Servo Driven Brass Pressure Gauge

While wandering about a junk shop a while back I found two brass pressure gauges. Thinking that they would be an interesting way to display the water level in the rainwater harvesting system I looked at adding a servo control.

As the larger gauge has more space I started with that one for a conversion. The brass was a bit tarnished so I stripped the gauge down and polished anything that was polishable:

The bourdan tube that is used to measure the pressure (the circular tube attached to the bulky brass tube at the bottom left) takes up a lot of space in the gauge so I decided to remove it. This means the gauge won't easily measure pressure again, but that use is unlikely in the future. I made a bracket from some sheet steel for the servo, and the result is below:

This shows a piece of wire connecting the servo arm to the needle mechanism as I was concerned that a rigid link would jam. Once this flexible link was tested and found to work, I tried a rigid link:

This was fine as there was enough bend in the link to cater for the arc swept by the servo arm.

This video shows the gauge being driven from the PWM output of an arduino:

 

This is a front view of the gauge operating: