Norton Motorcycles 1950s

Today in Motorcycle History

Adventures of Dr. Arthur Pistonock-Henderson and the Rev. Pat McNutty

The Varsity Team of 1926

Pistonock-Henderson on left and McNutty in the centre; others are unidentified: does any surfer know who they are?


Apologies for the dropsheets, paint tins and scattered detrius. More information...

This remarkable story has just been discovered and although the manuscript was in terrible condition, the Science Museum and the University of Somerset have been able to read it with the use of specialised carbon dating equipment. I thank them for their assistance.

Mr. John Pistonock, worked in Jas L Nortons Bradford Road workshop from 1904 to 1907. He was a skilled engineer, having come from a family of steam and beam engine pioneers. He married Miss Charlotte Pugh-Henderson, daughter of Pugh (Hurley-Pugh fame); they were childhood sweet hearts. (see links page for more information on Hurley-Pugh motorcycles). They had 12 children, the eldest being Arthur Lansdowne Pistonock-Henderson; the 'Pugh' was dropped from the name after John fell out with Charlotte's brother, Roger, over the ownership of the design, and consequently the patent of the 'thrunging sprocket'.

Arthur Lansdowne Pistonock-Henderson went to Cambridge to study medicine, where he met Pat McNutty at the Varsity Motorcycle Club; both owned circa 1927 Model 19 Nortons! McNutty was studying a joint honours degree in Theology and Mechanical Engineering and was later to become the Vicar of Spagforthe on Fosse. Together they designed, constructed and competed the unique Desmodromic Single Valve Pot Engine (DSVPE)

The description commences at the inlet...

Using a series of eight Binks 'Rat Trap' carburettors, mounted on a rotating 'carb-wheel' which was driven off the drive side crankshaft main shaft by a series of sequential thrunging sprockets and incorporating a central axial fuel delivery pipe, this unusual set up allowed a direct relationship between the engine speed and the volume of the inlet charge.

At rest (before the starting procedure was commenced) only one Rat Trap is lined up with the inlet port of the pre-combustion expansion chamber, whose outlet is the double venture shaped inlet tract system which ingeniously incorporates a series of concentrically arranged ports which convey both the inlet combustion mixture and the exhaust gases. Control of the port openings is by a series of floating shafts which operate 2 'flapper' valves each. The whole mechanism is regulated by the use of an extension governor which is also driven by the thronging sprockets via a set of bevel gears and Oldham couplings.

After the engine is first fired up (according to the theory) and as engine speed increases, the sequential series of thronging sprockets cause the carburetor wheel to rotate faster allowing each rat trap to momentarily spin by the inlet tract and a fresh charge of the secret fuel mixture (another story here! ) to enter the pre-combustion expansion chamber. This chamber has a series of 24 pressure-release valves adjusted to open at 10 psi, 20 psi, 30 psi and so on in jumps of 10 psi upto a potentially dangerous upper limit of 240 psi. Each one of the pressure-release valves is connected to a whistle, expertly tuned by the musical McNutt to give a slightly differing note, so that when the 23rd valve is fully open, and just one short of the maximum at 24, the rider can just hear above the exhaust note, the 'Charge of the Light Brigade' and consequently be warned that Armageddon is perilously close!

These valves can also be linked up, by the reed valve movement in the whistles to a second expansion chamber which is used as a damping unit to compensate the massive forces developed in the concentric multi-port inlet tract, which houses the single valve. The valve is made from Jessops grade G2 high Chrome-Manganese Austenitic steel. It is massive, the stem length is almost 8 inches, the stem diameter is 21/32 inch and the head diameter measures 3 17/64 inch! It weighs 6lbs. The forces generated are very great and the inertia Newton Rating Poundage Scale dictates the use of desmodromic opening and closing.

