PSRU design advantages

"Morgans" wrote in message
...

"ADK" wrote in message
news:X6TXf.28774$%H.11944@clgrps13...
This is probably going to open old wounds. What I would like is
experienced input on the advantages, for economic, efficiency and
longevity etc. of different types of redrives.

I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled,
configuration driving a long drive shaft to the prop.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Warning,Warning, Danger, Danger, Will Robinson!

Yep, that is a really big can of worms.

The redrive is not as big a problem as you think. You get into a mess
when you start talking about long drive shafts.

Torsional resonance has brought many of the great minds of the flying
industry to their knees. No joke. I don't have all of the links at hand,
but someone here does. Start by googling torsional resonance.

Then, be afraid. Be very afraid.
I you don't get afraid, keep looking, until you get afraid, because you
need to get afraid, or you don't understand the problem.
--
Jim in NC


The long driveshaft is a problem. Unlike a car, in an aircraft you put the
driveshaft in between the crankshaft and the flywheel. Not the place for a
driveshaft. My recommendation is to couple the driveshaft to the
engine/reduction unit with one of the shot filled fluid couplings. They
kill any feedback and pretty well damp the reinforcement that makes the
driveshaft go totally bonkers. Then use the largest diameter tubular
driveshaft you can fit into the space available. That will tend to put the
resonant frequencies into a range you won't pass through or run in normally.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

ADK

Look up Molt Taylor and his Aerocar system. He used a pusher
arrangement and seemed to have most of the problems solved with long
shaft back to prop.

His bird may still be flying some place to exhibitions?

Am sure someone will jump in here and give data on his bird and how he
coupled shaft to engine with a "power glide" clutch or some such. It
allowed a small amount of slippage at each power stroke to prevent the
pulse being transmitted to drive shaft and prop as I recall.

Best of luck with a difficult problem.

Big John
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On Sun, 02 Apr 2006 16:39:19 GMT, "ADK" wrote:

This is probably going to open old wounds. What I would like is experienced
input on the advantages, for economic, efficiency and longevity etc. of
different types of redrives.

I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled,
configuration driving a long drive shaft to the prop.

("Big John" wrote)
Look up Molt Taylor and his Aerocar system. He used a pusher arrangement
and seemed to have most of the problems solved with long shaft back to
prop.

His bird may still be flying some place to exhibitions?


http://www.airventuremuseum.org/coll...%20Aerocar.asp
EAA site with links at the bottom:
*Taylor Aerocar Design and Construction
*Taylor Aerocar Manufacturers History
*Taylor Aerocar Specifications
*Taylor Aerocar Virtual Exhibit

http://www.goldenwingsmuseum.com/Aircraft.html
Golden Wing's Museum Collection

http://www.goldenwingsmuseum.com/Air...ero%20Car.html
1954 Taylor Aero Car/Aerocar.

http://www.goldenwingsmuseum.com/Photo's/Aero%20Car-2.jpg
Bigger pic


Montblack
It would fly tomorrow - after some minor touch ups and an annual. Don't know
when it's scheduled to go up again. They take the car out and run around the
airport from time to time. School kids love the Aero Car during their tours.
It last flew maybe 5 years ago. Maybe 6?

"Montblack" wrote

It would fly tomorrow - after some minor touch ups and an annual. Don't
know when it's scheduled to go up again. They take the car out and run
around the airport from time to time. School kids love the Aero Car during
their tours. It last flew maybe 5 years ago. Maybe 6?

I'm almost positive that I have seen it fly at OSH, within the past 3 years.
Last year, perhaps?

It was in the 1:00 PM showcase.
--
Jim in NC

Big John wrote:

ADK

Look up Molt Taylor and his Aerocar system. He used a pusher
arrangement and seemed to have most of the problems solved with long
shaft back to prop.

His bird may still be flying some place to exhibitions?

