Mott Taylor/IMP Drive Shaft Vibration Dampener
TMBesch
(and I believe sold) for the Imp? Is there a current source for them? And
any Idea of the dimensions? I want to dampen my engine pulses and hope to
put one of these in the redrive or on the shaft. I would appreciate any
leads.
Thanks,
Thom Besch
Avid Flyer MK IV (54%)
Tom Betz
>
> Does any one know about the vibration dampener that Mott Taylor designed
> (and I believe sold) for the Imp? Is there a current source for them?
I thought he used a Chrysler fluid coupling.
-- Tom Betz ----------- <http://www.pobox.com/~tbetz> ------ (914) 375-1510 --
tb...@pobox.com | Now that the living outnumber the dead, | tb...@panix.com
-----------------+ I am one of many. -- Laurie Anderson +------------------
- The whole world is a beautiful place to play music. -- Jerry Garcia, 1969 -
Charles K. Scott
tmb...@aol.com (TMBesch) writes:
> Does any one know about the vibration dampener that Mott Taylor designed
> (and I believe sold) for the Imp? Is there a current source for them? And
> any Idea of the dimensions? I want to dampen my engine pulses and hope to
> put one of these in the redrive or on the shaft. I would appreciate any
> leads.
>
> Thanks,
>
> Thom Besch
> Avid Flyer MK IV (54%)
It's a kind of dry coupling universal joint. It may present problems
attempting to squeeze it into the limited space of your Avid Flyer.
Corky Scott
John R. Johnson
uses a hollow disk on the driven side. The output shaft connects to a
plate inside the disk that is rippled. You put shot into the disk. The
weight of shot you use determines the coupling coefficient and the torque
that it will break loose at. This coupling could be easily built into
a pulley.
It has some drawbacks. No matter how you turn the output shaft it won't
couple back. You need the centrifugal force to throw the shot against the
outside of the hollow disk to grab the plate and couple torque. No
prop starts! It is kind of an autowindmill feature!
It is fairly heavy, several pounds for low horsepower version used in the
Imp. Molt uses it to decouple engine vibrations from his long driveshafts
to avoid destructive torsional vibration in the drive shaft. In a belt
driven reduction system, the belt does pretty much the same thing for
torsional vibration damping.
Remember, in an aircraft, the propellor makes an excellent flywheel. Since
you normally leave the flywheel off of the crankshaft to save weight, you
have your reduction system inserted between the crankshaft and the flywheel.
The result is some pretty heavy alternating forces on the reduction system
everytime a cylinder fires. The bigger the cylinders, the worse the jerks.
The gears in a geared aircraft engine are AMAZINGLY HUGE. You can keep the
unit loads low by making the gears BIG, you can do like the Merlin engine
in the P-51's and put a torsion bar between the crankshaft and the gears,
or you can use a belt drive and soak up the vibrations in the belt. All
have their limitations, strengths, and weaknesses. All add weight. One
is necessary if you want to turn your engine at RPM's where it does well,
while keeping your propellor turning at RPM's where it does well.
To put the whole thing in perspective. Renault built a GEARED aircraft
engine in WWI. They wanted to turn it up to 2000 RPM to really get some
power out of it, so they put in a 2 to 1 gear reduction unit so they could
turn the propellor efficiently at 1000 RPM!
John
Dirk Rackley
>Does any one know about the vibration dampener that Mott Taylor designed
>(and I believe sold) for the Imp? Is there a current source for them? And
>any Idea of the dimensions? I want to dampen my engine pulses and hope to
>put one of these in the redrive or on the shaft. I would appreciate any
>leads.
>
>Thanks,
>
>Thom Besch
>Avid Flyer MK IV (54%)
The damper was a pod that had an abrassive wave plate inside that was
filled with shot. The pulse would bunch the shot against the wave's in
the plate and couple the prop to the engine. This of course would
allow the wave plate to recoil agaist the shot and damp it from the
engine.
Scott Ryder who frequents here has the contact for the "Flexodyne"
and will probably answer you.
