a long way toward
explaining this. Though the gasoline car is equipped with a 25-
horse-power motor, it seldom uses more than 40 to 50 per cent of
what is available; in fact, assuming the vehicle to be in good condi-
tion throughout, it probably does not require more than 10 to 15 horse-
power to drive it on the level, at any speed up to 30 miles an hour.
The electric on the other hand, ha« a 2i-horse-power motor
which is really a 10-horse-power motor, or 5 horse-power at least,
and which may be 15 horse-power, when occasion demands it, as
many of these motors are capable of overloads up to 500 per cent of
their normal capacity. Furthermore, there is the extremely important
factor of speed and its complement, wind resistance. Speeds are so
slow in commercial vehicle practice that wind resistance is prac-
tically a negligible factor, even with the towering bodies of motor
vans which present a very large area, as this influence does not make
itself apparent much under speeds of 25 miles an hour. Discussions
which have taken place regarding this seemingly great discrepancy
in the motive-power equipment of the average electric and gasoline
car, recall those regarding the same feature of the pioneer electric
street cars as compared with their predecessors. Two, or three
horses at most, sufiiced to haul the cars up grades that some of the
first power-driven cars with 15-horse-power motors could not get over.
In any case, why should it take 15 horse-power to drive a car that
had formerly only required a team of horses to move it? Weight
and speed were naturally not taken into consideration, as the old
horse car was as light as a wagon and ran much easier, though the
general misconception prevailing as to just what a horse-power is
and what a horse is capable of were principally responsible. Care-
ful experiments carried out by an English engineer have proved con-
clusively that the average draft horse is capable of exerting the
equivalent of all the way from 4 to 13 horse-power for periods as long



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COMMERCIAL VEHICLES 13

as five minutes at a time. Consequently, the light car with its two
horses really had available several times as much power, based on
the horse-power unit, as appeared to be present.

Motor Suspension. Since the employment of spur-gear drives
has become less general, the motor is usually suspended from the
frame by means of transverse members riveted to the side rails, and
is placed near or slightly forward of the center of the chassis, in
order to give the best distribution of weight This is an advantage
that is not obtainable when the motors are hung from the rear axle,
or too close to it. In view of the high speed at which the motors
run — 1,800 to 2,000 r. p. pi. or more — a reduction in two stages is
necessary to avoid the employment of excessively large sprockets.
The first step is from the motor to a countershaft by means of a single
silent chain of the Morse or Renold type, the motor being suspended
in such a manner that it may be moved a short distance one way or
the other to permit of adjusting this chain to the proper tension.
The large sprocket on the countershaft, which serves to cut down
the speed in the proportion of about 1 to 5, also embodies a differen-
tial or compensating gear of the usual bevel or spur type, thus making
it possible to employ a solid one-piece axle, instead of weakening
the latter by inserting the balance gear in it. This is an important
feature as the rear axle must bear 60 to 70 per cent of the total weight
of both car and load. From the countershaft, chains are run to each
pf the driving wheels. The relative positions of the countershaft
and rear axle are maintained by heavy adjustable radius rods, at-
tached forward to the outer ends of the countershaft, and at the rear
to the axle. These take the stress of the drive off the springs and
counteract the tendency of the chains to draw the rear axle toward
the countershaft under the pull of the motor.

Where two motors are employed, as in the Studebaker 2,000-
pound wagons, they are suspended side by side from the frame by
special swinging hangers with their armatures practically in line with
one another. But each motor is entirely independent of the other and
serves to drive one of the rear wheels to which it is directly connected
by means of a roller chain, passing over a small sprocket on the arma-
ture shaft of the motor forward and a large one on the hub of the
driving wheel at the rear, there being but a single step in the speed
reduction in this case. As there is no mechanical connection between



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14 COMMERCIAL VEHICLRS '

the two motors, or between the two driven wheels, the latter are free
to rotate at different speeds when necessary and a compensating gear
is dispensed with altogether. This also gives the further advantage
of not losing traction entirely when one of the driving wheels turns
loosely on ice, mud or sand, as is the case with the differential, which
nullifies the driving effort applied to the opposite wheel when its
mate revolves freely. Chain drive as now employed is not only more
efficient, but less noisy and much easier to maintain and repair than
the spur-gear drive formerly in vogue, though the protection of the
chains by suitable cases to keep off mud and maintain lubrication
would be an improvement.

