Precision• and Rapidity in GEAR PRODUCTION
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How a Specialist Concern Has Set Itself Out to Meet In an Efficient Way the Rigorous Demands of the Motor Industry
TOOSSIBLY no class ..E of component used in the building of commercial motors is so much entrusted to the care of specialists as are gears. The reason is not far to seek; accuracy and rapidity of product4on are essential, and these entail intricate plant of great cost. For many of . even the largest vehicle makers to lock up so 'much as £2,000 per machine would be commercially impracticable, whilst for those in a smaller way of business it would be impossible. In these circumstances the specialist compan, steps in to fill a vital rdle; no name has better cause to be known in this connection than that of the E.N.V. Engineering Co., Ltd., Ilythe Road, Willesden, London, N.W.10.
Twenty years ago the concern was founded ; in its career it has built a popular aircraft engine, an example of which was installed in the first allBritish machine to fly the Channel. To-day its principal products are gears, including spiral-bevel gears up to 2 ft. in diameter, and spur gears up to 3 ft.
A speciality is the hypoid gear, which permits the pinion to be offset thus
enabling the propeller shaft , to be mounted lower, in turn reducing the platform or floor height—an important point in commercial-vehicle construction. These gears. are made in sizes up to 1 ft. 0 ins. diameter ; they somewhat resemble spiral bevels, but the pinion can be of a larger diameter for any given ratio ; in consequence the strength is increased. These gears have been supplied for transmitting up to 240 b,h.p.
During a tour of the factory we observed other activities of the company. One large shop is engaged exclusively upon the production Of complete rear axles. In this shop isa most ingenious testing machine. The axle is clamped in position on top of two laterally adjustable pillars. The pinion Shaft is coupled to an electric motor and the ends of the axle shafts are connected to the armatures of two dynamos by means of the standard wheel-fixing Studs.
After seeing that the brakes are free a switch on the control board is depressed and the speed gradually rises until it be desired to hold any particular rate of rotation. Depression of another control knob keeps the motor driving at the speed reached at the selected moment.
if all be well and the axle is to he speeded up the control is operated .again and the gradual acceleration continues from the point of its interruption: When the maximum desired speed has been attained the motor and the dynamos automatidally reverse their functions and the axle is tested on the over-run—n point sometimes overlooked. The machine works silently so that the axle can be tested in this important respect without interference. By measuring the_electrical input and output the axle efficiency can be checked.
Other products, of which many types are manufactured for some of the largest factories in the industry, are differentials. Naturally this is .repetition work, once the design has been approved. A large batch of automatics is employed for this work.
Of particular interest is the class of machine which, among its other tasks, numbers the boring, threading, facing and drillim=b of nosepieces for rear axles; in addition these automatics— for there are several gangs of them— carry out groups of six operations on crown wheels. Once set up the table revolves after each operation and the
six parts are brought into position below the correct tools ready for the next cut or whatever the operation may be.
The time saved by machines of this type means literally hundreds of pounds put into the pockets of vehicle inaker, as there is no waste in transport from one machine to another.; the use of one jig per part suffices for each series of operations.
In the assembly department we noticed a batch of complete gearboxes being Prepared for one of the most prominent constructors of commercial vehicles. This is another class of product for which the company's special plant is extremely well suited. It is quite common for gear shafts to be machined to a tolerance of half a thousandth of an inch.
Obviously it is highly important, in the interests of silence, that gears be machined and ground to very fine limits. With spiral bevels the usual tolerance on the back of the crown wheel is .002 in.; all operations are performed while the crown wheel is located from the bore ; in no circumstance is this varied, so that uniformity and concert • tricity are assured.
Gas asd electric furnaces are em
ployed for heat-treatment. The temperature control is thermostatic,' and recording charts are always kept. A
detail point, but, nevertheless, one which means a great deal in service, is that all the crown wheels, when being quenched in oil, are gripped in dies so that there can be no chance of distortion occurring.
Camshafts are yet another everyday job at the E.N.V. works; they are produced to meet the requirements of makers of light petrol engines or large oil engines, and some of the camshafts for powerful Diesel engines are made up to 12 ft. to 15 ft. in length.
A visit to the works shows that in these days of large-scale production quality and quantity can go hand in hand.