*** Shake, Rumble, and Humm!___________________________________
| _ |
| Dirk Rackley | Anything! Given sufficient |
| Vortecs Aircraft *--{*}--* propulsion will fly. |
| Vancouver WA Rule 1. |
| Maintain propulsion. |
---------------------------------------------------------------
Nicholas Pasch
>In article <4ku6f4$8...@newsbf02.news.aol.com>
>tmb...@aol.com (TMBesch) writes:
>
>> Does any one know about the vibration dampener that Mott Taylor
designed
>> (and I believe sold) for the Imp? Is there a current source for
them? And
>> any Idea of the dimensions? I want to dampen my engine pulses and
hope to
>> put one of these in the redrive or on the shaft. I would appreciate
any
>> leads.
>>
>> Thanks,
>>
>> Thom Besch
>> Avid Flyer MK IV (54%)
The coupling is made by a company called Dodge, not the Chrysler Corp
car division. The coupling is called a Flexidyne coupling. It appears
to be a Fluid coupling, but I seem to remember that it is filled with a
solid shot material. The coupling on the Mini Imp is about 10" in
diameter and about 5"thick. It looks like an automatic transmission
torque converter on the outside. Note that you can't prop an engine
through a Flexidyne coupling, and there is effectively no load and no
flywheel action on the engine until it runs up to idle speed. This
means that it is easy to have a "kick-back" on start up, unless the
ignition advance is significantly reduced.
Regards,
Nick Pasch
Dan Nafe
: In article <4ku6f4$8...@newsbf02.news.aol.com>
: tmb...@aol.com (TMBesch) writes:
: > Does any one know about the vibration dampener that Mott Taylor designed
[snip]
: It's a kind of dry coupling universal joint. It may present problems
: attempting to squeeze it into the limited space of your Avid Flyer.
Isn't the coupling filled with small ball bearings?
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Dan Nafe, Safari Internet d...@safari.net
http://www.safari.net
John R. Johnson
nothing to do with Chrysler Motors. It is basically a fluid coupling
that uses metal shot for the fluid.
John
On 16 Apr 1996, Nicholas Pasch wrote:
>
> >In article <4ku6f4$8...@newsbf02.news.aol.com>
> >tmb...@aol.com (TMBesch) writes:
> >
> >> Does any one know about the vibration dampener that Mott Taylor
> designed
scott rider
>Does any one know about the vibration dampener that Mott Taylor designed
>(and I believe sold) for the Imp? Is there a current source for them? And
>any Idea of the dimensions? I want to dampen my engine pulses and hope to
>put one of these in the redrive or on the shaft. I would appreciate any
>leads.
>
>Thanks,
>
>Thom Besch
>Avid Flyer MK IV (54%)
Thom,
The damper was a "Flexidyne" that works by rotating a plate inside a
container full of shot. At High rpm, the shot packs the input plate tightly,
at low rpms, pulses force the plate to move a little, dampening vibrations.
I have seen one flying in a BD-5, pilot/builder Pat Jones, with a KFM engine,
direct drive. The KFM was mounted high. Pat added fan blades to the outside and
used it as a cooling fan, if memory serves, blowing air from the engine
compartment forward to go over the cylinders and out under the blisters for
the cylinder heads.
Molt had a lot of machining done by Chad Willie in the Lake Oswego, OR
area. I believe Chad and his son supplied Molt with parts for the drive
systems. Jerry Holcum also worked with Molt in his Longview shop, but
when I contacted both of these guys, it seemed like a dead end.
I would try to find a manufacturer of the flexidyne and let them know you need one
to smooth the pulses of your cement mixer or HVAC system. I am not sure if Molt
built them or bought them.
Scott Rider, Own Opinions, BD-5 builder (now 77%)
e-mail me for phone numbers, I respect the privacy of others.
jgraham
>
> On 16 Apr 1996 11:52:42 GMT, Charles K. Scott (Charles...@dartmouth.edu) wrote:
> : In article <4ku6f4$8...@newsbf02.news.aol.com>
> : tmb...@aol.com (TMBesch) writes:
>
> [snip]
> : It's a kind of dry coupling universal joint. It may present problems
> : attempting to squeeze it into the limited space of your Avid Flyer.
