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Autogyro

Wallis AutogiroAn aeroplane that flies by virtue of the lift generated by freewheeling rotating wings set 'windmill' fashion above the fuselage. The forward motion of the autogiro provides the force to keep the rotors turning so unlike a helicopter the autogiro cannot hover.


Visit: www.autogyro.com for more model autogyro information.

The British Rotorcraft Association www.gyroplanes.org is the representative body for Autogyros and Gyroplanes in the UK - primarily 'full size' aircraft, but some of the skeletal ones are smaller than the bigger fixed wing models flying nowadays. Model flying is encouraged in the Association since it provides valuable insight into the behaviour of rotors and aircraft without such serious risk to wallet, life and limb.


The Story of Whirlygig

The details and info on building and flying of an autogyro of the Benson or Wallis type e.g. a pusher engine and propeller.

By: Bob Lane


I first became interested in this type of flying machine when I found the website of the Autogyro Company of Arizona and the many links to the Gyronuts in the USA, I then obtained many books from the library from Leonardo to De La Cierva and the history of helicopters. All the advice on the web advises against own design models until some experience is gained on proven types, not me I've jumped in at the deep end and to tell the truth most own design models I've made have flown albeit some better than others.

Whirlygig

My gyro has a 3 bladed rota with carbon fibre strips for stiffening and are perfectly balanced with a 55" diameter, 27.5" radius with a flat bottom Clark Y section with a 2"/50mm chord, 5/16"/8mm thick at 1/3 or 16.5mm back from the leading edge. Using the formula 27.5 x 27.5 x 3.141 = 2375.38sq.ins. / 16.499sq.ft. of rota area. The centre 7" diameter including the hub and bearing would not produce any lift so the lifting area of the rota would be 2336.9sq.ins. / 16.22sq.ft. so as the weight of the model is 1.75kgs/61.6ounces the loading is 3.79 ounces per sq.ft., well below the maximum of 5 ounces per sq.ft. for a rota of this diameter, but the lighter the better as with any model. I originally tried a 2 blade rota with a Teeter hub, but it would not autorotate hence 3 blades.

The blades are higned with Tupperware type plastic at an angle of 20 degrees (called Delta 3) so that the advancing blade rises (cone angle = dihedral) and the incidence reduces the blades cannot go too high as there is a stop to prevent them from folding upwards, this should reduce lift and prevent rolling to the retreating blade. The blades are fixed to the hub by a single bolt and sandpaper layer between blade and hub allows the blades to move around if they hit anything. I have a jig to reset the blades to 120 degrees on site if this should occur.

The rota is controlled in pitch only by a servo, a piano wire loop on the rudder prevents a blade strike in the event of a hard landing. When the rota is tilted forward a small electric motor with a 15 tooth gear taken from a Phillips 3 head rechargeable shaver and powered by a very small 3.6 volt rechargeable pack taken from an old hands free BT phone engages a 90 tooth gear fixed to the rota hub and a micro switch sets it in motion. When up to speed and with the glow motor pulling it forward the rota is tilted backwards e.g. (up elevator) the gear disengages and autorotation should take place due to the forward airspeed, and it should fly.

The tailplane is fixed but the incidence can be adjusted. The rudder is all moving by closed loop wires, the servo also steers the front wheel. So we have rudder for yaw, rota for pitch and throttle for climb or decent. The engine used is a Russian MVVS .21 glow or diesel (can be either by changing the cylinder head) fitted with a 10" x 6" pusher prop and a small spinner. There is room to use an electric starter between the engine and the rudder.

It has yet to be test flown, but has been taxied and hopped so far. I have made more blades as spares in case.

Bob Lane


Update

I have made the rota fully articulated (roll and pitch) it would not spin up fast enough to lift off so I′m using a stronger motor and a remote battery on the ground that is plugged in and unplugs when the rota is up to speed and moves forward to take off. It almost lifted off but tipped to the left hope next time to succeed.

Contra blade Gyro Power SC 52 four stroke, Sanwa radio rudder elevator and throttle, An RCM&E plan some time back and called Als Gyro.

A Ken Wallis style of autogiro, Bob Lane.

Wallis type Gyro G-CRKT

Weight 2.6kg (5.75lbs), 3.85 oz per square ft of rota loading.


Teeter type Rota Clark Y flat bottom section of 66" diam. x 2.5" chord. Balsa TE stock, hard LE with carbon fibre tows covered with heat shrink. Pre-rotator driven from a MVVS .49 glow motor with a tuned pipe, with disengauge facility.


Rudder and steerable nose wheel, with loop to protect the rudder. Sprung axle. Swing away tailplane so that a starter can be used. 11"x8" pusher prop with a spinner. The Rota spin up from the engine is 13 to 1 ratio and disengauges at 461rpm when the engine reaches 6000rpm.


Pitch and Roll on Rota using an elevon mixer working high torque servos. A Petes Pilot / Ken Wallis to 5th scale to complete the model.

Construction is Balsa / Liteply / Aluminium. Nose pod is glassfibre made over a styrene mould that was melted out when set.

So far the model has not flown, but taxies and steers very well. Bob Lane.


Another of Bob Lane's models.


A 1.5cc pull start car engine powered Cricket to be test flown next.