To: Arm out the window;
"the guy giving the talk had 2 rulers held together with a bit of a coning angle,"
I assume that the two rulers were held together end-for-end, with a slight coning angle between the two.
The concept of 'universal joint' [Hooke's joint] and 'knuckle joint' are only used, to my knowledge, in reguard to 2-blade teetering rotors. These joints represent the teetering hinge. The Bell 47 had an 'X joint' in its hub and I think this is where the expression 'universal joint' [Hooke's joint] was applied. I do not know of any currently made helicopter that now incorporates the second hinge, with the possible exception of the Safari (mini belle). All teetering hinges are now 'knuckle joints' but some people still refer to them as [Hooke's joints].
The speeding up and slowing down of the blades of a teetering rotor are the result of the Coriolis effect. The two blades accelerate and decelerate at the same time, therefor there is no requirement for lead-lag hinges.
Some people refer to this teetering action and the associate speed change as being the result of Coriolis [Conservation of Angular Momentum]. Others refer to it as being the result of the Hooke's joint action. They are really one and the same.
If he had the rulers crossed as an X, then I don't know what the h--l I'm talking about
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Project:
UniCopter.com
[This message has been edited by Dave Jackson (edited 22 June 2001).]