R22 Corner
Iconoclast
Join Date: Sep 2000
Location: The home of Dudley Dooright-Where the lead dog is the only one that gets a change of scenery.
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To: Dave Jackson. .. .The original Bell rotorheads had metal bearings to allow teetering. The first underslung heads also had metal bearings and as the heads evolved the metal bearings were replaced with elastomeric bearings. They do not provide a restoring force and do not function as a spring. The aerodynamic and mechanical forces far outweigh any type of resistive or restorative force exhibited by the elastomeric bearing. You might feel resistance if you were to teeter a static head but this resistance is minimal compared to the other forces involved.. .. .The only exception to this is the rotorhead used on the Bell AH-63 which competed against the AH-64. The elastomeric elements in the teeter hinge were so strong as to allow a man to stand on a blade several feet from the teeter hinge without deflecting the blade. The purpose of this spring was to minimize the excessive flapping of the blades during Zero G, which could lead to mast bumping. The spring was designed to meet the nap of the earth flight characteristics required by the design spec.. .. .NB The Bell design lost the competition.. . . . <small>[ 10 March 2002, 20:57: Message edited by: Lu Zuckerman ]</small>
Join Date: Nov 2000
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Grainger,. .. .There is no intention to imply that any of today's' helicopters are 'broke', only that tomorrow's helicopters must surly have improvements over today's. The purpose of this posting is related to my own SynchroLite project. I hesitated in referring to the Robinson, but then felt that it represented a good comparative lead-in to this idea.. .. .Also, the word 'Robinson' tends to draw a crowd, at least on this forum. <img border="0" title="" alt="[Big Grin]" src="biggrin.gif" /> . ._______________. .. .Lu,. .. .Thanks for your reply and mention of the Bell AH-63. This is exactly what my 'thoughtless' idea is about. . .. .Is there any additional and related information that might be of value. I tryed looking up the YHA-63 but only came up with a 4-blade Bell 409 and a 2-blade 309 King Cobra.. . . . <small>[ 11 March 2002, 05:52: Message edited by: Dave Jackson ]</small>
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Dave,. .Those are known as "Hub Springs" which hold the teetering head at 90 degrees to the mast. When cyclic is added, and the disk tilts away from 90 degrees, the spring imparts a force on the mast that adds control moment, like an articulated head. An elastomeric device on some teetering rotorheads does not qualify as a hub spring, since the rubber elastomer is actually almost non-existant in comparison to rotor forces. Three things are bad about adding a powerful hub spring:. .. .1) the spring introduces a dynamic mode with little damping, so a flap damper might have to be added to avoid resonant conditions that might make real problems. Articulated rotor blades don't need a flap damper because the aerodynamic damping of a flapping blade is significant, but with a teetering head, that damping is cancelled by the other blade flapping in the opposite direction.. .. .2) The spring has to be a hum-dinger to make much control power. For a 10,000 pound machine like the S-76, an articulated rotor delivers about 1500 foot-pounds per degree of flapping for use as control. That is 10% of the weight of the machine on a 1 foot lever arm(!). A spring that can deliver 10% of the weight of the machine per degree would be a packaging and structural problem.. .. .3) That large moment would play havoc with the dainty rotor mast, transmission mounts and airframe structure of the typical teetering rotor helicopter. Note the "simple" job of installing a 4 bladed moment-generating rotor on the previously teetering Y Huey and Z Cobra, a project that threatens to sink Bell helicopter as the entire helicopter (except the data plate) is beefed up.
