Isotta Fraschini Asso 750

The Isotta Fraschini Asso 750 was an Italian W 18 water-cooled aircraft engine of the 1930s. Produced by Isotta Fraschini the engine displaced just under 48 l (2,900 cu in) and produced up to 940 hp (700 kW). Together with the Asso 200 and the Asso 500 the Asso 750 was part of a family of modular engines, that used common and interchangeable components to lower production costs.

Asso 750
Preserved Asso 750
Type W 18 piston engine
National origin Italy
Manufacturer Isotta Fraschini
First run 1934

Technical description

The W-18 Asso 750 had three six-cylinder in-line banks made of chrome-manganese steel, each joined by a single cast aluminum head for each bank of cylinders.

Operational history

A version with an effective power of 940 hp (700 kW) was optimized for the Savoia-Marchetti S.55X used for the trans-Atlantic flight of Italo Balbo.

Variants
Asso 750
Direct-drive, unsupercharged.
Asso 750 R.
Development with modified crankcase and crankshaft, fitted with a 0.658:1 reduction gear. Maximum power output 940 hp (700 kW).
Asso 750 R.C.
Asso 750 R.C.35
The 750 R. fitted with a supercharger, rated altitude of 3,500 m (11,500 ft).
Asso 750 M
A 57.25 l (3,494 cu in) racing development with 150 mm (5.9 in) bore and 180 mm (7.1 in) stroke, for the Macchi M.67, re-designated Asso 1000 Ri.

Applications

Engines on display

At the Italian Air Force Museum two Isotta Fraschini Asso 750 are exhibited: A direct-drive Asso 750 and an Asso 750 R.C.35 with reduction gear and supercharger.

Specifications (Asso 750)
3/4 front view

Data from Il motore Isotta Fraschini Asso 750[1][2]

General characteristics

  • Type: W-18 liquid/water-cooled
  • Bore: 140 mm (5.5 in)
  • Stroke: 170 mm (6.7 in)
  • Displacement: 47.6 l (2,900 cu in)
  • Length: 2,196 mm (86.5 in)
  • Width: 1,060 mm (42 in)
  • Height: 1,060 mm (42 in)
  • Dry weight: 630 kg (1,390 lb)

Components

  • Valvetrain: Overhead valves 2x inlet and 2x exhaust per cylinder
  • Supercharger: No supercharger fitted to this variant: supercharger available in other variants - (R.C.35 rated to 3,500 m (11,500 ft)).
  • Fuel type: Gasoline 87 Octane
  • Oil system: pressure
  • Cooling system: Liquid/water
  • Reduction gear: Not fitted to this variant: reduction geared variants available (0.658:1 R. and R.C.35).

Performance

  • Power output: Normal 800 hp (600 kW) at 1700 rpm; Take-off 850 hp (630 kW) at 1750 rpm; Max 900 hp (670 kW) at 1900 rpm
  • Compression ratio: 5.6:1
  • Specific fuel consumption: 0.485 lb/hp/h (0.295 kg/kW/h)
  • Oil consumption: 0.00187 lb/hp/h (0.00114 kg/kW/h)
  • Power-to-weight ratio: Normal 0.95 kW/kg (0.58 hp/lb) max 1.129 kW/kg (0.687 hp/lb)
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See also

Related lists

References
  1. "Il motore Isotta Fraschini Asso 750" (PDF) (in Italian): 655–657. Retrieved 6 November 2018. Cite journal requires |journal= (help)
  2. "Aero Engine Data Sheets:Mechanical Data tables:Italian Aero Engines". oldengine.org. Retrieved 7 November 2018.

Further reading
  • Cei, Leoniero; Fiore, Amedeo (1934). Il motorista d'aviazione (in Italian). Milan: Ulrico Hoepli.
  • "Jotti da Badia Polesine". Annuario dell'Aeronautica Italiana. Milan.: Libreria Aeronautica: 222. 1934.
  • "Foreign Aero Engines at Olympia". Flight. Vol. XXI No. 30 (1074): 761–778. 25 July 1929. Retrieved 8 November 2018.
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