ONE OF the most fascinating unfolding model engineering stories in recent times has been the progress of the Napier Dagger aero engine being built by Norman Lawrence. Just a couple of times a year, Norman takes it to exhibitions for all to see the progress he is making. It is also a source of inspiration for many.
The model is a tour de force. It is an engine of H-24 configuration with all the detail work that involves. It is all made by conventional machining, no CNC is involved, making it even more remarkable.
Norman has always been more than happy to show the engine, which has become more impressive with each passing year. Not just to show it, but to talk to countless visitors about his project.
He also likes to encourage others to show their work. The Dagger will next be seen at the Model Engineer Exhibition in December. Norman says: “I hope many others will enter models or put them on their club stands this year."
For the past hundred-odd years many of the world class judges at the Model Engineer Exhibition competitions have been chosen from within the SMEE ranks and, in addition this year, two highly respected SMEE members, Mike Law and Steve Eaton, have been appointed by My Hobby Store to secure entries for competition and ‘loan’ models, as well as look after the various clubs that are organizing displays and demonstrations. The SMEE itself is, once again this year, organizing impressive areas of displays and demonstrations plus the usual lectures.
As an unfinished model, Norman’s Dagger will be on display, but not in competition. Looking at it now, it is getting to look like it is close to being finished. However, there is still a lot of work to be completed. Meanwhile, you will be able to see rather more of it than would be the case with the finished article. For example, most of the ‘internals’ have yet to be installed, so you can let your jaw drop at the sight of 24 sets of pistons, valves, etc. However, it is the full engine which has the greatest impact.
It is a wonderful looking piece of engineering. It is something that Norman has been passionate about since a teenager, after seeing one in Flight magazine. He promised himself that one day he would build a model of the Dagger. During five years in the RAF, it was always on his mind. And in the following decades.
He finally started work on it nine years ago.
First task was to get hold of some drawings and, as a member of Napier Heritage, eight were bought from them and further information from the RAF Museum Hendon and scaled down. Norman also had the opportunity to visit Hendon and photograph the preserved Dagger there. Various other publications provided some essential information “things like the number of bolts on a part, and drawings of the gearbox which had to be scaled and dimensions calculated.”
Some parts were re-drawn in detail for producing parts in the workshop.
When looking at the model one is amazed at the amount of work. But that is not even half the story.
“More work has gone into jigs than the engine itself. Pails full!
“For instance I used six jigs on the basic parts of the carburettor. There must have been 15,16 or more used in total on the carb. And there is nothing simple about many of the jigs, with datum points vanishing on curved surfaces.”
Norman was never going to be anything other than an engineer. His father made him his first lathe in the 1940/50s. After five years in the RAF he was occupied with things like fitting Vincent engines into Norton motorcycles in the days when racing car builders had to buy complete Norton bikes to get an engine and the bikes were re-fitted with other powerful engines.
Norman worked for himself for many years, with a workshop producing items for the RAF, Atomic Energy Authority, Boulton & Paul and parts he designed for drilling rigs for BP. That stopped when he was ill, but it meant that he could get on and start the Dagger, and moved from his workshop to his home workshop with some nice machinery including a Bridgeport milling machine, Hauser jig borer, SIP rotary table, DSG and Hardinge lathes.
The original Napier Dagger was designed by Frank Halford, a development of his Rapier H-16 engine. Its H-24 layout gave a compact and powerful engine, basically two vertically opposed in-line engines placed side-by-side, driven by parallel crankshafts. The layout gave a well balanced engine which ran smoothly up to 4000rpm. The engine was used in aircraft such as the Hawker Hart and Handley Page Hereford bomber in the 1930s.
Norman’s model is of the Dagger VIII, the final development of the engine. With a bore of 3.813” and stroke 3.75” displacement was no less than 16.8 litres (1027 cu in) all in a package 80” x 22.5” x 45.125”. Compression ratio was 7.75:1.
There are two valves per cylinder and the engine is fitted with a single speed centrifugal type supercharger. Power output was 1000hp at 4200rpm at 8750 ft and +4lb per sq in. In a description of the prototype Martin Baker MB2, the Dagger was described as sounding like a sewing machine and, unlike succeeding Martin-Baker fighters, the Dagger never let the MB2 down.
The Dagger evolved into the Napier Sabre, another H-24, but with liquid cooling and sleeve valves, and was one of the most powerful piston engines developing 2200hp.
So what is left to do on Norman’s model? The carburettors are now finished. Next it will be the boost control followed by the oil pumps and the filter arrangement and finally housings for the vertical drives from the camshaft. Then it has to be stripped down and final fittings made, and re-assembled. It doesn’t sound much, if you say it quickly, but it does, for example, include cutting lots of gears including bevels in case hardening steel. Once that’s finished there is the variable pitch and prop.
So it will be a while before it is finished, and for light relief Norman is finishing off a Columbia locomotive to the Martin Evans design.
Photo 1 - Norman (left) with exhibition visitor
photos 2-7 all by Norman Lawrence showing Dagger progress
