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Rolls-Royce Flying Bedstead / Thrust-Measuring Rig / TMR


The Bedstead, officially called a Thrust-Measuring Rig (TMR), was the brainchild of Doctor A.A.Griffith of Rolls-Royce. It was a flat riser which hovered on the deflected exhaust gases of two Rolls-Royce Nene jet engines. Compressed air nozzles provided directional control. The data gathered during the Bedsteads' test programme in the mid-1950s led to the development of a special turbojet engine for jet-lift, the RB108.

This was a radically new approach towards the development of vertical take-off aircraft. Basically it consists of a tubular frame, said to measure about 20 ft. across, on which are mounted two Nene engines having a common, downward facing tail pipe. Space is also provided for fuel tankage and the pilot is seated in the normal attitude on the top.

The weight amounts to some 3.5 tons, and is a little less than the total maximum thrust from the 5,000 lb. thrust Nenes. The two engines are mounted horizontally, facing away from each other, the exhaust gases being turned through 90 degrees to enter a common downward directed tail pipe. The thrust so obtained provides for direct vertical jet-lift of the rig.

Control in the pitch, roll and yaw planes is obtained by means of air jets bled from the Nene compressors. No aerodynamic control surfaces are used.

Capt. R.T. Shepherd, who was Rolls-Royce's chief test pilot until 1951, made the first fully-free flight trials on August 3, 1954. During the previous 12 months or so, the " jet-lifter " had undergone tethered flights, the amount of tethering being progressively relaxed as more experience was gained. The rig has since also been flown by Mr. H. Bailey, the company's chief test pilot, and Sqn. Ldr. Harvey, of the R.A.E.

Flights have been made involving hovering and sideways and vertical movement. Landing is said to be very light and incurs no sudden drop. As with a helicopter, horizontal motion is produced by tilting the lift component, in this case from the propulsive jet, and a horizontal as well as a vertical thrust is obtained in this way.



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