Hi! Karim /All
IMHO you have the incorrect info. probably a misunderstanding .
With a direct drive low RPM engine of say 120 hp you will not get the
maximum torque you could get from a 120 hp high rpm engine geared down to
the same prop speed.
The 80% gear box loss may be a relevant factor but the torque at the prop.
on the geared engine
could well be superior even so, not withstanding any extra ordinary
capability of the diesel!
Power , torque , and RPMs are all inter -related( HP = 2#NT/33,000 where #
is 3.142,N is RPM and T is torque in ft lbs.) For instance the 4 cylinder
1600cc Rotax at 5,500 RPM with a gearbox takes a 6 cylinder 3,000cc Jabiru
at 2900 RPM direct drive to be in the same "ball park"
The differentiation amounts to whether you feel happier with a high revving
engine stressed to high limits carrying a gearbox permantently or a sweet
sounding direct drive plodder without the borderline stresses.
If anyone wishes to "pick spots " off these statements I'd be pleased to
have their pleasure, but do it on the Forum so we can all benefit .
BTW the Chief Engineer at the PFA is called Francis Donaldson.
Regards
Bob Harrison G-PTAG
-----Original Message-----
From: forum-owner@europaclub.org.uk
Subject: Re: Runway length
......... the wilksch is a direct drive engine unlike the rotax that is
geared. That means out of the quoted 120hp that the engine is rated at, you
will only get approximately 80% of the total power since there a loss
through the drive train etc. Talk to Donald Francis, chief PFA engineer and
he will explain all to you. Talked to him in detail about this.
karim.
# 420
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