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2013/7/6 Portable tachometer, Frahm vibrating-reed type, aluminum / steel / glass, made by Biddle Instruments, Philadelphia, Pennsylvania, United States of America, 1960-1990, used at Caltex Lubricating Oil Refinery, Kurnell, New South Wales, Australia, 1960-2011. Click to enlarge.

Portable vibrating-reed tachometer

1960-1990

The Frahm tachometer contains tuned steel reeds that differ in length and thus in natural vibration frequency. When it is held against the casing of a machine, the reed that resonates with it, and thus vibrates most strongly, will indicate the vibration frequency of the machine. The user reads the frequency, in hundreds of revolutions per minute, from the scale. The instrument was patented by German physicist Hermann Frahm in 1904, made in the USA between 1960 and 1990, and used to check machine...

Summary

Object No.

2013/7/6

Object Statement

Portable tachometer, Frahm vibrating-reed type, aluminum / steel / glass, made by Biddle Instruments, Philadelphia, Pennsylvania, United States of America, 1960-1990, used at Caltex Lubricating Oil Refinery, Kurnell, New South Wales, Australia, 1960-2011

Physical Description

The tachometer consists of a grey cast aluminium box containing an array of tuned steel reeds which differ in length and thus in natural vibration frequency. Two linear scales sit on the top face of the box, alongside the square white tops of the reeds and under a flat glass cover. When the device is held against the casing of a vibrating machine, the reed that matches its vibration frequency will be observed to vibrate much more than the others, as it resonates with the machine. The frequency, in hundreds of revolutions per minute, can be read from one of the scales. The top scale runs from 2000 to 3500 revolutions per minute (rpm) and the lower scale from 3500 to 5000 rpm. Two groups of five raised lines run down the long sides of the box to provide grip, while the shorter sides and base are plain.

Marks

Above the scales: RESONANT REED FRAHM TACHOMETER. Each letter of the name FRAHM is enclosed in a box, and there are short horizontal lines above and below the R and H, and two horizontal lines above and below the A; all these elements form a logo that suggests vibrating reeds. Below the scales: BIDDLE INSTRUMENTS X100 RPM MADE IN USA. Above the lower scale: CAT. 312236 / PAT. NO. 188,345.

Dimensions

Height

75 mm

Width

160 mm

Depth

80 mm

Production

Notes

Dr Hermann Frahm of Hamburg in Germany invented the vibrating reed tachometer, for which he was granted US patent 759,513 in1904. The 'ornamental design' of this particular tachometer was covered by patent 188,345 granted to Frederick Lombard of Dublin, Pennsylvania in 1960 and assigned to James G Biddle Co, which made this tachometer in Philadelphia, Pennsylvania, USA, between 1960 and 1990.

James G Biddle is now owned by Megger and is part of the AVO group.

History

Notes

This tachometer was used by plant operators to check the angular speed of items of equipment with rotating shafts, including motors and pumps.

Source

Credit Line

Gift of Caltex Refineries (NSW) Pty Ltd, 2012

Acquisition Date

18 January 2013

Cite this Object

Harvard

Portable vibrating-reed tachometer 2019, Museum of Applied Arts & Sciences, accessed 20 January 2020, <https://ma.as/460833>

Wikipedia

{{cite web |url=https://ma.as/460833 |title=Portable vibrating-reed tachometer |author=Museum of Applied Arts & Sciences |access-date=20 January 2020 |publisher=Museum of Applied Arts & Sciences, Australia}}

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