The name of Charles Sgonina languished in obscurity until fairly recently, when George Cohen included the amazing 'Sgonina Special' in his 'Flat Tank Norton' book. Created originally as a speed upgrade for his Norton 'Brooklands Road Special', Sgonina (born in 1901) eventually built a Double-Overhead-Camshaft conversion for the former sidevalve machine, and honed the motorcycle into a spindly and extremely purposeful tool, on par aesthetically with George Dance's sprinting Sunbeams, but with far more technical interest.I recently asked Bill Phelps to fill me in on his old friend Charlie's story, and the following is edited from an article Bill wrote in a 1966 V.M.C.C. newsletter:
"Charlie is in the engineering trade in Cardiff; my first encounter with him was several years ago, when I required some work on my motor-cycle. He does not talk much about the Twenties, when he rode in many International events, and it was a few years after my first encounter with him that he did chat some on the Vintage era.
He bought his first motor-cycle in 1918; a belt-driven 4hp Triumph. His next machine was an Enfield, which gave him his first taste of chain drive. Next, at age 18, he purchased a secondhand 'B.R.S.' Norton (example above), belt-drive with a certificate that it had lapped Brooklands at 70mph. With this machine, Charlie entered the world of motorcycle competitions, and in 1919 he converted it to O.H.V., using a steel cylinder with detachable inlet and exhaust ports - this was three years before Norton introduced their own OHV machine. He raced the bike at Weston Speed Trials and won a few events, then at Pendine [beach], then at Style Kop, Birmingham - he raced Graham Walker in a Novice event, and managed to beat him; they formed a lasting friendship.
Even in the late Forties Charlie wrote articles for Graham, who was editor of Motorcycling.
However the engine of his Norton had a short life; the piston cracked around the gudgeon pin, then Bang! Only the camwheels were salvageable... But by now the Speed Bug had bitten, and Charlie managed in 1920 to persuade Norton to part with an actual T.T. frame and gearbox. His new engine wasn't as good as the first OHV, but with alterations it eventually get a move on, performing in quite a number of events with moderate success.
(above, Sgonina on his OHV machine, with Dr. Lindsay and Jack Thomas on their sidevalve racers, 1920).Charlie said, "About this time I started to alter valve timings and cam design and found out what a lot of study must be put in on this subject, as to make a cam that looks good is just silly. Anyone thinking of making new cams must first of all consider valve gear reciprocating weight, strength of valve springs permissible, and from this work out what kind of constant acceleration cam would be suitable. I always tried to fill the cylinder as full as possible at fairly high engine revs, and run on a compression ratio to suit the hottest plugs available which meant that I was running on a lower compression ratio than many and yet getting more power."
In 1922, after building his own frame, he added a chain-driven Overhead-Camshaft cylinder head, which caused a considerable stir (above); a number of drives were tried, as the chain thrash at certain revs was disconcerting. The best solution [remember, this is pre-Weller tensioner for chains] was to drive the magneto and camshaft on the same chain, but soon Sgonina switched to a vertical bevel gear drive, which cleaned up the appearance, solved the chain thrash, but did not increase speed.
There were plenty of troubles with pistons and and head joints, and a con-rod broke just below the gudgeon pin. There was little trouble with the valves though, using heat-treated Tungsten steel. He used a Petrol-Benzole fuel mix, and always rode his machines to events, but was not always lucky enough to ride them home!
He tried supercharging this engine but was disappointed, and after having a few fires the project was dropped. You can be assured that the flame coming from a blower will beat any brazing lamp!
In 1923, Charlie's last modification to this engine was a 90-degree inclined-valve Double Overhead Camshaft cylinder head - this was fully 14 years before Norton introduced their own DOHC motor. The Sgonina Special used bevel drive, a steel cylinder and silicone alloy die-cast piston. This was his first attempt at die-casting, and made at least six before making a really good one. The pattern for the cylinder head was quite a difficult piece of work and some beautiful castings were turned out. He was surprised at the strength of the valve springs required to prevent valve float, as only light thimbles were used between valves and cams to keep down reciprocating weight. This new engine was installed in a modified Sunbeam Sprint chassis.
This engine was never fully developed, but seemed to have great possibilities and even in this state was better than any of Charlie's previous efforts, being reliable and speedy and with slight alterations would have been ideal to run on alcohol fuel. It was road tested early one morning down Allensbank road in Cardiff and clocked 86mph.
Unfortunately he broke his arm practising on a grass track - with this, and the ban on motor racing on public roads, and the trade depression, Charlie had no encouragement to continue, but once the speed bug bites, you never seem to give it up, and he began to race on four wheels.."Many thanks to Bill Phelps for the article, and George Cohen for the use of the images from his excellent 'Flat Tank Norton', which you can order here.