Dan,
I think Larry was just doing a bad job of saying he doesn't agree with all
the modifications to the KR like rotary engines, IFR equipment etc...
In my studying of the rotary which seemed to be the perfect substitution
for a traditional piston engine, and the closest thing to a turbine
reliability, but with better economy, I found that the single rotor was the
best weight application to the KR. The 2 rotor was too heavy in the installed
weight for the little KR. The single rotor solves the weight problem, but you
lose the redundancy of the twin rotors. Also the single rotor only puts out 80
hp, so it is not much of an improvement over the VW, for more weight and more
complicated install. Literally the PSRU weighs as much as the engine in the
single rotor application. The fuel economy is not what we need if you do not
want to carry alot of fuel. From what I have read the torque output is better
with the GM 4.3 V6 in Dana's application, and in ours would be better achieved
with a strong 2180 with PSRU, or a Corvair installation. Liquid cooled does
have its advantages in keeping the engine at a more constant temp, but room
must be made for adequate cooling, even if you have to hold short for an
extended period of time, as we sometimes do waiting on a heavy jet to land at
Sanford. They will not let you go until 3 minutes after for wake turbulence,
so this can be 5-6 minutes at idle after taxi and runup. A builder must take
this in to account or he will find himself being towed back to the FBO with his
engine overheated. The single rotor installed weight is somewhere around 200#
so says Atkins Rotary. That is with radiators and PSRU. At only 80hp output,
that is alittle low for me. I am looking at the Honda Accord 2.0L engine, or
the GM 3.4V6 as an upgrade to the VW, after test flying and proving the present
setup is good. It will give me a baseline based on the designer's intentions
as to how much improvement will be seen with the engine change. Both of these
engines have a similar dry weight to the Continental O-200, but raise the hp to
125, & 190 respectively. What is really impressive is what happens to torque
that the direct drive engines miss out on, and that is the multiplication
caused by using a PSRU. The PSRU 1.63:1 ratio raises the 200 foot pounds of
torque provided by the GM motor, to 326 foot pounds of torque due to the use of
a PSRU, according to Robert Finch. This makes the weight penalty incurred by
use of the PSRU more than pay for itself, even if one uses it with a VW engine.
It does not increase HP, but as Embry Riddle has found out while testing the
new diesels, the rated HP is not as important as the torque applied to the
prop. These new diesels are rated at 125bhp, yet produce as much torque to the
prop as the O-360, and so are achieving as good if not better performance than
the O-360 in the C-172s and the Diamond Twinstar, with better economy.
As Larry F is so famous for saying, your results may vary....See ya at Sun N'
Fun....
Colin & Bev Rainey
KR2(td) N96TA
Sanford, FL
[email protected]
or [email protected]
http://kr-builder.org/Colin/index.html
