Schmid Mechanism Revealed! by Nathan Chronister

Home , Glider (aircraft), Glider (sailplane)

SPRING 2018

t was 1942 in the shad- owed years of the second I world war when the first manned ornithopter took flight. Sadly lost, along with much else due to the circum- stances of the war, Adalbert Schmid’s great achievement is starting to see new light.

Schimd’s work is known from several articles published in Adalbert Schmid’s 1942 manned ornithopter in flight. Germany after the war. He flew a manned ornithopter in 1942. Initially it was powered Schmid stated his ornithopter to a small, mysterious hub, by the muscles of the pilot and used a circular wing motion, which formed the base of the towed aloft for a flight of 900 and he provided two simpli- wing. Something in that small meters. Subsequently, a small fied drawings of mechanisms hub was flapping the wing. motorcycle engine was added. for producing such a motion. That allowed the ornithopter The drawings alone could not The hub mechanism remained to take off on its own. Flights be translated into a practical a mystery until I noticed a of 15 minutes were reported. mechanism. They show a ro- small bump, faintly visible in tating wing, but they don’t the grainy photo. I realized The design of the ornithopter reveal how to keep the wing this was the axle of a gimbal is known only from Schmid’s upright as it goes around in mechanism. The bent drive simplified description and the circle. shaft of Schmid’s sketch three photos somewhat lack- would pass through the gim- ing in detail. After examining Studying the photos, I noticed bal, and this would allow the these materials, off and on for what looked like an opening wing to move in a circular several years, I finally began in the side of the fuselage. path while remaining upright. to tease out some secrets of From this portal emerged the design. what appeared to be a drive With this new understanding, chain, like on a bicycle. A I set about the task of building sprocket conveyed the power a model of the Schmid mech- PAGE 2 Flapping Wings

The stage is set for someone to build a flying model, or even a full-size “replica” of Schmid’s ornithopter. This would serve as a demonstra- tion of its airworthiness and help raise awareness of the historic accomplishment.

Wright or wrong?

Gustav Whitehead made the first successful flight of an airplane in 1901. Two successful replicas lent support to the eyewitness accounts that described White- head’s airplane flying over their Connecticut town. The recon- Adalbert Schmid’s drawings hint at a mechanism for circular wing flapping. But structions, along with other evi- some important details were missing. dence, have led to Whitehead now being recognized for building the first successful airplane. anism. First I modelled the rangement causes the wing The Wright Brothers’ flights drive mechanism in a 3D incidence to vary throughout made in North Carolina in 1903 CAD program, in order to the flapping cycle. The wing were marginal by comparison. work out the necessary dimen- pitches up slightly for the up- The best was an 852 foot straight- line flight that ended in a crash. sions and some details of the stroke, and it pitches down That hardly qualifies as the sus- construction. Building this slightly for the downstroke, tained and controlled flight for mechanism was challenging allowing it to maintain the which it was often claimed. for me, because it is complete- correct angle of attack. ly different from other ornithopter mechanisms that I have built before.

I used a miniature plastic drive chain on the model, giv- ing it a scale-like appearance. Since I don’t have any dimen- sions, it’s not actually to scale. The plastic chain has a lot of friction, but the Schmid mechanism itself spins freely. Per- haps the circular motion of the wing is more efficient than a typical flapping mechanism.

Until I built the model, I did- n’t understand why Schmid had the hub pointing up at an A photo of Adalbert Schmid’s ornithopter shows a mysterious, compact flapping mechanism that is apparently driven by a bicycle chain and sprocket. angle. Now I see that this ar- Spring 2018 PAGE 3

Articulated by Donald V. Cook

everal years ago, I built S some test models of jointed wings - not rigid like a modern airplane. Articulated, like a bird skeleton, or human. My goal was not to actually fly these things, but just to be able to fold the wings. I wanted wings that were more port- able, more manageable, for the lone pilot when he’s not in the air. Safe on the ground, less sensitive to being blown away when at rest. But also capable of unfolding at the will of the pilot when the time for takeoff was right.

The first model is Tinker Toy- like, but it tells the story. The scale is 1½”=1’. So, my man is 6 ft. tall and his wingspan is a whopping 40+ feet. I wanted him to be able to stand up with his wings folded at his sides. You can see the skeleton joints clearly: fingers, ploys the articulated sections wrist, elbow, shoulder, and an nicely, but I offer no sugges- extra one added for good tion as to retraction. measure. The joint pieces are friction-fit so they can be easi- The third model is simply a ly adjusted. I envision that a dowel cut in several lengths. Guillow wings end-to-end, future pilot would launch Here I wanted the joints to be resulting in a 24” span. Then I hunched over and fly in a hor- flexible enough to fold up, but cut the wings and jointed the izontal posture. No ideas are also springy enough to auto- sections back together. The suggested as to how the wings matically unfold into a fully joints are hinged and sprung would deploy or retract. extended wing. I glued pieces with rubber bands. The bend- of cable tie strap into slots ing moments at the joints Second is a ¾” foam wing cut sawed in the ends of the dow- were obvious, so 3 bands were from housing insulation. Ob- els. The arm did unfold spon- added at the shoulder, 2 the viously no skeleton required taneously, but not as com- elbow, and one for the wrist. in this version. Here the joints pletely as I’d hoped, as the The glider flew well after that are cut flush: tape hinges ap- plastic stays slightly bent. adjustment. In this version, plied on one side of the panel, extending the wing is auto- the other side secured with And the fourth model is a matic - they pop out neatly by rubber bands at each joint. In modified Guillow glider. To the rubber tension. Retraction, action, the rubber tension de- give more length, I joined two however, remains unsolved. PAGE 4 Flapping Wings

Schmid ornithopter mechanism. The sprocket turns a bent The gimbal mechanism is driven by the bent rod and controls rod, which produces the basic circular motion of the wings. the angle of incidence as the wing moves around in a circle.

Payload-Lifting Ornithopter Contest

Do you have what it takes to build a huge ornithopter capable of lifting a bowling ball high in the air? Check out contest rules and information on our web site:

www.ornithopter.org

There is a $1000 cash prize.

The author’s reconstruction of the Schmid mechanism used an electric motor and a miniature plastic drive chain.

Published by: The Ornithopter Society 118 Callodine Avenue Buffalo NY 14226

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Suggested Donations: Student: $12.95 Hobbyist: $24.95 Professional: $49.95 This close-up view shows the gimbal mechanism that helps direct the movement of the wing. Search “Adalbert Schmid” on Youtube if you would like to see it in action. www.ornithopter.org