Auto Conversion, reduction using a manuaul transmission
Scott VanderVeen
seems to me and my curious mind, that a forward mounted Chevy V-8, with a
manual transmission, via an axel could drive a rear prop. A tunnel would be
the integrated through the fuselage, but other than that what would preclude
this from working?
I know a gear manual gear box is about 100lbs, but you could have one
reworked to remove the gears you don't need, along with clutch etc. and keep
the gear that would give the best ratio 2:1, 2.5:1
I did a few sketches:
http://www.arrow4graphics.com/xplane2.jpg
http://www.arrow4graphics.com/xplane1.jpg
Thank you in advance.
Scott VanderVeen
Alan Dranct
I'm not an engineer, but I've got a couple of comments. Nice sketches
by the way..
Moment = force * perpendicular distance to line of action. LOA is
the axel from transmission to prop. Distance isn't all that small
with a good sized prop.. Force (torque from the engine) will be
large. I think the twisting or vibration forces on the axel/prop or
gear box attachments might break them.
Complexity: I think it might be possible.. But could be a plumbing
nightmare.. Didn't some people with BD-5s try something like this?
I know there are people with a far better understanding of Physics
around here so I'll leave it at that...
C.D. Damron
with its transmission. He would shift it as needed.
Alan Dranct wrote in message <67furts70j1j7bai9...@4ax.com>...
jerry wass
w/ U joints to keep the L/R ratio down to a safe level--or be 6 or 7" in
diameter. I have some tail rotor shafts for a chopper that are 4-1/2"
in diameter and only 5Ft long.[.080 Alum tube}. L/R = length/ Radius of
Gyration.
Bruce A. Frank
attempt to build a PSRU for the V-6 STOL. Problems with durability
caused him to move on to the cogbelt design.
Bruce A. Frank
Bruce A. Frank
--
Bruce A. Frank, Editor "Ford 3.8L Engine and V-6 STOL
BAF...@worldnet.att.net Homebuilt Aircraft Newsletter"
| Publishing interesting material|
| on all aspects of alternative |
| engines and homebuilt aircraft.|
*------------------------------**----*
\(-o-)/ AIRCRAFT PROJECTS CO.
\___/ Manufacturing parts & pieces
/ \ for homebuilt aircraft, TIG
welding
0 0
David Rahman
boom tail
you could eliminate the drive shaft,or most of it.
Chow for now.
David
Dan Thomas
Automotive transmissions aren't designed to handle high power
loadings for extended periods. A car in cruising configuration uses
little power, maybe 30 or 40%. Imagine pulling a trailer up a steep
hill at full throttle; the transmission will overheat and burn out
before too long.
I used to fool with motorboats. Auto transmissions didn't work
too well there, either. There are purpose-built marine transmissions
that are designed to take the power, and some that have reduction or
overdrive capability also use cooling systems. Not much airflow around
the tranny in a boat.
And yes, they're heavy. The extra weight and friction losses
just about negate any power gained.
Dan
'RJ' Cook
longitudinal flexibility of the long shaft. Both are resolvable.
To insure natural torsional vibrations of the system are well above those of
normal operating range, a relatively heavy shaft is required to reduce
torsional flexibility. The other option, presuming the shaft is strong
enough to withstand the primary drive torque, is to make the shaft very
flexible in torsion (like a quill shaft), therefore keeping the torsional
resonant frequency, and all significant nodes around primary resonant
frequency, so low they aren't within the operating range of the system.
Additionally, use a torsional damper tuned to the shaft system's natural
resonance to manage a buildup of torsional vibration energy. A flexible
shaft will result in some whip during startup and shut down, which might be
managed by introduction of a flexible or fluid drive into the system I
believe that the management of torsional vibrations will be the toughest
task to accomplish.
The other obvious challenge for this configuration would be management of
longitudinal flexibility, and therefore critical shaft speed. The critical
shaft speed must be significantly greater than the maximum system operating
speed. This dictates subdivision of the shaft into short enough
longitudinal sections, utilizing roller bearings as supports, to reduce
longitudinal flexibility and increase the critical shaft speed of the
segments. This is generally the easiest of the 2 problems to solve.
