OS Helicopter Engines

Ogawa Model Manufacturing Co Ltd of Osaka Japan.

OS were well established as manufacturers of powerful high quality engines having started out in 1936.  Unfortunately they were more expensive than contemporary UK products due to import and distribution costs so could only be afforded by the more 'affluent' modeller.

Note that OS also made the Cougar range of radio equipment however, this was only until 1975 after which they concentrated on engine development.

Link here for full pictorial history to modern day of OS engines.


1970 advert - OS engine prices in Australia??


OS Max-H60 - Engine test - Aug 1971

Note that in later years the designation 'H' would be used by most manufacturers as a generic code for the specific helicopter variant of an engine however, for this model in the OS range it is (as yet) not the case.  Also known as the 'Gold head' engine and fitted with the latest 1971 revised carb; cross-flow scavenged with a power output of 1.08 Bhp at 14200 Rpm (5% nitro) silenced.


1972 advert

OS Series 72 Carb - Review - 1972 - revised operation due to the 71 version infringing on helical barrel movement patent in Japan...???


1973 advert


Aug 1974 advert

OS Max-25RC - Engine test - Apr 1974

Developed from the 20 size engine to utilise the same castings and mounting thereby allowing a silencer to be used with out any loss of performance to the previous 20 when un-silenced.  Fitted with the latest OS type 21 carb and with loop scavenging, power not quoted.

OS Max-H60F GR (Blackhead) - Quick look and preview test.

More powerful version of the 'Gold head' engine and called the 'black head' model (just to confuse with the Webra 'Black head'??).  Still loop scavenged bit with a slightly larger carb than the '73' model giving a power output of 1.1 bhp @ 13500 Rpm (5% nitro) silenced; very respectable given that the OS silencer was considered one of the most noise reduction effective of the period.


Nov 1975 advert  

Complete revision of many engines incorporating Schnuerle scavenging as standard for the performance models with cross-flow porting kept for 'budget' models.

OS Max 60F - Engine overview of development of the cross-flow model - Feb 1975

OS Max 60F-SR - Engine review - Jul 1975.  General comments and checks but no power figures.

OS Max 60F-SR - Engine test - Sep 1975

Full test and construction review.  Engines came supplied with the OS-704 silencer and the type 74 carb giving a power output of 1.25 Bhp @ 15700 Rpm (5% nitro) silenced.  This equated to a loss of 20% compared to un-silenced though it was reckoned the outlet pipe could be opened up a little to release more power without an real noticeable noise increase after all the silencer was designed for the lesser powerful engines.


Feb & May 1976 adverts

OS Max 40F-SR comparison - Engine review comparison to the Webra Speed 40 - Jan 1976

OS Max 40F-SR - Engine test - May 1976

Full test of the high performance Schnuerle scavenged model; fitted with the latest OS-743 silencer and type 4B carb gave 0.87 Bhp @ 15300 Rpm (5% nitro) silenced.


Sep 1977 advert

Introduction of the 25 Schnuerle scavenged FSR engine, the genesis of the OS range of small helicopter engines that was to become the defining model through its various incarnations (up to a 37!!!) over the next forty years.

OS 45FSR-H introduced to the Japanese and American market.


May 1978 advert  

OS 25FSR - Engine review - Jan 1978

Apart from bore and stroke the engine was completely redesigned over the plain bearing 25RC; supplied with the OS-762 silencer and type B automatic carb but no power figures quoted.

OS 45FSR-H - Engine review - Feb 1978.  Bore and stroked version of the aero 40 FSR with quoted power as 1.3 Bhp @ 15000 (silencer ??) with a revised 4C carb for better mid range response and large heat sink head.


Feb 1980 advert

Second helicopter engine, the OS 50FSR-H designed with the same principle as that for the 45H i.e. increased bore and stroke with the same layout to allow a direct replacement.


OS 61FSR-H - Engine review of the latest OS helicopter engine variant - Nov 1981.


OS 61FSR-H - Engine test - Sep 1982.

OS 28F-H quick look

OS 28F-H - Engine review - Nov 1982; OS now had helicopter engine variants covering the three major model size ranges.


OS Max 50 FSR-H - Engine test - May 1983.

Very powerful helicopter specific engine at 1.26 BHP with silencer, oft fitted in lieu of an Aero 60 given its extremely good carburation which for a helicopter was paramount in achieving reliable flight.






1988 - OS 7 series carb strip  -

1988 OS 46 first look

1989 advert New releases.

1990 - OS32F-HX engine review  - 

1992 - OS 60B carb instructions

1994 - OS 20C carb instructions   3H and 20C carbs

OS Max 61 SXH & RXH manual  -  Ring engine version



OS Max28FSR-H Dykes piston ring (0.9 / 16K rpm) / Max32FSR-H Dykes ring and rear cone start / Max45FRS-H ringed(1.3 / 16K rpm) / Max50FSR-H dykes (1,45 / 15K rpm) / Max61VF-H rear exhaust ringed (1.7 / 16K rpm) / Max61VF-H ABC rear exhaust ABC piston/liner (1.7 / 16K rpm) / Max61FSR-H ringed (1.7 / 16K rpm) / Max61FSR-H ABC piston and liner (1.7 / 16K rpm) / Max 46HSF


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