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  • #16
    I wrote to Gyro-Tech to inquire if they make a 7" chord blade. Waiting for response. I like what I see but it appears their current offering of blades are for heavier 2-place gyros. Eager to learn more about this company.

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    • #17
      Just got a nice reply from Agnieszka at Gyro-Tech. Currently they only offer the 216mm (8-1/2") chord blades. I do not know how they would perform on a light single-seater like a GyroBee. Sport Copter has 2 chord sizes, the larger for the heavier machines. As a purely academic question, what kind of difference in flight characteristics / behavior is typically found with wider chord blades on a light machine? Slower RRPM? Sluggish response? Greater tendency for flapping? Obviously there's a reason narrower blades are used on lighter machines, but I don't claim to understand all of the physics behind it.

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      • #18
        Thank you for the flight test report , good to hear the positive results.
        Greg Spicola
        Com Helicopter/ Gyroplane CFI
        Brooksville FL

        gyro.greg@yahoo.com

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        • #19
          Brian go to the gyro-tech website and they have a modified blade that is only 8" in chord and they will make a 4 meter length of less if desired.
          Best Regards,
          Eddie Sigman,Polvadera,nm
          (575) 835-4921

          Comment


          • #20


            Given that the RAF OEM hub bar and blades are so poorly designed and made, with such an abysmal service life,
            I am very happy for my fellow RAF2000 owners that Gyro-Tech of Poland is offering a reasonably priced and apparently superior-to-RAF replacement.

            Also, carbon-fiber rotor blades might be the best future option for gyros.

            This is not unqualified praise for Gyro-Tech since I have several issues of design contention, and they haven't decades of gyroplane experience.
            However, the RAF rotor system was so bad that it's not difficult to improve upon OEM, and it seems that G-T has so far done so (but not optimally, as I'll describe).


            The factory balancing paid off because I will not have to make any adjustments at all, the blades are smooth
            and I noticed instantly that the cabin shake and rudder pedal vibrations were completely gone.
            Yes, and such was the natural benefit of buying new rotors/bar with their factory teeter towers.
            This was pointed out to you by a few folks here (me included) as well as by Trenna from Sport Copter.
            However, you had installed Sport Copter rotors/bar in your old/worn RAF teeter towers, with unsurprisingly unsatisfactory results
            (which you repeatedly misblamed on the SC blades themselves).

            Are you still using your custom shimmy dampeners attached to the mast scissors?

            Did Gyro-Tech include a polar chart from their PB-4 balancing?



            The blades and hubbar are the exact length as the RAF parts so the 30' diameter is maintained.
            So, G-T is now making blades longer than specified limitations on their website? Which airfoil are yours?


            The only metal is the bushings installed for the mounting bolts and the tip weights.
            How are those metal tip weights attached, and what is their weight? What is the tensile strength of the fastener?
            The reason I ask is because a 350rrpm/30' diameter blade produces ~625Gs at the tip. 400rrpm produces ~750Gs.



            teeter tower:
            The rather deeply inletted factory name would seem to provide many possible stress risers. Such was a needless risk for brandname placement, IMO.
            Exactly what spindle bolt bearings are in the teeter block, and how often must they be greased? What is their service life?



            needle bearings in the Sport Copter teeter tower:
            Since the SC design includes Zerk fittings for each tower, I've not found needle bearings to be any hassle.



            hub bar:
            You say that the blades have no service life, but what about the hub bar? It certainly hasn't an infinite life.

            Regarding its design, I do not care for the very long tension strap bolts.
            Even through its bushings, such bolts are more subject to bending loads.
            Also, there is very little surface contact with the hub bar. (see photo below)

            For those reasons, I think it preferable to mount the straps directly against the hub bar, as is common in the industry.
            The larger surface area friction makes for a stronger assembly, while the bolts endure less bending force (if any).

            Also, I really do not prefer G-T's reduction of section inward of the lateral pair of tension strap bolts.

            The G-T hub bar radii should have been actual radii vs. milled flats (which can more easily collect stress risers).



            bolts (tower block, tension straps):
            the flight testing has been delayed because the 1/2" bolt that hold the rotor head on was to short,a new AN bolt from ac spruce will be here today.
            Since the other G-T bolts are not AN-spec, I presume the spindle "Jesus" bolt also was not?
            What is G-T's reason for not using cadmium-plated AN bolts/nuts?

            Also, the four tower block bolts seem ~.125" short, as I've heard from multiple sources that many A&Ps and FAA inspectors
            like to see at least 2-3 complete threads beyond the nut. (This would be a convenient time to replace them with proper AN hardware.)


