Original Document

ALLEGHENY, March 8, '87

DEAR MB. BRASHEAR,

Here is a rough sketch of the model I described in detail yesterday and of which I want material for 3 copies. To recapitulate essentials, a1 a2 a1 a2 are two hollow brass rods 100 centimetres long 2.5 at 3 cm. diameter. They are very light and hold within long twisted rubber springs which act by their torsion on the wheels, p.p. is the supporting plane, strengthened on the front by a rib, held by sliding collars which move along the rods and with an angle adjustable on these collars. The point of support is 1/3 the depth of plane from front. The wheels carry four vanes. S.s.s.S. length of each vane 15 cm. width at broadest 5 cm. A stiffening wire runs outside. Angle of vanes adjustable. r is the rudder shaped like the tail of a child's dart. + It is revolvable on the light central rod d.d. and had better if possible be adjustable in 3 ps. above or below this rod as well as concentric with it. As shown in fig. 4 the end of each axle should project with a square head to admit of the rubber spring being wound up by a key also. (Fig. 1) there should be a trigger 11 to release the wound-up wheels by.

As to Weight, Area, Power and Speed.

Weight of whole is limited, to about One Kilogramme, or to 1. gramme, to every 20 centimetres of sustaining plane surface. It is supposed that we can store up 500 turns of the rubber in each rod representing in English measure about 500 ft. pounds each. This may take about 1/3 pd. rubber each. The maximum pitch of the wheels will be an angle of 45° giving probably (allowing for slip) about 50 cm. advance for each turn. i.e. 20 turns per second then will give, on this (assumption) about 20 miles an hour.

The whole is to be constructed with a constant eye to future modifications. That arrangement will be best which allows size of planes-vanes etc. to be altered after trial. If light brass tubing can be found in stock enough for several models should be ordered.

S. P. LANGLEY

Credit: John A. Brashear, The Autobiography of a Man Who Loved the Stars, (New York: Houghton Mifflin Co., 1925).