Direct drive versus gearboxes is an interesting point. Direct drive can be
lighter and yes you don't have gearbox rattle however the Rotax 912S for
example has a max prop speed of 2386. That means prop tip speed is much less
than direct drive and efficiency is up. Slower prop speed is particularly
more efficient at the slow speed end of the flight envelope, that is take
off and climb. Prop speed greater than 2500 will result in considerably less
efficiency in Europa type aircraft.
Noise is becoming a huge problem in Europe and I think the days are numbered
for noisy aircraft flown purley for pleasure. Noise off the prop is
predominatley a function of the tip speed. Tip speed (in m/sec) = prop
speed in rpm * prop diameter in cm * PI / 6000.
Fuel consumption of a Rotax is a fraction of that on an O200 (not a problem
to our cousins stateside where gas still costs around 20p / litre). However
don't forget if you want range you have to carry the fuel so if the fuel
consumption is 30% greater your range is reduced correspondingly.
Water cooled verses aircooled. Aircooled is much simpler to install and
maybe simpler to maintain but is it as stable regards temperature change.
Plus I don't see to many cars with aircooled engines?
Last of all - has anyone else done this before. I reckon it takes 10 times
as long to be a trail blazer. If someone has done what you think is a good
idea copy them. It'll take far longer to do it yourself.
Points to check?
1 Propeller efficiency may reduce the effective power
2 Propeller tip speed may make the aircraft noisy
3 Fuel consumption at a given speed may effect cost and range
4 Cooling
5 Has someone else done all the donkey work
Well that's what I think.
Jerry
lts@avnet.co.uk
http://www.avnet.co.uk/touchdown
----- Original Message -----
From: <ptag.dev@ukonline.co.uk>
<europa@avnet.co.uk>
Subject: RE: Continental O-200
|