            ____
            While I'm relieved for my fellow RAFnauts that they've now a new affordable way to upgrade from RAF's sucky bar/blades, there still remain some remaining RAF issues:


            the RAF OEM torque tube:
            A very poor design, with little conception of aluminum's properties. The photo below is of a torque tube that broke upon impact (not in flight).
            Notice the meager mass of material between the spindle bolt and pitch bolt hole. It's only about .5".

            I've handled this very part, and although you can't see it from the photo, the crystalized interior is clear evidence that the metal has been worked.
            There's simply too much dynamic stress going on inside that cubic 1" of aluminum.

            Has one ever failed in flight? Not that we know of, but what service life can one rationally expect from the RAF torque tube?
            As typical with most RAF parts, who can really say. Thus, if anyone is replacing their RAF bar/rotors, I think they'd be wise to also replace
            their RAF torque tube (with, at the very minimum, a new OEM part).

            If OEM cost/availability is any issue, I've a 370 hour used part which I could sell to someone wanting to replace their much higher time part. PM me if interested.

            Quite frankly, fabricating a custom steel tube out of 4130 would be be a very simple matter, with lightening holes easily added.

            The Sport Copter rotorhead/torque tube is a far superior design, and I considered its $3,000 price an "insurance policy" well spent.



            the RAF OEM trim system:
            This is the other very poorly designed system, which applies trim forces to the control system (i.e., the lower control yoke) rather than properly to the rotorhead directly.
            I think the lower control yoke is rather dainty as it is (and RAF PN40 agrees), thus adding trim forces there was a mistake.
            A parallel trim system outside the control system is wise, and my Sport Copter 4-way air-trim provides a "secondary" control system which could save my life.


            ____
            In summary, the Gyro-Tech teeter towers/hub bar/rotor package seems a qualitative upgrade from RAF OEM parts, and I'm glad that it's flying well for eddie,
            but don't become complacent about the other flight critical junk still in the RAF.

            Also, until this G-T package has been flown for many hundreds of hours on the RAF, the old adage applies: "a new broom sweeps clean".

            Regards, Kolibri

            Attached Files
            Last edited by Kolibri; 01-11-2018, 05:20 PM.
            PP - ASEL (Piper 180, C206, RV-7A), SP - Gyro (Calidus, RAF, SC2), soloed in gliders; checkride soon

            Wasn't happy with my RAF's pitch instability, so I installed a Boyer H-Stab to my great satisfaction!

            "
            When an honest but mistaken man learns of his error, he either ceases to be mistaken -- or he ceases to be honest."

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            • #21
              There is no question that good engineering and attention to materials science are playing important roles in your product choices. I have hung on every word of your discussions. And I'm grateful that you all are willing to share your knowledge and experience, that we will fly stronger and more safely.
              Regards

              Frank

              Comment


              • #22
                Kolibri you wrote:
                "Also, I really do not prefer G-T's reduction of section inward of the lateral pair of tension strap bolts."

                Why? Did you do an engineering structural analysis and found deficiencies? Or this is just a hunch?

                Kolibri:
                "For those reasons, I think it preferable to mount the straps directly against the hub bar, as is common in the industry.
                The larger surface area friction makes for a stronger assembly, while the bolts endure less bending force (if any)."

                Again have you done an engineering analysis or this is also just a hunch.
                Averso uses this method and over 1.5 decades has no reported issues. When you pre-cone most of the bending loads are reduced


                The company not having flown 100's of hours on a RAF is a valid point but how do you think they are going to get there? Someone who owns RAF has to do it. They certainly won't go buy an RAF and do it for RAF owners since the group is very low in numbers

                Kolibri wrote:
                "Since the other G-T bolts are not AN-spec, I presume the spindle "Jesus" bolt also was not?
                What is G-T's reason for not using cadmium-plated AN bolts/nuts?

                Also, the four tower block bolts seem ~.125" short, as I've heard from multiple sources that many A&Ps and FAA inspectors
                like to see at least 2-3 complete threads beyond the nut. (This would be a convenient time to replace them with proper AN hardware.)"

