Royal Enfield is this month showing its Project Origin replica – a meticulous recreation of its first-ever motorcycle (or motor-bicycle) from 1901 – as part of the brand’s 120 year anniversary celebrations.
The original prototype model developed in 1901 by Frenchman Jules Gobiet had been lost to time and so too had the original design blueprints and original drawings. Until now, all that remained were a few period photographs and promotional advertisements that gave some basic graphic clues and information as to how the bike looked and might have functioned.
Royal Enfield assembled a team that was tasked with delving through the history books to unearth as much information as possible, working collaboratively with both Royal Enfield UK and Indian technical centres, as well as with Harris Performance and other experts from within the vintage motorcycling community.
A most unique element of the motor-bicycle is the mounting position of the 1 3/4 hp engine, which was clamped onto the steering head above the front wheel, which in turn drives the rear wheel via a long crossed-over rawhide belt.
Original designer Gobiet hoped that powering the rear wheel would reduce the side-slip commonly associated with front wheel driven Werner motor-bicycles. Unlike most other engines, the Royal Enfield crankcase was horizontally split. This avoided the disastrous consequences of oil dripping onto the front wheel from leaky vertically split crankcases.
Lubrication was total loss, the rider squirting a charge of oil into the crankcase via a hand oil pump located on the left side of the cylinder. This would burn off after 10 to 15 miles at which point another shot of lubricant was required.
The cylinder head housed a mechanical exhaust valve and an automatic inlet valve. The inlet valve was held closed by a weak spring and opened by vacuum. As the piston travelled down the cylinder, the inlet valve was sucked open allowing a charge of air-fuel mixture in. A contact breaker assembly on the timing side axle triggered a trembler coil, which sent a rapid succession of pulses to the spark plug. This resulted in a good burn despite running at very low revs.
Starting the machine required pedal power, and then once the engine fired, the carburettor was opened from its tickover to full-on position by a hand lever located on the right side of the petrol tank. There was also no throttle – speed was modulated by the use of a valve lifter which was opened by a handlebar lever.
To slow, the rider applied the valve-lifter. This opened the exhaust valve and as there was now no vacuum in the cylinder, the automatic inlet valve stayed shut and no air-fuel mixture entered the cylinder head. As soon as the rider closed the exhaust valve, the inlet valve opened and the engine fired. Hence, an observer might think the engine was intermittently cutting out when, instead, the rider was simply controlling his speed.
With all this background information gathered it was then a case of the ‘Project Origin’ team combining new-world technologies with old-world skills and practices to start the full reconstruction of a faithful working replica from the ground up. As the build took form it was quickly apparent as to the level of craftsmanship and expertise that were required to manufacture certain component parts of the motor-bicycle.
One of the most complex and intricate elements lay in the construction of the folded brass tank, which was masterfully handcrafted from a single sheet of brass – folded, shaped, hammered and soldered using age-old tools and techniques now almost forgotten to modern manufacturing.
The tubular frame of the motor-bicycle was brass-braised by the team at Harris Performance as well as a number of hand machined brass levers and switches. The engine was completely built from scratch, and with no reference blueprints or technical diagrams to refer to the team was required to intricately study the few photographs and illustrations available from 1901 in order to develop CAD designs for each component part which were then either individually hand-cast or machined from solid.
In addition, the team hand turned the wooden handles, manufactured the front and back band brakes, and had the carburettor built from scratch. The turn of the century period original parts that were sourced; the paraffin lamp, the horn, the leather saddle, the wheels – were all reconditioned and nickel plated to give the impression that the finished Project Origin motor-bicycle had just been unveiled to the public for the very first time at the 1901 Stanley Cycle Show, as would have been the case 120 years ago.