How many revs is that

Hi

I just this week bought this rev counter/tacho what I would like to know is what period it comes from and what it was used on? It is approx 3 1/2 diam, cable drive at an angle, offset at the base.

If you look closely at the face of the gauge, right under "R.P.M.", in tiny letters, it reads "Hundreds".

This tach reads from 300 to 2400 R.P.M, with "red-line" at 2300 R.P.M.

These cable-drive tachs usually connected to a special fitting on the distributor, or other connection to the camshaft.

Wonder what it was used on?

( took a second look at the photo - the style of the numerals makes me wonder if this was an aviation tach ?)

Possibly WW2 military truck, like one of the big diesels that were big and weak (like a railways cup of tea) . The Hercules and Cummins of that era did not spin very freely. It does not look like one out of a tank that I remember.

diesel trucks used to run in this range at maximum. a lot of 50's thru 70's ran in the 1700 to 2100 rpm range. now a lot are programed to run 1200 to 1600 rpm and some even less!

Possibly some off road equipment like a bulldozer or road grader. S.W. made tacs for many applications. Is there a model or part number on the gauge ? Maybe you can look that up.

I worked in the mines, and usually, with exception of trucks, the diesel engines were

governed and had no tachs at all more often than not. As I recall 2400 was a max on

some of the earth moving scrapers (because road speed/momentum on rubber tired

vehicles can overrun governor speeds). I am sure no expert, but i would guess maybe

Kenworth or peterbilt over the road trucks no later than 1950 due to the stylized

SW scripting. How about marine?

Looking more closely at the tach it has a "telltale" red needle behind the main pointer. it has 63900 42 cast into the diecast base so it is possibly from a military or naval engine taking that the 42 refers to the year of manufacture. Against that the rim still has traces of nickel on it.