RAH'er has forced landing

[Ron Wanttaja]

From Monday's FAA accident summary:

IDENTIFICATION
Regis#: 4449E Make/Model: EXP Description: EXP-
Date: 12/18/2004 Time: 1950

Event Type: Incident Highest Injury: None Mid Air: N Missing: N
Damage: None

LOCATION
City: LEESBURG State: FL Country: US

DESCRIPTION
ACFT MADE AN EMERGENCY LANDING NEAR A ROAD 15 MILES SOUTH OF LEESBURG, FL

N4449E is an "EZ" registered to a George Graham...RAH'er George Graham's
Mazda-powered Long-EZ, I believe. Congrats to George for not only coming
through with a whole skin, but for bringing off a off-field landing in a hot
homebuilt without damage.

Ron Wanttaja

[Dave S]

A little update on George...
pasted from a list-serv regarding the Mazda rotary conversion that I
frequent... The problem wasnt the engine.. it was the peripherals.. and
the pasted bit below is from a maker of PSRU's who was uninvolved with
the accident airplane:


George Graham, one of the early aviation rotary adopters, isn't on the
list so though I'd pass along his latest. After 200+ hours, his second
Mazda manual transmission (2nd gear) PSRU stripped it's gears and he
dead sticked safely on a road about 10 miles from Leesburg Fl yesterday.
No damage to him or plane but he doesn't want to take a chance on the
transmission again. I'll be building him an RD-1A. He glided about 20
miles from an altitude of only 5000 ft with the prop freewheeling!

PASTE complete..

The glide distance has since been re-evaluated, but overall everyone is
glad it worked out ok.. and on a secondary personal note its refreshing
that the engine itself was not the point of failure

Dave

Ron Wanttaja wrote:
> From Monday's FAA accident summary:
>
> IDENTIFICATION
> Regis#: 4449E Make/Model: EXP Description: EXP-
> Date: 12/18/2004 Time: 1950
>
> Event Type: Incident Highest Injury: None Mid Air: N Missing: N
> Damage: None
>
> LOCATION
> City: LEESBURG State: FL Country: US
>
> DESCRIPTION
> ACFT MADE AN EMERGENCY LANDING NEAR A ROAD 15 MILES SOUTH OF LEESBURG, FL
>
> N4449E is an "EZ" registered to a George Graham...RAH'er George Graham's
> Mazda-powered Long-EZ, I believe. Congrats to George for not only coming
> through with a whole skin, but for bringing off a off-field landing in a hot
> homebuilt without damage.
>
> Ron Wanttaja

[Corky Scott]

On Tue, 21 Dec 2004 03:00:05 GMT, Dave S >
wrote:

>The glide distance has since been re-evaluated, but overall everyone is
>glad it worked out ok.. and on a secondary personal note its refreshing
>that the engine itself was not the point of failure
>
>Dave

Dave, my feeling is that it does not matter that the engine did not
fail, the PSRU did and the result is the same: No engine and a forced
landging.

I wondered about using a transmission for a PSRU instead of a PSRU for
a PSRU. The problem with using a transmission is that the all the
gears except for fifth, are designed for light usage. In otherwords
they weren't designed to be used continuously with the engine pulling
50% or more power. George's transmission is not the first to fail
because of this.

Using the transmission for a PSRU is not necessarily a bad thing, but
the gears that will be used and the bearings that support the gears
may need to be re-evaluated.

Corky Scott

[Matt Whiting]

Corky Scott wrote:

> On Tue, 21 Dec 2004 03:00:05 GMT, Dave S >
> wrote:
>
>
>>The glide distance has since been re-evaluated, but overall everyone is
>>glad it worked out ok.. and on a secondary personal note its refreshing
>>that the engine itself was not the point of failure
>>
>>Dave
>
>
> Dave, my feeling is that it does not matter that the engine did not
> fail, the PSRU did and the result is the same: No engine and a forced
> landging.
>
> I wondered about using a transmission for a PSRU instead of a PSRU for
> a PSRU. The problem with using a transmission is that the all the
> gears except for fifth, are designed for light usage. In otherwords
> they weren't designed to be used continuously with the engine pulling
> 50% or more power. George's transmission is not the first to fail
> because of this.
>
> Using the transmission for a PSRU is not necessarily a bad thing, but
> the gears that will be used and the bearings that support the gears
> may need to be re-evaluated.

I've not seen this before. This may be true for passenger cars, but for
pickup trucks, OTR trucks, off-road equipment, etc., each gear is
equally likely to be used and typically full throttle is more likely to
be used in the lower gears. I've never heard of any of the gears being
designed for "light" usage in any manual trans with which I'm familiar,
but I'm not that familiar with pax car manuals.

It used to be that 4th gear in most four-speeds was 1:1 and this was
often accomplished by simply connecting the input and output shafts
directly with a collar. So, I suppose this could have been more rugged
as the gears were just along for the ride at that point. However, some
new transmissions have the 5th or 6th gear as a overdrive gear, and
occasionally even the 4th, and may not even have a 1:1 ratio. In these
designs, every speed is being driven through the gear set/layshaft.

If you have a design reference for transmissions being designed to not
handle full torque in anything but high gear, I'd be interested in
seeing it. Also, if you have a list of such transmissions that would be
interesting as well.

