In 1946, Brantly started flight testing the B-1 prototype (NX69125), which used a 150 hp Franklin O-335 engine in the fabric fuselage and two three-bladed rotors that rotated at 320 rpm and were fitted coaxially.
The collective, cyclic, and differential controls were enclosed in the rotor hubs and ran in an oil-bath.
Each rotor blade weighed 5.5 kilos.
It also had a fixed wheel undercarriage with a tailwheel under the tailfin.
Data from [2]General characteristics Performance