Bolly

[pluessy]

If you are still after a Bolly pitch gauge, mine is available?

 

 

[IBob]

Among the systems Bolly suggests, is the time-honoured method of using a straight edge to a mark on the floor.

 

They note that nobody seems to think this is good enough. More on that later.*

 

Here is the DIY rig I just used to do my initial setup.

 

1 block of hardwood, planed flat. One edge of this flat will rest on the prop where the pitch is to be measured.

 

Since the prop blade has a continuous twist along it's length, a dome-headed screw is placed to lift the opposite edge. So when in place, the block is contacting the prop on the straight edge on one side, and the screw on the other, ensuring I am measuring the angle at the straight edge.

 

1 aluminium strap hook to hang the block on the prop.

 

1 cheap laser 'level', unused gift from relative.

 

This doesn't give blade angle, but does allow all blades to be set the same, and works fine, with excellent repeatability. (In use, I put a bit of masking tape over the screw to avoid marking the prop.)

 

*Having completed and triple checked all blade pitches, I did the simple sums on the accuracy:

 

Distance from blade to floor mark approx 1200mm.

 

Circumference of circle with 1200mm radius approx 7535mm

 

So 1 deg = 7535/360 = 21mm

 

That is, each degree will show as a 21mm shift of the mark on the floor.

 

I was able, without difficulty, to pitch the blades within 2mm of each other, according to the mark on the floor.

 

Which is one tenth of a degree.

 

(Note: prior to using the laser, I went through the same exercise using an aluminium straight edge from blade to floor. Using the laser revealed that, while I had been able to set 2 blades to almost identical pitch, the third blade was over half a degree out. I put this down to the difficulty of presenting the straight edge to the narrow rear face of the blades, and would not reccomend it.)

 

 

 

 

 

[Blueadventures]

Negative to the last question. The Bolly pitch tool is graduated to 1/2 degree and very difficult to read. It also suffers from friction and is unstable when holding on the prop blade (needs to be kept accurate and still in 2 axis). I spent a long time adjusting my blades when I installed my new Bolly.

Now I have made a precision tool that gives me repeatable results in a few seconds flat and found over 1/2 degree of variations. Preparation work is to have accurate station markings on your blades (I use 500mm from the hub, serves also as the pull-point for the engine friction test).

 

Then set the trailing edge of the blade level through the spirit level (bubble), record the reading on the clinometer and go to the next blade. Pull the prop very slowly and from the top blade to minimise aircraft movement (this set-up is not sensitive to aircraft movement, unlike the stick/laser method).

 

There is a bit more work involved if you are installing a new prop as you need to calibrate the 0 line first. For checking the pitch on each prop or to change the pitch from a known position, real quick and easy.

 

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I agree, my opinion of the bolly prop pitch tool it that it is 'ordinary' as a precision pitch tool.  I like thier props and have purchased a three blade set and they fly nice and I would purchase another set.  In my opinion they need to revisit a tool for adjusting the pitch. The one I made suits me and the idea to add the laser pointer was a winner. (Thanks to forum member who told me about them)  No hassles adjusting the pitch and getting the blades as close to even as I can. Results are better than ever in the past with other tools.  I had the use of a loan bolly pitch tool.  My comments about the bolly pitch tool are my experiences and I believe valid comments that some others would agree with. Cheers