Matt

[Jason Marshall]

Matt Whiting wrote:

>
>
> I've not seen this before. This may be true for passenger cars, but for
> pickup trucks, OTR trucks, off-road equipment, etc., each gear is
> equally likely to be used and typically full throttle is more likely to
> be used in the lower gears. I've never heard of any of the gears being
> designed for "light" usage in any manual trans with which I'm familiar,
> but I'm not that familiar with pax car manuals.
>
> It used to be that 4th gear in most four-speeds was 1:1 and this was
> often accomplished by simply connecting the input and output shafts
> directly with a collar. So, I suppose this could have been more rugged
> as the gears were just along for the ride at that point. However, some
> new transmissions have the 5th or 6th gear as a overdrive gear, and
> occasionally even the 4th, and may not even have a 1:1 ratio. In these
> designs, every speed is being driven through the gear set/layshaft.
>
> If you have a design reference for transmissions being designed to not
> handle full torque in anything but high gear, I'd be interested in
> seeing it. Also, if you have a list of such transmissions that would be
> interesting as well.
>
> Matt
>
I would think that if anything the lower gears would have to be be
beefier than the higher ones, at least on the output shaft. Torque
increases as rotational speed decreases, right? This is why axle shafts
tend to snap when starting a heavy load from a dead stop.
I just replaced fifth gear in my Nissan NX a month or two ago. It was
pretty much worn out, and not really beefy to begin with. You do spend
most of your time driving sitting in your highest gear so it will see
the most wear, but not necessarily the highest torque loads. All the
gears are equally wimpy, but the 1st and 2nd shifting collar is a little
longer and engages more teeth than the others. This seems to confirm
that 1st and 2nd are stronger gears than 4th or 5th.This car has the
smallest tranny I've ever worked on and one look inside would make you
REALLY glad you aren't flying behind it. Those gears are tiny, and
eyeball engineering would lead me to believe they aren't up to the job
of swinging a prop. Graham's two failures pretty much confirm this. I
can't imagine the mazda's gearbox is any beefier than this one. Flying
with one of these is 'experimental' all right.

Jason
Challenger-II

[Corky Scott]

On Tue, 21 Dec 2004 11:46:46 -0500, Matt Whiting
> wrote:

>I've not seen this before. This may be true for passenger cars, but for
>pickup trucks, OTR trucks, off-road equipment, etc., each gear is
>equally likely to be used and typically full throttle is more likely to
>be used in the lower gears. I've never heard of any of the gears being
>designed for "light" usage in any manual trans with which I'm familiar,
>but I'm not that familiar with pax car manuals.

Matt, it isn't a matter of being strong enough to withstand occasional
pulls at full throttle, it's the continuous use that appears to be the
problem, and also that this may be a problem endemic to transmissions
being used as PSRU's.

My curse is that I read a LOT. One of the many articles I read a
number of years ago was about a builder trying to use a Honda Goldwing
engine for his airplane engine. This engine has an integral
transmission which he used as the PSRU. He used second or third gear
for his output gear and the transmission failed, like George's.

The reason for the failure, if I'm remembering this correctly, was
that the lower gears were not designed for continuous transmission of
power, at least not at the power levels required for flight. Whether
it was the width of the gears or the size of the bearings that
supported them, or even if there were bearings supporting the shaft, I
don't know. It could also have been a problem with prop loads on the
output shaft, not sure. But the transmission as a psru failed.

It could be the gears that failed, or it could be that the output
shaft could not stand up to the prop loads, don't know how George
supported the output shaft.

In any case, George should be congratulated for safely landing an
airplane with a decoupled prop that has one of the higher landing
speeds for light airplanes around. Putting down after a total loss of
thrust is never easy unless you practice frequently and even then you
always know it's just practice and a blown approach can be salvaged by
advancing power and trying again.

But the real thing is the real thing, and while some people flying
Long E-Z's manage to be at around 60 mph when touching down, most I've
heard of are faster than that to prevent the nose from pitching down
prematurely and uncontrollably.

Good job George.

Corky Scott

PS, I hope George posts here what failed in the transmission. It
would be illuminating.

[Dave S]

Corky Scott wrote:
> On Tue, 21 Dec 2004 03:00:05 GMT, Dave S >

>
> Dave, my feeling is that it does not matter that the engine did not
> fail, the PSRU did and the result is the same: No engine and a forced
> landging.
>
(snip)
>
> Corky Scott

It sure matters to me. The mazda rotary is about the only auto
conversion that I have even given any serious thought to. I have one
assembled on a stand at the hangar waiting to be put on the airframe. We
are hoping to fly it to Osh 2005 (so we have a timetable to try and
meet, safety permitting) ANY power loss incident involving one concerns
me greatly since I am going to be one of the follow-on experimenters
behind the trailblazers. I'm using a commercially produced PSRU.. not a
transmission made into a PSRU... so yea.. it matters quite a bit to me
that the power failure wasnt in the engine itself, but one of the
peripherals.

So far, in the past 6 months, the list of Mazda engine casualties has
included 3 blown turbos (2 by one person), one of those blown turbo'd
engines ALSO had a shoddy rebuild by a local race shop that contributed
to power probs. There has been a blown oil cooler (fashioned from an a/c
evaperator core) resulting in a dead stick landing into Spencer
NOLF/Helicopter field and then this tranny failure. By and large, almost
all of the failure modes are being attributed to causes other than the
heart of the engine failing. And ALL of the failure modes involve either
substandard labor or the use of automotive accessories in a manner they
were originally never intended for. This is actually refreshing that the
engine itself is not the problem (no bad cranks, blown seals, etc)

The dead stick plane actually looks like its going to be flyable now
without a rebuild (pilot pulled power immediately when the oil cooler
blew, and when he tried to advance the throttle slightly, it stumbled
and died. Actually appears that it didnt seize or scorch the rings.

