Evershed and Vignoles Generator s/n 24798 Polished two part wooden box 5.5" x 8.5" x 6" high with leather carrying handle and fold away crank handle. Handle geared to 8 pole generator comprising horse shoe magnets, armature and brass ring commutator. Interior coiled spring return for 2 core output lead.The 200 volt output is obtained from the two lower outside brass wheel collectors shown in the picture below. The reel mechanism needs attention. Acton, North London, UK

Jon Clafton who has collected Evershed & Vignoles stuff for the last couple of years or so has sent me a picture of the cable reeling mechanism on his generator and the cable connector which possibly is designed to work with the ohmmeter he also owns.

Jim (AB7NW) has suggested that some hand generators made by Evershed and Vignoles were used for powering radios, could this be what it was for? He has written about the 600 volt Evershed and Vignoles Hand Generator used on the 1930 Mackay Aerial Survey Expedition into the Australian Outback.It was taken along as an emergency backup generator to the generator on the airplane and ended up getting used extensively on the expedition when the main generator failed.

Arnold Kaandorp notes that around 1900 hand driven generators were also used for medical purposes. In combination with a Ruhmkorff coil it was popular to treat a patient with electric shocks.These machines were mostly in beautiful wooden boxes complete with all kinds of impressive sondes and electrodes.

John Newman suggests that it looks like a field telephone ringer and that 200 volts would be about right. Though telephone ringers were usually a.c.

Brian Styles suspects that it was used as a separate generator in a precursor of the Megger because he has an Evershed ohm-meter which has NO generator and supposes it pre-dates the all-in-one classic Megger - of which he has a few examples in the heavy teak boxes.

Nick O'Reilly looked the company up in a 40 year old "Who Owns Whom" - this confirms that at this time they belonged to the British American Tobacco Company. He is convinced that the item is older than suggested and the date is around 1910 and perhaps even older. The brass plate (by and large) had been replaced a tin-plate trade plate by the 1920s. The reason that the name plate shows no patent number is because the company patented almost everything that they manufactured, therefore the plate could be attached to all of their output without the expense of having to produce a different one for each product. Also, very many products were the subject of more than one patent number.

Clive Jackson has provided a description and pictures of a similar item which he is thinking of selling on eBay. It measures 7" tall and is 6 1/2" by 6 1/2" in plan and also is housed in a polished wooden box with leather handle.Inside the door there is a fixed piece of card (Unfortunately a corner was torn off by his children some years ago) giving tech. specs and instructions. It is clear from the instructions that it was used to test cable insulation.The generator appears to be very much the same as mine although the design of the handle on his appears to be more elementary and the serial number would seem to indicate that it is an earlier model than mine.

I have "Direct Current Electrical Engineering" by JR Barr published by Pitman 1908 Which describes "..........Sidney Evershed's ohmmeter or 'Megger'...." This is a combined instrument, the generator and the meter sharing the same magnetic field. Although there is no picture of the construction it would seem to be the same principle to that used on modern hand driven insulation testers.

Francois baltimore@libertysurf.fr was searching information on the web about a hand generator when he came across this page and found that he had one which was very similar. The label on his reads: "Evershed & Vignoles Ltd., London, No. 12867, Patent, 200 volts, 100 revs".

The one he has is not exactly the same because it has no reeling mechanism in the top of the box. He found his in an antiques shop in Alston, 25 km south west of Hexham in Northumberland. There are many former lead mines in this area and he wonders if it could have been built as a generator for detonators. Pictures of his generator are shown below:

There are several Villages /Towns called Crook, but Crook, County Durham has a Grey Street and is not too far from the lead mining area in Northumberland. Martin is quite a common name in the North East of England.

This seems to me to indicate that all three generators predate 1908 and they were intended to be used for cable testing in conjunction with an ohmmeter BUT may have been made before or after! The mention of the word electrostatic seems to indicate that Clive's was used for testing insulation resistance. There may have been additional clues on the missing corner of the label.