As the motors commonly employed are wound to take current
at 80 to 85 volts, the battery consists of 44 cells, divided into three
or four groups of cells held in separate oak boxes, or trays as they are
termed, to facilitate handling. This voltage is standard, regardless
of the size of the vehicle, the latter being compensated for by chang-
ing the capacity of the battery. Thus, for very small delivery wagons,
the cells each contain three positive and four negative plates of
medium size giving an 85-ampere-hour discharge capacity, while
a 1,000-pound wagon is equipped with a battery having nine-plate
cells with a capacity of 112 ampere hours; a 2,000-pound wagon,
eleven-plate cells of larger dimensions, giving 140 ampere hours;
and so on in accordance with the size of the vehicle and the load it
is designed to carry. However, the weight of the battery increases so
rapidly with increase in capacity that it has not been found desirable
to attempt to use very large units.

In the very small delivery wagons listed some years ago, it was
customary to carry the battery on the floor of the vehicle, putting a
second flooring above it to accommodate the load. This practice
has been abandoned for obvious reasons, as it made both the loading
floor and the center of gravity of the vehicle much too high. Prac-
tically all electric vehicles at the present time have the battery under-
slung, z. ^., carried in a cradle supported from the frame of the
chassis. This cradle is enclosed as a battery box for protection against
mud and water, and has hinged doors at the ends through which the
battery may be introduced or removed. By this arrangement the
weight of the battery, which is the heaviest single item in the entire
construction, is distributed evenly between the forward and rear



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wheels and leaves the entire floor space of the wagon available for
the load. . All of the wiring between the battery, controller, and
motor is carried beneath the floor and is protected from injury.

Control. The controller itself is placed either beneath the seat
or under the footboards in the case of delivery wagons and light
trucks, and is similar in construction to those employed on street
cars, but of much smaller size due to the low voltage and compara-
tively small amount of current to be handled. It is operated by a
small hand lever and provides three to five speeds ahead and two
or three reverse, all of which are obtainable by moving the same lever,
although a special lock or catch must first be operated before the
vehicle can be moved backward. This usually takes the form of
a pedal or kick plate which may be depressed with the heel and fre-
quently must be held down while reversing. It automatically returns
the controller to the ahead position when released, in order to pre-
vent the vehicle from being backed inadvertently.

At first, arrangements for steering took the form adopted on
the earliest gasoline cars, that is, the tiller or hand-lever form, but,
owing to its numerous shortcomings, this has now disappeared on
all but the lightest wagons. Left-hand control is often provided,
i. e.y both the controlling lever and the steering wheel are placed on
the left side of the wagon, which is most convenient on delivery wagons
as the driver's helper may leave and enter the wagon without going
round the vehicle.

Wheels. The usual artillery pattern, wood wheels are employed
and are almost universally carried on ball or roller bearings. Their
sizes reveal the conflict between the influence of ordinary delivery
wagon design and automobile practice, as some have 36-inch front
and 42-inch rear wheels — ^an old time horse-drawn wagon standard —
while others have 32- or 34-inch wheels all round as has become
customary in automobile building. The larger wheels are advanta-
geous, however, as they run easier on poor pavements and consume
slightly less power, their greater diameter being compensated for by
a correspondingly greater drop in the speed reduction from the motor
to the rear wheels, in order to keep the speed of the vehicle the same.
By modifying the design of the axles or frame, or both, the loading
platform of the wagon may be kept at the same height relative to
the ground, regardless ot the size of the wheeb, so that the employ- •



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ment of larger diameters is becoming, more common. This, again,
is but a reflection of the tendency of design in gasoline pleasure car
construction, in which 42-inch wheels are now employed, and affords
an instance of reversion to original standards, as pioneer automobiles
were all of the high-wheel type.

