$20 R/C helicopters are available in Wal-Mart that climb and turn on demand (kinda). For $100 you get a fully controllable model with counter-rotating rotors that anyone can fly like a pro in after an hour or two of practice. Double that and a 3-D-capable, ready-to-fly helicopter is available to you, complete with a spread spectrum radio, gyro stabilization, a brushless motor, and Li-Poly batteries... with a computerized charger. Engineers have labored endlessly to bring this state of the art technology to all corners of the world. It was not that way all so long ago.
To wit, take a look at this article from the March 1969 edition of American Aircraft Modeler, that reported on Germany's first ever R/C helicopter competition that was held in the fall of 1968. There were no kits (let alone RFTs), no special heli engines, no gyroscopes, no carbon fiber blades, to "how-to" manuals, not even any reserved frequencies for the newly arrived proportional radio control systems. All helicopters there were designed and built from scratch, and no two looked alike; large number or unique color schemes were not necessary to keep track of a cookie-cutter production craft.
As the photos in the article show, quite a bit of impressive design and machining went into those birds. The owners were true craftsmen with a high level of knowledge of how helicopters fly. Ask your average heli flyer today about gyroscopic precession requiring the rotor control input to be made 90° ahead, and in the direction of rotation, of the desired output, and he'll likely reply with a deer-in-the-headlights look. Don't expect a scientific explanation of the function of the flybar providing stabilizing inertial through angular momentum, either.
Enjoy the photos, and appreciate the pioneers who took the financial, time-consuming, disappointment-filled arrows on their way to, sometimes, success.
Model World... on the International Scene
Ewald Dietrich tuning up the motor on his torque-reaction helicopter. Fuselage is made of fiberglass polyester. Won second place in flight-evaluations event, a very short flight at that! Control systems is non-proportional type, control by CG shifting.
Most of the models were torque-reaction types of several configurations, engine above, below, and even in the middle. This Sikorsky cargo 'copter by Dr. Schlattmann has motor below where cargo is hung. Fixed engine speed, collective-pitch control.
This interesting design by Bergenkotter has engine forward, driving rotor and anti-torque rotor. Uses Supertigre 60 with centrifugal clutch, bevel gears and belt drive at rotor. Engine, collective, and tail-rotor control. Although ingenious, did not fly.
Willy Rolf uses transversely positioned engine, driven rotor, anti-torque control, and pitch action by CG shift. No provision for left-right control, so it only will be flyable under most ideal conditions. However, rotors are balanced for self-stability.
A remarkable and way-out torque reaction 'copter with engine-driving lower blades and fuel tank, and torque turning upper blades. Fixed throttle and collective pitch on both rotors! Two engines geared to same shaft are balanced together. By Stehr/Dortmund. Wonder how you start the engine?
This is a well-designed and built gyrocopter, but not flown because there was no event for it - perhaps there should be next year. Design by H. Glafey, has Supertigre 40, nicely shaped body, teetering and balanced rotor assembly, and rudder control.
This UHD 1 scale model is an attempt to copy the rotor and control system of the real 'copter. Rotors are auto-stabilized, driven, have full control. Tail rotor also controlled. Did not fly successfully. Although designs may be flyable, pilot and control-system limitations may be the biggest 'copter problem.
Fascinating torque-reaction 'copter somehow transfers fuel to rotating engine from fixed tanks. Tail rotor is driven, fore-and-aft control by CG shift through rotor-tilting, and collective pitch. By G. Stoerig. Aluminum-tube frame.
This is scale Sikorsky S58 by Dieter Schluter which won 500 marks for best flight, straight up - and down! It has fully controlled rotor and anti-torque tail rotor. Powered by Supertlgre 60 with worm drive to main rotor.
Most of the parts in the rotor head of the successful 'copter were handmade, carefully assembled by brazing, soldering, and bolting. Rotor blades can flap, swivel. Controlled in pitch collectively and cyclically. Lots of work there!
The tail rotor is meticulously designed four-blade unit. At 3000 rpm the stresses on balsa blades and the fittings are great, but when properly balanced and tracked, they will give serviceable operation. No airfoil as such is used. Function is to oppose torque of driven main rotor, and for rudder steerage in flight.
Photos by Flug Magazine and the author.
First model R/C helicopter competition in Germany had one successful flight but 20 stomping, sputtering, crazy-crashing attempts, yet each model was an ingeniously crafted masterpiece.
MY purpose in attending the Harsewinkel Model Helicopter Show was to help provide an informational link between American and German modelers to keep everyone abreast of the latest designs and developments.