>
> Isn't the coupling filled with small ball bearings?
>
> ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> Dan Nafe, Safari Internet d...@safari.net
> http://www.safari.net
Yes, It is a DODGE truck FLUIDYNE. It was two couplings filled with
ball bearings or steel shot. It is necessary to avoid torsional
vibration. Without it there is certain disentigration of the drive
shaft followed by certain disentigration of the airplane.
j. graham
jgraham
jgraham
>
> In <4ku6f4$8...@newsbf02.news.aol.com>, tmb...@aol.com (TMBesch) writes:
> >Does any one know about the vibration dampener that Mott Taylor designed
> >any Idea of the dimensions? I want to dampen my engine pulses and hope to
> >put one of these in the redrive or on the shaft. I would appreciate any
> >leads.
In my earlier post I said that it was a DODGE FLUIDYNE. I think that
the correct name is FLEXIDYNE as mentioned by others. I remember
that it was on Dodge Trucks and I heard that it activated the
cooling fan of the engine. Molt Taylor was a true genius and he
certainly demonstrated it with his wonderful designs. He was a
rival of Bill Lear of Lear Radio and Lear Jet fame.
j. graham
Paul Lamar
: It was a "Chrysler Fluid Coupling." This is a wiggle plate coupling that
Thank you John for an excellent explanation of this complex problem.
Paul Lamar
scott rider
Regarding your post (not quoted to save space), it is not
universally accepted that drive belts do enough damping
to prevent torsional resonance. I have a sprag clutch installed
in my system that uses a belt because belt only systems
dont work in my app.
Scott Rider
BD-5 builder,
Own opinions.
brian whatcott
says...
>
>tmb...@aol.com (TMBesch) wrote:
>>Does any one know about the vibration dampener that Mott Taylor designed
>
>The damper was a "Flexidyne" that works by rotating a plate inside a
>container full of shot.
For what it's worth: Colin Chapman specified a rather large donut
on each of the two final drive shafts of his sportscar line: the Lotus Elan.
This sort of design would at least stay coupled....
Brian
Warbird Driver
complete airframe, less engine and drive train that could be flying in
no time with an engine. The driveshaft idea seems abit spooky to me,
ala BD-5 but the airframe looks like a real flying machine. Itty Bitty
wings! yee ha!
--
Keep'em Flyin,
____________________|_____________________
Doug Rozendaal ATP, B-25, PBY, \ \_|_/ /
CAF 16577, EAA 359305, WOA 10371, \ ___| O |__ /
IAC21991, NATA 1261, AOPA 773530 _____\_________|___|__________/_____
/ ' \
"Real Airplane have Round Motors" _/ \_ "and
Pistons"
Tom Betz
>
> Does anyone know anyone flying a Taylor IMP, I know of a nearly
> complete airframe, less engine and drive train that could be flying in
> no time with an engine. The driveshaft idea seems abit spooky to me,
> ala BD-5 but the airframe looks like a real flying machine.
The driveshaft is pretty time-tested, the Flexidyne coupling having been
innovated in the sixties by Dr. Ed Lesher on his all-metal Teal pusher.
Taylor picked the idea up from Lesher.
I don't know of a single accident caused by the failure of one of these
units. Can anyone bring one to mind?
Do I remember right that the Teal is in the EAA museum?
Dirk Rackley
Also used in Fiat and Sunbeam as well as others. I have offten wondered
how well these would hold up, and how well they would dampen the
pulses.
Charles K. Scott
in...@intellisys.net (brian whatcott) writes:
> For what it's worth: Colin Chapman specified a rather large donut
> on each of the two final drive shafts of his sportscar line: the Lotus Elan.