RJ
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"Scott VanderVeen" <arro...@hotmail.com> wrote in message
news:dhGv7.36336$My2.18...@news1.mntp1.il.home.com...
Dan Horton
longitudinal flexibility of the long shaft. Both are resolvable.>>
Well said Mr. Cook.
Scott, go to: www.prime-mover.org/engines/Torsional
Read the article by Donald Hessenaur as many times as necessary. Very
good torsional vibration primer, and a good story too.
The critical shaft speed problem is equally serious, but a lot easier to
solve.
Dan
George A. Graham
> Automotive transmissions aren't designed to handle high power
> loadings for extended periods.
Mine works good. I think that boats and cars unhook the engine for
startup, thus the torsionals are isolated.
The Curtis AirCobra used a setup similar to what Scott is looking for,
with the engine behind the cockpit driving a front mounted gearbox through
a long driveshaft.
All that said, I would look elsewhere for a plastic pusher, the Velocity,
Cozy and AeroCanard are all great airplanes.
George Graham
RX-7 Powered Graham-EZ, N4449E
Homepage <http://bfn.org/~ca266>
The Blakers
thing with the WW-II P-39 Airacobra.
"Bruce A. Frank" <baf...@worldnet.att.net> wrote in message
news:3BBF5B85...@worldnet.att.net...
J&DKahn
I think, is the one with the explanation of propeller gyro loads. It
explains why engines like VWs and Corvairs are able to tolerate propeller
loads with only a small bearing journal at the prop end.
johnk
Dan Horton <dhp...@aol.com> wrote in message
news:20011007014650...@mb-fn.aol.com...
Bill Daniels
Additional questions?
Could the shaft be made of filament wound carbon fiber/epoxy? This should
be very stiff and light compared to a metal shaft.
If the tranny doesn't need to be "shiftable", how about a single ratio
planetary gearbox? Again, lighter and stronger.
How about a strong, light planetary box at the rear of the shaft so that the
shaft turns at crankshaft speed? That would put less torque on the shaft.
"'RJ' Cook" <rco...@houston.rr.com> wrote in message
news:GbNv7.44566$pN2.14...@typhoon.austin.rr.com...
Bruce A. Frank
Excellent site!
--
Dan Horton
<<Excellent site!>>
( www.prime-mover.org/engines/Torsional)
Glad you like it. (1) Mr. Hessenaur manages to convey the lay basics
better than anything I've seen. (2) It illustrates that even though torsional
vibration is an old science, it can confuse some pretty bright people. (3)
Last, it's a nice illustration of how powerplant design problems can create
airframe problems. Note the use of a strobe to find them.
One the critical shaft RPM issue, did you catch Steve's comments in
Contact #61?
Dan
be...@bellatlantic.net
derivative of those used in offshore boat racing but the principle was the
same. The ERacer has always struck me as the best engineered of all the auto
engine conversions I have seen, especially considering it was mid-engine and
liquid cooled. A drawing of the ERacer firewall rearward is the cover photo of
the EAA _Alternative Engines_ book.
Take a look at http://listproc.eracer.org/hangar_html/ for ERacer info.
--beeky
Dan Horton
<<The article I found most interesting, with the most relevance to most people
I think, is the one with the explanation of propeller gyro loads.>>
Yes. A comment on those articles: Both authors attempt to calculate the
mass moment of inertia of the subject propeller. Calculating the MMOI of a
complex shape like an airplane prop is silly if you have access to the actual
prop. You can easily hang it from the shop ceiling, count oscillations for a
time period, and calculate it's exact inertia, no assumptions required. You
can do the same with crankshafts, flywheels, belt sprockets, and every other
component in a torsional system.
The physical test setup found in Rotax SI 11 UL 91 E works well. It's
just two pieces of safety wire 72" long and 12" apart. Don't need the formula
on page 3 unless you're trying to select an approved Rotax prop/gearbox
combination.
