Tribute to Engine Builder:

Allan Roberts (New Zealand)

Last Update: July, 2005.


This page showcases the amazing diversity in the engine building work of Allan Roberts.

The photos and the descriptions of the engines on this page were most kindly provided by another exceptional Kiwi engine builder, Murray Lane. Click here for a sample of Murray's work.

Click on any photo to view the larger version; click on the label the photo below to read a little mode about the engine (many will go to the same text).

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About The Builder

If you were impressed with the engines, prepare to be humbled when you read about the machinery Allan made them on. Here's the story as told by Murray:

Allan was born in England and shifted to Australia with his folks when he was four. There he served his time as a tool maker. I have known him since 1987 when he came to New Zealand to oversee the installation of machinery for the first aluminium can factory in the country. He spent the period '93 to '96 in South Africa, doing the same thing there. Once the factories were up and running, he assumed the managerial position responsible for the can manufacture operation and performance. The NZ factory supplies to many countries around the Pacific rim.

Allan's first engine was the 60, made in 1972. This was followed by the twin 120. The Mason Mastiff and Chennery Gnome had been completed, and the Blackmore Bentley started before he came to NZ in 1987. The Gypsy was made while he was in South Africa. Apart from the Bentley and the Hercules, Allan took only a year or less to make all the rest.

Allan took his Bentley to the Midlands Model Engineering Exhibition around 10 years ago where it was presented with the top award. He has been a guest speaker for many organisations, at which several of the engines are run. The Bentley runs and sounds like a multi-cylindered motor bike and starts very easily.

All machining has been carried out in his own workshop, under the house, which is just large enough to swing a cat. His machines are very modest: a second hand Hercus lathe, which he had to do up about ten years ago, and a RF25 mill/drill which he bought new. Add to this a Ryobi bench drill which is only good for small holes. Both the lathe and the mill have had their feet jacked up to make the machines a bit more accurate. A digital read out was fitted to the mill after shifting to SA.

The Hercules was finished to its present state before he went to SA. The reduction housing fits over the drives to the sleeves and all 21 shafts fit perfectly in the bearings in the housing. This engine was made before the DRO was fitted to the mill. I guess being a tool maker by trade helps, but he has not been actively involved in this type of work professionally for a long time.

I keep having a dig at him to finish the Hercules, but like me, he has spent most of the last couple of years repairing RC trainers each week ready for the following weekend. Boy are we ever sorry we got mixed up in such a soul destroying hobby. Of course we both blame each other for starting, and are waiting for each other to say, 'that's it, no more'!

Murray Lane, Auckland, New Zealand, July 2005.



About The Engines

60 single

Builder's original design for a water-cooled 60 based on an OS Blackhead. This was used for some months in Allan's radio controlled trainer.


120 twin

Builder's original design; tandem version of the 60. Note one cylinder is air-cooled, other water cooled.


6.5cc sleeve valve single

Builder's design; 6.5cc, 21mm bore, 18mm stroke. Comments. This little engine was built to prove the sleeve valve design for the Bristol /Hercules engine.


Airdisco V8 (two)

Eric Whittle design; 1/9 scale, 10.6cc, bore 11.7mm, stroke 12.7mm, 7000 rpm, 12x6 propeller. Model Engineer Vol 174-6. Original 200hp. Comments. Allan had problems getting these engines to run, due to the mechanical friction when new, and lack of weight in the crankshaft. Eric advised a 3" diameter flywheel until run in. A carburation problem never allowed them to run through the full rev range.


Bentley BR2 rotary

Lew Blackmore design; 1/4 scale, 347cc, bore 33mm, stroke 45mm, 1300rpm, 27.4" propeller. Model Engineer Vol 148-150. Original 24.9 litre, 235hp @1300rpm. This engine has clocked up several hours running at many displays, and always starts very easily.


Hercules 730

Builder's design scaled from an original engine (unfinished); air cooled radial sleeve valve engine, 1/4 scale, 600cc, bore 35.5mm, stroke 44.5mm. Has copper junk heads as per original. Original 38.7 litre, 2500hp @ 2400rpm. I have been trying to get Allan to finish this engine which has been in its present format for over ten years. It only requires the auxiliary drives at the rear to finished it off. I have a number of photos of other parts. There are 70 rings in this engine.


De Havilland Gypsy

Builder's design scaled from an original engine; 1/4 scale, four cylinder air cooled, 60cc, bore 25.6mm, stroke 30mm, 18" propeller. Original 9.2 litre, 185hp @ 2100rpm.


Satra 440

Four cylinder air cooled engine, 40cc, bore 23.8mm, stroke 22.2mm, 2+hp @ 7500rpm, 18x6 propeller. A Bruce Satra design for spark or glow plug. Appeared in Engineering in Miniature magazine.


Gnome 'Monosoupape' B2 rotary engine

Les Chenery design; 1/5 scale, 64cc, bore 18.9mm, stroke 25.4mm, 24" propeller. Original 12.8 litre, 100hp @ 1200rpm.


V12 air cooled engine

Martin Ohrndorf original design; 99cc, bore 20mm, stroke 22mm, 21" propeller, 1000-5000 rpm, 4.3kg.


Roberts 9 cylinder air cooled radial engine

Builder's original design; 54cc, 7-1/4" OD, 8500 rpm, 18x6" propeller. This engine was designed to go in a 1/4 scale Bristol Gladiater, in which the engine had to be less then 7-3/4" diameter.


Vega twin

Air-cooled vee twin, David Parker original design; 9cc, 19mm bore 15.9mm stroke, 8,000 rpm with 12x6 propeller. Model Engineer Vol 156. Allan fitted this to his RC controlled trainer but found that it did not have enough power.


Wankel rotary aero engine

Builder's original design; 10cc. 3,000 rpm to start; turns 20,000 rpm with a 12" propeller. Has lip seals but is extremely thirsty.


Jet FD 3-64

Kurt Schreckling design, 75,000rpm, idle 20,000 rpm; 2.5kg thrust.


Turbo prop engine

Gearbox ratio 14/1, prop speed 8,000 rpm, propeller three blade 24x10.


Pulse jet

Design off the Internet


Mason Mastiff

LC Mason original design; water cooled, flat 4 cylinder, side-valve engine, 24cc, 19mm bore, 22.2mm stroke. Model Engineer Vol 139-40.


Engine collection

The interesting part of this picture is the jet engine test stand on the left-hand side. As well as having all the auxiliary equipment to run the engines, it can also measure the static thrust of the engine. The engine is mounted on a platform, which runs on linear bearings. A mechanical linkage via a fish weighing scale reads the pressure.