Jon Clafton has a 200V generator (serial number 17465) identical to mine. The rotary flex 'dispenser' is in perfect condition and the entire device works perfectly.His still has the original cable and fitted connectors. He also has another generator (serial number 18550), similar to the 200V one, but that one simply has two output terminals, and is 20V. He also has four Evershed & Vignoles megger insulation testers similar to the one featured below. These all have the original date on the underside of the lid. The oldest one he has is dated 1912, and the newest is dated 1920. He notes that the generator part of the meggers is very similar to the stand alone generators.

I think I now have the answer for the intended use for Clive Jackson's generator shown above. This picture (from Instruments of Science: An Historical Encyclopedia by Robert Bud and Deborah Warner (01 December, 1997) - Garland) shows an early Evershed and Vignoles insulation tester. I wonder where all the associated meters went and why the generators have survived?

Jon Clafton who collects Evershed & Vignoles generators and meggers has recently picked up a very old generator and an accompanying ohmmeter. Pictures of these are shown below. He thinks the generator was made in the late 1890s and the ohmmeter the early 1900s.

These are the instructions printed on the lid of the above meter.

Adjust the Ohmmeter until the bubble is in the centre of the spirit level.

Place the generator not less than 18 inches away from the Ohmmeter and couple its terminals to the terminals G1 G on the Ohmmeter. Couple the mains to be tested to the "LINE" and "EARTH" terminals of the Ohmmeter. Turn the Generator handle steadily in either direction at any speed above 110 revolutions per minute, and the Ohmmeter index will point to the resistance under test.

When making tests in the neighbourhood of dynamos and generally when very accurate results are required two observations should be made, first when the generator is revolving in one direction and then in the other. The mean of the two readings so obtained gives the value of the resistance under test.

Jack Davidson.C.Eng. FIEE. thinks this goes back to the 1890s when E & V produced their first insulation testers, (now universally known as Meggers). This famous brand name dates back to 1905, when the first portable insulation tester was introduced with the MEGGER brand name on it. This would have been similar to this one recently sold on eBay

He says "The generator was originally designed by a Mr Goolden of Messrs. Easton, Anderson & Goolden and the generator was used separately from the instrument itself probably to obviate interference by the permanent magnet fields of the generator. Evershed & Vignoles took over the manufacture, not sure when, and raised the voltage to 200 d.c. from the original 120V. The lower voltage was probably to test installations at the working voltage, commonly 110V at that time, but someone then thought that twice the working voltage would be a better test, which is what we do today, with 500V. d.c. test for supply voltage around 250.

On p.89 of Sir David Salomans' book, 'Electric Light Installations, Part 3' published in 1894 there is a picture of such an instrument and its hand generator connected by 'curly' single conductors rather than the self-coiling cable reel which my item has.

He wonders if '247' is the actual number and '98' signifies the date, 1898? It isn't likely that production quantities could have reached a five figure number in those early days, but you never know what coded information serial numbers contain.

The book illustration looks very like the photograph of Clive Jackson's generator, it is square rather than rectangular, with a door forming the side opposite to the crank handle.

The 1894 picture shows a well finished handle, with an ebonite, (presumably), hand-grip, much like the later Post Office Telephones magneto generator for bell ringing at 70V. a.c. Perhaps Clive's one has had a handle replacement or repair, the same seems likely with the simple leather strap in place of the proper leather handle with metal fittings.

He doesn't think these generators are for firing blasting detonators as these are usually a.c. thus doing away with commutator and brushes, which wouldn't much like the inevitable dust, and d.c. isn't necessary anyway. From the beginning insulation testers had a voltage coil and a current coil combined in the movement." (Ayrton and Perry design, see below)

Simon Eastwood sent me pictures of his very similar generator generator which is made by Everett Edgecumbe. This is also a 200 volt model serial number 8145. Everett joined Edgecumbe in 1900 so this generator would have been manufactured after this date. see: http://www.museumoftechnology.com/cic.html and the firm still exists see: http:// www.edgcumbe.co.uk/metrohm/about.html

Ayrton and Perry

William Edward Ayrton (1847 - 1908) English engineer and inventor, with his colleague John Perry (1850 - 1920) invented many electrical measuring instruments. In these, use was made of an ingeniously devised flat spiral spring (as used in modern analogue meters) which yields a relatively large rotation for a small axial elongation.

They also invented the principle of moving a pointer by the combined fields of separate voltage and current coils thus enabling power or resistance measurements to be made with only one instrument. They used fixed coils at right angles to each other and there was a magnetised needle at the pivot end of the pointer. There was no problem with coil connections since they were fixed and then as now, there was no control spring. The needle doesn't come to zero until the test terminals are shorted and the generator operated.

Evershed & Vignoles tidied things up. They made a double moving coil,one for voltage and one for current. They were fixed together, but not at right angles. The pointer was fixed to the coil assembly and the coil connections were ligaments, no hairsprings since the only influence on the coils was that of a powerful permanent magnet. This got over the gradual loss of magnetisation which the Ayrton and Perry instrument suffered from. It also enabled the generator and meter to be combined into one instrument as it was no longer necessary to obviate interference from the permanent magnet field of the generator.

The earlier instruments had two massive bar magnets with pole pieces at both ends, so that one end did for the moving coils and the other provided the generator field.These two pictures from Jon Clafton show the general construction and the second the generator without magnets and meter movement.

Craig Douglasfrom New Zealand sent me pictures of his megger instrument wondering how old it was. Fortunately he has the instruction manual with the patent number on the title page.Looking at UK Patent Numbers leads to the conclusion that it was manufactured after 1926. Connections to the current and pressure coils from the meter movement are brought out to terminals to enable the instrument to be used with a bridge box.

Another refinement was an auxiliary coil in series with the voltage coil and moving over a horn shaped projection on one of the pole-pieces which enabled the scale to be more evenly calibrated.

This is the principle of analogue insulation testers,(see:Megger , Safety Ohmmeter and Metrohm) but the voltage and auxiliary coils are combined into one but still move over the horn shaped projection. For more information see 'Electrical Measurements & Measuring Instruments' by Golding published by Pitman 1935

Evershed's patent. The answer to much of the speculation above is revealed in the US patent 639849 a small part of which is reproduced here.

"Be it known that I, SYDNEY EVERSHED, a subject of the Queen of Great Britain and Ireland, residing at London, England, have invented a new and useful Improvement in Portable Hand-Dynamos, (for which I have made application for Letters Patent in Great Britain under No. 1,758, bearing date January 25, 1899,) of which the following is a specification.

This invention relates to portable hand dynamos, such as are used for testing purposes or for firing electric fuses or the like purposes, where a small current t of high electromotive force can be utilised; and it consists in an improvement whereby the frictional resistance to rotation (of importance in such small appliances) is reduced to a minimum both in the armature-bearings and in the commutator, the current is collected with highest electromotive force, the hand 'which is made collapsible when not in use and is then in a protected position, and connection to any instrument or object, at a reasonable distance from the generator, is rendered easy and rapid without the use of loose wires, which may be mislaid, and without any binding-screws projecting from the portable box containing the dynamo.

Figure 1 is a plan of the box, with the lid open, containing the dynamo in the body of the box and the winch-handle ready for operation issuing therefrom and the connection device in the inside of the lid."

If you wand to read more and to view other patents try this link www.google.com/patents

Evershed & Vignoles Ltd., Acton Lane Works,Chiswick co-founded by Sydney Evershed (1858 -1939) in 1895 was taken over by AVO Ltd. Avocet House, 92-96 Vauxhall Bridge Road, London, SW1. AVO was a member of the Metal Industries Group of companies. Though known for their Avometer general purpose multimeter see here, they made a wide range of test gear including valve testers. The Acton Lane works closed down at about that time - around 1986. The current range of products can bee seen at: http://www.avointl.com/

The firm Megger Ltd. is now based at: Archcliffe Road, Dover, Kent, CT17 9EN, United Kingdom.