ACHIEVING i CCURACY IN CHAIN PI DDUCTION
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How Hans Renold, Ltd • Manufactures and Assembles the Various Components of Its Products
An Important Organization that has Steadily Been Built Up from a Small Beginning
IN describing the methods that are employed in large works it is not our usual practice to deal with the history of the business or its founder. In the case of Hans Renold, however, we make an exception, recognizing the strong personal element that has always been present in the development of the manufacture of really accurate chains for driving machinery.
Hans Renold was born in Switzerland in 1852, and at the age of 18 entered the Polytechnic School at Zurich. In 1873 he came to England and .worked as a draughtsman. In 1879 he bought for f300 a business in Salford, which was the foundation of the Renold organization for the manufacture of highclass chains for various power-transmission purposes.
The chains made at that time called for no high degree of accuracy, but the introduction of the tricycle, which was quickly followed by the "safety " bicycle— as it was called at that time, in order to distinguish it from the tall machine, now known as the " penny farthing "—created a demand for a light, strong chain of accuratmAtch and good finish in every respect.
The machinery in the factory that he had bought was found to be inadequate for making such chains, so he invented and made special machines for dealing with each separate component, so that at that early period in the history of chain-making Renold was able to produce a chain, the joints of which worked freely, but without undue backlash, and the pitch of which could be relied upon for accuracy.
The next step was to improve the materials used, and for this purpose a testing department was set up, with the result that the weight of chains was greatly reduced and their wearresisting qualities increased.
One of the most outstanding features of this business is that, without outside assistance, it grew from small beginnings to a great organization ; as fast as money could be accumulated out of profits, building progressed and plant was installed. The centrally situated works in Manchester even-Wally becoming too small, the Burnage works at Didsbury were laid out with garden surroundings and every possible convenience and even luxury to make the lot of the workers as pleasant as possible. Mr. Renold has attained his 77th year, and still takes a keen interest in the conduct of the great
business that he has built up. .
In the production of good-quality chains which have to transmit power at high speeds, one of the first things B 32 to consider is the selection of the steels that are to form the component parts. In the Renold factory there is all the chemical and physical testing apparatus usuallyto be found in such departments of engineering works.
On the physical side there is the usual machine for testing tensile strength, elongation, etc., both, f or materials and for chains when made up. Apart from the usual machines there is a twisting test, which is particularly useful in detecting " pipe "—that is, a seam of impurity running lengthwise in a bar or strip.
The machine used for this purpose was designed and
made in the works, it consisting of two chucks, one fixed and one rotatable. The strip to be tested is placed in the chucks, the one being rotated until a given number of turns have been imparted in one direction, told the chuck is then rotated in a reverse direction, until the strip is net only made straight, but is given the same number of turns in the opposite direction. Our photographic *views show the machine and a strip in which a " pipe" has. been detected.
Another test to which sheets of steel are subjected is that of doming or bulging by pressing a ball on to the sheet while it rests over a hole. The sample shown is part of a sheet which has failed to show the required degree,; of ductility.
When the metal of which the strips and sheets are composed has been proved to be satisfactory, they go to the pressing department, where presses of all sizes are arranged for the various kinds of chain ; two of the largest of these presses are shown in an accompanying illustration.
The strip of steel is automatically fed through the press. Links for the roller chains, after being cut out from the strip, undergo a chamfering operation which is carried out by placing them automatically under a die which, by pressure, forms the chamfer. This process causes the edge of the link to be spread out on the side where the chamfer has been made, so it is necessary to perform a shaving operation on it to bring the edge to right angles with the surface. One of our views shows the portion which has been shaved off.
The next operation is that of punching the holes, the two holes being formed at the same time. The presstools used for this purpose require to be made with the greatest care, as on the distance apart of the holes depends the accuracy of the pitch of the chain. Any error here 'produces what is known as an accumulative error. 2.n inaccuracy of 1/1,000 in. would, in a chain of 100 links, mount up to 1/10 in.—an error that could be easily detected were two chains to be hung up side by side.
One of the most remarkable features of the operations carried on in these works is the automatic sorting and assembling of the parts, as in none of the assembling processes is each individual part handled by the operator.
In _the assembling of the roller and bush types of chain many ingenious devices are employed in the sorting of the various parts so that they may be placed in magazines from which they are fed one by one on to their place for automatic assembly.
The shouldered barrels that are pressed into links are produced in great quantities, and, after being rumbled to remove burs and after heat treatment, have to be placed on long wires which guide them into the magazines. The tedious operation of handling each barrel was at one time a matter of hand work, but one day a girl operator was seen stabbing the bulk of the barrels with the wire, trusting to luck that some■of the barrels 'would find their way on to it.
This led to the idea of a continuously rotating tray in which the,barrels are placed in great bulk. Two long wires are fixed so that their ends project well into the mass of barrels. As the tray revolves the wires gradually become filled with the barrels, which work their way up in a surprising manner until the wires are completely filled, when they are removed and replaced
with others. The barrels are then slid off the wires into their magazines, from which they are fed to a place between two links; these are pressed on to the shouldered part, no hand ever touching any of the components.
It is hardly necessary to point out that where entirely automatic assembly such as that carried on in these works is relied upon the parts must be produced to extremely fine limits of error, otherwise this assembly would not be possible. For this reason all tools and gauges have to be kept up to a high standard of accuracy.
The address of Hans Renold, Ltd., is Burnage Works, Didsbury, Manchester.