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d3dw(at)sbcglobal.net
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 Posted: Sun Aug 31, 2008 7:04 pm Post subject: Kit Planes accident and reliability article |
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Frank,
to be honest, the reason we suffered the failures we did with the valve guides is that these engines were rebuilt by people unfamiliar with aviation. Rhiner had the work done by another shop during the last of his tenure and that system followed until you and I started making waves.
The valves guides failed since they were Knurled guides. After mine failed twice, I got another old soob and rebuilt it, but used the original guides, which were never taken out, and just transfered the redrive and intakes systems to the new engine. This engine has done very well without using guides with shoulders, etc.
What I am saying is that these engines were shoddy work and done without an understanding of aviation...knurled guides...that is the sickening part to me. An original soob, or a soob with stock guides would do well if properly installed...though the shoulders and better materials is a plus for sure. don
LarryMcFarland <larry(at)macsmachine.com> wrote:
[quote]--> Stratus-List message posted by: LarryMcFarland
Hi Frank,
The Kit Planes article is extremely well done and I don't contradict
what you said below. Their data only said internals of automotive
conversions and
perhaps carburetor systems were better represented than type certified
engines. The facts are not disputed, that cooling, ignition, fuel
systems and redrives
will be problematic so long as the user builder isn't totally aware of
what a good installation requires. It does take a little more education
for a Subaru
owner than for a Lyc or Cont because certified engines don't allow much
room for variation. If the owner does the study, I believe the Subaru
is capable of being
a better engine in cost per hour for the average builder. It's about
$8K for a Subaru now and $20+K for a Jabaru or 912 and much much more
for the TC engines.
I'm not an engine guy either Frank, but I learned a lot from the
difficulties you experienced and the travails you'd posted before me.
I also made mistakes, but none that cost any serious money or downtime
thanks to you.
Very best regards,
Larry McFarland 601HDS at www.macsmachine.com
Hinde, Frank George (Corvallis) wrote:
[quote] --> Stratus-List message posted by: "Hinde, Frank George (Corvallis)"
Hmmmm.....
I think that's a little bit of a sweeping statement there Larry..If you remember I suffered three valve guide failurs in my Subaru conversion..I would say that as I had only 400 hours that was an appalling failure rate..Fourtunately I was able to re-engineer the package and fix a fundamental flaw in the suppliers product, but that's only because I have a lot of experience in this area.
Most folks I fear have little clue about such things, or about killer vapour lock, how to engineer a cooling system etc.
If somebody with my experience can have such troubles (and who bought an engine package to avoid having to mess with the conversion itself) then the average Joe has no chance.
I would be interested to read the article because anecdotal evidence would appear to dissagree with your statement.
Hopefully the market will weed out poor engine conversions...But at a potentially great cost.
Don't get me wrong there are one or two really good auto conversions, but they certainly are not cheaper on the initial installation cost (comparing an Eggenfelner Soob with an experimantal Lycoming clone) and if you add the extra cooling drag of a water cooled engine vs an aircooled (at least on a fast airplane) then fuel consumption is going to be worse....Ok that last statement is fiercely debated...
Where auto conversions really shine is in rebuild costs are much less..But is that really a big factor in the overall cost of an airplane?..I personally doubt it.
Frank
601 HDS Soob 400 hours
RV7a 330 hours IO360 WAAY faster and better MPG than the Zodiac....Also runs on pump gas
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frank.hinde(at)hp.com
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| Posted: Tue Sep 02, 2008 7:03 am Post subject: Kit Planes accident and reliability article |
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All good there..I guess my point was that shoddy workmanship was the reason for these failures, but there maybe other similar failure modes in different engine packages.
Of course my experiences have made me biased too, but I guess getting parts rebuilt from an aviation shop with years of experience just seems like a very good idea when compared with a guy in a cylinder head shop who shrugs his shoulders when you look at him in disbelief at locktited/knurled valve guides as he says.."Thats how we always do it"..Yes and its just tried to kill me for the third time!
Also the engine package is very application specific..I.e for a relatively slow airplane like the Zodiac then an 8k Soob conversion is probably a pretty good deal (assuming you can be sure to avoid the shoddy workmanship...I.e go to Ram Performance).
For a higher horsepower (and slicker airframe) a 180-200HP conversion will cost very close to what a an experimental Lycoming clone will cost..Add to that the higher fuel consumption due to the drag of radiators (thats my position until it has been proved otherwise) and the auto converstion really does not look like it represents any savings at all..I mean lets assume an engine life of 2000 hours and an extra gallon per hour due to the extra drag of the automotive conversion...Well thats $8000 over the life of the motor..Now that significantly reduces any cost savings of the automotve conversion.
Certainly I am not arguing the modern engine itself in its intended application (i.e a car) is less reliable than an a Lycoming...But when you convert everything, deal with all the computers, figure out a vapour lock proof fuel system, add a reduction drive...well you can see that the converted engine is a very different animal than it was when firmly planted on the ground
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