A very basic machine, it was designed by Cuthbert Clarke and resembled a three-wheeled sidecar in most respects.
The car was powered by a 3.75 hp single-cylinder, two stroke, 270 cc Villiers engine[4] and had a friction drive two-speed transmission, using two cork covered wheels of different sizes, chain driven by the engine.
They were controlled by a lever which could be pushed or pulled to engage drive and had a central neutral position.
Braking was on the rear wheel only and used shoes operating on the outside of the transmission drum.
The first Xtra was a single seater (monocar) with a light plywood on ash frame body with an occasional seat behind the driver on top of the engine.