“Understand Your Car,” by H. A. Hazell, A.M.I.M.I. (Sir Isaac Pitman and Sons, Ltd., price 5s.)
A new edition of this little book has recently appeared, with many new illustrations. It is a useful work for the novice to study, but it tends to be written around Morris cars, rather than to generalise. On the other hand, we certainly hope that these cars do not employ 10 degrees of forward inclination of “the stub axle pin” in endeavouring to obtain castor-action, as the author states is done on cars in general in the chapter on “Steering and Braking”! There also seems to be confusion between stub axle inclination to attain centre-point contact and king-pin inclination to attain castor-action. Diagrams give some idea of what Ackerman steering is, but the text, although describing it as “the most interesting point,” does not really explain how the steering-arm angles are calculated, only why different angles of turn are required at the road wheels. Drivers are advised to reduce speed in a gale, because “when the speed of the car is increased so the weight on the ground will be reduced” — surely some gale, or some car!
We think experienced engineers may find disagreement with the statements that the “action of the differential gear is simple,” and that decarbonising and valve-grinding are more complicated with an o.h.v. than with a s.v. engine. Although a description of the almost-defunct “wet” clutch is included, hypoid and worm drives are dismissed as “more silent” than others, no mention of lower transmission lines being made. Moreover, the author describes, under “Suspension,” a particular 1/2-elliptic leaf system in some detail and completely ignores independent suspension or any other layout. Likewise, torque-tube transmission might not exist, and in describing the final drive mention is made of “approx. the 5 to 1 reduction in top gear,” with no explanation that this ratio varies appreciably between different cars. Odd driving hints have crept in and would seem out of place, particularly when we are told to allow the knee to lift when letting in the clutch and are cautioned to always reduce speed for cornering. Only one firing order is quoted for 4- and 6-cylinder engines. In his preface the author refers to visualizing how the touch of the foot on the accelerator causes the car to move away — in this he surely pre-supposes the Invicta “Black Prince.”
In this small 164-page book driving, maintenance and a description of the modern car are combined and it seems that the author has hurried too quickly through the mass of material at his command. As a rather casual introduction to the modern motor-car this book could represent 5s. well spent. Apparently this is the sort of thing many people require, for “Understand Your Car” is now in its third edition. Some changes have been made in this edition, we are glad to see, notably in the former vague statement that main and big-end bearings are “lubricated from a gallery in the crankcase,” but we are surprised to find a T-head engine in the illustrations depicting the functioning of the Otto cycle.