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Dave, I read through this a bit too quickly the first time. I thought you were meaning to replace Robinson flapping hinges with a spring.. .. .As far as the teetering hinge goes, most of the cons have been identified. One other that I think would apply is if you increase the forces required to move and hold the blade from its mean flapping angle, then you increase the aerodynamic loads required which comes with a performance penalty. Of course the size of the penalty is directly related to the strength of the spring, so if you're talking small spring then all the cons are small but so are the benefits.. .. .The pros you mentioned seem valid. I wonder if you combined the droop stops with the spring to create a centrifugally released centering spring. With the rotors stopped you get all the static benefits of the spring but with them turning, the springs pull away from the mast and it teeters normally. Just a thought.. .. .With my original (mis)read of your post (replacing Robinson flapping hinges with a spring), I think there may be benefits. It seems to me that the Robinson design works fine except in some extreme (outside envelope) cases. Perhaps the spring would allow that envelope to be expanded?
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Correct me if I'm wrong, but wasn't "the spring in the teetering hub" thing done with the Bell 222?. .. .(edited for word omission). . . . <small>[ 11 March 2002, 05:19: Message edited by: Flight Safety ]</small>
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Nick,. .. .Thanks for the clear and elaborate coverage of 'Hub Springs', plus the concerns you brought up. . .. .The Ultralight craft must weigh 254 lbs or less, therefore it will be impossible to add the additional strength (and related weight) required to give any reasonable amount of 'hub spring' induced control moment to the fuselage. The weight of the rotor disk is a small portion of a craft's gross weight. I wonder if it might be possible to add just a small amount of 'hub spring', thereby at least controlling the moments of an unloaded rotor disk and providing a degree of safety? . .__________________. .. .Heedm,. .. .Perhaps the aerodynamic load that you mention might be a positive, since it is the force that is providing the faster response to the control input. We all three seem to be in agreement, that the weight penalty will be humongous for any significant amount of 'forced rotation'.. .. .The initial thinking was directed at an operational rotor. The elimination of the droop stops was sort of a freebie, just like Sprocket's idea regarding the elimination of tie-downs.. .. .Best that we leave Robinson out of this thread <img border="0" title="" alt="[Smile]" src="smile.gif" /> ; but your idea would make for an interesting discussion on a separate thread.. . . . <small>[ 11 March 2002, 22:38: Message edited by: Dave Jackson ]</small>
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Dave,. .A small spring could serve as a soft bumper to help reduce the effects of mast bumping. Several aircraft have this, including V-22 (which has a zero offset gimboled rotor head). .. .This whole subject underscores the neat idea behind the articulated rotor. Its strong head moment is a product of the centripital force, which creates high head moment with no weight penalty of a spring (although the increased moment requires stronger masts, transmissions and airframe structure).. .Nick
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Nick,. .. .Thanks for the remarks.. .. .The study of rotor head configurations is certainly interesting. There would appear to be a correlation between phase lag and rotor control. A simple teetering rotor will have a 90-degree phase lag and a delayed control. At the other 'hypothetical' extreme, an absolutely rigid rotor will have a 0-degree phase lag and instantaneous control.. .. .As you have said, nothing is free; with greater control comes greater weight. . .______________ . .. .I want to look deeper into a low level of 'hub spring' on the SynchroLite. It may reduce the phase lag slightly, but what the heck, the hub already has delta-3 playing with the phase lag. What's one more factor. <img border="0" title="" alt="[Smile]" src="smile.gif" />. . . . <small>[ 12 March 2002, 07:28: Message edited by: Dave Jackson ]</small>
Join Date: Mar 2002
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How much to own an R22?
Like a lot of other R22 hirers, I fancy getting one for me'self in a vain hope that it'll be cheaper for me than hiring one from the local school. Someone told me an R22 costs about £35/hr to fly if you own it - but neglected to say how much it costs to buy the thing!. .. .From what I can find out - they cost £100k+ new, so I'm probably looking at second hand - which seem to vary from £50-80k depending on hours left - or even £15k for an expired one (post 2200hrs) - which I understand will cost £55k in spare parts to get airborne again!!!. .. .Can anyone give me a breakdown of how much it might cost? Can you buy/lease them like cars? . .. .Any help gratefully received.. .. .Prempting the fact that its going to be A LOT - has anyone ever tried (or fancy) forming an R22 syndicate?. . . . <small>[ 22 March 2002, 15:13: Message edited by: Rotor Horn ]</small>
Rotor :. .. . Are we related ?. .. . Second, may be worth posting in Rotorheads pointing them to this thread - there are people there who are doing / have done that.
