Standby Alt/Aspd gage conversion

[kattz]

I have a standby altimeter/airspeed indicator for my B737 simulator. This is the real gage, not a sim product.

Originally, this is operated by both dynamic air pressure from a pitot tube for airspeed and static air pressure from a static air pressure port for altitude.

It operates from a bellows that is driven by each type of pressure. The airspeed unit uses about 15° of travel on an input shaft attached to the bellows and I can drive it from a servo using a rod, ball link, and output arm.

This servo must be stepless and cogless. Recommendations? Doesn't need much force.

The altimeter is a whole different beast. It expands the bellows motion by 20 times for full operation. Looks like a clock or very fine watch inside.

I can partially gut this unit and use a small continuous-rotation servo to drive the altimeter. But there is a barometric pressure preset knob that offsets the altitude to zero based on the current air pressure at ground level. How to keep this function?

Please, I need help with this.

Thanks.

Kev

[mickc]

It can be done, I have converted 2, and assisted another builder to do his.

You will need to remove all the bellows and mechanical components to fit in the required parts.   With some skill and clever engineering, you can retain the baro function as well.

I can send photos etc if you are up to the task [emoji4]

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