Am sure someone will jump in here and give data on his bird and how he
coupled shaft to engine with a "power glide" clutch or some such. It
allowed a small amount of slippage at each power stroke to prevent the
pulse being transmitted to drive shaft and prop as I recall.

Best of luck with a difficult problem.

Big John

Ok,

I think it's also used on the Imp and Mini-Imp.


The "clutch" consists of two (wavy surfaced) plates with lead shot
loaded between them.

As the thing spun up, centrifugal force packed the shot solid, but
there was enough "give" with the shot to absorb the "jerk" (4th derivative?).


Richard

no idea why that came out in past tense...

The aircraft I am interested in is the G802 Orion, designed in France in the
80's. It had problems with a long drive shaft and so I am interested in how
others have solved a similar problem. It also incorporated a Flexidyne type
coupler but it still had problems.
I work in aviation but there isn't a lot of good suggestions (printable)
from the people and engineers I work with.


"Richard Lamb" wrote in message
ink.net...
Big John wrote:

ADK

Look up Molt Taylor and his Aerocar system. He used a pusher
arrangement and seemed to have most of the problems solved with long
shaft back to prop.

His bird may still be flying some place to exhibitions?

Am sure someone will jump in here and give data on his bird and how he
coupled shaft to engine with a "power glide" clutch or some such. It
allowed a small amount of slippage at each power stroke to prevent the
pulse being transmitted to drive shaft and prop as I recall.

Best of luck with a difficult problem.

Big John

Ok,

I think it's also used on the Imp and Mini-Imp.


The "clutch" consists of two (wavy surfaced) plates with lead shot
loaded between them.

As the thing spun up, centrifugal force packed the shot solid, but
there was enough "give" with the shot to absorb the "jerk" (4th
derivative?).


Richard

no idea why that came out in past tense...

"Richard Lamb" wrote in message
ink.net...
Big John wrote:

ADK

Look up Molt Taylor and his Aerocar system. He used a pusher
arrangement and seemed to have most of the problems solved with long
shaft back to prop.

His bird may still be flying some place to exhibitions?

Am sure someone will jump in here and give data on his bird and how he
coupled shaft to engine with a "power glide" clutch or some such. It
allowed a small amount of slippage at each power stroke to prevent the
pulse being transmitted to drive shaft and prop as I recall.

Best of luck with a difficult problem.

Big John

Ok,

I think it's also used on the Imp and Mini-Imp.


The "clutch" consists of two (wavy surfaced) plates with lead shot
loaded between them.

As the thing spun up, centrifugal force packed the shot solid, but
there was enough "give" with the shot to absorb the "jerk" (4th
derivative?).


Richard

no idea why that came out in past tense...


It is indeed used on the Imp and the MiniImp. Molt used it on most of his
designs and spent quite a few years getting the bugs worked out of it. It
is NOT "two wavy surfaced plates" but just a little different.

The driven part is a cylindrical case with a charge of shot in it. When the
case is driven the "fluid" shop is packed tightly against the outer diameter
of the spinning cylinder. The output shaft has a single "wavy" plate on the
end of it. This plate is enclosed in the cylinder with the shot. As the
shot gets packed into the rim of the case it grips the plate and transmits
the power to the output shaft. If you try to drive it backwards all the
plate does it turn in the loose shot and warm it up a bit. Like a "sprague
clutch" from a helicopter, it only transmits power in one direction. By
varying the load of shot in the cylinder you can vary the coupling
coefficient and "set" the breakaway torque for the unit. It cannot transmit
damaging torques from torsional vibration back through the coupling because
the output shaft "breaks away" before a crippling torque is reached. You
don't want it to break away at too low a torque either, or you will
basically have a "slipping" clutch in your drive train.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

"Highflyer" wrote in message
...

"Richard Lamb" wrote in message
ink.net...
Big John wrote:

ADK

Look up Molt Taylor and his Aerocar system. He used a pusher
arrangement and seemed to have most of the problems solved with long
shaft back to prop.