                Though I agree that using AN hardware on aircraft is a good idea specially in the US, engineering wise and technically there is absolutely no magic in AN hardware that is not in industrial hardware. Class 8.8 bolts are basically equivalent to AN tensile strength and have same soft bending qualities. Class 10.9 is sometimes used as teeter bolt in Europe and it is strnger than AN but slightly harder. The main advantage of AN hardware is
                1) Cadmium plating which is banned in many other parts of the world due to its toxic nature and environmental impact but it provides better resistance against rusting compared to zinc plating.
                2) Its easy to get AN hardware and know you are getting a quality spec with short thread lengths without having to do custom bolts. At least in North America

                These are however not huge technical or engineering advantages. I wouldn't think twice flying a metric bolt laden machine if it was properly engineered and bolts were not garden variety hardware store bolts but good quality ones. The requirements for threads showing is to guarantee full nut (nylon) engagement. One thread is plenty. Even half thread showing is enough. What you really don't want is bottoming out on the threads or putting more than one thread on the shank in heavy shear load. It'll fatigue because it will be able to rock around because of the minor diameter of the thread on one end compared to the shank on the other end . About the only bolt I would be ok replacing with equivalent AN bolt would be 8 mm to an AN5. An M10 bolt is bigger in diameter than an AN6. A M12 bolt is smaller in diameter than AN8. These differences are important and a bolt that fits too loose can create pre-mature fatigue. Don't blindly go changing bolts unless you have an engineering background and understand the application. Some places it will not matter and some areas it really does.
                Last edited by fara; 01-13-2018, 08:49 AM.

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                • #23
                  Fara thanks for your support and input,however you are just pouring fuel on the flames.
                  Best Regards,
                  Eddie Sigman,Polvadera,nm
                  (575) 835-4921

                  Comment


                  • #24
                    Originally posted by eddie View Post
                    Fara thanks for your support and input,however you are just pouring fuel on the flames.
                    :). Let it burn. $50 for Playing the engineer. Kolibri went first and found the daily double. LOL

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                    • #25


                      Fara that is really good usefull information about metric vs American AN hardware and bolt threads.I would like to think

                      that the Europeans already know about aircraft related fastners,and that the AN bolts are not the only quality fastners

                      in the world. Some people are so narrow minded that they can't accept the fact that the Europeans in some areas are

                      way ahead of the curve.




                      Best Regards,
                      Eddie Sigman,Polvadera,nm
                      (575) 835-4921

                      Comment


                      • #26
                        Originally posted by eddie View Post

                        Fara that is really good usefull information about metric vs American AN hardware and bolt threads.I would like to think

                        that the Europeans already know about aircraft related fastners,and that the AN bolts are not the only quality fastners

                        in the world. Some people are so narrow minded that they can't accept the fact that the Europeans in some areas are

                        way ahead of the curve.



                        Eddie: I do not know of European Metric aircraft hardware standard. I don't know if one exists. However, the industrial specs (DIN 931, ISO 4014, ASME ANSI B18.2.3.1M) are fine and strength and processes are defined and they provide a good data source to select metric hardware equivalent to AN or NAS hardware.
                        The main problem with metric hardware is that the threads are usually longer from these industrial specs. So either you carry extra weight with a bunch of threads sticking out or like AutoGyro etc. you get them customized but then its hard to get replacements in the same thread lengths.
                        AN hardware, of course you can get them from many sources without calling up the manufacturer. So there is an advantage but its not one of strength or some engineering magic. Many people think that threads on industrial hardware are cut instead of rolled, bunch of BS. Most all manufacturers of hardware roll their threads because they have to be mass produced and its simply much faster than cutting them.
                        Last edited by fara; 01-12-2018, 05:23 PM.

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                        • #27
                          I am one of those I always thought that industrial threads were cut instead of rolled and yes the exact size of AN bolts is important.
                          Best Regards,
                          Eddie Sigman,Polvadera,nm
                          (575) 835-4921

                          Comment


                          • #28
                            Originally posted by eddie View Post
                            I am one of those I always thought that industrial threads were cut instead of rolled and yes the exact size of AN bolts is important.
                            :). Many people think so. But I would be foolish if I owned a factory making fasteners in bulk to "not" roll threads. It costs much more to cut them.
                            For example read:
                            http://www.portlandbolt.com/technica...threads-bolts/

                            Comment


                            • #29
                              If it was me in the pilot's seat, you can bet I would be comparing/measuring the bolts&nuts coming out of the aircraft, and writing all the comparisons/measurements down. Being a decent mechanic and only a half-assed mechanical engineer, I always sight-compare, thread match (old vs new) and if its metric, replace it with aircraft quality metric, or US if its only a little bigger, but the same chemically. I also check my android "ConvertPad" app for exact metric to US comparisons. But that's just me. I got a small ass and it won't take too many hard landings anymore, heh heh.

                              I also have my torque wrenches calibrated pretty often. Nothing like an over-torqued bolt with stretched threads to mess up a good. job.
                              Regards

                              Frank

                              Comment


                              • #30
                                I also check the manuals for the given vehicle, for whether the torquing is to be done hot or cold. Over the years, I've learned that every manufacturer has different specs that way.
                                Regards

                                Frank

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