① RC 1/4 SCALE 9 CYLINDER BENTLEY ROTARY ENGINE AVRO 504K LMA MODEL AIRCRAFT SHOW RAF COSFORD – 2013
(PART ONE OF TWO)
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CLICK HERE TO SEE PART TWO OF THIS AMAZING MODEL FLYING POWERED BY THE BENTLEY –
ian redshaw flew the avro 504 in the video ,the builder and owner andy johnston kindly gave me these details –
Engine details:
¼ scale
9 cylinder four stroke
33mm bore, cast iron liners of 1mm wall thickness and aluminium finned barrels
45mm stroke
347cc, compression ratio 5.6:1
Super unleaded petrol with belts’n’braces 50:1 oil mix. (I use Bel-Ray HR1 fully synthetic ester 2-stroke racing oil.)
Total loss force fed oil system via engine driven oil pump, approx. 30cc per 10 min flight using Bel-Ray
Rpm range 700-3500
Prop. is 27 ½” diameter x approx. 23″ pitch, period scale blade shape made by EAT propellers, sadly now no longer since the death of Eric Thomas.
Weight 7kg
Avro 504K details:
¼ scale David Boddington/Nexus plans scaled up to 27% (to give sufficient cowl clearance for engine)
Wingspan 116″, 2.95m
O/A length 100″, 2.54m
Covered in Linen Solartex, top surfaces sprayed with Flair Spectrum PC 10 Brown
All markings freehand with Humbrol
Two coats Ronseal Diamond Hard Matt varnish brushed on all over (isn’t affected by oil/petrol or nitro glow fuel )
All up weight 23kg
Futaba 12FG TX 2.4Gig
Futaba R-6014 HS RX x 2
SM Services Opto Isolators x 2
Ignition and RX batteries 2000mAhr Eneloop
Power to servos 3,300 NmH subC via opto isolators
Servos are a mix of Hitec metal geared and Futaba, all non-digital
16 ferrite rings to combat the interference from the unshielded vintage ignition system
The Avro was designed around the Bentley with the provision for exchanging it for a Zenoah 62. The Avro’s maiden flight was on 31st March 2012 with the 62 (and 3kg lead up front, the difference in weight between it and the Bentley) to prove the airframe and it was a great success so a further six flights were made to complete the CAA tests on that day before making the swap and further tests.
The Bentley engine build started in August 2004, it’s test run was 9th January 2008 and the maiden flight in the Avro was 6th April 2012.
There are no noticeable effects of gyroscopic precession from the rotating Bentley affecting the handling unduly, just a slight difference in left and right which may be due to torque and the coarse-pitch propeller. Twenty-two flights with Bentley to date (23/07/2013).
Regards
Andy Johnston
FILMED AT AN RC MODEL AIRCRAFT SHOW RUN BY THE LMA ( LARGE MODEL ASSOCIATION ) AT RAF COSFORD – WOLVERHAMPTON – SHROPSHIRE / STAFFORDSHIRE – WV7 3EX OVER THE WEEKEND OF 20th & 21st JULY – 2013,
