Rigid & Articulated Heads
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RW-1,
Charles Kaman might shudder to hear; "... a model of a Kaman intermeshing?"
This model, with its rigid hubs and two blades per rotor, will experience (or has experienced) very high vibration during forward flight.
Trivia,
A close-up of the hubs and swashplates is interesting. They have set the phase lag at approximatly 45-degrees. If the craft had basic teetering rotors, the phase-lag would be 90-degrees. If they were able to produce 'absolutely' rigid rotors, the phase lag would be a theoretical 0-degrees.
Charles Kaman might shudder to hear; "... a model of a Kaman intermeshing?"
This model, with its rigid hubs and two blades per rotor, will experience (or has experienced) very high vibration during forward flight.
Trivia,
A close-up of the hubs and swashplates is interesting. They have set the phase lag at approximatly 45-degrees. If the craft had basic teetering rotors, the phase-lag would be 90-degrees. If they were able to produce 'absolutely' rigid rotors, the phase lag would be a theoretical 0-degrees.
Join Date: Jul 2002
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412 M.R.
Jumping back a few items in this thread.....
Since it was mentioned, The main rotor system in the Bell 412 is actually a "soft-in-plane" rigid rotor, flex-beam type. (straight out of product data) I'm not a rotors guy, but I've been told that being "soft-in-plane" makes it behave more like an articulated rotor than a rigid rotor. It's technically called a rigid rotor because it doesn't really have a hinge like an articulated, it instead bends the material that attaches it to the mast to create almost the same effect. ..... if that helps.
My understanding is the fully articulated has the best ride - which makes sense since the blades are able to move with the most independence from the aircraft. A soft-in-plane rigid rotor is very close and differs only by the fact that there's no physical hinge.
The teetering rotor is next, as far as pure ride goes. The 2-per-rev can still get you though, but systems like the nodal beam suspension on the 206L-4 tranny correct for that, and gets the ride about as good as you can get with a teetering rotor.
BO-105s and the like, with true rigid rotors, are akin to sports cars with stiff, or almost non-existent suspensions. They can do fantastic maneuvers, but the price you pay is a rough ride. Every bump that goes into the rotor gets translated into the airframe. Every gust that lifts a blade gets translated into the airframe, etc. But I tell you it’s wild to watch them stand on their nose as they take off. On a rigid, when you tilt the disc... the whole world tilts with you.
Nick Lappos used to have some diagrams explaining all this stuff on his website but my link to it doesn’t work anymore.
Since it was mentioned, The main rotor system in the Bell 412 is actually a "soft-in-plane" rigid rotor, flex-beam type. (straight out of product data) I'm not a rotors guy, but I've been told that being "soft-in-plane" makes it behave more like an articulated rotor than a rigid rotor. It's technically called a rigid rotor because it doesn't really have a hinge like an articulated, it instead bends the material that attaches it to the mast to create almost the same effect. ..... if that helps.
My understanding is the fully articulated has the best ride - which makes sense since the blades are able to move with the most independence from the aircraft. A soft-in-plane rigid rotor is very close and differs only by the fact that there's no physical hinge.
The teetering rotor is next, as far as pure ride goes. The 2-per-rev can still get you though, but systems like the nodal beam suspension on the 206L-4 tranny correct for that, and gets the ride about as good as you can get with a teetering rotor.
BO-105s and the like, with true rigid rotors, are akin to sports cars with stiff, or almost non-existent suspensions. They can do fantastic maneuvers, but the price you pay is a rough ride. Every bump that goes into the rotor gets translated into the airframe. Every gust that lifts a blade gets translated into the airframe, etc. But I tell you it’s wild to watch them stand on their nose as they take off. On a rigid, when you tilt the disc... the whole world tilts with you.
Nick Lappos used to have some diagrams explaining all this stuff on his website but my link to it doesn’t work anymore.
Last edited by Avnx EO; 19th Sep 2003 at 23:18.
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Vfrpilotpb,
The model helicopter has conventional swashplates and feathering (pitch) hinges. Their current method of steering is very close to that of the Kamans. Here's an excerpt from the e-mail accompanying the picture.
The model helicopter has conventional swashplates and feathering (pitch) hinges. Their current method of steering is very close to that of the Kamans. Here's an excerpt from the e-mail accompanying the picture.
Helicopter seen in a fair in Switzerland sunday 7th of september. It has 5 hp, rigid rotors and it use both ciclic for roll, ciclic for fore and aft, opposite ciclic for yaw. I have spoken with its builders and they said that they used this control sistem to avoid the reversal yaw problem, they also told me that they thought to use difference in collective for roll, (in R.C. models it's easy to try different mix control by changing electronical parameters) but thay haven't tried yet because it works well as it is.