His bird may still be flying some place to exhibitions?

Am sure someone will jump in here and give data on his bird and how he
coupled shaft to engine with a "power glide" clutch or some such. It
allowed a small amount of slippage at each power stroke to prevent the
pulse being transmitted to drive shaft and prop as I recall.

Best of luck with a difficult problem.

Big John

Ok,

I think it's also used on the Imp and Mini-Imp.


The "clutch" consists of two (wavy surfaced) plates with lead shot
loaded between them.

As the thing spun up, centrifugal force packed the shot solid, but
there was enough "give" with the shot to absorb the "jerk" (4th
derivative?).


Richard

no idea why that came out in past tense...


It is indeed used on the Imp and the MiniImp. Molt used it on most of his
designs and spent quite a few years getting the bugs worked out of it. It
is NOT "two wavy surfaced plates" but just a little different.

The driven part is a cylindrical case with a charge of shot in it. When
the
case is driven the "fluid" shop is packed tightly against the outer
diameter
of the spinning cylinder. The output shaft has a single "wavy" plate on
the
end of it. This plate is enclosed in the cylinder with the shot. As the
shot gets packed into the rim of the case it grips the plate and transmits
the power to the output shaft. If you try to drive it backwards all the
plate does it turn in the loose shot and warm it up a bit. Like a
"sprague
clutch" from a helicopter, it only transmits power in one direction. By
varying the load of shot in the cylinder you can vary the coupling
coefficient and "set" the breakaway torque for the unit. It cannot
transmit
damaging torques from torsional vibration back through the coupling
because
the output shaft "breaks away" before a crippling torque is reached. You
don't want it to break away at too low a torque either, or you will
basically have a "slipping" clutch in your drive train.

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )



I can really only agree with part of that. I did not reread the entire
brochure, but the clutch itself does not appear to be unidirectional, and it
is not intended to be a torsional dampener. However, the soft start
certainly would have eliminated resonance at srating motor speed, which
proved to be the most vexing problem in the Contact! article regarding the
BD-5. It could have made that other problems a lot easier to solve as well.

I have never personally seem any of Molt Taylor's aircraft, and I don't know
which specific parts he used, but a Dodge Flexidyne brochure is available
at: http://www.dodge-pt.com/pdf/brochure...s/dmr_1513.pdf

Peter

IF you had to design a PSRU, to drive a pusher propellor via shaft, what
would your experience dictate? Thinking along the lines of a gearbelt, chain
or gear. Please, I would appreciate the collective experience available on
this group. I have decided on the aircraft, but want to make it the most
reliable and safest it can be.

"ADK" wrote in message
news:X6TXf.28774$%H.11944@clgrps13...
This is probably going to open old wounds. What I would like is
experienced input on the advantages, for economic, efficiency and
longevity etc. of different types of redrives.

I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled,
configuration driving a long drive shaft to the prop.

ADK wrote:

IF you had to design a PSRU, to drive a pusher propellor via shaft, what
would your experience dictate? Thinking along the lines of a gearbelt, chain
or gear. Please, I would appreciate the collective experience available on
this group. I have decided on the aircraft, but want to make it the most
reliable and safest it can be.

"ADK" wrote in message
news:X6TXf.28774$%H.11944@clgrps13...

This is probably going to open old wounds. What I would like is
experienced input on the advantages, for economic, efficiency and
longevity etc. of different types of redrives.

I am leaning towards a cog-belt reducer in a 6 cylinder, liquid cooled,
configuration driving a long drive shaft to the prop.




The collective experience is zilch = nada = squat = undefined.

THAT is what everybody had been trying to tell you.

Wait a second. Look around the airport.

How many shaft driven propellers do you see?

Have you ever seen?

If you are heart set on doing it, I sincerely wish you luck.

But I can't offer any further advice - 'cuz they ain't none...



Richard