Franklin O-335

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O-335/6AC
FranklinO335engine1.JPG
Type Flat-6
Manufacturer Franklin Engine Company

The Franklin O-335 (Company designations variations on 6A4) was a series of air-cooled aircraft engines of flat-six configuration.

Design and development[edit]

These engines were commonly vertically mounted and used to power many early helicopters in the United States. They were closely related to the 2A4 and 4A4 2- and 4-cylinder engines. In various subtypes, the 6A4 remained in continuous production from 1945 to the time Franklin's United States operations ceased in 1975, with versions continuing in Polish production into the 1990s.

In 1947 this engine was modified into a water-cooled version by the Tucker Car Corporation for use in the 1948 Tucker Sedan. Tucker liked the engine so much that he purchased the Aircooled Motors/Franklin Engine Company and it remained under the ownership of the Tucker family until 1961.

Variants[edit]

O-335
Military designation
6A-335
180 hp (134.2 kW) at 2,800rpm
6AL-335
150 hp (111.9 kW) at 2,600 rpm
6A4-125
125 hp (93.2 kW) at 2,200rpm
6A4-130
130 hp (96.9 kW) at 2,200rpm
6A4-135
135 hp (100.7 kW) at 2,450rpm
6A4-140
140 hp (104.4 kW) at 2,375rpm
6A4-145
145 hp (108.1 kW) at 2,600rpm
6A4-150
150 hp (111.9 kW) at 2,600rpm
6A4-165
165 hp (123.0 kW) at 2,800rpm
6A4-200
200 hp (149.1 kW) at 3,100rpm
6AG-335
220 hp (164.1 kW) at 3,400rpm
6AG4-185
185 hp (138.0 kW) at 3,100rpm
6AGS-335
260 hp (193.9 kW) at 3,400rpm
6AS-335
240 hp (179.0 kW) at 3,200rpm
6V-335-B
210 hp (156.6 kW) at 3,100rpm
6V-335-B
210 hp (156.6 kW) at 3,100rpm
6V-335-A1A
200 hp (149.1 kW) at 3,100rpm
6V-335-A1B
200 hp (149.1 kW) at 3,100rpm
6V4-165
165 hp (123.0 kW)
6V4-178
178 hp (132.7 kW) at 3,000rpm
6V4-200
200 hp (149.1 kW) at 3,100rpm
6VS-335
225 hp (167.8 kW) at 3,200rpm

Applications[edit]

Specifications (6AL-335 / 6A4-150-B3)[edit]

Franklin O-335/6AC Engine.

Data from [1]

General characteristics

  • Type: 6-cylinder air-cooled horizontally opposed direct drive supercharged aircraft piston engine
  • Bore: 4.5 in (114.3 mm)
  • Stroke: 3.5 in (88.9 mm)
  • Displacement: 335 cu in (5.49 l)
  • Length: 37.4 in (950.0 mm)
  • Width: 30.8 in (782.3 mm)
  • Height: 21.6 in (548.6 mm)
  • Dry weight: 307 lb (139.3 kg)

Components

  • Valvetrain: OHV, 1x inlet valve, 1x exhaust valve operated by pushrods
  • Supercharger: mechanically driven supercharger
  • Fuel system: 1x Marvel-Schebler MA-3SPA updraught carburettor
  • Fuel type: 80 Octane gasoline
  • Oil system: 80 S.U. secs (15.6 cs) grade pressure fed at 40 psi (275,790 Pa), wet sump
  • Cooling system: Air-cooled
  • Delco-Remy direct cranking electric starter motor

Performance

  • Power output:
  • (Take-off): 150 hp (111.9 kW) at 2,600 rpm for take-off
  • (Normal): 150 hp (111.9 kW) at 2,600 rpm at sea level
  • (Cruising): 112 hp (83.5 kW) at 2,350 rpm at sea level
  • Specific power: 0.45 hp/in³ (20.35 kW/l)
  • Compression ratio: 7:1
  • Specific fuel consumption: 0.51 lb/hp/hr (0.311 kg/kW/hr, 229.5 US.gal/hp/hr) cruising
  • Oil consumption: 0.01 lb/hp/hr (0.006 kg/kW/hr, 4.5 US.gal/hp/hr) cruising
  • Power-to-weight ratio: 0.488hp/lb (0.8kW/kg)
  • B.m.e.p.: 137 psi (945 kPa)

See also[edit]

Related development
Comparable engines
Related lists

Notes[edit]

  1. ^ Wilkinson, Paul H. (1945). Aircraft Engines of the world 1945. New York: Paul H. Wilkinson. pp. 80–81. 

References[edit]

  • Gunston, Bill. (1986) World Encyclopedia of Aero Engines. Patrick Stephens: Wellingborough. p. 57
  • Erickson, Jack. Horizontally Opposed Piston Aero Engines
  • Wilkinson, Paul H. (1945). Aircraft Engines of the world 1945. New York: Paul H. Wilkinson. pp. 80–81. 
  • US Department of Transportation Federal Aviation Administration Type Certificate Data Sheet E-238 Revision 12, December 8, 1994.