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Delta Head

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Ray Pinchin18/02/2013 17:09:57
8 forum posts
3 photos

I have seen references to a "DELTA HEAD" for use on autogyros, but can't find much detail on the subject. I'm interested to know how the work and if there are any advantages of this type of head?

Richard Harris18/02/2013 20:22:22
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2077 forum posts
1938 photos

The delta head in its most simplest form is a way to help spin up of the rotor blades, as you are probably aware the blade has to be able to flap upwards.

What the delta head cleverly does is to utilise this flapping up force at slower RPM's, each blade has seperate hinges which are offset normally by 15 degrees. So when the blade flaps up the nature of its hing position also puts the blades centre line into negative incidence. As the blade gets up to speed this upward flap is reduced as the cone of the blades flattens out. Normally some form of packing wedge is appartent to keep the blade in a slight negative attidude full RPM.

These type of heads use some form of flexible material as the hinge which is sandwhiched between the head plates. Polypropylene or Fibre Glass sheet are the norm for this.

 

 

 

 

 

 

Rich

Edited By Richard Harris on 18/02/2013 20:23:31

Stephen F18/02/2013 21:06:31
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33 forum posts
19 photos

Rich. Is the HK C30 head classed as a delta head, the hinge plate is angled by about 15 degrees. It is similar to the heads designed by the late Jochen.

Stephen

Richard Harris18/02/2013 22:52:17
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2077 forum posts
1938 photos

Stephen,

Yes it is, I believe (but don't quote me) it was pioneered by Jim Baxter. 15 degrees seems to be the magic angle as it allows goood spin up without too much loss of lift. When i tried the HK head and blades on my Fire Fly the thing didn't float as much, I am sure the standard head kills lift.

 

I have made a quick sketch of what I have tried to describe, hope it makes sense?

 

delta head pdf.pdf ii_0001.jpg

 

Rich

Edited By Richard Harris on 18/02/2013 23:04:27

Richard Harris18/02/2013 22:57:40
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2077 forum posts
1938 photos

Fixed it!

Edited By Richard Harris on 18/02/2013 23:04:43

Mike T23/02/2013 01:03:53
423 forum posts
28 photos

Rich - thanks for the drawing, but you may want to revisit it - I think one of your angles is a bit squiffywink

Malcolm - coolwind.co.uk28/02/2013 12:13:52
177 forum posts
33 photos

Rich,

Thats an ingenius bit of thinking and problem solving design by Jim or Jochen, but begs the question as to how this effect is achieved on the plain triangular delta plates used in many designs? or do we just rely on having a constant negative shimming on the blade mount?

Thanks

Malcolm

Richard Harris28/02/2013 17:44:34
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2077 forum posts
1938 photos

Mike,

Yes I see it, I will have to alter it !

Malcolm,

Generally a shim is added as far as I am aware, I know Tom steams a twist his blades to achieve spin up aswell.

But, I beleive in as litle or no shim as possible and having a thinner flexible plate to help with the nosing up problem.

It is each to his own.

Rich

Tom Wright 228/02/2013 17:53:10
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3908 forum posts
297 photos

Hi Guys.

I have used blade twist with great success ,but these days use a a modest shim angle as the loss of lift on my lightly loaded designs is negligible, and ensures very easy spin up without charging all over the field .

Easy spin up IMO is an essential feature for Autogyro first timers ,but a more critical balance between shims and best performance may be required with heavier models .

Well made blades with no l/e undercut will spin up without shims but may take more time .

Tom.

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