Marc Wiese wrote:
I know this is not of rotary interest, but it has some interesting
points in it we should keep in mind. I hope a semi-professional
rotary
conversion could be as appealing and economical. Read it
FWIW......
-------------------------------
Subject: The diesel report
From: Thomas Borchert (EDHE) 100137,2113
All,
Well, I've flown the diesel Diamond and spoken at length with the
people
at Diamond. I have yet to talk to Frank Thielert, maker of the
engine,
but here's my preliminary report.
First, keep in mind I'm writing this from a European perspective,
where
<<<Lots-O-Snips>>>
Ok, that's all I can think of at the moment. Questions?
Thomas Borchert (EDHE)
If the FAA certifies this Mercedes A class engine they will also
have
to
certify MecanAir's Mazda based 13B rotary.
What makes you say that Paul? Funk certified a Model A ford engine in
the 30's and that does mean that they have to certify all modelA
engines.
Vance
The rules must have changed. As I understand it the factory must
supply a paper trail on all the parts. As I recall there are two
certifications. You can certify the engine but then you must also
certify the manufacturing facility. Is Mercedes certifying these parts?
BTW A lower RPM larger diameter prop CANNOT make up for THAT much
difference in HP. What say you you about that Vance?
180/125 is 144%. Since your average prop is 85% that means
the prop they are running is 122.4%. Wow! A prop that can generate HP!
160/125 is 128%! 128% of 85% is 108%. Still... unbelievable
prop efficiency. Sounds like bull shit to me.
I think the reason the diesel airplane claims the same climb with
125 HP as opposed to the 180 HP Lyc is the diesel has a constant
speed prop. Apples and oranges. Not a fair comparison.
If they both had fixed pitch props it would be an out and out
lie. Not the first time this company has lied about performance.
BTW who is Thomas Borchert? Does he work for Diamond?
Is this a press release?
Paul Lamar
Those are a lot of the same questions, and conclusions that I came to
after
reading this. The original publications were comparing static thrust
between the Diesel with a constant speed prop and a fixed pitch on the
Lyc. which bogs the lyc down to less than 125 hp. The rate of climb
is probably wishful thinking with a large helping of BS because the
Lyc is stating to make some useful HP at climb speed even with a fixed
pitch prop. The large dia slow prop starts losing significant advantage
as you pass 100 mph (still better but the difference is approching
the same dull pencil curve). Yes they can flat rate the Diesel up
to some altitude, but at the alt. most of us fly the Lyc is still
making more than 125hp and hp is hp (if you are not lying)
A fact worth noting is that it looks like the four place Diamond
Diesel will be primarily the twin engine version.
On the certification note - some VW derived Limbach's are certified
in Germany, and used on certified motor gliders in the USA. I do
not know how they work the paper trail on those. Those are undoubtedly
all new parts from individual suppliers, and mostly not VW. Any
rotary certification would involve a lot of money, and some control
over new part suppliers.
Vance J
Some rambling thoughts folks:
In auto trim, we buy horsepower but drive torque. What do we really look
at for airplanes? My 96 VW Passat TDI makes a whopping 90HP but has nearly
the same torque as a V6. I understand that I have five gears to play with
to get to 120MPH, but it gets there pretty quickly and still gets 40MPG.
Wouldn't a fixed-pitch comparison between a gas and diesel engine still
require different props due to the differences in torque? Or are we worried
about HP and/or Torque -- are we ultimately looking at thrust?
Nope -- NOT an engineer. :-)
Andy H
HP is what makes airplanes fly. Torque is what ever the PSRU gear
ratio says it is. The gear box does not change the HP.
HP = Torque X RPM. Up the Torque and down the RPM and the HP stays
the same.
Paul Lamar
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