REFLECTOR: A question about engines

Al Gietzen ALVentures at cox.net
Sat Feb 5 18:34:51 CST 2005


Randy;

 

I've written tomes here in the past about engine selection, and I guess it's
in the archives somewhere; but I will add a few comments again.

 

I spent considerable time researching engine choices before I chose. I don't
advocate either certified or auto conversion.  As Andy said, it is very much
a personal thing. I will say that going alternative engine is definitely not
for everyone; but for me, I could not have been satisfied bolting on a
standard aircraft engine.  I am fortunate, I think, in that I have fairly
extensive background in engineering design and analysis, and I have been a
sort of driveway mechanic since I was a kid.  I think both of those are very
helpful, unless there is a standard to follow.

 

And there really isn't - yet.  That's why I can't disagree entirely with
Dave Dent's view that auto engines don't work.  The stats are probably in
his favor, because a lot of trial and error goes on, and almost every
installation is different in significant ways. There are just too many
'firsts' to avoid things going wrong.  So I don't think Ronnie "whimped out"
at all. He made a smart choice for himself.

 

I was after two basic things.  Better performance and better reliability.
The better performance is the easy part.  Aircraft engines are well proven,
and the installations are standard, but I am not impressed with the design
from either point of view.  There are still the occasional valves dropping
into cylinders, the connecting rod - and even crankshaft - failures.  For
the basic engine, my research convinced me that you cannot beat the
simplicity and ruggedness of the rotary for aircraft application.  And, its
power to weight ratio is right up there among the best.  I also like that it
allowed me to make a more streamlined cowling (more hours).

 

Beyond that there are other advantages of smoothness, and much lower
downstream operating (repair) costs, etc.  And there are other
complications.  Ron mentioned what are the two main complications; reduction
drives and cooling systems.  Both are solvable, and I think the redrive
issues are being pretty well addressed once everyone began to understand
about torsional resonance issues.  Tracy Crook's planetary reduction drive
is reasonably well proven for the rotary, although I may be the first to
prove it on a 3-rotor.  

 

Designing a cooling system requires some understanding of fluid flow, heat
transfer, aerodynamics of scoops, and more; as well as some knowledge of
what has worked for others.  There are quite a few systems flying and
working now, but probably not two alike.  But it can be made to work, you
just have to be thorough.

 

My installation is pretty much one-of-a-kind.  It has certainly added to the
hours on building, I don't know how many, but somewhere in the 500-700 hour
range (out of over 3000).  Overall the calendar time of my project has been
paced mostly by available hours and $$, and since much of the engine work
overlapped other stuff, I don't think the custom engine added more than 6 -
8 months.  I also did custom work on the airframe which added time.

 

My setup is probably ideal for an XL, although for that I might add a turbo.
So after I have flown for 500 hours or so, and everything is working fine,
you can copy mine.  I'm guessing you'll want to be flying before then.

 

If you haven't already been there, you can see more about my engine at 

http://members.cox.net/alg3/airplane.htm .  Follow the links to 'Engine', '
<http://members.cox.net/alg3/Dynamometer%20test%20report.htm> Engine
Dynamometer Test', and 'engine run video'.

 

Now if I can just get all this EFIS and avionics stuff wired up, I might
eventually get it in the air!

 

Best of luck with your project,

 

Al

 

 

 

-----Original Message-----
From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
Behalf Of Randy Wharton
Sent: Friday, February 04, 2005 4:23 AM
To: reflector at tvbf.org
Subject: REFLECTOR: A question about engines

 

I bought my XL kit last summer after taking the company XL-5 for a spin and
loving it. 271TC has a Continental 550 on it, and I've just kind of planned
on putting the same on mine. But I'm really getting daunted by the $40-45000
price tag, especially when I hear guys talking about Chevy V8s, Subaru's
etc, even though I know that water cooling adds a new level of complexity,
not to mention weight to the plane.

 

I know that if I throw the question out there about what people recommend,
I'm going to get a ton of different answers, because everyone probably loves
the powerplant they have, but I'm not committed to any particular one at
this point. I'm quite sure that the Conti 550 is the premier powerplant,
assuming that a Conti 550 is in the budget, but what I haven't found is a
source (pamphlet or article, or something like that) that lays out the pros
and cons . As with any engineering task, there are advantages and
disadvantages that have to be weighed according to how the engineer wants to
play the game, and much of it comes down to a personal choice.

 

Is there a single source for information on the tradeoffs between
Continentals, Lycomings, Chevy's, Subarus, Mazda's, etc? I'm guessing
probably not. But in any case, I'd welcome a discussion on what the
considerations are for various options. I know it's a nebulous question, so
I'm ready for a massive download of information. Thanks!

 

Randy Wharton

N248RB XL-RG

http://clik.to/velocity

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