Dave

[Matt Whiting]

Corky Scott wrote:

> On Tue, 21 Dec 2004 11:46:46 -0500, Matt Whiting
> > wrote:
>
>
>>I've not seen this before. This may be true for passenger cars, but for
>>pickup trucks, OTR trucks, off-road equipment, etc., each gear is
>>equally likely to be used and typically full throttle is more likely to
>>be used in the lower gears. I've never heard of any of the gears being
>>designed for "light" usage in any manual trans with which I'm familiar,
>>but I'm not that familiar with pax car manuals.
>
>
> Matt, it isn't a matter of being strong enough to withstand occasional
> pulls at full throttle, it's the continuous use that appears to be the
> problem, and also that this may be a problem endemic to transmissions
> being used as PSRU's.
>
> My curse is that I read a LOT. One of the many articles I read a
> number of years ago was about a builder trying to use a Honda Goldwing
> engine for his airplane engine. This engine has an integral
> transmission which he used as the PSRU. He used second or third gear
> for his output gear and the transmission failed, like George's.

That wouldn't be too surprising as airplanes require much greater
continuous power output than cars or motorcycles.


> The reason for the failure, if I'm remembering this correctly, was
> that the lower gears were not designed for continuous transmission of
> power, at least not at the power levels required for flight. Whether
> it was the width of the gears or the size of the bearings that
> supported them, or even if there were bearings supporting the shaft, I
> don't know. It could also have been a problem with prop loads on the
> output shaft, not sure. But the transmission as a psru failed.

This is the part I don't buy as there is nothing different about the
lower gears than the higher gears. This is the part I think is a myth.
I believe that ANY gear selected in the GW transmission would have
failed under long-term high power output. I don't think this is an
issue preferential to the higher numerical ratio ("lower") gears.


> It could be the gears that failed, or it could be that the output
> shaft could not stand up to the prop loads, don't know how George
> supported the output shaft.
>
> In any case, George should be congratulated for safely landing an
> airplane with a decoupled prop that has one of the higher landing
> speeds for light airplanes around. Putting down after a total loss of
> thrust is never easy unless you practice frequently and even then you
> always know it's just practice and a blown approach can be salvaged by
> advancing power and trying again.
>
> But the real thing is the real thing, and while some people flying
> Long E-Z's manage to be at around 60 mph when touching down, most I've
> heard of are faster than that to prevent the nose from pitching down
> prematurely and uncontrollably.

Absolutely. An E-Z would not be high on my list of airplanes to land
off-field.


> PS, I hope George posts here what failed in the transmission. It
> would be illuminating.

That it will.


Matt

[[email protected]]

On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
> wrote:

>
>The reason for the failure, if I'm remembering this correctly, was
>that the lower gears were not designed for continuous transmission of
>power, at least not at the power levels required for flight. Whether
>it was the width of the gears or the size of the bearings that
>supported them, or even if there were bearings supporting the shaft, I
>don't know. It could also have been a problem with prop loads on the
>output shaft, not sure. But the transmission as a psru failed.
>
>It could be the gears that failed, or it could be that the output
>shaft could not stand up to the prop loads, don't know how George
>supported the output shaft.
>
>In any case, George should be congratulated for safely landing an
>airplane with a decoupled prop that has one of the higher landing
>speeds for light airplanes around. Putting down after a total loss of
>thrust is never easy unless you practice frequently and even then you
>always know it's just practice and a blown approach can be salvaged by
>advancing power and trying again.
>
>But the real thing is the real thing, and while some people flying
>Long E-Z's manage to be at around 60 mph when touching down, most I've
>heard of are faster than that to prevent the nose from pitching down
>prematurely and uncontrollably.
>
>Good job George.
>
>Corky Scott
>
>PS, I hope George posts here what failed in the transmission. It
>would be illuminating.
>


What really beats on the gears, and what automotive use does not
experience, is the harmonics. Harmonics load the gears in BOTH
directions, with in the order of 10 times the steady state torque.

That tends to shear off teeth!!!

[Bob Korves]

> wrote in message
...
> On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
> > wrote:

> What really beats on the gears, and what automotive use does not
> experience, is the harmonics. Harmonics load the gears in BOTH
> directions, with in the order of 10 times the steady state torque.
>
> That tends to shear off teeth!!!

Torsional resonance has been a problem with many PSRU units, over many
years, including units from big manufacturers of certificated equipment. If
resonance is not carefully studied and tested for, you are almost guaranteed
to have a problem.

Does your car have a harmonic balancer on the crankshaft? Why do you
suppose it is there?

I work with big trucks and we have a problem there with torsional resonance
from the power pulses of the big diesels, especially at high torque and low
rpm (sound familiar?). If, for instance, one removes a clutch with a
dampened disc and replaces it with a clutch with a solid disc, the
transmission input shaft splines might shear -- or the transmission gears --
or the differential gears. It is almost impossible to convince a customer
that his cheap clutch replacement caused his rear axle to fail, but it did!
Truck component manufacturers put a lot of effort into finding and
eliminating resonance. I hope your PSRU designer did too...

