AIRCRAFT INVESTIGATION

performance calculations for the Roberts 6-X aircraft engine

Roberts 6-X liquid-cooled two-stroke 6 -cylinder inline engine 75 [hp](55.9 KW)

Design : Edmund W. Roberts 

introduction : January 1914 country : United States importance : **

applications : Benoist XIV

normal rating : 75 [hp](55.9 KW) at 1225 [rpm] at 0 [m] above sea level

reduction : 0.9 , valvetrain : SOHC

weight reduction gear : 2.8 [kg]

fuel system : two carburetors oil system :

weight engine(s) dry without reduction gear : 127.8 [kg] = 2.24 [kg/KW]

bore : 114.3 [mm] stroke : 127.0 [mm]

valve inlet area : 16.7 [cm^2] one inlet and one exhaust valve in cylinder head

gasspeed at inlet valve : 22.4 [m/s]

throttle : 90 /100 open, mixture :13.0 :1

stroke volume (Vs) : 7.820 [litre]

compression volume (Vc): 1.983 [litre]

total volume (Vt): 9.802 [litre]

engine height : 80 [cm]

engine length: 0.00 [m]

specific power : 7.2 [kW/litre]

torque : 436 [Nm]

engine weight/volume : 16.0 : [kg/litre]

average piston speed (Cm): 5.2 [m/s]

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intake pressure at 0 [m] altitude Pi : 0.98 [kg/cm2]

mean engine pressure (M.E.P.) at 0 [m] altitude Pm : 6.08 [kg/cm2]

compression pressure at 0 [m] altitude Pc: 7.20 [kg/cm2]

estimated combustion pressure at 0 [m] Pe : 28.75 [kg/cm2]

exhaust pressure at 0 [m] Pu : 3.84 [kg/cm^2 ]

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compression-start temperature at 0 [m] Tic: 391 [°K] (118 [°C])

compression-end temperature at 0 [m] Tc: 563 [°K] (290 [°C])

average engine wall temperature at 0 [m] : 476 [K] (202 [°C])

caloric combustion temperature at 0 [m] Tec: 2241 [°K] (1967 [°C])

polytroph combustion temperature at 0 [m] Tep : 2250 [°K] (1977 [°C])

estimated combustion temperature at 0 [m] Te (T4): 2221 [°K] (1948 [°C])

polytrope expansion-end temperature at 0 [m] Tup: 1240 [°K] (966 [°C])

exhaust stroke end temperature at 0 [m] Tu: 1145 [°K] (872 [°C])

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emergency/take off rating at 1394 [rpm] at sea level : 78 [hp]

Thermal efficiency Nth : 0.329 [ ]

Mechanical efficiency Nm : 0.719 [ ]

Thermo-dynamic efficiency Ntd : 0.237 [ ]

design hours : 108 [hr] time between overhaul : 4 [hr]

dispersed heat by cooling fluids at 1225.00 [rpm] at 0 [m]: 102.06 [Kcal/minuut/litre]

** internal heat transfer (a1): 5154.03 [Kcal/minuut/m2)

required cooling surface : 3.47 [m2]

fuel consumption optimum mixture at 1225.00 [rpm] at 0 [m]: 21.10 [kg/hr]

specific fuel consumption thermo-dynamic : 254 [gr/epk] = 341 [gr/kwh]

estimated specific fuel consumption (cruise power) at 0 [m] optimum mixture : 350 [gr/kwh]

estimated sfc (cruise power) at 750 [m] rich mixture : 358 [gr/kwh]

specific fuel consumption at 0 [m] at 1225 [rpm] with mixture :13.0 :1 : 377 [gr/kwh]

estimated specific oil consumption (cruise power) : 45 [gr/kwh]

Literature :

Roberts Motor Company Aircraft Engines | Old Machine Press

Praktisch handboek vliegtuigen deel 2 page 10

ROBERTS 6X AEROPLANE ENGINE | Simanaitis Says

DISCLAIMER Above calculations are based on published data, they must be

regarded as indication not as facts.

Calculated performance and weight may not correspond with actual weights

and performances and are assumptions for which no responsibility can be taken.

Calculations are as accurate as possible, they can be fine-tuned when more data

is available, you are welcome to give suggestions and additional information

so we can improve our program. For copyright on drawings/photographs/

content please mail to below mail address

(c) B van der Zalm 01 January 2021 contact : info.aircraftinvestigation@gmail.com python 3.7.4

notes :