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Manufactured By:
American Steam Gauge Co.
Boston, MA

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Title: 1889 Article-American Steam Gauge Co., Thompson Steam Indicator
Source: The Steam Engine and the Indicator, 1889, pgs. 412 & 413
Insert Date: 9/17/2019 7:43:45 PM

Image Description:
The Thompson Indicator

The claims for this indicator (Figs. 200 and 201) are that the parallel motion is the most accurate of any in use in such instruments, and that errors, said to exist in drawing correct vertical lines, do not appear in the limited movement of the pencil in taking diagrams from steam engine and other cylinders with this instrument.

The paper cylinder movement is so constructed that the tension of the coiled drum spring within the paper cylinder can be increased or decreased for different speeds of engine.

The diameter of the piston is 0.798 inch, equal to one-half inch area. These indicators are fitted with a "detent motion" consisting of a pawl and spring stop, by the use of which the paper drum cylinder can be stopped and a change of cards made, without unhooking or disconnecting the driving cord.

The advantage of this arrangement is that the cord being entirely free, runs loosely with the motion of the engine, and the paper drum being stationary, cards can be changed without the least disturbance of adjustments. Again it obviates the change of adjustments, and is particularly valuable to amateurs and others not familiar with the use of the indicator.

US Patent: 167,364

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1889 American Steam Gauge Co., Thompson Steam Indicator
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1889 American Steam Gauge Co., Thompson Steam Indicator (Sectional View)
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