Right, and the Elan's were famous for being extremely sensitive to
power inputs and shifting technique. Being jerky with the clutch could
result in the car boinging and leapfrogging down the road as the rubber
doughnuts compressed and released their energy from the rough shift.
Corky Scott
Bob Duckworth
Porsche uses a rubber damper in the clutch (shaft to disk) in their 944.
The 944 Turbo uses a spring clutch.
THe rubber deteriorates, the springs break.
They both work well but I think the rubber feels better.
Note this is a front engine/rear transaxle car with a shaft
in a tube running at engine RPM back to the clutch/transaxle.
Try working out torsional vibrations in 5' long shaft
running from 500 to 7000RPM with varying load.
The Triumph GT-6 used donuts on the half shafts like the lotus.
There was a WW2 tank with a radial aircooled motor :-)
Don't know what kind of damping it used but they put rubber
blocks on the treads for running on paved roads.
I guess no one on RAH is building with molded plywood.....
Can anyone use an ARC5 R32? 108-135MHz, needs a little work.
Did the P-51 have an auto 'type' engine?
Better get some coffee.....
-bob
--
Bob Duckworth Consulting, 960 Ralph McGill Blvd. Atlanta GA 30306-4447
bobs' address is r...@ka4ybr.netmha.com 404-888-0389(V) 892-2301(FAX)
Buy Sell Trade Surplus Computer Electronics Datacom Telecom since 1981.
Fax or email your list for a fast cash offer. Watch for listserv catalog.
John R. Johnson
> John,
>
> Regarding your post (not quoted to save space), it is not
> universally accepted that drive belts do enough damping
> to prevent torsional resonance. I have a sprag clutch installed
> in my system that uses a belt because belt only systems
> dont work in my app.
>
Yes, I can only agree. Drive belts do provide a significant amount
of torsional damping. Not necessarily enough. I am far from convinced
that a "sprag clutch" will provide any significant torsional damping
without wearing out pretty rapidly. My understanding it that they were
primarily used to keep the rotor and transmission in a helicopter from
having to turn the engine in an autorotation situation. They are also
used in many Continental starter drives to keep the engine from turning
the starter, while allowing the starter to turn the engine. With a
grip/release cycle time in milliseconds, the dynamics within the clutch
would be awesome. I really doubt that any useful life would be obtained
if it were actually operating in that mode.
The problem with most gearboxes in aircraft engines comes when the gears
alternate back and forth between driving and driven. This changes the
side of the tooth that is taking the load, and continually allows and
takes up any clearance you have, and you must have some, between the
teeth.
If you look at the operating limitations for most geared aircraft engines
you will see that they recommend avoiding any rpm near the zero thrust
rpm for that reason.
John
Mark Kromer
>
> In <4l9cd0$l...@zoom2.telepath.com>, in...@intellisys.net (brian whatcott) writes:
>>For what it's worth: Colin Chapman specified a rather large donut
>>on each of the two final drive shafts of his sportscar line: the Lotus
>>Elan.
> wondered how well these would hold up, and how well they would
> dampen the pulses.
Mercedes Benz used a similar rubber donut in the half shafts of their
6.3 and 6.9 liter sedans. They performed the function of u-joints.
I understand they worked reasonably well and lasted even under the
strain of those rather large motors.
Mark Kromer ma...@trvlnet.com
Nicholas F. Pasch
>Does anyone know anyone flying a Taylor IMP, I know of a nearly
>complete airframe, less engine and drive train that could be flying in
>no time with an engine. The driveshaft idea seems abit spooky to me,
>wings! yee ha!
>--
The Taylor Mini Imp was not supposed to be a particularly sporty or
difficult machine to fly. As originally designed, it couldn't even be
spun. With increased control throws the behavior got a little more
responsive, but still, it was never assumed to be aerobatic in any real
sense. With no prop blast, it's hard to see how it could be areobatic,
the BD-5 press notwithstanding. If it isn't too obvious, the Mini Imp was
comparable to the BD-5 in many ways. Most of the comparisons go in favor
of the MiniImp. It didn't fall on its tail when you got out, It didn't go
white-knuckles below 75kts. It, typically, didn't take 2,500hrs to build.
