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Speedo and Tacho dashpot?
Seabeowner:
Can someone explain how the dashpot on the tach and speedo meter works?
Have a tach apart. The needle is driven up by a fight between the magnetic coupling at the bottom and the coiled spring on the shaft. That bit seems simple. Above the spring is the dashpot. What goes on in there? The dashpot itself seems fixed to the shaft as does the needle above it. So it all moves together.
Plus tips for refilling with silicone oil.
McCabe-Thiele (Ted):
Only thing I know is there is a damper arrangement so the needle does not flutter all over the place - I've sent my gauges to be overhauled by Kent400 as I'm no clocksmith! My old Triumph 21 had some sort of gear like speedo it flicked like the seconds on a watch up & down.
Sesman:
Chronometric: Wonderful instruments.
McCabe-Thiele (Ted):
--- Quote from: Sesman on September 24, 2021, 07:59:57 PM ---Chronometric: Wonderful instruments.
--- End quote ---
Yes they were and I belived it when it said I was doing 91 mph (before the 60 mph limit was introdunced on rural roads) happy days!
AshimotoK0:
A little tube is fixed to the fixed bridge at the top.... this dips into the dash-pot (attached to the needle spindle) with high viscosity silicone oil in it. When the needle shaft/dash-pot rotates, there is viscous drag between the oil in the dash-pot and the tube fixed to the top bridge. This provided the needle damping.
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