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#21
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The control linkage that actually tilts the head is mounted 90 degrees away from the actual intended movement. It appears that BJ took gyroscopic precession into consideration when he designed this head. But, like I said, nobody, not even BJ, would ever consider this approach for a new design. He used this design because it was the best he could come up with at the time that didn't violate anybody's patents. I'm going to change it myself as soon as is feasible. Dennis. "Andrew Crane" wrote: OK - silly question. On the face of it, it seems to make a lot of sense to do it this way - simple connection - you could probably lose the swashplate somehow too - fewer cyclical forces on components - less chance of mast bumping What are the downsides other than potentially odd handling? I should imagine that the control forces would be enormous and pushing the rotor head forwards would cause the fuselage to pitch backwards for a start-off. Regards Andrew -- Inweb Networks. Quality internet and telecoms services Sales: 08000 612222 Support: 08704322222. http://www.inweb.co.uk E1 call share - 65%. 0800, 0845 and 0870 numbers - best rates. Resellers welcome Dennis Hawkins n4mwd AT amsat DOT org (humans know what to do) "A RECESSION is when you know somebody who is out of work. A DEPRESSION is when YOU are out of work. A RECOVERY is when all the H-1B's are out of work." To find out what an H-1B is and how Congress is using them to put Americans out of work, visit the following web site and click on the "Exporting America" CNN news video: http://zazona.com/ShameH1B/MediaClips.htm |
#22
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"Andrew Crane" wrote in message ... wrote in message ... To avoid this problem, BJ tilted the entire rotor head rather than changing the pitch cyclicly. In fact, the pitch on the blades only changes when the collective is moved and not the cyclic. This results in the grease being retained for a longer period of time. It still needs frequent regreasing, but at least you don't need a new set of bearings after each hour of flight. OK - silly question. On the face of it, it seems to make a lot of sense to do it this way - simple connection - you could probably lose the swashplate somehow too - fewer cyclical forces on components - less chance of mast bumping What are the downsides other than potentially odd handling? I should imagine that the control forces would be enormous and pushing the rotor head forwards would cause the fuselage to pitch backwards for a start-off. Not if you do it right. Dennis, I had no idea BJ did that. If you remember, I wanted to "rid" my coaxial of the swashplate. Reading the above post, I got excited about the loss of the swashplate but how did BJ keep collective control without one. Or did I misunderstand? Phil Andrew, I'll guarentee that if you tilt the mast "my way", the tail doesn't pitch down. I'm tilting a mast at a very low CG....PLUS.... I'm moving it forward to slightly change to a forward CG. Same for left, right and to the rear. Sounds weird but works. It add control complexity, but at least it's not up in the head spinning. Phil Back to lurk mode. |
#23
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Actually, I think you misread it. The scorpion DOES have a traditional swashplate. The linkages to and from it are a little different, but that's all. It has only two control rods to it. There is a pivot mechanism at the rear to hold it at a third point. It does not slide up and down on the shaft. On the top side, there is only one linkage which is connected to the hub itself and not the blades. This linkage is what tilts the rotor head. The collective is totally separate. It is a cable that runs from the collective control, through the shaft, and out to a sissors joint on the hub that changes the pitch on the blades. On this design, the blades only change pitch when the collective is moved and not cyclicly as in a regular helicopter. So, with the Scorpion design, the swash plate is not used for the collective control and is only used for the hub tilting mechanism. There are other swash plate designs that use a pivoting rod inside the rotor shaft that are not as reliable. The Mini-500 uses this approach. Personally, I would not fly in a helicopter that had this kind of swash plate mechanism as there is no way to inspect it to make sure its still connected properly. Such a critical component needs to be out where you can shake it. Dennis H. "PW" wrote: Dennis, I had no idea BJ did that. If you remember, I wanted to "rid" my coaxial of the swashplate. Reading the above post, I got excited about the loss of the swashplate but how did BJ keep collective control without one. Or did I misunderstand? Phil Dennis Hawkins n4mwd AT amsat DOT org (humans know what to do) "A RECESSION is when you know somebody who is out of work. A DEPRESSION is when YOU are out of work. A RECOVERY is when all the H-1B's are out of work." To find out what an H-1B is and how Congress is using them to put Americans out of work, visit the following web site and click on the "Exporting America" CNN news video: http://zazona.com/ShameH1B/MediaClips.htm |
#24
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#26
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#27
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Dennis...
I will admit that I've only seen ( up close and personal) a Scorpion ONCE in my 20 year career as a heavy helicopter mechanic, inspector, chief inspector etc. etc., and that one look was MORE than enough for me. I don't even have enough imagination, nor do I care to, picture cyclic change without blade pitch change. Maybe Sikorsky and Bell, and Boeing et.al. are missing something important all these years, huh? I never saw ANY real helicopter that slings grease the way you're talking about unless something is RADICALLY WRONG. Therein lies clue #1. I always thought they should just put servos in the thing, hand ya a radio and let you keep your distance. I could make better rotor head parts in my cellar, and you strap your ass to that thing? I STRONGLY suggest a have look a a few REAL helicopters for some good design comparisons any of which can be done before or after you have your head examined. Good Luck! Bob V. |
#28
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The scorpion head is not the best design in the world. However, as far as the tilting, an R22 doesn't really tilt on a U-joint, but an optical illusion makes it look like that. The scorpion really does tilt. I have looked at the R22 head and this looks like a nice one. I am planning some kind of hybrid between the R22 and Bell using elastomeric bearings. There is no grease in an elastomeric bearing. This, of course, assumes that I don't find a cheap one on ebay. Dennis. "Bob" wrote: Dennis... I will admit that I've only seen ( up close and personal) a Scorpion ONCE in my 20 year career as a heavy helicopter mechanic, inspector, chief inspector etc. etc., and that one look was MORE than enough for me. I don't even have enough imagination, nor do I care to, picture cyclic change without blade pitch change. Maybe Sikorsky and Bell, and Boeing et.al. are missing something important all these years, huh? I never saw ANY real helicopter that slings grease the way you're talking about unless something is RADICALLY WRONG. Therein lies clue #1. I always thought they should just put servos in the thing, hand ya a radio and let you keep your distance. I could make better rotor head parts in my cellar, and you strap your ass to that thing? I STRONGLY suggest a have look a a few REAL helicopters for some good design comparisons any of which can be done before or after you have your head examined. Good Luck! Bob V. Dennis Hawkins n4mwd AT amsat DOT org (humans know what to do) "A RECESSION is when you know somebody who is out of work. A DEPRESSION is when YOU are out of work. A RECOVERY is when all the H-1B's are out of work." To find out what an H-1B is and how Congress is using them to put Americans out of work, visit the following web site and click on the "Exporting America" CNN news video: http://zazona.com/ShameH1B/MediaClips.htm |
#29
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#30
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Good on You Dennis! Just remember, It's just a machine, there's NO
Magic!!!!!! Cam.. |
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