To: Jiff
Here is my response to your posting. Regarding your last point, I will be most happy to have you contact me directly.
Here are your comments with my responses:
1.
"Frank, there has been a large debate recently on the PPrune web site about the R22 and R44 head design, what's your view point", I asked.
"The person who started that has since been discredited as an engineer", Replied frank.
RESPONSE:
It is nice to know that Frank Robinson thinks of me as a discredited engineer. There are a lot of American and European aircraft companies that seek my services that would disagree with him.
2.
"If the blades have the ability to flap independently but cant advance or retreat, how does the design of the head work", I asked.
"Its very complicated and you wont be able to understand it", the lecturer replied.
RESPONSE:
The responder was an idiot for saying that and only shows that he has limited understanding of the mechanics of the Robinson Rotor head. Because the blades are free to flap the blades will also want to lead and lag but they are restrained by the cone bushings. The energy imparted by the leading and lagging tendency will cause the blade to exhibit spanwise bending. This bending is reacted by the cone bushings and causes them to wear in an elliptical pattern. This cyclical energy transfer is also reacted by the teeter bushings and they wear in the same pattern but to a lesser degree. The total energy is also reacted by the main rotor shaft and it exhibits cyclical torsional bending.
Draw you own conclusions about the answers but I'm damb sure I know which impression I was left with !!!!
RESPONSE:
What were your impressions? I'm sure that the members of this forum woulld like to know as I surely would like to know.
Lu,
We were shown a rotorhead which was damaged as a result of continually pulling to much power (cattle mustering in Oz), the area's on the head where the damaged occurred looked unusual and I would like to discuss this directly with you.
RESPONSE:
Can I assume that the damage you allude to was mainly in the cone and teeter hinges. This will manifest itself to a greater degree on helicopters used in mustering as they are flown with a great deal of maneuvering that manifests itself in higher leading and lagging loads but it can also manifest itself in any Robinson but to a lesser degree. On the Oz Robbies if the bushing wear is excessive the through bolts passing through the bushings will also wear and be significantly weaker. Also the bushing wear will actually allow the blades to lead and lag and since there is no damping effect the blade will come up hard on the bushing (stop) further exacerbating the condition and the ride quality. High power application has minimal effect. It is the high maneuvering loads that cause the problem on the head you describe.