I armed myself with 50 copies of the Sept. American Aircraft Modeler, blueprints on John Burkam's "High Time" free-flight helicopter and a German road map.
Three years ago, Harsewinkel was a quiet little town of about 1200 persons. Today, thanks to Simprop Electronics and International Harvester, the population is in the thousands and growing.
The model flying field is just outside town, located in a nice flat area with perfect visibility. When I arrived there, several people were getting their models ready. After the first hour, all my copies of AAM were gone and I was in a daze from seeing models that staggered the imagination. (I could have sworn I saw Leonardo Da Vinci and Jules Verne walking around.)
I checked out a good and wild idea by Hans Knaf and his son. Would you believe 9% pounds of Chopper powered by a Super Tigre 60, dual-output transmission (21:1 main rotor and 10:1 tail), a centrifugal clutch which cuts in at 3000 rpms and controlled by the new Simprop Digi-5 proportional rig? Hans didn't like all that HP going to waste out of the exhaust pipe, so he tapped it off and now it powers the oil pump for his transmission. He has to change oil quite often but the "tranny" works like a charm.
Sunday morning I stood in a light rain with a thousand other people and watched model after model snort, stomp, sputter, chase people and do everything . . . except fly. That's right. Not one model actually flew. There was one man who got his machine to lift off for a 20-foot flight straight up, and 21 feet straight down. That flight (?) got first place for Dieter Shirlter who built a Sikorski CH-53 that must be seen to be believed.
His design was a semi-scale job of the U. S. Marine Corps "Jolly Green Giant." Dieter spent four years of concentrated work to produce this 46" beauty. R/C was via the Simprop Digi-7, power by a Supertigre 60. What really shook me up was that his 9%-lb. monster has over 11% lbs, of lift. A 15:1 gear box turns his scale rotors at 800 rpm for the main, and 3000 for the anti-torque rotor.
Everyone cheered as he collected over $500 in prize money, and 30 hrs. free instruction in a people-size helicopter. Dieter also received a special prize, an 18" bronze bust of John F. Kennedy and, for a fraction of a second, things grew solemn. Then Dieter smiled from ear to ear. The crowd went wild with applause.
After comparison of the designs I saw, four problems stand out as the reasons these models didn't fly. Cyclic pitch was almost non-existent. Rotor blades were too thick (some as much as 3/4"). Receiver interference caused by static electricity generated by movement of the rotor blades, and the problem of too fast a model, and too slow pilot. If we can't solve the last problem, model helicopter flying might be restricted to those of us with two heads, five hands and good nerves.
Only three of the designs I saw could really be called true helicopters. The other designs were close except the motor was not in a fixed position. That means, if a large pusher prop is turning one direction and facing down, the natural torque causes the engine and its attached rotor shaft to turn in the other direction. Not a true "chopper" to be sure, but it sure solves the problem of too much torque.
I was constantly asked by reporters from many countries and officials of the meet, "Where were American competitors?"
If you are getting tired of the lack of challenge offered by the normal run-of-the mill model (no angry letters please), let me know if you're interested. I could also use info on new ideas to tell my German friends.
I believe this is one of the last big challenges in modeling. Without stepping on anyone's toes, I'd like to know how many of you feel as much satisfaction as did Dieter Shiilter. By Jack L. Schlecht
This belt-drive system 'copter had troubles with belts resonating and coming off the pulleys, so no real flight attempt was made. Its workmanship was the finest seen. Design is workable, has engine speed, clutch, collective pitch, anti-torque tail rotor, but no cyclic
Vell, you zee, mein friend, if der mass equals angular velocity, unf if die wind ist gayen in das roundger spinnen . . . Would you believe, this is a workable design? Shroud around engine's propeller increases torque reaction. Controls appear to be collective, cyclic, with rudder and fixed engine speed. Design by Hultsch.
Although crude, this model has all normal helicopter controls, cyclic, collective, directional, and throttle. It did not fly at meet, but has flown before. Hans Knaf found he had too much power, so collected castor-oil-rich exhaust for lubrication for the gear box. Swiveling, teetering and self-stabilizing rotor.
Here is the one and only successful flight! It went up and down successfully under adequate control. Showed that model design is only half the effort.
Engine installation shows worm drive to rotor and direct to tail rotor. All-up weight is 9½ lbs. but lift is 11½ to 12 lbs. Supertigre 60, proportional radio. Engine-to-rotor ratio is 15 to 1. Main rotor turns 800 rpm, tail rotor 3000 rpm. Tail wheel is realistically full-swiveling. Considering that a real helicopter requires constant operation of both hands, arms and feet, how does one fly a model with just two hands on transmitter control sticks?
Posted January 29, 2011