As the engine speed increase and hence the pre- combustion chamber pressure also rises, the incoming charge to the inlet tract enters all 5 of the concentrically arranged ports, set within the massive aluminium-magnesium composite inlet manifold. A con rod- direction-monitoring-lever, which operates a convoluted linkage to one end of the ring of shafts that are located in the walls of the concentrically arranged ports, hence when the conrod is on the down stroke, the inlet tracts are opened to the pre-combustion chamber. Conversely, when the conrod is going up, the flapper valves are closed for compression or open for exhaust gases to exit via the single, but very big 'Brooklands Can'. The shafts open and close the flapper valves which then determines the direction of the gas flow in the inlet tract and thus allowing the inlet and exhaust gases to be kept apart.

The timing set up is crucial to ensure maximum efficiency; the primary thronging sprocket incorporates a sensor which synchronises:

1 The rotating speed of the carburetor wheel

2 The fuel flow rate to the central axial delivery pipe

3 The throttle openings of all 8 rat traps

4 The amount of transverse movement in the floating inlet shafts and hence the opening and closing sequence of the flapper valves

5 The relative pressures in the pre-combustion and damping chambers

6 The extension governor

7 Thronging sprocket RPM

8 Desmodromic operating mechanism

There is no magneto to 'spark' the engine, because after incorporation of the single valve ( 3 17/64 inch)into the cylinder head there was no room left to put a spark plug! Consequently the fuel mixture was developed to ignite under compression; the C.R. being a staggering 65 to 1. the squish band clearances were always a guarded secret and unfortunately no figures are available. Rumour had it that they were some where near 0.0005 of an inch!

The thinking behind the One-Valve engine stems from the philosophy of all engineering fundamentalists of reduction theory:

"Why use two when one will do"

Jas L Norton, himself used the reduction principle to a lesser degree than Pistonock-Henderson, in that he stayed with single CYLINDER engines. Pistonock-Henderson, following his studies at Cambridge, learnt about the 'maximists' and hence took the reduction theory to its extreme; he discarded the exhaust valve.

So why were 8 carbs used and dozens of thronging sprockets? Pistonock-Henderson had wanted to use his own design of carburettor which infact was the original 'flat slide' unit, pre-dating the controversial Gardener by many years. Using a 1st W.W. 300mm 'Big Bertha' shell case and his Uncle's garden spade he ingeniously fabricated a huge and very simple carb'. Although tests showed the carb' to have excellent 'full bore' properties, the frequent explosions and flame damage within the pre-combustion expansion chamber when starting up the engine, meant that the P-H Flat- Side had to be side-lined and an alternative system developed. Enter the Reverend Pat McNutty; and known as 'RPM' or 'Flat Out' by his close friends.

NcNutty was an Ulsterman, of fiery temperament, but brilliant mind. While at Cambridge he had combined the mechanical theories of his engineering studies to the esoteric pursuits of his Theology lectures to establish the school of 'Mechanical Experimental Semantic Sophistication' thinking, known in learned circles as 'Messy thinking' or 'Mess' for short.

Whereas, Pistonock-Henderson was a fundalmentalist reductionist, his old University friend was precisely the opposite. McNutty was a believer in 'Sophistication' and attempted to make everything more complicated. This contrast between the two men, a classical dichotomy of reason, provided the ideal opportunity for creative discussion. Faced with a problem, such as the carburettor issue on the 'Single valve' engine, they could never agree, no compromise would ever take place and resolution was determined by a game of 'French Cricket' (subject of another story), the result of the 'Carb Cricket Match was in the Reverends favour and subsequently his other hobby of Nocturnal Rodent Watching could be incorporated into the design. McNutty had bought a 'job lot' of Rat Trap carbs by mistake, thinking they would help in his studies of rodents by catching them alive. He had fixed 8 of them onto a small bicycle wheel and had mounted the whole assembly on the floor of his Church. He would then position himself behind the altar to watch the wandering rodents climb into the open bore of the rat trap and when all eight were full, the wheel would spin at such a speed that the rats were subjected to high centripetal forces to put them into a hypnotic state. He could then stop the wheel, let out the rats, which were fully hypnotised and McNutty could then have them at his mercy! One evening he invited Pistonock-Henderson to join him in a rodent session, but that's another story!


