1916 Packard Twin Six How Many Cylinders
From the brochure
The Three Qualities Desired
STEADY improvement in the design and construction of motor cars for many years past has made the user more and more exacting in his demands, but from the time when the first practical car made its first run on the road, there have been three things which every motorist asked for-MORE RANGE OF ABILITY, GREATER SMOOTHNESS and LESS NOISE.
Year by year has seen each of these demands reiterated, although each year some improvement has been made, and today the demand is still the same, though we have come much closer to Absolute Quietness, Absolute Smoothness and the Maximum Range of Ability desired.
The average motorist desires more range of ability because he likes to accelerate rapidly without changing gear, to sweep up steep grades without the trouble of handling the gear shift lever, and, above all, perhaps, without the noise inseparable from indirect gearing.
He likes smoothness and quietness because the presence of noise and vibration are distressing to the nerves when long endured, but to find the way properly to combine the three qualities has taxed the ingenuity and skill of engineers all the world over.
Rapid Early Development * Throughout the first stage of motor car development one principle stood foremost, and this was the principle of splitting heavy stresses into lesser ones.
The single cylinder gave way to the two, because the latter came nearer to satisfying the demand. So did the two go out before the four, and the four, in turn, vanish at the perfection of the six, for the same reason. All the way, the tendency has been to make each impulse, each explosion in the motor, smaller in magnitude, but to get the power by many impulses in quick succession.
Six Cylinders Satisfactory for a Time * For a long time the six-cylinder motor seemed to fill the bill completely, but gradually reasons were discovered which made it seem advisable to split up the driving force still more, and we shall show what these reasons were and upon what solid ground they are based.
An Analysis of Motor Principles * Firstly, it is easy to see that the force of an explosion must be in proportion to the volume of gas exploded, so that the punch given to the piston and the corresponding recoil kick on the cylinder is greater as we make the cylinder larger. With a six-cylinder motor running slowly, as when pulling slowly through traffic on high gear, it is possible to feel each kick, each effort as the charge is fired in one cylinder after another. A four-cylinder will not run so slowly because there is a pause between each explosion, but in a six, the explosions overlap a little. Still, when the accelerator pedal is depressed, the push, push, push of each successive explosion can be felt by every occupant of the car.
As the speed rises, this sense of effort disappears, as the explosions follow faster on each other, but in most sixes we reach a point where there arises distinct vibration. This comes from a different cause, namely, the weight of the pistons, and it is more difficult to overcome as we make the engine larger. Let us see why this is. …
Content
- HOW MANY CYLINDERS?
- PART OF AN ADDRESS TO PACKARD SALESMEN
- BY J. G. VINCENT
- VICE PRESIDENT & CHIEF ENGINEER PACKARD MOTOR CAR COMPANY
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