Also note that changing ANY component in the drive train can mess up the
torsional dynamics, which is a bad thing for a bunch of experimenter
homebuilders. Even cutting down a metal prop a couple inches. Why do you
suppose that the FAA will allow a 25 hour test period with a certified
propeller/engine combination, but 40 hours without?
Resonance is a big reason.
-Bob

[Peter Dohm]

> wrote in message
...
> On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
> > wrote:
>
> >
> >The reason for the failure, if I'm remembering this correctly, was
> >that the lower gears were not designed for continuous transmission of
> >power, at least not at the power levels required for flight. Whether
> >it was the width of the gears or the size of the bearings that
> >supported them, or even if there were bearings supporting the shaft, I
> >don't know. It could also have been a problem with prop loads on the
> >output shaft, not sure. But the transmission as a psru failed.
> >
> >It could be the gears that failed, or it could be that the output
> >shaft could not stand up to the prop loads, don't know how George
> >supported the output shaft.
> >
> >In any case, George should be congratulated for safely landing an
> >airplane with a decoupled prop that has one of the higher landing
> >speeds for light airplanes around. Putting down after a total loss of
> >thrust is never easy unless you practice frequently and even then you
> >always know it's just practice and a blown approach can be salvaged by
> >advancing power and trying again.
> >
> >But the real thing is the real thing, and while some people flying
> >Long E-Z's manage to be at around 60 mph when touching down, most I've
> >heard of are faster than that to prevent the nose from pitching down
> >prematurely and uncontrollably.
> >
> >Good job George.
> >
> >Corky Scott
> >
> >PS, I hope George posts here what failed in the transmission. It
> >would be illuminating.
> >
>
>
> What really beats on the gears, and what automotive use does not
> experience, is the harmonics. Harmonics load the gears in BOTH
> directions, with in the order of 10 times the steady state torque.
>
> That tends to shear off teeth!!!

That's part of what I was also thinking, but there's more:

In the car or truck, the use of the clutch tends, over time, to randomize
the gear teeth in use at any specific parts of the power and compression
strokes. As I understand it, use of the same gear teeth all the time is a
common problem in spur gear transmissions. The problem is much worse if
applied to both gears--although that would be surprising in a jproduction
gearbox.

In addition, many people may omit all or part of the flywheel and clutch to
save weight. That could prevent the harmonic damper on the other end of the
engine from doing its job. And those little springs in the driven plate
should provide a lot of isolation once the engine is up to speed.

Finally, a lot of the support for the gears and bearings inside the
transmission is provided by the pilot bearing at the flywheel--especially on
rear wheel drive vehicles. A missing pilot bushing could place tremendous
bending loads on those little needle bearings between the input and main
shafts ...

Does anyone know which kind of transmission (transaxle or an in-line with a
straight through fourth gear) he was using, and what all failed in the
transmission besides the gear teeth?

Peter

[Matt Whiting]

wrote:

> On Tue, 21 Dec 2004 14:32:57 -0500, Corky Scott
> > wrote:
>
>
>>The reason for the failure, if I'm remembering this correctly, was
>>that the lower gears were not designed for continuous transmission of
>>power, at least not at the power levels required for flight. Whether
>>it was the width of the gears or the size of the bearings that
>>supported them, or even if there were bearings supporting the shaft, I
>>don't know. It could also have been a problem with prop loads on the
>>output shaft, not sure. But the transmission as a psru failed.
>>
>>It could be the gears that failed, or it could be that the output
>>shaft could not stand up to the prop loads, don't know how George
>>supported the output shaft.
>>
>>In any case, George should be congratulated for safely landing an
>>airplane with a decoupled prop that has one of the higher landing
>>speeds for light airplanes around. Putting down after a total loss of
>>thrust is never easy unless you practice frequently and even then you
>>always know it's just practice and a blown approach can be salvaged by
>>advancing power and trying again.
>>
>>But the real thing is the real thing, and while some people flying
>>Long E-Z's manage to be at around 60 mph when touching down, most I've
>>heard of are faster than that to prevent the nose from pitching down
>>prematurely and uncontrollably.
>>
>>Good job George.
>>
>>Corky Scott
>>
>>PS, I hope George posts here what failed in the transmission. It
>>would be illuminating.
>>
>
>
>
> What really beats on the gears, and what automotive use does not
> experience, is the harmonics. Harmonics load the gears in BOTH
> directions, with in the order of 10 times the steady state torque.

Another myth. All engines and drivetrains are susceptible to torsional
harmonics. Why do you think engines have harmonic dampeners on them?
And flywheels? That is one advantage of automatic transmissions, the TC
damps the torsional vibrations from the engine and prevents them from
reaching the transmission and drivetrain. Most standard shift vehicles
have spring hub clutch disks to help cushion the drive train.

Automobiles and certified aircraft have been designed to avoid or
control harmonics. Some experimental engine/PSRUs have been also, but
unfortunately, some have not.

Matt

[Blueskies]

Doesn't the 'mazda' rotary mnimize this pulsation?

[Morgans]

"Matt Whiting" > wrote

> I believe that ANY gear selected in the GW transmission would have
> failed under long-term high power output. I don't think this is an
> issue preferential to the higher numerical ratio ("lower") gears.
>
> Matt

A short story might provide a little insight to the design factors involved.

