Some Notes on the Bristol Cherub and its Inner Works
by J. Riend
Photographs by Mr. Richard Grainger
Published 10 Mar 2023; Revised 16 Mar 2023
While conducting research on Jack Irwin’s Meteormotor, I noticed the very interesting Bristol Cherub engine in Caunter’s 1930 book [d]. Always on the lookout for a new vintage engine to model, I set out to see what I could find on this engine with its unfamiliar (to me anyway) valve train. I quickly discovered there in precious little detailed information to be found on this engine despite it being quite popular in period light planes. I did eventually find several Journal/Magazine articles and an Instruction manual for the Cherub 3, but none of them had that all important detailed cross section drawing showing us what is going on inside the engine.
Decent photographs of the engine are also scarce but I did get several high-resolution photo hits from a Museum in Poland [a] and a Scale Model site in the UK [b]. The Polish Aviation Museum in Krakow has a Cherub I on display. Their photos show their Cherub I, clean and freshly painted on their display stand.
The UK photos find was even more rewarding. Turns out the Cherub 3 engine depicted in the article [b] was recently refurbished by the son of the father-and-uncle team that designed the Granger Archaeopteryx aircraft it was going in.
Mr. Richard Granger was kind enough to share various Cherub 3 related items from his personal records including, a trove of Cherub 3 internal component photos (taken at Vintech during the rebuild), an instruction manual for the Cherub 3 and article by his uncle and father on the design of the Archaeopteryx aircraft.
In the end there were no drawings found that might lead to a 3D model (still hoping Rolls-Royce Heritage Trust, Bristol Branch will answer my request for information on the Cherub). But through the generosity of one individual we are getting a glimpse of the Cherubs inner works.
Special thanks to Mr. Richard Granger for sharing his Cherub photos.
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| Cherub 3 Walk Around. Rightmost image. lower left, has the best view of the valve rocker. | |||
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| Cherub 3 Walk Around | Magneto | As Received: Cherub 3 | As Received: Cherub 3, Cherub 1 |
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| Crankcase | Right Hand Cylinder | Cracked Cylinder Head | Cylinder Head Casting, New Head |
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| New Cylinder Head | Miscellaneous Cherub 3 (top) | Miscellaneous Cherub 3 Parts (top) | |
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| Center and Right Bottom: Cherub 3 valve springs, rocker shafts with fingers, pistons, big-end bearings, connecting rods. | Cherub 3 Oil Pump, Pistons | Cherub 3 Induction Tee, Nose Case, Pistons | Cherub 3 Cylinder Heads, Barrels |
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| Cherub 3 Valves and Guides | Cherub 3 Induction Tee, Nose Case, Connecting Rod Big-End Bearings | Cherub 3 Camshaft and Crankshaft | Cherub 3 Crankcase, Induction Tube, Crankshaft |
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| Cherub 3 Camshaft | Cherub 3 Rocker Shafts with Fingers | Cherub 3 Miscellaneous Parts | |
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| Cherub 3 Oil Pump Feeds | Cherub 3 Oil Pump | Cherub 3 Reassembly | |
References
a. Polish Aviation Museum in Krakow
b. The Granger Archaeopteryx
Nottingham Model Aero Club
Aero Modellers Forum: 1/2 scale Granger Archaeopteryx
c. Shuttleworth, Old Warden Park, Biggleswade, Bedfordshire, SG18 DX
d. Light Aero Engines, A Practical Manual Describing the Chief Types of Light Aero Engines, and Giving Instructions for Their Maintenance. By Cyril Francis Caunter. · 1930, Bristol Cherub engine, pp. 22, 91-94
e. Aviation, Vol. 20, No. 15 (Apr 12, 1926 ), New York, pp. 555-556, ill.
f. Aviation Week Mar 19, 1923.
g. Flight, the Aircraft Engineer, Vol. 18, No. 2, 1926, London, pp. 19-22, ill.
h. “Bristol Cherub”, The Aeroplane, Vol. 30, No.1 (Jan 6, 1926), London, pp. 22-24, Ill.
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