Chevy LS2 and Trans??? any real issues besides weight

Sorry Bill, but I don't see how the drive shaft would (or could)
reduce engine vibration.

It _might_ reduce drive shaft harmonic responses.
Or it might actually increase harmonic responses.

Too many variables to call it without specifics.

But, in general, heavier parts respond to higher frequencies.

Lighter parts are more likely to respond to lower (closer
to engine frequencies.

Not much help today, am I...

Richard

Richard Lamb wrote:
Copy that, Corky.

One thing that doesn't get discussed much is the idea of
direct drive auto conversions.

The VW is usually done that way, and I know of one V8 setup that
runs direct drive.

Direct drive eliminates the many advantages of properly geared
installations, such as crank protection against prop impacts or
stoppages, the offset in crank to propeller line which enables the
engine to sit lower in the airframe, and the lower noise of slower
turning propellers. In many installations it is possible to start and
run the engine without a propeller attached, making maintenance and
troubleshooting easier.

wrote:
On Wed, 16 Nov 2005 08:16:00 -0800, Richard Riley
I read your test description a long time ago, I agree it's very
impressive. My impression is that the Sube guys are asking a lot more
out of a lot less displacement than the V-6 guys. Any comment?

That's why smaller engines can safely rev higher for longer periods.
But I still cringe when I see the kind of high rpms necessary for the
Subie's to produce the power they claim.

I don't think power to displacement ratio is the best or only comparison
between engines. The engine's ability to get rid of heat is an
important consideration, so is the strength of the crankshaft and
bearings (at least the weakest one, whether it's the journal, big-end
rod bearing, or even wrist-pin). Small engines, or small cylinders
anyway, have an inherent advantage for getting rid of heat, that's
geometry for you (volume and surface area don't increase at the same rate).

Also, just rpm doesn't tell the whole story. Piston speed (pretty much
rpm x stroke) is probably a better way of looking at it. Here's some
numbers:

Chevy LS-2 stroke 3.62" 400hp at 6000rpm 724 inches/second
Rotax 582 stroke 2.52" 65hp at 6500rpm 546 inches/second
Subara EA-81 stroke 2.64" 100hp at 5500rpm 484 inches/second
Pratt R2800 stroke 6" 2000hp at 2400rpm 480 inches/second
Rotax 912 stroke 2.4" 100hp at 5800rpm 464 inches/second
O-360 stroke 4 3/8" 180hp at 2700rpm 394 inches/second
Jabiru 3300 stroke 2.91" 120hp at 3300rpm 320 inches/second
Chevy (again) stroke 2.64" (derated) 3500rpm 308 inches/second

By the way, I have them in order of fastest to slowest piston speed. I
snuck in a few extra examples for fun. I don't have a TBO for the
Double Wasp

Of course, I don't think these comparisons tell the whole story either.
Food for thought though.

On Wed, 16 Nov 2005 13:47:22 -0600, "Montblack"
wrote:

Did so :-)

"The engine must pass 600 cycles without any sign of failure. We typically
run 1200 cycles and a probe test will run 1600 cycles. That's a (sic)
excellent gasket killer test. Head gaskets are the first to fail because of
the rapid expansion and contraction."

When I transcribed the article originally, I put the (sic) in at that
point to denote that "a" is incorrect grammar in that sentence. It
should have been "an".

Corky Scott

On 16 Nov 2005 14:24:21 -0800, "Richard Lamb"
wrote:

One thing that doesn't get discussed much is the idea of
direct drive auto conversions.

The VW is usually done that way, and I know of one V8 setup that
runs direct drive.

In my opinion, a direct drive setup for an auto conversion should have
some kind of crank support bolted on to the engine block. Something
that basically becomes the drive flange and is designed to withstand
the kind of thrust loads that any propeller will apply to the end of
the crank.

If you look at direct drive engines built to turn props, the end that
has the prop flange usually has a very long bearing surface so that
the prop flange has support.

Auto engines aren't designed to have props bolted to the drive end,
they are designed to transmit power to a drive shaft that is supported
so that no side loads are imposed on the crank. That being the case,
the end bearing simply isn't adaquate to support a prop. In my
opinion.

I've seen bolt-on hubs that add this bearing support. At a minimum
I'd want one if I was to attempt a direct drive auto engine.

Replica fighters and pursuits are particulary good examples of
airplanes that require a heavy engine in order to properly balance the
center of gravity. WWI pursuits with liquid cooled engines had heavy
engines and not that much power. But they swung enormous props
compared to today's similar powered aircraft engines.

They often were redlined at only 1500 to 1800 rpm. The prop had to
have a large diameter and also have a wide cord in order to produce
the necessary thrust at those rpms.

In order to produce 180 hp at only 1800 rpm, given that they were very
low compression and unsupercharged, they had a large displacement.

Corky Scott

"The engine must pass 600 cycles without any sign of failure. We
typically run 1200 cycles and a probe test will run 1600 cycles. That's a
(sic) excellent gasket killer test. Head gaskets are the first to fail
because of the rapid expansion and contraction."

