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James Wimshurst

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April 1888.
April 1888.
1891. Wimshurst Alternating Influence Machine.

James Wimshurst, (April 13, 1832 – January 3, 1903), was an English inventor, engineer and shipwright. Though Wimshurst did not patent his machines and the various improvements that he made to them, his refinements to the electrostatic generator led to its becoming widely known as the Wimshurst machine.

Wimshurst was born in Poplar, England, and was the son of Henry Wimshurst, a shipbuilder of Ratcliffe Cross Dock. Wimshurst was educated at Steabonheath House in London and became an apprentice at the Thames Ironworks until 1853 with James Mare.

In 1865, he married Clara Tribble.

In 1865, after Wimshurst was transferred to Liverpool, he worked at the Liverpool Underwriters' Registry.

In 1874, he joined the Board of Trade as a chief shipwright surveyor at Lloyds.

Later, in 1890, he became the Board of Trade's representative at an international conference in Washington.

Wimshurst dedicated large amounts of his free time to experimental works. Besides his electrical activities, he invented a distinctive vacuum pump, a device to indicate ship stability and methods for electrically connecting lighthouses to the mainland.

In 1878, he began to experiment with electrical influence machines for generating electrical sparks for scientific and entertainment purposes.

Beginning in 1880, he became interested in electrostatic machines of the influence type. His house in Clapham, England, had a versatile workshop which had a wide variety of tools and devices for electric illumination. Wimshurst constructed several of the known types of electrostatic generators, such as those created by W. Nicholson, F. P. Carre and W. T. B. Holtz. To these predecessors, Wimshurst made many modifications with the result known as the Holtz-Wimshurst machine.

Shortly afterwards, Wimshurst developed a duplex machine. The device had two disks turning in opposite directions, with metallic conducting sectors on the surfaces of each. Compared to its predecessors, this machine was less sensitive to atmospheric conditions and did not require an electric power supply. This form of the machine was also improved by other developers (such as the Pidgeon machine developed by W. R. Pidgeon, which increased the electrical induction effect and its electrical output).

In 1882, Wimshurst developed his Cylindrical Machine.

By 1883, his improvements to the electrostatic generator led to the device being widely known as the Wimshurst machine.

In 1885, one of the largest Wimshurst machines was built in England (and is now at the Chicago Museum of Science and Industry).

In 1889 Wimshurst became a member of the Institution of Electrical Engineers.

In 1891, he reported a machine that generated high-tension alternating currents.

In 1896, his multiple-disk machines (up to 8 disks) found a new use as Roentgen ray generators for radiography and electrotherapy.

In 1989 for his contribution to medical science, he was elected a Fellow of the Royal Society.

In 1903 he died in Clapham, England, at the age of 70. [1]

A lecture delivered by Mr James Wimshurst on Influence Machines at the Royal Institute on April 27th 1888.

I have the honour this evening of addressing a few remarks to you upon the subject of influence machines, and the manner in which I propose to trea the subject is to state as shortly as possible, first, the historical portion, and afterwards to point out the prominent characteristics of the later and commonly known machines. In 1763 Wilcke described a simple apparatus which produced electrical charges by influence, or induction, and following this great Italian scientist, Alexander Volta, in 1775 gave the electrophorus the form which it retains to the present day. This apparatus may be viewed as containing the germ of the principle of all influence machinesyet constructed. Another step in the decelopment was the invention os the doubler by Bennet in 1786. He constructed metal plates which were thickly varnished, and were supported by insulated handles, which were manipulated so as to increase a samll charge. It may be better for me to explain here the process of building up an increased charge by electrical influence, for the same principle holds in all the many forms of influence machines. This Volta electrophorus, and these three black boards, will serve for the purpose. I first excite the electrophorus in the usual manner, and you see that it then in fluences a charge in its top plate; the charge in the resinous compound is known as a negative, while the charge induced in the top plate is known as positive. I now show you by this electroscope, that these charges are unlike in character. Both charges are however small and Bennet used the following system to increase them. Let these three boards represent Bennets three plates. To plate number one he imparted a positive charge, and with it he induced a negative charge in plate number two. The with plate number two he induced a positive charge in plate number three. He then placed the plates one and three together , by which combination he had two positive charges in practically the same space. With these two charges he induced a double charge in plate two. This process was continued until a desired degree of increase was obtained. I will not go through the process of actually building up a charge by such means, for it would take more time than I can spare. In 1787 Carvallo discovered the very important fact, that metal plates when insulated, always acquire slight charges of electricity; following up those two important discoveries of Bennet and Carvallo, Nicholson in 1788 constructed an apparatus, having two discs of metal insulated in the same plane. Then by means of a spindle and handle, a third disc, also insulated, was made to revolve near to the two fixed discs, metallic touches being fixed in suitable positions. With this apparatus he found that small residual charges might readily be increased. It is in this simple apparatus that we have the parent of influence machines, and as it is now a hundrew years since Nicholson described this machinein the Phil. Trans., I think it well worth showing a large-sized Nicholson machine at work tonight., (Fig 11). In 1823 Ronalds described a machine in which the moving disc was attached to and worked by the pendulum of a clock. It was a modification of Nicholson's doubler, and he used it to supply electricity for telegraphy working. For some years after these machines were invented no important advance appears to have been made, and I think may be attributed to the great discoveries in galvanic electricity which were made about the commencement of this century by Galvani and Volta. Followed in 1831 to 1857 by the magnificent discoveries of Farady in electro-magnetism, electro-chemistry, and electro-optics. No real improvement was made in influencemachines til 1860, in wich year Varley patented a form of machine. It also was disigned for telegrapgh working. In 1865 the subject was taken up with vigour in Germany by Toepler, Holz, and other eminent men. In 1866 Bertsch invented a machine, but not of the multiplying type; and in 1867 Sir William Thoomson invented the form of machine which for the purpose of maintaining a constant potential in a Leyden Jar is exceedingly useful. The Carre machine was invented in 1868, and in 1880 the Voss machine was introduced, since which time the latter has found a place in many laboratories. It closely resembles the Varley machine in appearance, and the Toepler machine in construction. In condensing this part of my subject, I have had to omit many prominent names and much interesting subject matter, but I must state that in placing what I have before you, many of my scientific friends have been ready to help and to contribute, and, as an instance of this, I may mention that Professor Sylvanus P. Thompson at once placed all his literature and even his private notes of refernce at my service. I will now endevour to point out the more prominent features of the influence machines which I have present, and, in doing so, I must ask a moments leave from the subject of my lecture to show you a small machine made by that eminent worker, Faraday, which, apart from its value as his handiwork, so closely brings us face to facewith the imperfect apparatus with which he and others of his day made their valuable researches. The next machine which I take is a Holtz. It has one plate revolving, the second plate being fixed. To work the machine an especially dry atmosphere is required and an initial charge is necessary.The direction of the current is apt to reverse. It has no metal on the revolving plates, nor any metal contacts; the electricity is collected by combs, which take the place of brushes. The next machine for observation is the Carre, (fig 8). It consistes essentially of a disc of glass which is free to revolve without touch or friction. The current of this machine is constant. The Voss machine has one fixed plate and one revolving plate. Upon the fixed plate are two inductors, while on the revolving plate are six circular carriers. It supplies a considerable amount of energy and is self -exciting in ordinary dry atmosphere. It freely parts with its electricity from either terminal but the charge frequently changes its direction. I have experimented with the cylindrical form of the double glass disc machine. Two discs revolve near to each other in opposite directions. Each disc carries matallic sectors and has two brushes supported by metal rods.[2]

See Also


Sources of Information

  2. Engineering Journal, 4th May, 1888.