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Discussion Starter #21
At constant velocity the inclinometer should read the same as if stopped. Just the physics of it. Mine had only a small bubble in the top so I just topped it off with baby oil, only a cc or so. Could not find any source of leaks but did see a few drops on the dash under the unit when it was removed. It moved freely at all angles before topping off So we’ll see how it works this week.
 

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In theory yes, but no FJ moves at a constant speed, especially one driving over an imperfect surface at constantly changing throttle inputs from a human foot going over a bridge. It’s good enough for a “guesstimate,” but the toy in the FJ is by no means comparable to an aircraft inclinometer.
No inclinometer in an aircraft ... the instrument giving a similar display is the 'attitude indicator', but that is driven by a gyroscope.
 

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At constant velocity the inclinometer should read the same as if stopped. Just the physics of it. Mine had only a small bubble in the top so I just topped it off with baby oil, only a cc or so. Could not find any source of leaks but did see a few drops on the dash under the unit when it was removed. It moved freely at all angles before topping off So we’ll see how it works this week.
Eliminating the "small bubble" was probably the wrong thing to do. There has to be some way to accommodate the thermal expansion of the oil, or you'll be at high risk of cracking the ball (or the housing) when the fluid gets hot. Typical oil-filled pressure gauges, transformers, etc. will always have a small air bubble, a rubber diaphragm, or a metal bellows present to allow fluid expansion without 'hydraulic lock'.

I can't think of any way that a small air bubble at the top of the instrument would prevent free gimballing of the ball.

I don't know what the original fluid fill is, likely silicone oil for long-term inertness and freedom from any attack of the plastic housing.
 

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No inclinometer in an aircraft ... the instrument giving a similar display is the 'attitude indicator', but that is driven by a gyroscope.
That’s exactly my point, it’s not the same device.
 

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Discussion Starter #26
Why baby oil, where did you find info that said to add that?
Read a few older posts that talked about what fluids were used in compasses. Either alcohol or oil, and baby oil was suggested as a good viscosity mineral type oil. So I tried it. Seemed like about the same viscosity . Didn’t want to bother with getting old oil out with a syringe.
 

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That’s exactly my point, it’s not the same device.
My point was that the FJ clinometer, if installed in an aircraft and traveling at high speed, would work just fine IF the aircraft was not accelerating, decelerating, or turning.

The FJ clinometer is just gravity sensitive, not absolute speed sensitive, as long as no accelerations are present.
 

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Discussion Starter #28
Eliminating the "small bubble" was probably the wrong thing to do. There has to be some way to accommodate the thermal expansion of the oil, or you'll be at high risk of cracking the ball when the fluid gets hot. Typical oil-filled pressure gauges, transformers, etc. will always have a small air bubble, rubber diaphragm, or metal bellows present to allow fluid expansion without 'hydraulic lock'.

I can't think of any way that a small air bubble at the top of the instrument would prevent free gimballing of the ball.

I don't know what the original fluid fill is, likely silicone oil for long-term inertness and freedom from any attack of the plastic.
Great point on the expansion bubble. I took a little out to have a small bubble. Thanks.
 

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Second warning on this thread; Some don't seem to get the point of not thread crapping/hijacking and not making irrelevant and non constructive comments.

Read the rules please. Warnings are a courtesy.

Thank you!
 

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Many instruments and fluid damped gauges use glycerin as a suspension fluid. It is water soluble, and won't wreck anything if it leaks or gets spilled. It's cheap, and you can get it at any drug store or wally-world. Just my 2c.
 
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