For release Sunday 2 March 1980

March, 1980

TRIUMPH TR7 DROPHEAD

STRUCTURAL ENGINEERING AND SPECIFICATIONS

When Rover Triumph engineers came to re-design the drophead as the first monocoque, open TR7, they had the benefit of an inherently rigid structure. Studies of the dynamic characteristics of a roofless version, which included analysis by the computer design experts at Pressed Steel Fisher, Cowley, led to an ingenious combination of torsional stiffening and damping.

Stiffening comes from an additional box-section behind the seats, 'tying' into the base of the 'B' posts. In addition the rear quarter panels are extended down to "root" more rigidly into the body side sills. Exploiting the inherent strength of the doors, which already incorporate side-intrusion beams, there are additional tongue and groove fixings mounted above the normal anti-burst door latches.

Torsional damping is provided by an harmonic front bumper. By making use of the substantial front bumper armature, which is pivotted at its centre and fitted with carefully tuned weights at its ends, Triumph development engineers have provided an effective and weight-saving antidote to scuttle shake.

The proof of this combined approach came after 1,000 miles' testing over the MIRA pavé (equivalent to at least 100,000 normal road miles). Despite this gruelling experience the test convertible showed no signs of structural fatigue.

Triumph engineers sought to avoid any weight penalty in carrying out the topless conversion. Vehicle weight has a direct effect on fuel economy, and many open cars in the past have been substantially heavier than their closed counterparts.

(Technical specifications attached)

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