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In-Flight reconfiguring Airframe Rotor Disc Control
I've received some positive feed-back about this rotor system from pilots and engineers. One or two "uncertain critics". Let me know your thoughts about it. Completed the first power up last week-end. Been in the field so I am behind. Rotor blade chord width is a bit too short as well the span. Few more things to tweak. Hope to have it flying or crashing soon.:confused:
I have several more rotor systems, but those are only rough draft white papers. www.envisionhelicopters.com http://www.envisionhelicopters.com/J73_op_680x510.jpg http://www.envisionhelicopters.com/J83_op_680x510.jpg |
Preparing for 2nd power up. Waiting for CF blades. Also "skeltonizing".....(guess that is a word :bored:).....the CF airframe a little more. Always the small things. :ugh:More to follow.
Regards, Dave |
Dave,
Are there any cross-coupled forces when using weight shift control of a rotor? I'd imagine you would subconsciously learn to put the input in 90' ahead of required disk pitch / roll requirement, until flapback reaction reached equality. Arguably all helicopters are weightshift control, since they revector the lift thrust to achieve the desired flight (albeit less so with high hing offset rotors). |
Graviman,
This first prototype does not have feathering, only flapping with a delta 3 axis hinge with regard to coupling between pitch change and flapping there may be coupling of forces. It does not use a swash plate, the hub has a rubber grommet in the center to damper the flapping action. During the power up, I manipulated the tilting of the upper airframe and it has a small amount of back flapping as the rotor wanted to keeps it's original level plane. A servo adjustment will tilt the frame and rotor disc a little forward to start out so there should be less than a 90 degree reaction of the disc attitude when control inputs are made. The drive stick does not control the blade pitch cyclically............this version is fixed pitch and the larger gas version that I'm gathering materials for will be full collective, but still even with the full collective there will not be cyclic pitch control. Control rods will be attached to the pitch horns center the flapping axis. The functioning of rotor disc control for this system will be similar to that of the Baldwin tech craft and the V22 osprey, but the mast, frame & disc incidence will only be enough to vector the thrust and not a complete 90 degree reconfiguration of the rotor system for fixed wing flight. My understanding of rotor dymanics is elementary when compared to most. The mechanics are easy.....the kinematics involved or forces affecting the mechanics, I'm "warm and fuzzy" with, but some of the formulas make me feel as if I am playing chinese checkers with my toes. I am not like most when they come across something that puzzles them. Instead of shying away..I get a silly grin because I enjoy brain candy. It's like the little kid standing outside the glass window of the drug store. Only one lemon drop left and he still needs a few nickels. Let's just say that rotorcraft aerodymanics are my lemons drops and I'm saving all my nickels. The GEN H4 is similar as well, yet it is fixed pitch. The reason the 1st RC prototype is fixed pitch and only forward/aft tilt is due to my taking small steps. I addressed this approach during the patent process as well the DARPA white paper. That being said, I also must deal with lateral drift from the tail rotor during any attempt to hover because there is no lateral control. In all honesty, I plan to set back in a lawn chair, fire up a cigar when it's time for a untethered flight and see what happens. More to follow. Regards, Dave |
Dave,
If i understand correctly the dynamics will be very similar to the direct control autogyros. I hadn't spotted the R-pin teetering bearing with 30' delta three before. Yes this should work a treat although you may find that you need to tweak the delta three to minimise pitch-roll cross coupling. Some will be good for wee-wa and rotor coning (see the many discussions about R22 rotor head). This type of arrangement is often used for smaller machines where cyclic control loads will be minimal. The equations can be daunting, but stick with 'em - we'll help along the way. :) Mart |
Graviman,
Thanx. I'm always humble enough to ask for help since I'm an "uncertified basement engineer". Second "power up" this week-end, that is if the new blades make it here:ugh:. I chose a CF blade w/ a wider chord and it has about an inch more span than the other airfoils. Soon I will post short video clips on my site and I am certain that I will be directing you guys to view them and asking all of you questions about certain actions or moments that may develop. I can spot rotor blades when they need tracking, but you folks can look at the attitude of the airframe and spinning rotor system if you see a video clip and tell what may be causing it. I'm curious about the "what ifs" in the mechanical design of helicopters. If the results of published data state that a rotorcraft should not fly unless "X, "Y" & " Z are in order and I make a small scale prototype fly using "X", "Z" and eliminating or substituting "Y" by some other means......it is up to certified engineers to figure out why. I just wanted to see what would happen. I want to step outside the normal approach to see if it works. I also understand that there is a big difference when it comes to scaling up to full size. More to follow. Have a good week-end. Dave |
Machined a new rotor hub using industrial nylon. Got the new rotor blades, trimmed down rebalanced, and rebalanced again after attaching to hub. They have a metal leading edge spar. Good blade. I need to machine a new rotor mast. The 1/8" stainless steel mast apparently bent right at the cross pin gear lock area from the torque during the last power up. My fault. Using titanium rod now. Minor set back. More to follow.
