RE: OS 91 VRDF experts wanted
NOTES FROM OUR TECH DEPARTMENT
The O.S. Ducted Fan Engines are designed to develop high power at high RPM.
These are used in Jet (ducted fan) Models where the engine drives a turbine-
like impeller (compressor) that draws a large quantity of air through a shroud
to create thrust. These engines are NOT covered under the O.S. 2-year warranty.
Because this is a high-performance engine, reliability is sacrificed.
The Ducted Fan does NOT come with this engine. One must purchase the fan to fit
BOTH the engine size and the specific plane (these fan units are typically
manufactured by the same people who make the plane kit - a company like
Jet Hangar Hobbies (562) 467-0260 )
FEATURES: Rear Exhaust .
Schnuerle Porting
2-piece Crankcase
2-Crankshaft Ball Bearings
Rear-Mounted Carburetor
Drum Rotor Induction
ABN piston/cylinder (aluminum piston with a nickle plated brass
cylinder
INCLUDES: One Assembled .91 VR-DF Engine w/small head
One Set of Instructions and Poster
One Exhaust Adaptor w/screws and O-ring (OSMG2709)
Bellcrank for use with the remote needle assembly (OSMG7258-comes
with the engine!)
SPECS: Construction: Aluminum and Aluminum alloys
Displacement: 0.91 cu in
Bore: 27.7mm (1.09")
Stroke: 24.5mm (.97")
Max Output: 4.8 PS, 4.73 HP at 22,000 RPM
Practical RPM Range: 2,500 - 25,000 RPM
Weight: 662g (23.4oz)
Length: 133.5mm (5.26") from carb intake to front of drive washer
Width: 43.5mm (1.71") neglecting the engine mounting flanges
52mm (2.05") distance between mounting hole centers
Height: 103.3mm (4.07")
Crankshaft: 5/16-24
Needle Settings: High Speed: 2 turns out from fully closed
Low Speed: 2mm gap between the needle and spray bar
(looking down neck of carb) at full
_ throttle.
REQUIRES: Glow Plug (O.S. #8 or #9 (OSMG2691 is recommended)
Tuned pipe (we don't carry, contact the manufacturer of the kit).
Fuel with 20% MINIMUM lubricant content and 20%-50% Nitromethane
Wildcat Ducted Fan fuel exceeds these requirements
COMMENTS: This engine is the "small head" version of the .91 VR-DF engines.
This engine is designed to operate where space is at a minimum.
This engine works w/ Dynamax or Turbax fan units.
JBN 9.23.93
ir/jl
ADDITIONAL COMMENTS: It is suggested that the cutomer uses a Ramtec fan unit
as opposed to the Dynamax unit. The Ramtec has a much
higher pitch which "loads" the engine better.
updt lmm 4/14/09
– If you need more information, use