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Cheers Nr. . .. .Could possibly be the same person with schizophrenia - same pastime and same job by the looks of your profile... (IR35? B@st@rds.). .. .Cheers for the idea. Will attempt a posting to point from rotorheads as you suggest..
Depends on how many hours you fly to divide out the fixed costs. Also how many spindles and bearing sets you get through!!!!!!!!!!!!!. .. .For a CESSNA 150 (4 imp galls an hour)flying about 150 hours a year you would probaly pay over £35 an hour as an owner. For an R22 my guess would be at least double.. .. .If you find one at £35 an hour stand back or be killed in the rush!!!!!!!!
Join Date: Mar 2001
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For ownership of any helicopter you really need to be flying in excess of 250-300 hrs per to save money over hourly rental rates.. .. .If your usage is close to the above figures it may be worth a premium purchasing or leasing a machine on the basis that you have guaranteed access whenever you want.. .. .Take manufacturer's DOC figures with a big pinch of salt! . .. .Some rental rates include a free landing fee, which is obviously your own cost if you own the machine!
Join Date: May 2001
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As the owner of an R22, let me pass on this bit of wisdom to any sensible person contemplating making the investment.. .Run a mile.. .£35 an hour? Don't make me laugh.. .New, on the road, £130,000. Hourly costs - depends entirely on how lucky you are, and nothing else. Fuel, £25 an hour. Depreciation, £25 an hour, probably. Maintenance - pick a number. As an example, mine cost me just shy of £20 an hour last year in labour costs alone, no bits - and it did over 400 hours.. .Insurance costs me £100 a week before it turns a blade, and I've got a deal. Hangarage, scheduled maintenance, unscheduled maintenance, plus the constant risk that some ham-wristed prat is going to overcook it, bend it, or otherwise behave in an expensive manner.... .As to income, phooey. I'm quids in if somebody writes it off, but otherwise it's doing me no favours.. .If I'd been sensible I'd have taken the money down the Post Office and put it in my savings book.. .Do I sound all bitter and twisted?
Senis Semper Fidelis
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T/N, You sound like anyone who has found out the "real" cost of any High performance car. <img border="0" title="" alt="[Eek!]" src="eek.gif" /> . .. .RH,. .. .I may be interested in some sort of syndicate, perhaps you would E me at my profile. <img border="0" title="" alt="[Smile]" src="smile.gif" />
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IMHO owning your own helicopter never makes sense, if you look at it entirely from a financial viewpoint. However, it can be sensible to own, if you take into account some other aspects. I used an R22 many moons ago to build hours quickly around an existing career. I then used the R22 to help me get instructional work (under the old UK PPL(H) instructor exemption). Even using the aircraft for instruction at a busy flying school, it cost me big time. However, it enabled me to progress and gain experience and qualifications more quickly, so that I could give up a non-aviation professional career and become a well-paid helicopter pilot <img border="0" title="" alt="[Roll Eyes]" src="rolleyes.gif" /> <img border="0" title="" alt="[Roll Eyes]" src="rolleyes.gif" /> . The last bit never happened of course, but I love what I do.. .. .Don't really understand why, but syndicates and helicopters do not seem to work well. Maybe it is something to do with "instant access" not being possible with a syndicate.. . . . <small>[ 25 March 2002, 17:52: Message edited by: Helinut ]</small>
Join Date: Mar 2002
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Thanks for all the advice guys.. .. .From what's been said, my modest flying (<100 hrs pa) means it would make more sense to stick with the ad hoc flying of the school machine and build my hours up as my bank balance will allow.. .. .I'll have to wait for the lottery win after all <img border="0" title="" alt="[Wink]" src="wink.gif" /> . .. .cheers