![]() Each rotor mast is mounted at a slight angle, allowing the blades to intermesh without colliding. I now use a captured flight test stand.Intermeshing rotor helicopters, also known as synchropters, have two main rotors that spin in opposite directions and overlap with each other. After building hundreds of rotor blades I've stopped doing free flights until these problems are solved. On take off, the differential rpm resulted in large loops to a crash. This resulted in a arse over tea kettle crash. The rear rotor can be brought to zero rpm in certain conditions.no rpm no lift. While testing my models with uncoupled rotors the rotor rpm changed between each rotor with attitude change. The weight saving is the weight of 12+ feet of fuselage required on a Chinook with non-overlapping rotors.Īnother consideration for coupling rotor is both will have the same rotor rpm. The Chinook helicopter has a 34% overlap which allows two 60 foot rotors to be used on a 48 foot airframe. The weight saving of reducing aircraft length increases its useful load ie more gas or another passenger can be carried. The major thought behind coupling/synchronization is a way to reduce the required fuselage length to accommodate non-overlapping blades. The side-by-side-rotor arrangement would still have the stub wings or outriggers to worry about. The tandem arrangement also stows better-with with two-bladed rotors they can be aligned to make a long, narrow package and with three-bladed, hinged rotors you could fold the front rotor aft and the rear rotor forward. If the passengers are located near the forward mast, then they rear rotor is a blade-length away for safety. While the side-by-side-rotor arrangement is more attractive visually, on reflection, the non-overlapping tandem-rotor arrangement seems more palatable from a safety standpoint. I would think that you could have dual pitch trim, one to each rotor, and a mechanism to tweak the trim differentially for roll, and that would eliminate that issue, no? I am curious, though, about the need for a synchronization mechanism for the rotors. Even if you made it a pusher with the pilot forward you'd still risk having the rotors come smashing through the cockpit from behind in a crash. ![]() I agree that the idea of the rotor tips moving at high speed over your head is very disconcerting and I hadn't thought of that safety concern. Very interesting, Jean Claude, thanks for sharing your sketch and comments, and thanks Joe for expanding on yours. I did try coupling the two rotors but the additional weight was counter-productive with the model but for a full size gyro coupling is required.Ĭontrols are something different from standard gyros but I'll need to explain later cause Ma Ma wants to go to lunch. Kinda arse backwards! It worked much better with maintaining the same rotor RPM front and back on the model. A year later, the higher aft rotor pylon was change to a lower than the front pylon configuration. At first the Chinook design was used as an example for the layout for my first model. So far, I have found several differences between a tandem helicopter and a tandem gyro. I also changed to a captive test stand rather than free flight which saves time in making rotor blades. When this was changed, I had much more success when testing the tandem model. The opposite applies to my RC model requiring a airfoil with a down reflex. The front of the blade has a tendency to dip down at speed. This is a generally standard airfoil for full size gyros. I had been using the 8H12 airfoil which has a up reflex with my models. One of the most time consuming things was the airfoils used on RC models verses the real gyro. However, I have learned much through the use of RC models over the last several years. No one has enough money to make a big effort to answer all the technical problems of the tandem gyro. With this mind-set where will be no great growth of designs or capabilities. Then there is the cottage industries that cater to the Benson-style gyros that is economically un-interested in new aircraft. It seemed that no one would fly anything but Benson or Benson clones.Ī tandem rotor is much more complex than any Benson-style gyro and would require more flying experience that 95% of those in this sport today. ![]() There wasn't much support within the gyro community for larger aircraft either. To my dismay there wasn't airframes or rotor systems to accomodate my requirements. When I started looking at gyros, I wanted a gyro with a useful load of a thousand pounds. I would like to share some of the reasons that moved me toward the tandem configuration.
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