It did have the same problems with engine selection when it was designed.
The only flight issues I am aware of from conversations with several
flyers of the type are a tendency for the "short" version (without the
shark fin) to Dutch-roll, and excessive polar moment in roll if the tip
tanks are used. The polar moment issues were visible on takeoff as a
rocking on the landing gear. The tip tanks were not much recommended.
Regards,
Nick Pasch
brian whatcott
says...
>
///
>>
>>For what it's worth: Colin Chapman specified a rather large donut
>>on each of the two final drive shafts of his sportscar line: the
Lotus Elan.
>>
>>This sort of design would at least stay coupled....
>
>Also used in Fiat and Sunbeam as well as others. I have often
>how well these would hold up, and how well they would dampen the
>pulses.
>
John Graham noted privately - he must be one of the few who doesn't
spring to the keyboard to share his views with .homebuilt
readers.... :)
he saw Cosworth GP cars at Indianapolis with the same arrangement.
Rubber is said to have good damping properties ( in the right mix)
Brian
scott rider
>In <4l9cd0$l...@zoom2.telepath.com>, in...@intellisys.net (brian whatcott) writes:
>>says...
>>>
>>>tmb...@aol.com (TMBesch) wrote:
>>>>Does any one know about the vibration dampener that Mott Taylor designed
>>///
>>>
>>>The damper was a "Flexidyne" that works by rotating a plate inside a
>>>container full of shot.
>>
>>For what it's worth: Colin Chapman specified a rather large donut
>>on each of the two final drive shafts of his sportscar line: the Lotus Elan.
>>
>>This sort of design would at least stay coupled....
>>
>
>how well these would hold up, and how well they would dampen the
>pulses.
>
The recommended (if you call it that) drive for the BD-5 uses
the equivalent of 2 rubber doughnuts for the shaft coming from the
engine which allow the engine to vibrate in it's mounts without
overloading the bearings for the smaller of the reduction pulleys.
Then there is a belt from the lower pulley to the upper, larger, pulley.
Sometimes this belt is fitted with an idler wheel. (Good luck buying
a Gates belt, though). The upper pulley has a sprag clutch built in
which prevents the 51" long prop shaft from getting into torsional resonance.
The belt and doughnuts alone have been PROVEN to be a poor solution for the
resonance, with several systems coming apart in very little time. Early
in the development program Jim Bede put in the sprag clutch (one way clutch)
and it prevents the fundamental mode of oscillation where the prop shaft
acts like a spring absorbing the difference in torque caused by
pulses from the engine firing and the prop acting like a flywheel.
The prop shaft, by the way, was originally designed as a "hard" shaft, having
enough torsional strength to bring the fundamental mode of oscillation above the
normal speed, but later a switch was mande to a "soft" shaft with a lower
critical frequency, but with the sprag clutch to prevent self-destruction.
Do ground testing. Problems rarely get better in the air, and you are much better
off on the ground wishing you were up there than the other way around.
Scott Rider, Own Opinions, Not a PE.
BD-5 builder
scott...@ccm.hf.intel.com
brian whatcott
>
///
>I guess no one on RAH is building with molded plywood.....
The closest I've seen is the ads for ply-faced balsa:
Said to go on fast in strips a la molded ply - then gets glassed over.
Brian
scott rider
"John R. Johnson" <jo...@siu.edu> wrote:
>Yes, I can only agree. Drive belts do provide a significant amount
>of torsional damping. Not necessarily enough. I am far from convinced
>that a "sprag clutch" will provide any significant torsional damping
>without wearing out pretty rapidly. With a
>grip/release cycle time in milliseconds, the dynamics within the clutch
>would be awesome. I really doubt that any useful life would be obtained
>if it were actually operating in that mode.
>If you look at the operating limitations for most geared aircraft engines
>you will see that they recommend avoiding any rpm near the zero thrust
>rpm for that reason.
