Anybody have one of these speedo’s ?

[Ironhorse2022]

I was told by the PO that this is original equipment. The swing arm has a hole in it facing forward. Above it is a brass tube with a ball or plunger of some sort in it. I think it works by water being forced into the hole which pushes up the ball. This compresses the air above the ball. That air chamber is connected to the Speedo gage by a long tube. So essentially, the speedo is an air pressure gage correlated to speed. Is this correct ? I suppose the swing arm can rotate so it isn’t knocked off if you hit some Floating debris ?

 

[LDUBS]

Called a pitot tube. Measures speed of flow of air or water. Used on airplanes, boats, and test equipment (like for water hydrant flow tests).

 

[eeshaw]

Yep, what he ^ said.

 

[Ironhorse2022]

Great, thanks. Pretty cool I think. I’ll see how accurate the gage is vs gps in the spring.

 

[thill]

If you have it in clean water, it should be pretty accurate over a certain speed. Won't work if you are doing 2 mph, but once you get over 10, they are pretty good.