After you weigh, then time and count, use:
I = W[rT/(2pi)]^2/L, where
I = Inertia in slugs/ft^2
W = weight in pounds
r = radius of the wires from center of rotation, in feet (0.5 ft this case)
T = time in seconds for each oscillation (an oscillation is a swing, stop, and
reverse back to starting point)
L = pendulum length in feet (6)
Notice everything is in feet, pounds and seconds so the answer is in
slug-ft^2, which is what you'll find in most of the other equations for
torsionals, etc. The math is just multiply and divide stuff, so even a dumbass
country boy like me can put it to use.
For an actual 68" mahogany prop:
I = W[rT/(2pi)]^2/L
I = 6.62 [0.5x5.5/(2 x 3.14)]^2 / 6
I = 0.2114 slug-ft^2
There could be a lot of variation between prop designs with the same length
and base material. You need accurate inertia numbers to do both gyro loads and
system frequencies, so best to measure YOUR prop.
Dan
Dan Horton
be very stiff and light compared to a metal shaft.<
Sure. Question is, do you want it to be torsionally stiff? Shaft
stiffness is one of the variables you use to adjust system frequency. On the
practical side, how would you attach the end fittings? Tricky.
>How about a strong, light planetary box at the rear of the shaft so that the
shaft turns at crankshaft speed? That would put less torque on the shaft.<
Yes, but it worsens the critical RPM issue.
Dan
Dan Thomas
> Some very nice responses to this thread.
>
> Additional questions?
>
> Could the shaft be made of filament wound carbon fiber/epoxy? This should
> be very stiff and light compared to a metal shaft.
>
> If the tranny doesn't need to be "shiftable", how about a single ratio
> planetary gearbox? Again, lighter and stronger.
>
> How about a strong, light planetary box at the rear of the shaft so that the
> shaft turns at crankshaft speed? That would put less torque on the shaft.
>
>
Planetaries are probably the best bet for gearing systems. If
I recall correctly, Continental's Tiara engine used spur gears and had
propblems. The spur-geared Continental GO-300 (I think that's right)
used in the Cessna 175 had problems, too, mostly because it wasn't
operated at recommended RPMs. I have heard that the spur-geared
engines used in the bigger Cessna piston twins can offer headaches.
The old radials that used planetaries seemed to work well.
I am open to correction on all of this.
Automotive automatic transmissions use planetaries. Few gear
problems, more shifting clutch problems.
Now, I also remember something about the prototype BD-5. (Hope
I'm not going to make someone mad here for bringing up this airplane
again.) I think it used a variable-speed drive from a snowmobile
between the engine and prop shaft. Lower prop speed and more torque
for takeoff, with the prop RPM coming up as the airspeed increased
while the engine RPM remained relatively constant. The drawback was
that it did nothing for propeller efficiency because the pitch was
fixed, so that half the prop was still stalled early in the takeoff
roll, and tip speeds were still too high in cruise. Can't get around
the need for prop pitch variability. Shifting a trasnmission sounds
good but doesn't gain you much.
Dan
Marc McNaughton
The late Molt Taylor built successful long-driveshaft airplanes years - no,
decades - ago. His Mini-IMP put the engine behind the pilot, whereas his
'Taylor Bullet' was a two seater that had the engine (Revmaster) in front,
prop in back with a long shaft *exactly* like Scott has described and drawn.
The Bullet was around in the late '80's, I believe, although he only built
one prototype. I understand it's now in the Oregon Air Museum in Eugene,
Oregon.
Taylor handled the long driveshaft problem from several directions. The
biggest element was a dry-fluid 'clutch' called a "Flexidyne." It was a
disk-shaped container that was connected to the shaft from the motor. It was
partially filled with metal shot. Inside was a wavy circular plate that was
connected to the prop shaft. When the engine spun up, the shot was pasted
against the outer circumference of the container and engaged the wavey
plate, transmitting power to the prop shaft. The key thing was that the
plate could slip slightly in response to the power pulses of the engine,
effectively reducing torsional vibration in the shaft.
