Brantly, a weaving machinery expert with the Penn Elastic Company, designed and had made by that firm a helicopter with contra-rotating co-axial rotors, the lines of which had a very clean appearance.
The B-1 was fitted with two co-axial contra-rotating three-bladed rotors. Neither push rods nor cranks were visible in the rotary wing assembly. Actually, the collective, cyclic and differential controls were completely enclosed in the hubs and ran in an oil-bath.
A universal joint combining two hinges was situated at some 1.8 metres from the root of the blades. The radius of the non-flapping part of the blades was thus 1.8 metres.
Each blade weighed only 5.5 kilos and the rotors normally turned at 320 r.p.m. This rotorcraft made its maiden flight in 1946.
P.Lambermont "Helicopters and Autogyros of the World", 1958
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R.Simpson "Airlife's Helicopter and Rotorcraft", 1998
Technical data for B-1
Number of seats: 2, engine: 1 x Franklin 335 rated 150hp, rotor diameter: 9m, length: 5.33m, height: 2.36m, weight fully loaded: 907kg, empty weight: 601kg, cruising speed: 182km/h, range: 640km