Pistonock-Henderson and Jugs, his Housekeeper, post catatonic stupor!

Mcnutty's carb wheel setup was exactly the sort of complicated device which appalled Pistonock- Henderson's basic philosophy of reductionism and frequently his distress was manifested by catatonic stupor. He would be so upset by the protracted procedures, long winded and unsound logic of his friend that his response was akin to total engine failure. Totally motionless, he would sit upon his beloved 1926 model 19 Norton and take up the pose of the great Joe Craig would adopt while hurtling along the 8 mile Clady straight at the Ulster GP. In a racing crouch, 'chin under the tank top paint' and hands tightly gripped to the handlebars and with a manic grin, P-H stayed like this for days. Ignoring all basic instincts regarding biological functioning he would be found in a pool of Castrol 'R' and his own bodily fluids, disorientated and repeatedly jabbering some rubbish about only having one flywheel, one main bearing, one wheel or some other quasi-delusional belief pertaining to motorcycle reductionism. Pistonock-Henderson's housekeeper 'Jugs' was the only person able to rouse her master; by cleverly using a large oil suction gun in combination with a rack and pinion totally adjustable motorcycle workshop lifting bench, she was able to bring Pistonock-Henderson to his senses.

The two friends differed in other aspects beside their respective engineering philosophies. P-H was married and had an insatiable sexual appetite (according to Jugs), whereas McNutty was a virgin, married to the church and his multi-head universal milling machine. They had formed a solid relationship based on their love of Norton motorcycles, French cricket and total mistrust.

Both rode Model 19 Nortons and there was little to choose between them in local speed trials; they would frequently tie for first place, despite differing riding techniques. It is interesting to learn of how these two pioneer motorcycle engineers differed in their approach to obtaining maximum speed and efficiency.

P-H, a reductionist, removed the gearbox from his machine and reverted to the earlier belt drive set-up as found on 'Brooklands Single Speeders'. He would also remove both mudguards and the saddle; strangely, P-H would never sit on the saddle when he was riding, unlike his catatonic position. He would cut off the left hand side of the handlebars, and since there was no clutch, there would be no requirement for a clutch lever. The valve lifter, magneto lever and throttle lever were all incorporated into a single toggling switch which through its three dimensional axis controlled everything! It also meant that no other person could ride his machine because they could not master the remarkable spatial dexterity of P-H's right thumb, which had been triple jointed since his teenage years. In side the engine, the inlet cam wheel was removed and an extension fitted to the follower which allowed it to run off a modified exhaust cam. Both valves were retained, but the valve springs inner and outers (4 in all) were replaced by a single double hairpin valve spring, made by Trenco under special licence, who also made the extraordinary 'piston return spring' which was used on later versions of the Desmodromic Single Valve Pot Engine.

McNutty used a differing approach to engineering principles, which incorporated his 'messy' thinking ideas; he was a master at complicating systems, many of his fundamental beliefs stemming from his religious background, he claimed his ideas were messages from God, who had spent time with the late Jas.L. Norton. His Model 19 Norton incorporated TWO engines, linked together by a central crankcase fabricated from a flat sheet of steel; the left engine was connected by its right sided T/S mainshaft, via a series of thrunging sprockets to the D/S mainshaft of the right engine. Two top ends were used and the four cams retained so that valve timing could be varied between the left and right cylinders of, what was now, a 1200 cc vertical twin engine. Abandoning the total loss oil system, he modified 4 pilgrim pumps using a complex multi-chamber weir sump system to work alternately between feed and scavenge, and added additional oil feed pipes to both ends of the four rocker posts, all 4 cam follower/cam interfaces, and to each of the 8 main bearings (2 on each of the outer ends of the crank and 4 in the central supporting mount where the thronging sprockets lay. There were copper oil pipes everywhere!