My dad had a 80 Chevy Citation. I was driving it when someone lost control
and hit the rear end, sending it off the road, sliding sideways at about 40
MPH.

Seemed like only sheet metal damage was involved. A few months later, the
transmission failed, specifically, the Hi-Vol primary chain drive. My dad
got suspicious about the design, and since he was an engineer involved in
power transmitting to machinery, he looked up the specs for the sprockets
and chain, and the torque and HP rating of the engine. He could not believe
what he found.

GM had designed the primary drive with an over design safety factor of
around 1.1. Yes, 1.1!!! When there had been a slight miss-alignment from
the wreck, the sprocket failed. He still had to eat the repair, as GM
claims the part was correctly designed.

If this was typical, as to the margins involved in design, of major
manufacturers, I am not surprised the 2nd gear failed under this constant
use.

Oh, and I will add that I continue to drive GM, but would not use a gear in
that manner, unless I had verified the parts were up to the abuse I was
going to give them.
--
Jim in NC

[Matt Whiting]

Blueskies wrote:

> Doesn't the 'mazda' rotary mnimize this pulsation?

It may if the combustion event is more spread out than in a conventional
piston engine, but I haven't seen any power curves for a rotary. It
still has discrete combustion events that are converted to rotation, so
it will still have power pulses of some form. The only way to get away
from that is to have something with continuous combustion as in a turbine.


Matt

[Matt Whiting]

Morgans wrote:

> "Matt Whiting" > wrote
>
>
>> I believe that ANY gear selected in the GW transmission would have
>>failed under long-term high power output. I don't think this is an
>>issue preferential to the higher numerical ratio ("lower") gears.
>>
>>Matt
>
>
> A short story might provide a little insight to the design factors involved.
>
> My dad had a 80 Chevy Citation. I was driving it when someone lost control
> and hit the rear end, sending it off the road, sliding sideways at about 40
> MPH.
>
> Seemed like only sheet metal damage was involved. A few months later, the
> transmission failed, specifically, the Hi-Vol primary chain drive. My dad
> got suspicious about the design, and since he was an engineer involved in
> power transmitting to machinery, he looked up the specs for the sprockets
> and chain, and the torque and HP rating of the engine. He could not believe
> what he found.
>
> GM had designed the primary drive with an over design safety factor of
> around 1.1. Yes, 1.1!!! When there had been a slight miss-alignment from
> the wreck, the sprocket failed. He still had to eat the repair, as GM
> claims the part was correctly designed.

1.1 with what as the reference? Maximum engine torque output?


> If this was typical, as to the margins involved in design, of major
> manufacturers, I am not surprised the 2nd gear failed under this constant
> use.

I'm not surprised at 1:1 for this application. Airplane structures
typically use only a 1.5 safety factor. A bridge designer would shudder
at less than 5 and most use 10. The reality is that safety factors are
very application dependent and there is no "right" value. Most cars
last a very long time and drivetrains seldom fail so I'd say GM and
others have it about right.


> Oh, and I will add that I continue to drive GM, but would not use a gear in
> that manner, unless I had verified the parts were up to the abuse I was
> going to give them.

Why would you continue to drive GM vehicles if you consider them to be
designed poorly?


Matt

[[email protected]]

The continuous use of high power through a auto transmission is
what defeated auto-engine conversion guys in the boatbuilding world
many years ago. Even in the 50s and 60s, when transmissions were stout,
they couldn't get away with using them in a boat. The gears and
bearings would heat up and lose their strength and fail. I'm surprised
that more homebuilders don't know that.
I had a 283 in a 13 foot crackerbox-style boat, and the
transmission was a Warner Velvet-Drive marine unit. Forward was through
a massive clutch pack, no gears, and reverse had some impressive
gearing. The transmission was so heavy I could barely lift it, and it
had a substantial oil cooler to keep it happy.
A local guy tried an automatic trans from a car in his boat, and
had it fail in short order.

Dan

[Corky Scott]

On Tue, 21 Dec 2004 20:30:12 GMT, Dave S >
wrote:

>It sure matters to me. The mazda rotary is about the only auto
>conversion that I have even given any serious thought to. I have one
>assembled on a stand at the hangar waiting to be put on the airframe.

Dave, you missunderstand me. What I meant was, whether it was the
engine, psru, fuel pump, carburator, or ignition system that failed,
the end result is the same thing: a dead stick landing.

It doesn't matter to the pilot that the engine is running just fine if
the prop isn't connected to the engine anymore.

The point is to use something that will last. Preferably something
already tested. Or at least that's my attitude. I don't want to be
somebody's test pilot, I just want to fly.

Corky Scott

[Corky Scott]

On Wed, 22 Dec 2004 03:11:51 GMT, "Blueskies"
> wrote:

>Doesn't the 'mazda' rotary mnimize this pulsation?

Not if the Powersport saga is to be believed. Their initial efforts
resulted in a LOT of psru failures.

See:
http://www.powersportaviation.com/Home/Reduction%20drive/Reduction%20drive.htm

Ross Aero, on the other hand put together a planetary gear design and
seemed to suffer no torsional problems at all. They told me that some
engineer stopped in to tell them that he'd analized their reduction
unit and claimed that it would destructively vibrate at 300 rpm. Of
course the engine only sees that rpm during startup or shut down. The
rest of the time it's operating well above that.

