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

"MrV" wrote in message
oups.com...
truthfully the idea is to make an OKAY craft. i'm thinking 150 to
160kts with okay fuel burn.
now if i'm right i'd be running the tranny in like 4th gear. isn't
this where its designed to spend a good deal of its time ?

if i remember right, a car engine's output is not perfectly circular
its kinda eccentric. and something is neccessary to convert the
irregular motion into the circular motion for the prop


If you are thinking of the top gear in a trans with overdrive, the overdrive
isn't designed for high torques (read the owners manual - "do not tow
trailers in overdrive"). Plus it will speed the prop, not slow it down. If
you are thinking 4th out of 5 gears in the typical trans with overdrive,
then you have direct drive - not much pont in bolting on a trans just to get
out what you put in, eh?

The auto trans has everything you don't want and nothing you do. No gears
would be a better choice than the wrong gears.

The torque output is not exactly constant, but the flywheel damps most of
that out. A propeller, on the other hand generates torque pulses as it goes
by cowling and stuff - that can cause problems if you are trying to run a
drive shaft. Pusher aircraft are "worst case". Note that most piston engine
aircraft have the prop bolted right on the end of the crankshaft - nothing
required to account for the torque pulses from the engine (Ignoring the
cases where you excite the resonant frequencies of the prop).

--
Geoff
the sea hawk at wow way d0t com
remove spaces and make the obvious substitutions to reply by mail
Spell checking is left as an excercise for the reader.

actually i'm thinking 4th or 5th gear from a 6speed manual tranny.
from the LITTLE research i've done
3rd gear is like 1.43 and 4th is like 1.2 seems like a good range
3500rpm= 2400 prop rpm
or at 1.2 3250 rpm = 2700 prop rpm.

now wouldn't the prop vibs be less than the abuse the average tranny
takes from a daily drive ?

"MrV" wrote in message
oups.com...
actually i'm thinking 4th or 5th gear from a 6speed manual tranny.
from the LITTLE research i've done
3rd gear is like 1.43 and 4th is like 1.2 seems like a good range
3500rpm= 2400 prop rpm
or at 1.2 3250 rpm = 2700 prop rpm.

now wouldn't the prop vibs be less than the abuse the average tranny
takes from a daily drive ?

Resonate vibration is the killer in the aircraft powerplant world.

At every power pulse, the crankshaft winds up a little bit, and then unwinds
while waiting for the next power pulse. This can be a very large problem,
and can destroy a drivetrain. Aircraft engines get around it by making a
very stout driveshaft, but even then, some engine prop combinations are
plackered not to run at certain RPM's in continuous operations.

Do some research. There have been tons written on the subject, and even
though it does not make sense, driving a prop is way harder than a car
wheel, and avoiding the resonate problems.
--
Jim in NC

Morgans wrote:
snip.

At every power pulse, the crankshaft winds up a little bit, and then unwinds
while waiting for the next power pulse. This can be a very large problem,
and can destroy a drivetrain. Aircraft engines get around it by making a
very stout driveshaft, but even then, some engine prop combinations are
plackered not to run at certain RPM's in continuous operations.

Do some research. There have been tons written on the subject, and even
though it does not make sense, driving a prop is way harder than a car
wheel, and avoiding the resonate problems.

Actually, aircraft engines don't deal with it very well at all. Large
radials deal with it by having a high reciprocating mass, and the 65
Continental class of engine deals with it by low impulse and again a
high reciprocating mass, but geared light aircraft engines have been
largely troublesome. The Continental Tiara was a disaster and so was
the GO-300. The planetary gear case Lycomings were a little more
successful but they were also heavy.

A good "car" engine that is suitable for ski boat use is suited to
aircraft use if 1) any resonant peaks in its internal configuration are
figured out first, (the boat will do that!) 2) a proper drive is
selected and 3) propeller loads are transferred to the airframe from
the drive and not the engine itself. Dave Blanton had no torsional
resonance problems, although he was probably a little lucky, and
careful study of Kiekhaefer's marine I/O and the Soloy Allison fixed
wing conversion (which use Allison helo turboshafts, different from
their purpose built fixed wing cousins) will be helpful.

A good autoderivative engin package solves a lot of problems aviation
users have lived with for so long they don't consider them problems
anymore, such as a prop stoppage destroying the entire lower end of the
engine, and not being able to run the engine without a prop or test
club.

"Bret Ludwig" wrote in message

Actually, aircraft engines don't deal with it very well at all. Large
radials deal with it by having a high reciprocating mass, and the 65
Continental class of engine deals with it by low impulse and again a
high reciprocating mass, but geared light aircraft engines have been
largely troublesome. The Continental Tiara was a disaster and so was
the GO-300. The planetary gear case Lycomings were a little more
successful but they were also heavy.

Agreed. Part of the solution, is like I said, stout (read heavy)
crankshaft, along with, as you stated, high reciprocating mass.

Radial engines have stout cranks, plus massive master and slave rods.

A good "car" engine that is suitable for ski boat use is suited to
aircraft use if 1) any resonant peaks in its internal configuration are
figured out first, (the boat will do that!) 2) a proper drive is
selected and 3) propeller loads are transferred to the airframe from
the drive and not the engine itself.

Part of that "proper drive" for boats also use a rubber coupling between the
engine and the transmission, outdrive, v-drive, or prop shaft. The entire
output from the engine turns the rubber, then the rubber turns the drive.
In this manner, there is no metal to metal connection of the engine to the
drive. Every one I have seen uses one, but I'll be damed if I can remember
what the correct name is, at the moment! g Old age, or time of night?

Those units tend to absorb part of the pulse energy, and leaves a way for
the torsional energy to dissipate. They do eventually wear out, and a new
one has to be installed. AMHIKT. Very careful alignment is key to the unit
lasting as long as it should.

One of the more modern solutions is use of a toothed rubber drive belt, to
slow down the prop, and allow for a prop shaft and bearings that can deal
with all of the loads the prop creates. It also allows the belt to flex and
isolate the prop from the engine. They are pretty efficient, and have a 200
hour or more life expectency.

Dave Blanton had no torsional
resonance problems,

Some would argue that! g
--
Jim in NC