Dave http://www.envisionhelicopters.com/J84-0_op_680x510.jpg http://www.envisionhelicopters.com/J85_op_680x510.jpg |
Dave,
You could do far worse than to purchase a copy of "Theory of wing sections" by Abbott & Doenhoff. Don't be put off by the maths (which looks daunting to all of us) since there is a good section on lift / drag for various aerofoils currently in service. Theory of Wing Sections: Including a Summary of Airfoil Data The ideal for any aerofoil (to minimise lift to drag) is to operate as near to stall as possible. In practice the need to allow for manouvreing, payload and a practical flight envelope means blades seldom achieve this. Thicker choord blades are more suited to reduced rrpm, but should work just fine. Ultimately as long as it produces lift it is just a question of how to maximise performance / battery life... |
Finished the titanium rotor mast. I may need to replace the redcution gear due to an increase in mast diameter, which in turn I may need a motor with a bit more torque. The weight is the same as the smaller stainless, so no increase in overall weight. Waiting on additional bearings.....again, so I started work on the aluminum mockup so it reflects the updated tilt mech.
http://www.envisionhelicopters.com/J86_op_680x510.jpg http://www.envisionhelicopters.com/J93_op_680x510.jpg |
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Replaced the the off-set axises gimbal joint with a spherical bearing. Also shortened the vertical down tube to lower the upper airframe for attachment to the lower sliding spherical assembly.
http://www.envisionhelicopters.com/J92_op_680x510.jpg |
New mast bearings are in. Working on a different reduction gear. Diameter is .5mm smaller than the first one, it's a bit thinner and lighter, but the pitch guage is the same. Just need center spindle.
Dave http://www.envisionhelicopters.com/J95_op_680x510.jpg |
latest
Been a while since I worked on my CF prototype. Had foot operation/shock wave treatment to treat bone spur.....too much Infantry stuff and years of humping a ruck sack. I'm having issues with the gear hub.......fabing one...miss having my lathe. So, took a break from it and went back to the mock up again. Shortened the vertal fin and horizontal stab and drilled the tail boom to make it lighter. Working 3 projects at one time so I am way behind. A friend of mine who served in Iraq with me is working with me on an "Anti Torque Recovery System" (ATRS) for tail rotor failure. The particulars are going to be kept in the dark for a while. It's an idea that I came up with a couple of years ago and he was always a "trusty worthy" person I could show my ideas to. He made a suggestion about one part, so I made him a co-inventer. He's at Purdue getting schooled in aerodynamics, but his knowledge and input for this design was prior to his attending Purdue. He's also racking some flight time in fixed wing. More to follow.
http://www.envisionhelicopters.com/J99_op_680x510.jpg |
Gathering parts to build a "table top" demo assembly for tail rotor failur recovery set up. It will have a main fixed pitch rotor hub and tail boom w/ an electric TR that I can shut off to cause the torque to "Peg" the tail boom in one direction representing catostrophic failure. If I can engage the recovery assembly and cause the tail boom to stay between two "pegs" 180 degrees apart it will at least be better than "spinning to doom" and crashing. Even "fish tailing" or long drawn out airframe spin in a tight orbit may allow enough control to get it to the ground with out the "sudden" stop and die syndrome. We'll see. I'm behind on all my projects due to the holidays and the Army taking up my time. Boxing the CF prototype and taking it home over Xmas leave and try to finish it and get it to fly. Aluminum airframe will reflect the patent drawings..........single vertical down tube is being replaced with dual down tube/struts. More to follow.