The Ross Aero psru is what Tracy Crook initially used in his Mazda
powered RV-4. I gather he substantially modified it since then and
may now offer one of his own.

Corky Scott

[George A. Graham]

On Tue, 21 Dec 2004, Ron Wanttaja wrote:

> ACFT MADE AN EMERGENCY LANDING NEAR A ROAD 15 MILES SOUTH OF LEESBURG, FL
>

Hello guys, It was actually on a nice two lane road, no wires over it,
wide berms, no driveways or signs, and no traffic, at least until short
final.

I was climbing through 5500 ft when the note of the engine changed, I
checked the guages, all green, leaned the mixture, and reduced throttle.
Then heard a loud growl and then engine disengage from the prop.

I pressed "nearest" on my gps, and it listed Leesburg first, (I had just
left my friend there). I thought it said 30 miles distance, but that must
have been the heading, since Zepherhills would have been listed first.

Anyway, I had lots of time to select my landing spot, and picked a good
one. Which was near a divided highway. 11.5 miles from Leesburg.

Go ahead with your "I told you so's", just remember that there was not a
good alternative six years ago, and my junkyard gearbox has been good to
me.


George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>

[Bob Chilcoat]

Matt's response gives me an thought. Has anyone ever tried a torque
converter by itself as a PSRU? Seems like it might solve a number of
problems, be relatively light, and not subject to wear. Just a thought -
I'm sure there would be lots of new problems.

--
Bob (Chief Pilot, White Knuckle Airways)

"Matt Whiting" > wrote in message
...
> wrote:
<snip>
> And flywheels? That is one advantage of automatic transmissions, the TC
> damps the torsional vibrations from the engine and prevents them from
> reaching the transmission and drivetrain. Most standard shift vehicles
> have spring hub clutch disks to help cushion the drive train.
>
> Matt
>

[Bill Daniels]

Torque converters slip and convert HP into heat. Lossy.

There are torsional vibration dampers that are just high hysterisis
elastomers in a torque coupling that might help.

"Bob Chilcoat" > wrote in message
...
> Matt's response gives me an thought. Has anyone ever tried a torque
> converter by itself as a PSRU? Seems like it might solve a number of
> problems, be relatively light, and not subject to wear. Just a thought -
> I'm sure there would be lots of new problems.
>
> --
> Bob (Chief Pilot, White Knuckle Airways)
>
> "Matt Whiting" > wrote in message
> ...
> > wrote:
> <snip>
> > And flywheels? That is one advantage of automatic transmissions, the TC
> > damps the torsional vibrations from the engine and prevents them from
> > reaching the transmission and drivetrain. Most standard shift vehicles
> > have spring hub clutch disks to help cushion the drive train.
> >
> > Matt
> >
>
>

[Corky Scott]

On Wed, 22 Dec 2004 12:31:10 -0500, "George A. Graham" >
wrote:

>Go ahead with your "I told you so's", just remember that there was not a
>good alternative six years ago, and my junkyard gearbox has been good to
>me.

What's important here George is that you made it down safely and
without damaging your airplane. Not everyone manages to do this, some
die in the attempt. I'm really impressed.

The secondary part is I'd sure like to know what failed in the
transmission. It's helpful information so that future experimenters
can know about it.

It would also be helpful to know what you did, if anything to modify
the transmission to become a psru.

Thanks George, you really got a nice present for Christmas.

Corky Scott

PS, You're famous ;-)

[Matt Whiting]

Bob Chilcoat wrote:
> Matt's response gives me an thought. Has anyone ever tried a torque
> converter by itself as a PSRU? Seems like it might solve a number of
> problems, be relatively light, and not subject to wear. Just a thought -
> I'm sure there would be lots of new problems.

I suspect that heat generation would be the killer for a typical auto
unit. Also, I don't know if the lock-up clutch would work at the torque
levels required in AC use. Probably other problems as well, but I'll
bet heat generation would be a biggie, especially if the lock-up clutch
couldn't be used. And if the lock-up could be used, you'd have no
reduction ratio, which means you'd no longer have have PSRU, just a PU! :-)


Matt

[Blueskies]

"Corky Scott" > wrote in message ...
> On Wed, 22 Dec 2004 03:11:51 GMT, "Blueskies"
> > wrote:
>
>>Doesn't the 'mazda' rotary mnimize this pulsation?
>
> Not if the Powersport saga is to be believed. Their initial efforts
> resulted in a LOT of psru failures.
>
> See:
> http://www.powersportaviation.com/Home/Reduction%20drive/Reduction%20drive.htm
>
> Ross Aero, on the other hand put together a planetary gear design and
> seemed to suffer no torsional problems at all. They told me that some
> engineer stopped in to tell them that he'd analized their reduction
> unit and claimed that it would destructively vibrate at 300 rpm. Of
> course the engine only sees that rpm during startup or shut down. The
> rest of the time it's operating well above that.
>
> The Ross Aero psru is what Tracy Crook initially used in his Mazda
> powered RV-4. I gather he substantially modified it since then and
> may now offer one of his own.
>
> Corky Scott
>

I remember someone talking about a damper that was filled with steel shot or similar, but I cannot find a reference to
it now.

