Sorry I overlooked this posting.
Well it is pretty easy.
All you need for a gauge is:
* A servo-engine (S3003's are $5. The better HS-311 is $15)
* A 2mm shaft
* Two gears (Buy a bag of gears on eBay)
* 3+ pieces of plexiglas or Foamalux/Foamex
* A print of the gauge (Make your own)
* 2x 20mm spacer + 2x 5mm spacer (look for "M3 HEX")
* Craftmanship.
Most things (apart from the craftsmanship) can be found on eBay
I have posted two screen shots from a video I was trying to make on this subject (How to build a gauge). But the video is way too long so it needs some editing.
In this picture you can see my structure.
Attachment 8433
From right to left:
First I layer which a large hole for the gauge. This serves as a spacer the makes room for the needle.
Second a plate with the gauge on. I have printed my gauge on a sticker and mounted it on the plate. Very easy.
In the middle a small hole for the shaft and the needle is made from foamalux but you can also use plexiglass.
Then I use 20mm spacers before the two back plates.
The back end is made from two layers of plexiglass:
The first (The right one) only holds things in place. Is makes sure the gears not move apart and it adds stability to the shaft.
Between the two plates are two gears. One gear is mounted on the shaft. The other on the servo-engine. You need some sort of ratio as a servo only moves 180 deg but the gauge often needs 270 deg turn or more.
The last plate (far left) holds the servo-engine and the shaft.The white material is hard pressed cold foam. It is called Foamalux / Foamex and should be available at a DIY store (The kind that also sells MDF and plexiglas). But Plexiglas will also do.
Here you can see the front of the gauge. It needs to be mounted behind the MIP, so you only see the gauge through the hole.
Attachment 8434
My gauges is interfaced via SIOC and a OpenCockpits Servo card.
So as you can see, you don't need many materials, only some craftsmanship (and preferably better than mine :-P )
Cheers
Peter