Wimshurst electrostatic machine
Datecirca 1890
Inventory NumberDW0890
ClassificationElectrostatic Machine
Subject
Maker
French
?
Inventor
James Wimshurst
1832 - 1903
Cultural Region
Dimensions28.4 x 24.7 x 13.7 cm (11 3/16 x 9 3/4 x 5 3/8 in.)
Material
AccessoriesLeyden jars (2)
2 rubber pulley belts
DescriptionTwo contrarotating discs, probably made of hard rubber, mounted on metal pillars screwed into a black enameled iron base. Distributed around the circumferences of the discs are narrow strips of aluminum with longitudinal axes in the radial direction. On the same bearing as the large wheel is a smaller wheel at the hub around which is wrapped a pulley. The pulleys are wrapped around larger wheels mounted toward the bottoms of the pillars. Those wheels are turned by a metal crank with a rounded handle. One of the pulleys would be twisted into a figure 8 to make the wheel rotate in the opposite direction to the first.
On one side of the wheels is a neutralizing rod tapering toward circular ends. On the ends are fine wire contact brushes touching the wheel.
On the other side of the wheel is another neutralizing rod of the same design situated at right angles to the first. Also on that side are two glass Leyden jars sitting in two circular indentations in either side of the base. Above those jars is a bar mounted on one of the pillars housing the wheel bearing. On either side of the bar are rods running perpendicularly through it. One end of that rod is a fork straddling the discs with collecting combs touching the discs at each of their ends. On the other end of each rod pivots a nickel-plated discharge rod consisting of an ebonite handle at one end and a pair of unequally-sized coaxial spheres on the other.
The Leyden jars consist of glass coated with silver on the bottom of the inside and outside. They have brass rods connecting the inner coating with the metal bar above it. Closer to the middle of the bar are smaller discharge rods bent in the middle and facing one another.
On one side of the wheels is a neutralizing rod tapering toward circular ends. On the ends are fine wire contact brushes touching the wheel.
On the other side of the wheel is another neutralizing rod of the same design situated at right angles to the first. Also on that side are two glass Leyden jars sitting in two circular indentations in either side of the base. Above those jars is a bar mounted on one of the pillars housing the wheel bearing. On either side of the bar are rods running perpendicularly through it. One end of that rod is a fork straddling the discs with collecting combs touching the discs at each of their ends. On the other end of each rod pivots a nickel-plated discharge rod consisting of an ebonite handle at one end and a pair of unequally-sized coaxial spheres on the other.
The Leyden jars consist of glass coated with silver on the bottom of the inside and outside. They have brass rods connecting the inner coating with the metal bar above it. Closer to the middle of the bar are smaller discharge rods bent in the middle and facing one another.
Signedunsigned
FunctionThe machine is self-exciting, which means no external charge is necessary to set it in motion. Any slight difference in charge between the two halves of the discs is sufficient. Suppose there is slight positive charge on one half of each disc. When a carrier on that half of the disc passes the contact for the neutralizing rod, that rod passes a negative charge from the carrier on the negative side to the positive carrier. Due to the influence of the positive charge on the other disc, the neutralizing rod does not simply discharge the two carriers. Rather, it actually conducts enough charge to produce a net negative charge to that carrier.
Because the carriers are at right angles to each other, the other disc is always positively charged in that half demarcated by the two contact brushes for the neutralizing points. The result is four different charge relationships in four different quadrants. Two of the quadrants have opposite charges and two have like charges. The collecting brushes are positioned on the quadrants with like charges, so each one collects only one charge, which can be stored in the Leyden jars.
The rods with the balls on them are the discharge rods, most likely to discharge the Leyden jars, either to make the instrument safer to touch or for demonstration purposes. Wimshurst machines were often used to excite X-ray tubes.
Because the carriers are at right angles to each other, the other disc is always positively charged in that half demarcated by the two contact brushes for the neutralizing points. The result is four different charge relationships in four different quadrants. Two of the quadrants have opposite charges and two have like charges. The collecting brushes are positioned on the quadrants with like charges, so each one collects only one charge, which can be stored in the Leyden jars.
The rods with the balls on them are the discharge rods, most likely to discharge the Leyden jars, either to make the instrument safer to touch or for demonstration purposes. Wimshurst machines were often used to excite X-ray tubes.
ProvenanceDavid Wheatland purchased from F. Roux-Devillas, Paris, 7/27/64 (lot 2/555).
Central Scientific Company
Date: circa 1940
Accessories: 2 Leyden condensers made of Pyrex
One rubber **gutta percha?** pulley, rotted.
Object number: 1997-1-0634
Thomas Hall
Date: circa 1890
Accessories: pulley rope
Object number: 1997-1-1423
John Cuthbertson
Date: 1770-1815
Accessories: brown storage box, descriptive tag, thin strip of paper in box with the inscription "lucernal microscope" in David P. Wheatland's handwriting (which refers to figs. 47-48 and 51 in this series), page from the book "Old Science and Medicine" with a photographic copy of the first print from this series, entitled "The Large Electric Machine at Haarlem."
Object number: 1998-1-1087
Adix Company
Date: circa 1905
Accessories: imitation leather covered, velvet and satin lined case
Object number: DW0325