He also used a large OD, thin-wall aluminum drive shaft, appropriately
braced at critical lengths. He used the system on everything from his (Part
23 certified!) AeroCar to the Mini-IMP, to the Micro-IMP and on to the
Bullet, as mentioned above. The Micro-IMP put the Flexidyne in the hub of a
neat little variable-pitch prop that Molt was developing.
The Flexidyne is a commercial product from another company - I looked up the
product on the web and it looks like Dodge has bought the company. Here's
the link:
http://www.dodge-pt.com/products/pt_components/flexidyne/flexidyne.html
I haven't been very successful in finding articles about Molt and his planes
on the web, although the Mini-IMP is still being sold at the following site:
http://www.mini-imp.com/
Molt wrote an excellent article on the design of long, light driveshafts in
Sport Aviation many years ago - again, sometime in the eighties when he was
most active. I'll bet the EAA has it on archive.
--
Best Wishes,
Marc McNaughton
(remove the 'e' before "home" to reply via e-mail)
"Scott VanderVeen" <arro...@hotmail.com> wrote in message
news:dhGv7.36336$My2.18...@news1.mntp1.il.home.com...
'RJ' Cook
a nearly perfect solution, presuming heat that might weaken the matrix
material over time was not a factor. Stiffness and strength to weight
ratios are excellent.
RJ Cook CFII-SMEL
Aerospace Engineering, Retired
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"Bill Daniels" <wdan...@uswest.net> wrote in message
news:a0Zv7.11$aW1.1...@news.uswest.net...
J&DKahn
considered the Flexidyne more or less a panacea for torsional resonance
issues, although I've heard other comments that they don't stand up all that
well to long term use.
Molt spent a lot of time on a conversion using a Kawasaki Z1000 engine. He
had a reduction drive for it that used the Flexidyne and a HyVol chain.
Not sure why they abandoned it.
IIRC another serious drawback of the flexidyne is that the prop is free to
windmill when the outer housing isn't spinning.
On the issue of long drive shafts, there are simply so many fundemental
disadvantages to the configuration (weight/complexity) that while possible
it isn't all that practical in the real world. Which is the simple reason
the configuration is so rare.
johnk
Marc McNaughton <mar...@ehome.com> wrote in message
news:gl2w7.33710$8a.18...@news1.rsm1.occa.home.com...
> How soon we all forget!
>
>
'RJ' Cook
--
Aerospace Engineering, Retired
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
Charles K. Scott
be...@bellatlantic.net writes:
> Shirl Dickey took this basic approach for his ERacer. The transmission was a
> derivative of those used in offshore boat racing but the principle was the
> same. The ERacer has always struck me as the best engineered of all the auto
> engine conversions I have seen, especially considering it was mid-engine and
> liquid cooled. A drawing of the ERacer firewall rearward is the cover photo of
> the EAA _Alternative Engines_ book.
>
> Take a look at http://listproc.eracer.org/hangar_html/ for ERacer info.
Maybe someone can update my information but my understanding is Mr.
Dickey no longer flies behind an auto engine. I heard he changed it
out because he was tired of making forced landings.
Like I said, that's what I heard. Does anyone know differently?
Corky Scott
Charles K. Scott
dan.t...@pbi.ab.ca (Dan Thomas) writes:
> Planetaries are probably the best bet for gearing systems. If
> I recall correctly, Continental's Tiara engine used spur gears and had
> propblems. The spur-geared Continental GO-300 (I think that's right)
> used in the Cessna 175 had problems, too, mostly because it wasn't
> operated at recommended RPMs. I have heard that the spur-geared
> engines used in the bigger Cessna piston twins can offer headaches.
> The old radials that used planetaries seemed to work well.
> I am open to correction on all of this.
There's nothing wrong with a properly engineered spur gear, check Rolls
Royce Merlin. That engine used a spur gear reduction box and handled
from 900 hp at inception to over 2,000 horsepower later. They are
still being used in racing today and handle MUCH more than 2,000 hp.