Brakes. Owing to the comparatively low speeds, the braking
equipment usually consists of but a single set of drums attached to
the driving wheels. Against the inner faces of these, bronze shoes
are expanded directly on the steel face of the drum by means of a
pedal and the usual brake rigging beneath the car. As is the case
in practically all chain-driven cars, the braking drums carry the
driving sprockets on their outer faces. In case of emergency, the
vehicle may be brought to a sudden stop by reversing the motor,
although this subjects the motor as well as the entire vehicle to un-
usually severe stresses.

Tires. While solid rubber tires are most generally employed,
this is not necessarily so, as where the merchandise to be carried is
of a light or fragile nature, or where speed is to be one of the chief
features of the delivery service, pneumatic tires are preferable. They
not only reduce the liability to breakage, but also lessen the cost of
maintaining the vehicle in repair. However, as there are com-
paratively few branches of commercial service in which the pneu-
matic tire is economically practical, its use is very limited. The
solid tires employed vary in size from two to four inches, and for
weights in excess of the capacity of the latter, they are used in twin
form on the rear wheels.

Types. Fig. 1 illustrates the Studebaker 800-pound load capacity,
delivery wagon. It is equipped with a 40-cell Exide lead-plate bat-
tery, supplying current at 84 volts to two high-speed series motors
which drive the rear wheels directly by chains, as already described.
The vehicle has a speed of 2 miles to 12 miles per hour, and is capable
of traveling 35 miles on a single charge of the battery. The battery
is located almost direcdy under the center of the pressed steel frame,
and the battery compartment is built integral with the frame itself,
forming an inverted truss. The axles are heavy drop-forgings, and
owing to the use of two motors, no differential is employed on the
rear, the motors, battery, and all other parts of the mechanism
being carried by the springs, which, in the smaller types, are of the



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COMMERCIAL VEHICLES 17

elliptic type ordinarily employed in wagon-building practice. There
are two sets of brakes, each working independently, and arranged
to be applied by pedal levers, one set controlling expanding bands in
drums on the rear wheel hubs, while the other brakes are of the
same type but are mounted on the motor countershafts. Plain parallel
bearings are employed with ample bearing surface. The dimensions
of the 800-pound wagon are: wheel base, 84 inches; gauge, 59 inches;
wheels, 36 by 2 J inches front and 42 by'2i inches rear, the tire equip-
ment being solid rubber, though iron or wood tires ijiay also be had.



Fig. 1. Studebaker 800-Pound Electric Delivery Wagon.

In addition to the usual control, an emergency switch is provided
within convenient reach of the driver, making it possible to quickly
shut off the power from the motors altogether. This switch can only
be moved when in a certain position ; it also answers as a lock when
the vehicle is standing. One of the 1,500-pound Studebaker wagons
is shown in Fig. 2 with an open express type of body, and it will be
noted that its design is identical with the smaller vehicle already
described.

The Waverley electric delivery wagons are characterized by the
employment of a single motor, as is also the case with the majority



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18 COMMERCIAL VEHICLES

of others in this field. This drives to a countershaft, from which
the final drive is taken to the rear wheeb by the usual roller chains



Fig. 2. Studebaker 1500-Pound Convertible Station Wagon.

and sprockets. They are equipped with 42 cells of Exide lead-plate
battery, or erf the National battery. The dimensions of the 1,200-


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Online LibraryMedical Society of the State of North Carolina. AnCyclopedia of automobile engineering; a general reference work on the construction, operation, and care of gasoline, steam, and electric automobiles, instruction in driving, commercial vehicles, motorcycles, motor boats aerial vehicles, self-propelled railway cars, etc → online text (page 10 of 27)