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Going back to the off set axis gimbal fulcrum which will have about 3 degrees of lateral movement, giving the rotor disc about 5 to 7 degrees of lateral tilt as the hub/disc are a bit higher on the mast above the gimbal fulcrum; finished the dual down tube/struts and rid myself of the single tube; started the tilting mechanism, but only got the lateral tilt plate w/o bearing blocks and the sperical w/o it being attached to the pylon which I have yet to machine out of industrial nylon. The logitudinal lever that attaches to the tilt mechanism spherical pylon is not machined yet. The linear bearing that will allow the lever to have a telescopic motion as the upper airframe tilts forward/aft is not ordered. Wow is it expensive! for one 1/4" ID linear bearing. All changes reflect the design in the patent.
http://www.envisionhelicopters.com/J105_op_680x510.jpg http://www.envisionhelicopters.com/J106_op_680x510.jpg http://www.envisionhelicopters.com/J107_op_680x510.jpg |
Aft bearing block frame attached w/o bronze bearing or nylon pillow block; dual down tube/ strut complete.
http://www.envisionhelicopters.com/J112_op_680x510.jpg http://www.envisionhelicopters.com/J111_op_680x510.jpg |
X-mas vacation has me behind. Got the new reduction gear............smaller ratio. I'm sanding the titanium mast down today. I had hoped to have the gear mounted on the mast today, but I'm taking it slow on the sanding. Now that the diameter of the mast is being machined down, I no longer need a new lower mast bearing. But, now the diameter is smaller, I need a new upper mast bearing close to the main reduction gear.............such is custom fabrication. Second power up MLK week-end...maybe a tehtered flight.
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New updates at my web site. Gear mounted on titanium mast......now I need a new electric motor w/ larger spur gear.
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Latest carbon fiber test platform clip for servo actuation of morphing airframes.
Dave YouTube - HIR-3(Ipod Video).mov |
Aluminum airframe mock up prior to switching back to the gimbal joint. Shown here is a spherical in place of the gimbal which may work, but will require the use of the alternate tilt mechanism.
Dave YouTube - HIR alum Ipod Video |
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Going back to the off set axis gimbal fulcrum which will have about 3 degrees of lateral movement, giving the rotor disc about 5 to 7 degrees of lateral tilt as the hub/disc are a bit higher on the mast above the gimbal fulcrum |
Yep..you are absolutley right.............wrong choice of words. The distance, as you noted, was what I was making reference to. Thanx for pointing that out. Almost stepped on my crank with that one. Equal degrees, moments etc...........greater distance the farther from the fulcrum. Shoulda caught it
Regards, Dave |
Distance between the diameter ref.line to the end of the radius ref line
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Ok I thought you might have just misworded that. So how many degrees does it tilt? Or what did you really mean to say?
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Between 3 and 5 degrees depending on servo adjustments............but I have not measured it just yet. Made servo adjustments to prevent over manipulation or too much tilt. The tethered flight was postponed due to the mast bending from too much torque. I used stainless steel 1/8" round stock and the mast bent right where the cross pin goes through the mast to secure the main rotor gear. Used a thicker CP Grade 5 titanium stock for more strentgh and try not to add additional weight.
Dave |
Ok I was just curious. You can always change it if you need more. I just wonder how much will be needed for a real machine considering CG range, slope landing capability and amount of rotor flapback during max forward speed plus a margin beyond whatever the max is. Presumably a one man helicopter doesn't need a large CG range and will have a relatively low cruising and max forward speed.
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Yep..........I wanted to start the tilt out a little at a time. Servo arm change outs will give it more range of motion. Another pilot mentioned the same about the speed for a single place with regard to this design. I've only had to deal with the slope terrain stuff when I went to Air Assualt school some years back. Just a few years ago, we had a Chinook pilot hot dogging his bird when I was stationed in Alaska. He was reminded of his slope/rotor blade association "does and don'ts" very vividly. He came in a bit fast and swung the aft portion of the bird around...with a slope in the direction that his aft was going. Yep...you quessed it....rear disc hit the slope. Bird came down and rolled over a few times. Everyone was ok...little roughed up. Kinetic energy and gravity...lol. This platform is the first "baby steps". I'm still tweaking the the small CF frame and a few more mechanical things to do yet. And I still want to scale it up to a gas power. But small steps and it's fun to problem solve.
