1951 Vespa Siluro ‘Torpedo’
With Phil Aynsley
Possibly the most beautiful motorcycle I have ever photographed – the 1951 Vespa Siluro (Torpedo).
The Siluro was a follow up to the successful but much cruder-looking record breaking bike the company used the year before. That 125 cc machine had set 17 world records at Monthlery in France.
Corradino D’Ascanio’s very organic design was aimed at breaking the standing kilometre world record which it did on the 9th February 1951 with rider Dino Mazzoncini (wearing a long tapered faring on his helmet) on a closed section of the Rome-Ostia motorway. A time of 21.4 seconds was recorded with an average speed of 171.1 km/h.
A special water-cooled, horizontally opposed 125 cc twin-cylinder two-stroke motor was used that had an output of 17.2 hp at 9,500 rpm.
Unusually this design placed the geared together crankshafts on the outside with the pistons sharing a common combustion chamber and (almost) meeting in the middle, where the single spark plug was located. Bore and stroke were 42 x 45 mm and a four-speed gearbox was used.
Two carburettors were employed. The radiator was placed on the left side of the bike. The 3.00 x 10 inch tyres (about the only common factor to the production Vespas) were specially made by Pirelli.
Vespa and its chief rival Lambretta traded scooter world records during this period in a battle to prove which was best, and hence increase sales of their scooter models.
Lambretta (also named Siluro) took it back later in 1951 raising the average speed to 202 km/h with a 125 cc supercharged 2-stroke single based on their Model C motor that used a 18:1 compression ratio and made 20.75 hp at 9,700 rpm.
This still stands as these scooter record attempts were abandoned after rider Renato Magi was killed on an MV Agusta scooter streamliner later that year.
