PE Norman's Sparkie
Text and photos by Ken Croft, September 2008.
Additional archival research by Ron Chernich.
|Name||Natsneez engine||Designer||PE Norman|
|Bore||9/16" (14.29mm)||Stroke||1/2" (12.7mm)|
|Type||Spark Ignition||Capacity||0.124cuin (2.037cc)|
|Production run||1||Country of Origin||UK|
|Photo by||Ken Croft||Year of manufacture||1944|
Here is a rather unusual and unique engine I had for restoration some few years ago, and a little about the man who constructed it. The engine was the work of the well known but now sadly departed Percival Edward "PE" Norman. P.E. as he was called, was not just a modeller, being known to the wider world as an accomplished painter, musician, violin maker and sculptor. His sculpted wood paneling graced the main lounge walls of the Queen Elizabeth luxury liner and his skills were used to design and build unique trophies for the Aeromodeller magazine and the then S.M.A.E (Society of Model Aeronautical Engineers) National Championships. He was also an aeronautical artist of great note, with his oil paintings featuring on model magazine covers in both the UK and USA. I would guess while his name will be familiar to many older modelers in England and Australia, very few would be aware that he was also some kind of model engineer.
His love of scale biplanes was started by his older brothers, both World War I Royal Flying Corps (RFC) pilots. Many of his free-flight scale designs were published in the UK. Among those are the Sopwith Triplane, Gloster Gamecock, the Sopwith Siskin, Hawker Typhoon, Percival Mew Gull, and others. His scale models featured pendulum control in which he was quite expert. All feature extreme knock-apart construction, essential if they were to survive the initial trim flights! Stories abound of PE at Epsom Downs, generally shirtless, with models performing wild aerobatics as he trimmed and tamed them. He took great joy in having several of his scale free-flight models all in the air at once!
PE was well known for his pioneering efforts with ducted fan propulsion for models. These include the Mig 15, plans for which appeared in the Aeromodeller Annual 1955-56, his free-flight Javahawk which featured in the Aeromodeller, August 1959, and the single channel R/C Rapier that appeared in the June 1962 issue of American Modeler. Smaller all-sheet variations of the Javahawk for free-flight called the Shrike and Mini-delta, designed in collaboration with Bill Dean, appeared in American Modeller, November/December 1964.
He could be seen out flying his models on Fairlop common as his jets swished overhead much to the amazement of onlookers.
As might be expected from a violin maker, his ducted fan models had shapely fuselages modelled from steamed and twisted balsa and plywood sheet bonded together in the most incredible way. Ducted fan was always a bit iffy in the early days and few modellers have built his designs for this form of power.
He also designed some cheeky sports models called "Antspantz" and "Natsneez". Copies of the Natsneez are regularly seen tearing about making havoc at vintage rallies. At 31 inch span for a 2cc petrol engine, in it's day this was a high wing-loading high-speed rocket. Even with a modern 1cc engine, the model is ballistic! His original model was powered by an inverted petrol engine of about 2cc. The plans, as such, was published in Aeromodeller, November, 1944. A few years ago, one of his home built engines came to me for an attempted but largely unsuccessful restoration. I believe that this was the engine he used in his Natsneez.
So what of the engine? The man was a sculptor and musical instrument maker by trade. The February 1962 American Modeler biography credits him with 26 home made engines, several built without the benefit of a lathe! Certainly his innovative and individualistic approach shows in both the external appearance of the quirky little 2cc ignition engine, and on the inside too.
As an engine builder myself, I would have some difficulty in building this engine successfully as designed. The crankcase is split vertically, the two parts being held together with only three screws, two at the top and only one at the bottom. This makes it difficult to get a gas tight seal between the halves of the case. The cylinder liner slips into the assembled case, the bottom of the liner coming to rest on a ledge in the case. The liner must be a gas tight fit within the case, yet not so tight as to spring the case halves apart and allow a leak. In the region of the ports there is very little surface to provide a gas tight seal. The cylinder fins slip over the liner and the whole liner and fins are retained by just 2 screws at the front and one at the rear, each only very small at 8BA (Ed: about 2-56). The fins have to make a seal on the top of the cylinder liner; there is no "button" or other seal at the top end. The transfer passage is at the front of the engine, and twin exhaust ports are at the rear.
The positioning of the ports in the cylinder give rise to an odd piston shape. In order to get normal exhaust and transfer event timing, the depth of the piston skirt at the rear of the engine is considerably lower than at the front of the engine. A curved passage has been carved into the rear of the case to give clearance at bottom dead centre for this very low piston skirt extension. This sculpture can be seen in the previous photograph.
The counterbalanced crankshaft is steel and runs in a bronze bush pressed into the case. A small home-made ball thrust bearing between the crank disk and the crank case takes the forward load on the crankshaft. The crankpin is pressed and riveted in place. The front end of the bearing bush projects from the front of the case and is the mount for the timer in the usual way. The timer itself was of conventional design, though the frame was sculpted from magnesium, now very black with oxidation. For some strange reason, the crankshaft journal is tapered, being smaller diameter at the front than at the rear. I once read somewhere, but perhaps in a dream, that some O&R engines had a tapered crankshaft and bush in order to take up radial slack in case of wear. But maybe I made that up. Put it down to old age! Perhaps this too was P E Norman's idea. It would be rather odd if this was the case, since the thrust bearing would prevent any forward shaft movement, making the tapered-journal idea irrelevant.
Sculpted is a good word for this engine, after all that was the man's trade. The external shape of the crankcase has been whittled away by some means to leave only the metal necessary for the job, and then polished. The rear of the engine has a strange mount; neither radial nor a beam mount. It has two rearward projecting lugs each tapped for a single 6BA bolt. As can be seen in the photo of the engine with the tank attached, it was designed for inverted running.
Internally, there is machining only where necessary, and this appears to have been restricted to simple turning. There is no evidence of any milling, but there are marks which would indicate that general metal removal, and in particular the shaping of the transfer passage, has been achieved by chiseling, filing and scraping. The case is aluminium, so hand working would not be difficult. Remember, this guy was a sculptor, so that is hardly surprising.
I did attempt a restoration, involving re-boring and attempting to run the motor otherwise as found, which was not a great success. I tried a new liner and redesigned piston and porting, but all to no avail. The motor would run, but would not pull the skin off even a very lightly baked rice pudding. It leaked all over the place. Compression ratio was very low but I was not sure the fragile thing would stand much of an increase. The major problem was the effective sealing of the crankcase. It really needed the mating surfaces to be re-machined, then the hole for the cylinder in the assembled case to be re-machined. I was in danger of needing to make a replica engine rather than a restoration of the existing one, so I swallowed my pride and gave in. The motor was tidied up, all original parts installed, and it was handed back to its owner. He would rather have the original unadulterated 60 year old engine than a much modified almost-replica nothingness.
At least I had the privilege of having an engine through my hands that was the product of hands more gifted than my own. Have a look at the pictures of the engine in the condition as received. The photo here of the complete engine, with it's tank, shows it as it was when handed back to its keeper.
EpilogPE passed away in July, 1964, stricken while flying his Comper Swift on Epsom Downs.