Brantly B-1 helicopter - development history, photos, technical data

Brantly B-1
1946

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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N.P.Brantly was one of a number of engineers experimenting with helicopters in the immediate post-war period. In 1946, he started flight testing his Brantly B-1 helicopter which had been constructed by his employer, the Pennsylvania Elastic Company. In common with other designers, he decided on a counter-rotating co-axial twin rotor layout and the B-1 prototype (NX69125) was powered by a 150hp Franklin engine buried in the tube and fabric fuselage of the craft. The B-1 had a fixed tailwheel undercarriage and directional control was achieved through a small rudder on the sternpost - because the twin main rotors were expected to neutralise the normal torque effect. Brantly also designed the three-blade rotors with a fixed pitch central "star" and articulated outer blades which would resolve the aerodynamic problems of asymmetrical forces on the advancing and retreating blades.

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

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