An adjustable scale, Amsler type 4 planimeter, engraved "Stanley, Great Turnstile, Holborn, London" who would have been the retailer, not the maker in this instance. It is a relatively early one, serial number 15090, dating from c1888, and has calibrated settings for a number of metric and imperial scales.
A fine Amsler type 2 planimeter (unsigned). This is the fixed scale (no. 2) variety, serial number 22935, dating from c1896, in German silver, calibrated for measuring in square inches. A silver plate on the lid is inscribed "A. A. Cawkwell from the officials of the Engineering Dept. Wm. Doxford & Sons Sunderland".
A signed, Amsler type 6 planimeter, serial number 81352 dating from c1939. This planimeter is adjustable to a range of metric and imperial scales. It was retailed by Dobbie McInnes, whose name is printed on the case, and it is of the special type for measuring engine indicator diagrams. By setting the adjustment such that the distance apart of the two points on the top of the instrument equals the base length of the indicator diagram, the mean effective pressure can be read directly. Dobbie McInnes are perhaps best known as manufacturers of engine indicators for steam, and low speed oil & gas engines.
This Bakelite cased Allbrit planimeter, serial number 21681, is the adjustable type with a range of metric scales. Calibration details are recorded on the paper inside the lid. It was manufactured on 11th March 1954. I am indebted to Prof. Dr. Joachim Fischer of Ernst von Siemens Kunststiftung for this and other dating information for the planimeters in my collection.
Another adjustable Allbrit planimeter. The calibration sheet for this one (serial number 6477) is dated Sept. 1944. Unlike the one above this has a leatherette covered wooden box lined with blue velvet. It is calibrated for English units and there are several detail differences from the one above. I have also shown it assembled for use with the magnifier which can be rotated to read either the scale setting vernier or the measuring vernier. Below it is the checking bar supplied with all these instruments.
A fixed scale Allbrit B4 planimeter, also bearing the name of Stanley who supplied it to H.M. Government War Office at Woolwich on 24th April 1937 as part of a batch of six identical instruments SN 3205-3210. It is dated 1937 and its serial number is 3208. The magnifying glass for reading the vernier and the bar for checking the calibration were standard accessories. One revolution = 15 sq. inches.
Allbrit fixed scale, 1 rev = 10 sq in, planimeter, serial no. 13128. A later example than the larger model above, it dates from 1949. The calibration constant is recorded on the slip of paper in the bottom of the box.
This W F Stanley "Allbrit" "Zero-setting" planimeter bears the serial number 04768 and probably dates from the 1970s as the Q series was introduced in 1972. I also have the instructions which state that the instruments are no longer separately calibrated as they are accurately made to all have the same calibration. It is a fixed scale model and 1 rev = 100 sq cm.
This is the adjustable version of the Allbrit Zero-setting planimeter, serial number 01109. Instead of having a tracing point like the one above this one has a magnifier tracer with a fine circle in the centre. It has a foam lined case and checking rule.
W F Stanley “Allbrit” radial planimeter no. 19763 dating from ca. 1952. Scale 1 rev = .4” radius. These planimeters were used for finding the mean radius of circular charts. Originally it would have been supplied with instructions, a magnifier, and a special board.
in the top left hand corner is a chart centre. The arm of the planimeter has a groove in its underside, which slides along over the ball on the top of the chart centre as the tracing point is moved to follow the plot on the chart.
A planimeter by R & A Rost of Austria dating from 1967, type 641. It is a fixed scale 1:1000 planimeter complete with calibration bar, instructions and calibration certificate. The mechanism is essentially the same as in the Allbrit B4 but it is cased and the instrument has a silver crackle finish. Serial number 16204.
Teknor 95 IMP zero setting compensating polar planimeter, serial no. 33940. This instrument has a metal case and the following accessories: setting bar, screwdriver, allen key and spare pole point. An adjustable planimeter, made in Japan. It is actually a Koizumi KP-27 planimeter and dates from c1972.
A linear, square root planimeter, made of brass & steel, by Geo Kent Ltd, London & Luton, 8767/71. It is housed in a fitted mahogany box. There would originally have been a rail along which it would run, being a linear planimeter as opposed to the more usual polar planimeter (which all the previous ones are). It would have been used for evaluating flow rate charts. In use the arm with the knob on was moved such that the pointer on the other arm (moved by a cam following a curve on a plate attached to the first arm) followed the diagram. The shape of the curve followed by the cam was such that the mean flow rate & hence total flow over the period would be evaluated.
A Geo Kent ‘Venturi’ water flow rate meter in the Kew Bridge Steam Museum. The vertical axis of the chart is water flow rate and I have included this picture as this is the type of chart that my planimeter would have been used with. The non-linear nature of the vertical ordinate can be seen on the chart on the drum. This chart records flow rates of up to 170.000 gallons per hour over a one week period.
Basically a Venturi meter measures the pressure increase as the water passes through the throat of the meter. The flow rate is proportional to the square root of the pressure increase.
There are other Kent flow rate meters in the museum, some of which have a larger diameter drum. They were used at water pumping stations to record the rate and amount of water pumped.
Basically a Venturi meter measures the pressure increase as the water passes through the throat of the meter. The flow rate is proportional to the square root of the pressure increase.
There are other Kent flow rate meters in the museum, some of which have a larger diameter drum. They were used at water pumping stations to record the rate and amount of water pumped.
An Allbrit planimeter pole wagon in use with Allbrit planimeter 3208. The wagon also has “Negretti & Zambra” on it, who would have been the retailers. It has a black leatherette covered, blue velvet lined, fitted case.
The pole wagon was used with the tracing arm of a polar planimeter so that the planimeter could be used to measure longer areas than possible in its polar configuration. It thus became a linear planimeter. The pole wagon depended on its weight, the accuracy of the diameter of its knurled wheels, and the lack of any play in its needle bearings to ensure that it followed an exactly straight line.
The pole wagon was used with the tracing arm of a polar planimeter so that the planimeter could be used to measure longer areas than possible in its polar configuration. It thus became a linear planimeter. The pole wagon depended on its weight, the accuracy of the diameter of its knurled wheels, and the lack of any play in its needle bearings to ensure that it followed an exactly straight line.
Planimeters, used for measuring enclosed areas on drawings and maps, were invented by Jakob Amsler in 1854. He was professor of mathematics at Zurich University, Switzerland, but lived and had his workshop - founded in the end of 1854 - in Schaffhausen, Switzerland.