Corky Scott
Scott VanderVeen
when I was about 7-8 yrs old I asked my grandfather, a mechanic at the time,
about hooking up an electric motor to a generator and feed the electricity
back to the motor. He said it had something to do about propetual motion
and that it just wouldn't work, bummer. BTTDB.
-Scott
Dan Horton
<<Molt's shafting had a resonant frequency below that of operational
frequencies and the flexidyne clutch protected the shafting through these
RPM's.>
Good point. The soft shaft stiffness (and low system frequency) is
something that I suspect a whole bunch of people miss. They think a flexidyne
is some sort of magic "absorber" when it's really more like a centrifugal
clutch. Ain't gonna do much good if it's locked at a shaft RPM equal to the
system frequency.
Dan
David Taylor
The only weird part would be the power coming out and ducking back under
the engine.... But that might be an advantage because it could duck under
the passengers if it lined up right.
Wonder if this could be the answer for using a rotary engine?? 6000 rpm's
divided by 2.5 would be just about right for a prop wouldn't it??
Hmm ,,,, Peripheral port with dual feeding efi and redundant ignition,
Turbo normalised to bring up the torque.??
I'm going to go away quetly now...........
Too many toys and projects could ruin a man..............................I'fen he
was lucky....
Dave
Staying up late in Portland Or.....
PS:wow...> 25 threads in a row without going off topic......
-----------------------------------------------------------------------------------------------------
'RJ' Cook
one drawback, they are noisy. If noise isn't an issue, spur gears are the
lightest and most compact gears you can use. Beware, however, to size your
gears with not only drive torques considered, but torsional vibration loads
and accepted safety factors. The torsional vibration loads may actually be
the greater stress factor in many systems.
--
RJ Cook CFII-SMEL
Aerospace Engineering, Retired
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"Dan Thomas" <dan.t...@pbi.ab.ca> wrote in message
news:1a291bd5.01100...@posting.google.com...
'RJ' Cook
one of the more ideal automotive powerplants around for aircraft use. It is
smooth, light for its power output, compact, and Mazda engines are available
reasonably. This smoothness makes the requirement for a drive train less
critical. The engine LIKES A TURBO. Do a search under mazda rotary on the
web and you will find some interesting sites. The rotary would also be
perfect for a ducted fan project,as per an earlier post by me.
--
RJ Cook CFII-SMEL
Aerospace Engineering, Retired
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"David Taylor" <taylor...@dsl-only.net> wrote in message
news:3BC2A145...@dsl-only.net...
assa9
assa9
"'RJ' Cook" <rco...@houston.rr.com> wrote in message
news:zPxw7.33079$Kp2.17...@typhoon.austin.rr.com...
highflyer
They DID use a quill shaft to reduce the stiffness of the transmission
system and lower the torsional resonant frequency below the operating
frequency of the system. The Tiara did the same thing, for the same
reason. It did a LOT to help the gears live.
The Continental GO-300 got a bad reputation in the Cessna 175 because
people didn't believe the green line on the tach that said to avoid
operation below 2700 RPM. They tried to operate it like the O-300
to increase engine life and the result was torsional harmonics that
ate the spur gears in jig time. The gear in the GO-300 is a monster,
about three times the width of a similiar diameter gear in the
transmission of a car with greater horsepower. The huge overkill
in the gear was required to get past the resonant points in the
system and get it up to the recommended operating range.
I have seen the gearbox go through a couple of major overhauls of the
rest of the engine, when it was operated correctly! :-)
--
HighFlyer
Highflight Aviation Services
Dan Horton
<<Beware, however, to size your gears with not only drive torques considered,
but torsional vibration loads and accepted safety factors.>>
Badly done, torsional loads can easily be 50 times nominal torque. Been
there, done that. The current system is 6 times nominal when in resonance, by
actual measurement. I pass though the resonant range in normal operation, but
components are sized for it. No practical difference. Even if you place the
resonant range below the operating range you still pass through it during
startup, so as RJ says, you still have to size components for it.
Arrow Gear has a nice catalog for their stock cut and ground gears,
including design tech info in the back. Ground gears are expensive, but much
more durable.