("Charles K. Scott" wrote)
When I transcribed the article originally, I put the (sic) in at that
point to denote that "a" is incorrect grammar in that sentence. It should
have been "an".


Ok. Good grammar catch.

Now, back to the probe test .....What is it?

Just curious - How is it different from the 600 or 1200 cycle tests that it
runs to 1600 cycles?

Am I dense?

(Here's the whole paragraph, again)
Thermal cycle tests are run to define engine capability under cold
weather condition. We run the engine at full throttle at 4000 RPM,
bring it down to idle, stop it, switch the coolant valves to drain the
hot coolant, pump the chilled coolant from the chiller until the metal
temperature stabilizes at 0 degrees F. Frost forms on the outside of
the block, as the cold coolant rushes into the engine. When it
stabilizes at 0 F, we motor the engine, start it, come to full
throttle at 4400 RPM, the valves switch and the coolant temperature
starts to climb. It climbs back up to 260 degrees F. It takes 10 -11
minutes to complete one cycle. The engine must pass 600 cycles
without any sign of failure. We typically run 1200 cycles and a probe
test will run 1600 cycles. That's a (sic) excellent gasket killer
test. Head gaskets are the first to fail because of the rapid
expansion and contraction.


Montblack
Former '89 Probe owner

Richard Lamb wrote:

snip

Like it or not, (and FAA blessings aside) the aircraft engines we love
to hate
(or hate to love?)
evolved to fill that particular niche - and do it pretty well - all
things considered.

That's just it. They have not evolved. They are like the coelecanth,
which lives, but only in an isolated world.

I have on my wall a picture of an early Bonanza with a woman standing
in the door. Most people do not recognize her, even though she is
perhaps the most famous woman in the world, even 43+ years after her
death. The point is if you went to A&P school when that picture was
taken, or when she died 15 years later, you could go out to the Beech
plant and see a A36 Bonanza and be essentially qualified to work on
every system. The engine would be almost identical except slightly
bigger. The ignition system is the same heavy high tension magnetoes,
as used on tractors and other farm equipment. The fuel injection
replaces the carburetor, biut it's the same old Hilborn style if they
are using Continentals. Lycs have the RSA system which was not invented
in 1946 but pretty well known in '62 if I recall correctly.

Can you imagine a young car mechanic of 1945 shown a 2005 automobile?

The coelecanth, a good name for the museum piece free air cooled split
case bolt-on-cylinder LyCon.

coelecanth, huh? I had to look that one up.
(And then I thought you were talking about me - not the engines! :^)

I'd be willing to bet that the reason this fish has remained unchanged
for a gazillion years is that it fits the enviornment perfectly - AND
the
enviornment that it fits so well has not changed either.

Your argument is, perhaps, that government regulation has created an
unchangable enviornment - causing stagnated development?

Can't argue much against that.

I flew a Rotax 912 a while back.
Tiny little thing that looks more like a toy than an aircraft engine.
But it runs very smoothly, turns a whopping big prop, and - all in all
-
seems to be a very sucessful engine.

If I could only afford one...


Richard

"Charles K. Scott" wrote

When I transcribed the article originally, I put the (sic) in at that
point to denote that "a" is incorrect grammar in that sentence.

What does the (sic) stand for? I have seen it, and understand what it is
trying to do, but never have heard what the root of the meaning is.
--
Jim in NC

When I transcribed the article originally, I put the (sic) in at that
point to denote that "a" is incorrect grammar in that sentence.

("Morgans" wrote)
What does the (sic) stand for? I have seen it, and understand what it is
trying to do, but never have heard what the root of the meaning is.


http://www.askoxford.com/asktheexperts/faq/usage/sic

http://andromeda.rutgers.edu/~jlynch/Writing/s.html
From this link:

Sic.
Apart from necessary omissions and interpolations, your quotations should
always be exact, and any departures from the original should be clearly
indicated with ellipses or brackets.

Sometimes, though, you may have to quote something that looks downright
wrong. In these cases, it's traditional to signal to your readers that the
oddities are really in the original, and not your mistake. The signal is
"[sic]": square brackets for an interpolation, and the Latin word sic,
"thus, this way." (Since it's a foreign word, it's always in italics; since
it's a whole word and not an abbreviation, it gets no period.) It amounts to
saying, "It really is this way, so don't blame me."

George Eliot was a woman: if someone you quote gets it wrong, as in "George
Eliot's late fiction shows major advances over his earlier works," you might
signal it thus: "George Eliot's late fiction shows major advances over his
[sic] earlier works." Old spellings were often variable: if your source
spells the name Shakspear, you might point out with a [sic] that it really
appears that way in the original.

Don't use sic to show off with gotchas. Too many writers sic sics on the
authors they quote just to show they spotted a trivial error. If your
audience is unlikely to be confused, don't draw attention to minor booboos.
[Entry added 3 November 2000.]


Montblack