vorticey
"coning angle reduces thrust. by pushing the inside of the blade down (the elbow) coning is increased. "
I don't think that the offset will change the coning angle much from that of a conventional teetering hinge. In fact, a change in a coning angle from 2 degrees to 3 degrees (cosine 1) results in a thrust change of only 0.05%. This cone is also fighting the closure of the streamtube, so the change might be even less.
An early Sikorsky had a coning angle of 10 degrees.
"NO dave this is wrong. you missed out one thing, the rotor head plane, which is the same as the mast plane on a fully articulated or solid rotor systems as well as your drawings. However on teeter systems the head is always parallel the tip plane (please explain if it is not)."
I can't recall ever seeing a reference to 'rotor head plane'. There are four rotor planes of interest. They are described on;
Rotor Axes ___________________
Lu,
"This is an extremely difficult subject to discuss without diagrams. "
This diagram, from Leishman, may help. Its acronyms are described on the above web page.
___________________
rwm
"In a 206 it has an underslung teetering head, and it is very responsive compared to the similar head on a 204/205/212. "
The following is theory and not a fact, until Nick says so.
joke
. With forward velocity, a craft with a teetering rotor and a craft with an articulated rotor may have the same rate of response. This is because the craft with a teetering rotor could be rigged to have a greater rotor pitch change for a given cyclic movement. At or near hover, the articulated rotor is more responsive, for the reason given by Lu and Nick.
"my question is if this is for a home built, why worry about how responsive it is. "
The primary application for this idea would be the US Ultralight category. No licenses are required in this category, therefor it makes sense to have a helicopter that is as safe as possible for the low time pilots. A fast response, symmetrical intermeshing configuration and rotor governor will all contribute toward a safer helicopter.
All hinges on the rotor hub in sketch D/ will have delta-3, as does the Robinson's teetering hinge. Interestingly, this hub therefor offers another 'theoretical' advantage, that of a cone-pitch-coupling governor.
If the Tie-bar was to have an elastic property then as the rotor RPM slows, the cone of the disk will increase, by stretching the Tie-bar. This causes the cone-pitch-coupling (delta-3) to reduce the pitch of the blades and thereby help maintain rotor RPM.