Dan
Dan Horton
<<It sounds like a plain old velvet drive out of a competition ski boat??>>
Good example of why copying "just like" stuff doesn't work. It must be
"exactly like" or it's a guess. If you change any spring rate, inertial mass,
or exciting frequency, you've changed the system behavior.
In this case an exact copy of the marine system would still change the
prop. The marine prop would have an inertia perhaps hundreds of times less
than the aviation prop, operate in a more viscous media, and have little spring
rate between the blades and the hub. New system, unknown torsional beahvior.
Dan
'RJ' Cook
Torsional vibrations will kill any system (quickly) if not compensated for.
Now, a quill shaft or damper or fluid drive or some other system component
may be utilized to decrease the size of the gear reduction drive, but the
SYSTEM MUST be designed as a SYSTEM, not just assembling pieces that worked
well in OTHER SYSTEMS they was designed for.
--
RJ Cook CFII-SMEL
Aerospace Engineering, Retired
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"Dan Horton" <dhp...@aol.com> wrote in message
news:20011009114929...@mb-mp.aol.com...
'RJ' Cook
--
RJ Cook CFII-SMEL
Aerospace Engineering, Retired
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"assa9" <dpi...@yahoo.com> wrote in message
news:ts5p527...@corp.supernews.com...
Russell Kent
greater than normal amount of stress on the exhaust system. This is because of
two aspects of the Mazda Wankel's exhaust gases:
1. they are substantially hotter than other engines (about 1,700 deg). This
is hot enough to cause rapid oxidation failure of many commonly used metals
in exhaust systems. Consequently, some conversions uses Inconel or
stainless steel exhaust system components, both of which can be difficult
to fabricate with because of welding and forming issues.
2. because the Mazda 12A and 13B Wankel's are peripheral port exhaust engines,
the exhaust gas pulse exits at (near?) supersonic speed. This pulse can
induce vibration fatigue failure in the exhaust plumbing if not built to
withstand it. The upcoming Renesis Mazda Wankel (2002 year model) is a
side port engine, so the supersonic pulse should be less of an issue,
perhaps even a non-issue, but we will have to wait and see.
In turbocharged or turbo-normalized engines, the exhaust gas pulse is captured
between the engine's exhaust port and the turbine, so the structural strength
to resist the pulses can be limited to that small area. Likewise, the extreme
heat of the gases is *somewhat* limited to the same area.
Engineering an exhaust header for this engine is non-trivial: even Mazda's own
turbine housings (certain years) are prone to cracking.
A non-turbocharged engine will need the structural strength throughout, which
tends to make a very heavy exhaust system.
Also, the exhaust system (for both turbo and non-turbo) can be an undesirable
source of radiant heat under the cowl unless care is taken to properly shield
everything.
Russell Kent
Clifford Bradford
the engine.
"C.D. Damron" wrote:
>
> There was a guy a while back that installed a motorcycle engine complete
> with its transmission. He would shift it as needed.
>
> Alan Dranct wrote in message <67furts70j1j7bai9...@4ax.com>...
> >On Sat, 06 Oct 2001 16:26:49 GMT, "Scott VanderVeen"
> ><arro...@hotmail.com> wrote:
> >
> >> The Cirrus VK-30, no longer available, used a pusher configuration.
> It
> >>seems to me and my curious mind, that a forward mounted Chevy V-8, with a
> >>manual transmission, via an axel could drive a rear prop. A tunnel would
> be
> >>the integrated through the fuselage, but other than that what would
> preclude
> >>this from working?
> >>
> >>I know a gear manual gear box is about 100lbs, but you could have one
> >>reworked to remove the gears you don't need, along with clutch etc. and
> keep
> >>the gear that would give the best ratio 2:1, 2.5:1
> >>
> >>I did a few sketches:
> >>
> >>http://www.arrow4graphics.com/xplane2.jpg
> >>http://www.arrow4graphics.com/xplane1.jpg
> >
> >I'm not an engineer, but I've got a couple of comments. Nice sketches
> >by the way..