[Ed Sullivan]

On Wed, 22 Dec 2004 22:39:59 GMT, "Blueskies"
> wrote:

>
>"Corky Scott" > wrote in message ...
>> On Wed, 22 Dec 2004 03:11:51 GMT, "Blueskies"
>> > wrote:
>>
>>>Doesn't the 'mazda' rotary mnimize this pulsation?
>>
>> Not if the Powersport saga is to be believed. Their initial efforts
>> resulted in a LOT of psru failures.
>>
>> See:
>> http://www.powersportaviation.com/Home/Reduction%20drive/Reduction%20drive.htm
>>
>> Ross Aero, on the other hand put together a planetary gear design and
>> seemed to suffer no torsional problems at all. They told me that some
>> engineer stopped in to tell them that he'd analized their reduction
>> unit and claimed that it would destructively vibrate at 300 rpm. Of
>> course the engine only sees that rpm during startup or shut down. The
>> rest of the time it's operating well above that.
>>
>> The Ross Aero psru is what Tracy Crook initially used in his Mazda
>> powered RV-4. I gather he substantially modified it since then and
>> may now offer one of his own.
>>
>> Corky Scott
>>
>
>I remember someone talking about a damper that was filled with steel shot or similar, but I cannot find a reference to
>it now.
>
>
I can't recall the name, but they were used by Molt Taylor in his
pusher designs and were also used with the Honda Civic engine in some
BD-5s

Ed Sullivan

[Denny]

Not to be a putz, but if you had talked with the people in the old
days who started putting "car" engines in boats, they would have told
you that automotive manual transmissions were tried and generally found
wanting. Marine transmissions have spring or elastic couplings, similar
to those on auto clutches but bigger, and the gears are oversize.

A torsion damper of some type-either a spring or elastic coupling, a
quillshaft, or a belt or chain with a little stretch-is an absolute
necessity. There's a simple way of measuring the torsion flexion which
can be quickly used to troubleshoot the problems: on either side of the
coupling, a "tone wheel" or regularly spaced magnetic or optical 'mark'
is placed and a pickup-a LED/sensor or a simple solenoid coil (think
electric guitar or Hammond organ)is placed. The phase relationship
between the two signals is monitored and as the engine/load are cycled,
where the two signals "wobbles" is where the flexion is happening.
It's a simple test to rig up. OMC and Mercury have been doing this for
years. I know because I worked in a music store in Wisconsin and they
would buy a certain type of internally amplified guitar pickup for this
purpose.

[[email protected]]

On Wed, 22 Dec 2004 16:25:23 -0800, Ed Sullivan >
wrote:

>On Wed, 22 Dec 2004 22:39:59 GMT, "Blueskies"
> wrote:
>
>>
>>"Corky Scott" > wrote in message ...
>>> On Wed, 22 Dec 2004 03:11:51 GMT, "Blueskies"
>>> > wrote:
>>>
>>>>Doesn't the 'mazda' rotary mnimize this pulsation?
>>>
>>> Not if the Powersport saga is to be believed. Their initial efforts
>>> resulted in a LOT of psru failures.
>>>
>>> See:
>>> http://www.powersportaviation.com/Home/Reduction%20drive/Reduction%20drive.htm
>>>
>>> Ross Aero, on the other hand put together a planetary gear design and
>>> seemed to suffer no torsional problems at all. They told me that some
>>> engineer stopped in to tell them that he'd analized their reduction
>>> unit and claimed that it would destructively vibrate at 300 rpm. Of
>>> course the engine only sees that rpm during startup or shut down. The
>>> rest of the time it's operating well above that.
>>>
>>> The Ross Aero psru is what Tracy Crook initially used in his Mazda
>>> powered RV-4. I gather he substantially modified it since then and
>>> may now offer one of his own.
>>>
>>> Corky Scott
>>>
>>
>>I remember someone talking about a damper that was filled with steel shot or similar, but I cannot find a reference to
>>it now.
>>
>>
>I can't recall the name, but they were used by Molt Taylor in his
>pusher designs and were also used with the Honda Civic engine in some
>BD-5s
>
>Ed Sullivan
They were made by Dodge Power products, and I think they were called
FlexiDyne?

[[email protected]]

On Wed, 22 Dec 2004 15:45:03 -0500, Matt Whiting
> wrote:

>Bob Chilcoat wrote:
>> Matt's response gives me an thought. Has anyone ever tried a torque
>> converter by itself as a PSRU? Seems like it might solve a number of
>> problems, be relatively light, and not subject to wear. Just a thought -
>> I'm sure there would be lots of new problems.
>
>I suspect that heat generation would be the killer for a typical auto
>unit. Also, I don't know if the lock-up clutch would work at the torque
>levels required in AC use. Probably other problems as well, but I'll
>bet heat generation would be a biggie, especially if the lock-up clutch
>couldn't be used. And if the lock-up could be used, you'd have no
>reduction ratio, which means you'd no longer have have PSRU, just a PU! :-)
>

Just some clarification.

A fluid coupling is a lossy device - very lossy. A torque converter is
several orders of magnitude better, actually "converting" RPM and
Torque, very much similar to a gear train. Still lossy. You would NOT
want to use the lockup.

There WERE torque converters made with planetary gears in them as both
overdrives and underdrives. Not sure if anyone makes them any more.
>
>Matt

[Blueskies]

> wrote in message ...
> On Wed, 22 Dec 2004 16:25:23 -0800, Ed Sullivan >
> wrote:
>
<snip>>>>>
>>>
>>>I remember someone talking about a damper that was filled with steel shot or similar, but I cannot find a reference
>>>to
>>>it now.
>>>
>>>
>>I can't recall the name, but they were used by Molt Taylor in his
>>pusher designs and were also used with the Honda Civic engine in some
>>BD-5s
>>
>>Ed Sullivan
> They were made by Dodge Power products, and I think they were called
> FlexiDyne?


