Two direction tach

DaveBonds said

Industrial drive tach. There are internal combustion engines out there that are designed to run both directions. Typically, this was more common before people really started getting into fancy transmissions, before the automatic transmission was in common use as well as other types of transfer cases and gearboxes that allowed industrial equipment to have multiple speeds in both directions.

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There still exists both steam and marine diesels which run either way. Some boats / ships have no neutral or reverse. You simply stop the engine and start it the other direction.

Early Mercury outboards did this as well Some of them had TWO starter motors. My Dad's old boss went for a ride (he sold Johnson) with the competing 'Merc guy who wanted to show off. Came roaring up to the boathouse, and the damn thing would not start in reverse. Damn near went through the rear of the boathouse. This was in the late '50's

Stuff like the old "hot bulb" or "semi" diesels with run either way

Reversing diesel

[ame="http://www.youtube.com/watch?v=kmpY8dlw4QE"]Washington Diesel direct-reversing Tug Arthur Foss - YouTube[/ame]