Lemans
Well-Known Member
About torque and airscrews.
It seems to me that the more I know the less I understand.
Let me explain.
I like to replace my Rotax 503 by a small diesel 4-stroke engine.
Calculations are telling me that I need at least a turbo charged 700 cc. (42 inch³)
This engine gives an relative flat torque curve around 70 Nm. (620 lb/in)
Usable range on engine revs, 1700 – 4500 rpm.
The max. torque of the Rotax is 55 Nm in a very narrow range.
The reduction drive used whit the Rotax is a 2.58 so, the propeller torque is 142 Nm.
If I use a reduction on the diesel of 2.00 the torque at the propeller (airscrew) is 140 Nm.
Now, calculating the power output for the diesel , I come up whit 42 bhp while the Rotax specs give me a power output of 50 bhp.
Do I have to bother about the final bhp output or is only propeller torque important ?
Regards Johan
It seems to me that the more I know the less I understand.
Let me explain.
I like to replace my Rotax 503 by a small diesel 4-stroke engine.
Calculations are telling me that I need at least a turbo charged 700 cc. (42 inch³)
This engine gives an relative flat torque curve around 70 Nm. (620 lb/in)
Usable range on engine revs, 1700 – 4500 rpm.
The max. torque of the Rotax is 55 Nm in a very narrow range.
The reduction drive used whit the Rotax is a 2.58 so, the propeller torque is 142 Nm.
If I use a reduction on the diesel of 2.00 the torque at the propeller (airscrew) is 140 Nm.
Now, calculating the power output for the diesel , I come up whit 42 bhp while the Rotax specs give me a power output of 50 bhp.
Do I have to bother about the final bhp output or is only propeller torque important ?
Regards Johan