BINGO---
http://www.dodge-pt.com/products/pt_components/flexidyne/flexidyne.html

[Ernest Christley]

Corky Scott wrote:
> On Wed, 22 Dec 2004 03:11:51 GMT, "Blueskies"
> > wrote:
>
>
>>Doesn't the 'mazda' rotary mnimize this pulsation?
>
>
> Not if the Powersport saga is to be believed. Their initial efforts
> resulted in a LOT of psru failures.
>
> See:
> http://www.powersportaviation.com/Home/Reduction%20drive/Reduction%20drive.htm
>
> Ross Aero, on the other hand put together a planetary gear design and
> seemed to suffer no torsional problems at all. They told me that some
> engineer stopped in to tell them that he'd analized their reduction
> unit and claimed that it would destructively vibrate at 300 rpm. Of
> course the engine only sees that rpm during startup or shut down. The
> rest of the time it's operating well above that.
>
> The Ross Aero psru is what Tracy Crook initially used in his Mazda
> powered RV-4. I gather he substantially modified it since then and
> may now offer one of his own.
>
> Corky Scott
>

Tracy does in fact offer his own, now in two versions, a 2.17:1
reduction and a 2.89:1 reduction.

The torsion properties of the rotary is very small compared to a piston
engine. It still has to compress the gas, and then withstand an metered
explosion. But it doesn't have pistons completely reversing direction,
and it has a rather large rotating mass (the rotors and eccentric
shaft), which will absorb much of the pulse in inertial effects.

You can read about it on Tracy's website, but there are basically two
different design philosophies. Building the PSRU gearing tight, with
very small clearances moves the resonant frequency up. Build it loose,
and the resonant frequency goes down. The 13B has a RPM range of
something on the order of 800 to 7000 RPM (depending on tuning and how
hard the pilot wants to push his luck).

Powersport chose the former philosophy. Build it tight enough to put
the resonance above the 6000RPM range. This required incredibly tight
tolerances, which drove the price into the ridiculous range.

Ross Aero, by design or dumb luck, went the other direction. The amount
of play that is in the gears as taken from the truck's transmission is
enough to push the resonance down below the idle speed (ie, into the who
cares range).

Tracy Crook's design is based on the Ross, but with several improvements
that came about due to several problems that Tracy ran into. Several of
these units have been flying for years without problems.


--
http://www.ernest.isa-geek.org/
"This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

[Bob Korves]

"Ed Sullivan" > wrote in message
...
> On Wed, 22 Dec 2004 22:39:59 GMT, "Blueskies"
> > wrote:
(snip)
>
> >I remember someone talking about a damper that was filled with steel shot
or similar, but I cannot find a reference to
> >it now.
> >
> >
> I can't recall the name, but they were used by Molt Taylor in his
> pusher designs and were also used with the Honda Civic engine in some
> BD-5s
>
> Ed Sullivan
>

Dodge Flexidyne dry fluid coupling.

http://www.dodge-reliance.com/pdf/magazine/volume_12/flexidyne.pdf

http://www.mini-imp.com/drive_train_and_starting.htm
-Bob

[Stealth Pilot]

On Wed, 22 Dec 2004 12:31:10 -0500, "George A. Graham" >
wrote:


>
>Go ahead with your "I told you so's", just remember that there was not a
>good alternative six years ago, and my junkyard gearbox has been good to
>me.
>
you are one of aviations pioneers george.
not all pioneering efforts lead to anything in the long term.
honing anything useful takes time and often many dead end attempts.
we applaud your efforts.
what you have shown is that the approach is not too far off the mark.

6 years isnt too informative though.
how many hours were accumulated in those years?
how much work had the gearbox done before finding a home in your
aircraft?
Stealth Pilot
Australia.

[George A. Graham]

On Fri, 24 Dec 2004, Stealth Pilot wrote:

> 6 years isnt too informative though.
> how many hours were accumulated in those years?
> how much work had the gearbox done before finding a home in your
> aircraft?

The gearbox was used, over 80,000 miles when I got it, I installed new
bearings. It flew 415 hours in the six years. I suspect that the bearings
may have worn enough to disturb the gear lobe fit (but I don't know).
In hindsite, I wish that I had replaced the bearings at annual.

To share my understanding on other issues raised on RAH:

The Mazda Wankle has very low amplitude (strength) power pulses, since the
power stroke is over 130 degrees of the output shaft.

The frequency of power pulses is the same as a four cylinder four stroke
as there are two per revolution. However, if it starts on one rotor,
then every other pulse is removed, which lowers the frequency by one half.
That is not likely to happen on any other engine.

If you know the moment of inertia of each component, and the rate of
spring of the revolving mass, then you can compute the frequency during
which torsional resonance is likely. In my setup, that is 200 to 300 rpm
with both rotors running (double that on one rotor). The forces generated
by resonnance, approach infinity, so no "stronger" gears help much.

I did use an elastomeric dampener (clutch hub), and a quill shaft on
the tranny input (came with it).

Thanks for all of your kind words, I'm off to retrieve my airplane today.

George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>