> >
> >Moment = force * perpendicular distance to line of action. LOA is
> >the axel from transmission to prop. Distance isn't all that small
> >with a good sized prop.. Force (torque from the engine) will be
> >large. I think the twisting or vibration forces on the axel/prop or
> >gear box attachments might break them.
> >
> >Complexity: I think it might be possible.. But could be a plumbing
> >nightmare.. Didn't some people with BD-5s try something like this?
> >
> >I know there are people with a far better understanding of Physics
> >around here so I'll leave it at that...
> >
> >
David Taylor
"> <<It sounds like a plain old velvet drive out of a competition ski
boat??>>"
On a boat the drive shaft is stabilized with multiple support bearings
along the shaft in supporting rubber bushings. Not being a physics
savvy guy other that at the lightest level... It would seem to me that
what you need is
1. A good solid gear reduction unit.
Possibly the velvet drive style unit....
2. A support system for the shaft.
Couldn't you cancel vibrations in the shaft by irregular spacing
of support bearings along the shaft + using various hardness
rubber support bushings around the bearings. One option I
wondered about was running the shaft through a tube like a
944 porsche drive line but use several bearings inside the tube.
As far as exhaust temps, I ran a 12A in a 6 hour enduro last year.
The exhaust runs about 1400 at 6K rpm's IF you have the mix right.
At 8500 rpms down the straight it would surge to about 1600 WOT
in about 8 seconds. We get about 2 seasons out of .020 wall mild
steel for an exhaust. the most important trick is to let the pipes move
and get the collector as far as possible from the engine. I think for a
plane you should plan on at least 72" of exhaust. The primary pipes
should be no less than 42" long and the final pipe and muffler after
the collector needs to be 3" dia. The thing that usually does in our
exhaust is the backfire on down shifting, often splits the pipes.
Follow standard procedure and throttle back slowly and it
shouldn't be a problem.
I wouldn't turbonormalise a periferal intake motor, its too touchy
for detonation. But a nice large slow spooling tubo on a standard
street ported motor should work nicely. No leaded fuel allowed.
Oh well Its an interesting topic.....
Dave
'RJ' Cook
turbo normalized rotary should be a healthy setup. Would sure like to hear
you expand on your turbocharging concerns as the Mazda rotary is my number
one choice for an auto engine for a ducted fan at this point. The heat
available in the exhaust is what makes it an ideal candidate for turbos, and
the turbo is what makes the rotary a more efficient engine. The hot section
of the exhaust would surely need special attention by my way of thinking in
a turbo application.
All engines have supersonic port exhausts but the piston ported engines
generally have a very short blowdown duration making their heat release per
unit blowdown time more intense. I had not heard or read that the peak
exhaust gas temperatures were that high (1700 deg F) in an UNBOOSTED Mazda
engine. More research required I guess. Any recommended reading sources
anyone, specifically as to their exhaust characteristics when turboed?
--
RJ Cook CFII-SMEL
Aerospace Engineering, Retired
Aviation is not inherently dangerous, but,
like the sea, is terribly unforgiving of any
carelessness, incapacity or neglect.
"David Taylor" <taylor...@dsl-only.net> wrote in message
news:3BC3E361...@dsl-only.net...
Dan Horton
<Well, I did phrase it as a question,,,>
Yes, and thanks for asking.
<<On a boat the drive shaft is stabilized with multiple support bearings
along the shaft in supporting rubber bushings...... Couldn't you cancel
vibrations in the shaft by irregular spacing
of support bearings along the shaft + using various hardness rubber support
bushings around the bearings.>>
No effect on torsional vibration at all. It should be possible to design
a shaft with no supports, but I suspect boat designers go with the supports as
insurance against high hull-to-water impact induced g-loads. They would tend
to bow the center of a horizontal shaft, real bad news. A spinning shaft with
an unsupported bow in the center whips outward, an instant and violent
failure. It would vibrate for a fraction of a second, just before it tried to
cut the hull in two <g>
Don't really know why they use rubber-isolated bearings. I suspect it's
mostly because a boat hull is such a good sounding board. There would be some
vibration (noise), even if it's just bearing rumble.