Dave |
When Sikorsky first developed the XH-59 the engineers thought that because of the high control moment generated by the extremely stiff rotors they should reduce the amount of cyclic control available to the pilot. However, in certain flow conditions you still need the full cyclic range just to generate the minimum control moment for maintaining aircraft control. Unfortunately they learned this one the hard way by crashing the first prototype when the pilot ran out of cyclic control. Just food for thought...
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Helisphere,
Sorry it's been so long. I read your last post just prior to the 4 day week-end and then went to the field. Back and clean again......4 days in the woodline. I agree with you and I also believe that alot of testing is needed. This is not an endeavor to get rich, a quick start for a new line of helicopters or to solicit. It's just experimentation, that if proven valid, could be a new platform. Some folks in the respective "industry" are reviewing it. Most recent contact this past week, but I also told them that I did not believe that my platform was the answer for a UAV with regard to "simplified" controls because the concept of mechanical morphing and my theory of CG "flex" are not proven and again it's just a theory. There is emough stress learning the controls of rotorcraft for static airframes. I use the term "industry" loosley for a reason. Some I will not mention. The HIR platform was intended for sport aviation and civil use such as law enforcement for smaller departments that cannot afford a mutli-million dollar Twin Star, for example, but it's still not ready. I enjoy very much the mechanical problem solving and questioning the norm. As I have said before, I question often where does practical application end and novelty begin. I keep trying until physics and mathematics prove me wrong. Regards, Dave |
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Fabricated a new rotor hub to fit the blades; no issues with balance. Shortened the titanium rotor mast and mounted the hub to the mast with one of the first rubber grommets (upper) that will allow the hub to teeter flex. The blade bending should negate most of the dissymmetry of lift. Tail rotor mounted and wiring for the motor is "rough in" and not yet soldered. New mast bearing will be 11/64". Now I must re solder a new receiver antenna as some one came into my apartment while I was in the field, went through my stuff, pulled the antenna out of the receiver and went through some of my miliatry records. Seems like I can never win. The Apartment maintenance people were in the apartments changing filters. Should have the bearings mounted next week-end or the week-end after, I think I can solder the antenna this week-end. More to follow.
Davehttp://www.envisionhelicopters.com/1...op_680x510.jpg |
All,
internet has been down due to remodeling. using the library. 4th CG hang test good. First tethered flight this week-end. Fingers crossed. Dave |
This sort of thing would probably be more suited on rcgroups.com than here, as there are a few physics and aerodynamics traits that would prevent this design from being used on full scale machines.
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Perhaps....., but one patent in the works and DARPA and a few others reviewed it.....said it had merit.....whatever.
Look at Baldwin technologies: Baldwin Technology Company, LLC Then again....................... perhaps not. Mechanical morphing rotor control is possible. If not, we'll see. I've never owned an "RC" hobby copter except the one that I cannibalized for parts. Already preparing for the single place full scale. It's only the first of 6 different concepts. When mathematics and physics prove me wrong.....then I'll stop and find something else that "feeds the mind" in mechanical problem solving. I will not stop if someone makes a suggestion to do so. Most people come up with a good idea and often they listen to others and their dreams fall to the side. Mechanical problem solving is like OCD to me. I lose sleep over it, but it occupies my mind from the memories from Iraq..................and I love it. Thanks for the input though. No one holds the reins on innovation unless you allow them to do so. Best Regards, Dave |
davh12, neat concept. Keep it up and keep us posted.
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Birddog,
Thanks. Hope you and your family have a Happy Easter. Godspeed. Dave |
Lower mast bearing mounted, mast attached, main drive motor mounted. Picture below, airframe is inverted allowing the glue to dry for the lower bearing housing. Still on track for tethered flight tomorrow.
Dave |
Lower mast bearing housing came loose. Torsional flex developed during tether flight; forward/aft has good transition. Lateral had a tendency to roll over...........shaft collar lock was too close to hub not allowing enough room to teeter. Some of the weight is too high up on the airframe as well. Lowering the motor and widening the lateral foot print of the lower airframe. Changing a few things, re-balance/track and try it again.
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Dave |
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