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HelicopterMain Discussion › Is this what Delta-3 looks like?
01-28-2007 03:37 PM  10 years agoPost 1
gigi

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Port-au-Prince, Haiti

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This is a Vigor CS rotrohead. The pushrod from the Bell-Hiller mixer to the blade grip is angled in two direction, as can be seen from the pictures.

If there is one concept about helicopters I've had a hard time understanding, it's that whole Delta-3 thing, which I think this is all about.

1) WHY bring the mounting point of the pushrod at the blade grip to the mainshaft? If it were shorter, and the pushrod was vertical instead of leaning to the right on the first picture, what exactly would change?

2) What does Delta-3 have to do with the tail rotor of full-size machines which are not held rigidly vertical, but can flap sideways, like on a Jet Ranger?

Thanks,

Gigi

My heli spending has gone way down since I got a Honda 919 :-)

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01-28-2007 04:53 PM  10 years agoPost 2
mdu6

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Montreal

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No, this head does not have any Delta-3 has the teeter hinge point is in line with the blade-pitch arm.

I've found this text that describes it better. Others in this forum
will be able to describe/explain even better.

The CarterCopter uses delta-3 to help the high-inertia rotor track the tilting spindle faster and delta-3 also helps dampen the tendancy of a rotor to flap. As the blades flap their cyclic-pitch angle changes in a way that opposes the flapping. Delta-3 is common in helicopter tail-rotor hubs and is also employed by many Gyroplane designs. It is the technique of pivoting the see-saw hinge at an angle greater or less than 90 degrees.

While Gyros with a tilting spindle usually use Delta-3 to dampen flapping etc:, helicopters have their own technique that achieves the same effect. Helicopters achieve it in the way the blade-pitch-change-arm is positioned in relation to the position of the teeter hinge pivot point. If a pitch change control rod is connected to the blade-pitch-arm directly in line with the teeter hinge then the blade pitch remains the same when flapping. If however the blade-pich-arm is shortened so it is NOT in line with the teeter hinge then as the blade flaps up, the blade-pitch-arm will be pulled down because it is anchored to the blade-pitch-control-rod, thus reducing blade pitch. The pitch change increases as the blade flaps up more. This is exactly what delta-3 achieves. Like delta-3 it can be adjusted by the length of the blade-pitch-change-arms.

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01-28-2007 04:59 PM  10 years agoPost 3
AirWolfRC

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42½ N, 83½ W

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Another way to look at (positive) delta-3 is a linkage setup that changes the pitch of the blades so the rotor disk is induced to stay perpendicular to the main shaft.

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01-28-2007 05:24 PM  10 years agoPost 4
gigi

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Port-au-Prince, Haiti

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'Not easy to understand...

I'm going to need a picture to understand this stuff I just don't get it yet.

Thanks,

Gigi

My heli spending has gone way down since I got a Honda 919 :-)

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01-28-2007 06:39 PM  10 years agoPost 5
kangarooster

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Orlando Fl-USA

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HelicopterMain Discussion › Is this what Delta-3 looks like?
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