Dan
Dan Thomas
> There were several articles by Taylor through the 70s and early 80s. He
> considered the Flexidyne more or less a panacea for torsional resonance
> issues, although I've heard other comments that they don't stand up all that
> well to long term use.
>
> Molt spent a lot of time on a conversion using a Kawasaki Z1000 engine. He
> had a reduction drive for it that used the Flexidyne and a HyVol chain.
> Not sure why they abandoned it.
That mention of the HyVo chain drive reminds me: Wasn't it
Geschwender Aeromotive that developed redrives for Ford and Chev V-8s
back in the '70s? They used the Morris HyVo chain in those, and I read
somewhere that there are several Piper Pawnees flying with these
setups and are used daily in spraying operations, which sounds like a
pretty tough test of any redrive. The neat thing about the HyVo was
that it ran on sprockets that looked like gears, and the chain's teeth
were designed so that as they came to the sprocket and began to curve
around it their internal teeth would spread and take up all play.
There was no lash to speak of and so they didn't fail too easily if
operated at critical RPMs. The whole thing ran in an oil bath.
You can picture the tooth arrangment if you mesh your fingers
together with both palms facing down and fingers bent down at 90
degrees so they touch. As you bend your hands so the palms begin
facing each other the fingers move apart. If the fingers were between
a couple of gear teeth they would press firmly against the teeth.
Anybody still using these drives?
Dan
David Taylor
'RJ' Cook wrote:
> Interesting turbo normalizing comment. I would seem to me a intercooled
> turbo normalized rotary should be a healthy setup. Would sure like to hear
> you expand on your turbocharging concerns as the Mazda rotary is my number
> one choice for an auto engine for a ducted fan at this point. The heat
> available in the exhaust is what makes it an ideal candidate for turbos, and
> the turbo is what makes the rotary a more efficient engine. The hot section
> of the exhaust would surely need special attention by my way of thinking in
> a turbo application.
>
Snip----
The rotary engines only real achiles heel is the engine can not stand any
detonation, Pinging, knocking etc. It fractures the apex seals. So if you turbo
charge for power you really have to do your homework.(Mazda is still
working it out and they know what they are doing....) But I think a
normalising setup would make it a sweet engine. Just enough boost to keep
the engine from seeing the altitude. This would also cure potential mixture
problems. I have also been considering a motor with duel injection systems.
The SDS EFI system for the rotary suposedly works pretty well. I figure you
would hook up two complete systems. Set them up so you would use a a/b
switch to turn on one system at a time. The whole injection setup would run
something less than 3K. They even offer it with distributorless ignition.
I don't know if you can still buy them ,, but There used to be
housings with dual trailing and leading sparkplugs. (IMSA race parts...)
This would allow for a redundant ignition system.
I figure at the end the full engine setup (No PSRU or anything furthur)
Is gonna cost approx 15K with injection and plumbing, assuming your
mainly building for mild power and very tough engine..
Pieces that would cause cost/concern
1. Radiator: (Approx same size as chev v8.)
2. Oil cooler: (8Inch high by 24 wide by 3 to 4" deep )
Rotary engines shed most of their heat through the oil.
3. Exhaust: Rotary engines are similar to 2 stroke engines in that
they make best power with a reasonably tuned exhaust.
Myths:
"Rotary engines have no bottom end torque." - They actually pull nice and
smooth off the line when correctly tuned. I know a couple folks who tow with
them in rotary engine pickups.
"Mazda carb bad." NOT. If correctly set up it works fine. its like a 3 to 400
cfm carb depending on year. (search on Yawpower for more info and I'm sure
there are other souorces.) They can be modified nicely up to almost 600 cfm.
"Webbers are good on a rotary." ONLY if someone who know rotary engines
set them up (See Racing Beat). Also see Racing Beat if you want a Holley....
you have to do illogical and strange things to make a carb work on a rotary.
Oh well off to torture my pocket book with race parts......
Dave
Portland OR.