Howard wrote:

Harry:
    My thought at first was the same as yours....... I wanted about the
power a one rotor would put out.... however the numbers stack up very
heavily against the one rotor.    You will eliminate only around 30 lbs from
your engine over a two rotor...... strike one.....  You will need a redrive
which adds probably at least that much weight..... strike two,   You will
need probably the full flywheel weight plus some balance weights..... strike
3..... You will need the same number of accessories at the same weights as
the full engine... thus your power to weight ratio deterioriates..... strike
5.

    If one looks at a two rotor 13B torque curve it is quite possible to
pull 50-70 hp at direct drive prop RPM... the low end torque curve is very
flat.   My feeling is that a peripheral port housing with the ports timed to
bring bottom end torque in rather than top end power would definitely
enhance direct drive possibilities.... unfortunately nobody I know of does
this.
    Looking at direct drive.... eliminate 20 lbs flywheel weight.....
perhaps 25-30 lbs redrive weight..... My numbers say that a 2 rotor direct
drive engine will be lighter, simpler and inherently more dependable than a
single rotor engine with redrive...... so why bother????

                             H.W.

Harry Sheldon wrote:

Greetings & G'day Howard,
         Thanks for response & feedback....Hear what you're saying but local
criteria (Aus) and recent(relative) legastilative changes mean that we can now
have Ultra light experimental cat. MTOW 544Kg max stall 45Kt.
Every gram is significant and once your over 80-90 hp y'r in like Flyn.
I recon that pp na~ 90hp & turbo ~130   'tis adequate?
I can fly (after 40hr restriction zone) anywhere I want across this continent
without having to lodge a flight plan or any other BS ( common sense says that
I'll organise SAR watch anyway) But I'm not COMPELLED!
I am advised that series 4  13B rear housings  are considerably lighter than prior
or subsequent.
If attention is paid to anciliary eqpt I think much more than 30 lbs can be saved
without sacrificing significant reliability?  :-) whadayafink?
I've been going rou'n circles myself for months; same thoughts as your good self,
now decided, but still listening. Be pleased to get your response(es).
Harry S

 
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