How to measure the pitch?

[brendus]

just received my new 15-22r impellers and i want t measure the pitch for myself. how is this done using a vernier??? so to check wether its actually close to 15-22.
thanks

[engineermike]

I check mine with a digital caliper and get pretty good numbers. My method is as follows:

- Set the caliper to 5 mm.
- Scribe pencil marks on the tip of the blade 5 mm from the leading edge and 5 mm from the trailing edge.
- Set the caliper to 20 mm.
- Scribe pencil marks on the tip of the blade 20 mm from the first pencil marks.
- Set the prop on a flat surface with the TE facing down.
- Measure the distance from a flat surface to the bottom of the blade at each of the pencil marks.
- Calculate the angle using this formula:

LE angle = asin ((height 1 - height 2)/20)
TE angle = asin ((height 3 - height 4)/20)

Mike

[brendus]

awesome.thanks will give it a go now.