Two Sturmey Archer gearboxes were used to make a six speeder, but this device was only used at certain circuits where McNutty was able to successfully bribe the scrutineers, otherwise he had to retain the standard three speeder. With the extra power developed from the big twin all chains were replaced by triplex chain and a multi-plate clutch incorporating a 'slipper' centripetal twin satellite shaft to reduce rear wheel spin on take off! Double sided brakes at both front and rear and linked by a rod and cable linking system; two sets of handlebars (one for racing, t'other for testing) and many other totally useless pieces of metal were added to his mount. It weighed in at 586 lbs, where as P-H's machine was less than half that at just 201 lbs.

The power to weight ratios were remarkably similar, although the shape of the power curve differed.

Although both rode Norton's, their styles were different. P-H used the 'doggie' riding position technique, stripped to his under garments with shaven head enclosed in a pair of streamlined goggles and McNutty the 'straddling' method, wearing a set of 6mm thick donkey hide, 6 piece leathers (another story) and on top a full length trench coat. His crash helmet was huge, adorned with ornamental crowns and plummells of many colours, so heavy that it had to be strapped in place by a series of leather straps to the front and rear mudguard stays, which were infinitely adjustable by small duplex thronging clips.

They looked magnificent....

Dear Dr. Cohen,

I was fascinated to read your archive material about those old blighters, Pistonock Henderson and McNutty; I was in the Varsity Motorcycle team of '26, that's me in the picture, between my two old chums. We had some super times, I particularly remember the day we stuffed the Oxford team on their own turf. We managed to persuade the complete St.Catherines Hockey team to join us in the back of our workshop where we showed them the principles of 'tappet adjusting' was jolly good fun, I must say!

I recall the early trials of the desmodromic single valve pot engine at Spagthorpe aerodrome when 'Slasher' McGrath had both legs amputated just below the knee by eight whirling Binks Rat Trap Carburettors. Investigations proved beyond doubt that 'Stumpy' (his nickname was subsequently changed after this tragic accident) was at fault for foolishly trying to adjust the oil flow to the thrunging sprocket secondary coupling which caused the momentary lapse of concentration. This near fatal mistake would lead to 'stumpy' spending the rest of his days strapped into a Ner-a- Car as a pathetic shadow of his former self. I remember that there was no immediate damage to the engine or its components and 'Stumpy' was able to control the twin foot brake Nock-Nutty Manxman model despite the tremendous handicap of watching his legs being minced up by McNutty's ridiculous Rat-trap device and safely back to the pits. He was a brave lad!

Yours most sincerely,

Fabian 'Foxy' Faggot-Thorpe

Dear Doc,

I thought you would be interested in a quite amazing discovery. My great Uncle Archie J. Butterworth was a just a young lad when he first met those two motorcycle lunatics, Pistonock- Henderson and McNutty. He used to tell me about the sessions spent in the workshops testing the latest configuration of the internal combustion engine. Apparently there were many total disasters with regular visits from the local fire brigade to put out blazing sheds after an engine would disintegrate on the test bed.

Uncle Archie obviously learnt a lot from those 'pioneers of the unusual' and he patented a swing valve motor in September 1949 in which the inlet valve swings completely away from the inlet port and thus allowing the inlet tract to be free from obstruction, (unlike the more conventional 'poppet' valve) and consequently improving the quantity of inlet charge. I have managed to get hold of his prototype engine and the original drawings and patents.

The first dyno test showed that the engine developed 50 BHP! Not bad eh! Archie then abandoned the single cylinder engine and built a horizontally opposed four cylinder which produced 220 BHP. The single cylinder motor is being put in a featherbed frame and with some development we hope to be able to blow off the short stroke Manxes and G50s!

Yours faithfully,

Aero Mileo de Raceo.

Recommended Reading (not included in the original archive)

Camilla's Motorcycling and decency

The Spagthorpe Motorcycle Company