>John
>
John, We agree again. My application (BD-5) uses the sprag clutch to "pass
through" the forbidden RPMs. I would expect the life to be measured in hours
if I were operating the engine and prop at resonance and counting on a sprag
clutch to prevent the drive shaft from coming apart. (The clutch would
come apart instead)
I think it would be intellectually stimulating to design a pair of pendulum
counterweights to prevent destruction while operating near the resonance
point. But instead of that, I am just assuring that the system is tuned to
not be resonating near my desired operating rpms.
Also, I have heard of using a centrifugal clutch to avoid the resonance
rpms.
Scott Rider
Own Opinions, not a PE
SMilesCozy
Does anyone know who has the rights to Molt's designs, and if they are
currently available?
Steve Miles
Cozy MkIV chap 3
brian whatcott
In article <4lispu$c...@ornews.intel.com>, scott...@ccm.hf.intel.com
says...
///
>>>
>>>For what it's worth: Colin Chapman specified a rather large donut
>>>on each of the two final drive shafts of his sportscar line: the Lotus
Elan.
>>>
>The belt and doughnuts alone have been PROVEN to be a poor solution for the
>resonance, with several systems coming apart in very little time. Early
>in the development program Jim Bede put in the sprag clutch (one way clutch)
>and it prevents the fundamental mode of oscillation where the prop shaft
>acts like a spring absorbing the difference in torque caused by
>pulses from the engine firing and the prop acting like a flywheel.
>
>The prop shaft, by the way, was originally designed as a "hard" shaft,
having
>enough torsional strength to bring the fundamental mode of oscillation above
the
>normal speed, but later a switch was mande to a "soft" shaft with a lower
>critical frequency, but with the sprag clutch to prevent self-destruction.
>
Thanks, Scott: there's positively nothing better than engineering
verification in the application.
And racing applications don't necessarily work on planes.
Which started me musing: the nearly always unpopular Paul who seems to have
background in preparing car engines, continually warns of their dangers.
It goes without saying he doesn't do this to look like a big-shot - the
responses are almost all abusive.
When I thought about it, the most rational explanation is that he is
warning us because he would not allow the possibility of harm to others
through his inaction.
Not so much for the benefit of the abusive, but because 'It's the right
thing to do...." in view of what he believes.
A person who does 'the right thing' however unpopular gets a certain credit
in my book....
The area of concern is 'reliability'.
It's not something you can easily tell by looking.
Who would have (naively) thought that a 'hairpin' spring would hold an
ignition lead more securely than a nut and locknut could, onto a spark-plug?
I have little doubt that a car engine operated at 75% power is not going to
last as long as one run at 30% ( particularly with the current generation of
FI which can accurately meter part-throttle mixes.)
And yet, I have little doubt that a car-engine of the water-cooled variety
gets a much smaller temperature cycling than an air-cooled aero engine,
and OTHER THINGS BEING EQUAL ( they never are though...) this would ENHANCE
the water-cooled engine life.
You mentioned you don't hold a PE - no more do I, though I looked at the exam
syllabus :) - but I can at least appreciate one design fact-of-life:
Amateurs fasten on one or few factors -PROs try to balance them ALL.
Brian
Roger D. Mellema
In article <317A4A...@pobox.com>, Tom Betz <tb...@pobox.com> wrote:
~
~The driveshaft is pretty time-tested, the Flexidyne coupling having been
~innovated in the sixties by Dr. Ed Lesher on his all-metal Teal pusher.
~Taylor picked the idea up from Lesher.
~
I flew an Avid Flyer A with a 42 hp Cuyuna engine, a 3 to 1 planetary
reduction, and a flexidyne coupling. The strange thing is that the
majority of the coupling - the container holding the shot, was a part of
the propeller. The end of the drive shaft was connected through a bearing
to the "wobble plate" in the "hub" of the prop. You could start the
engine, rev it up, and just hold onto the prop to keep it stationary.
When you let go, the friction from the shot would start the propeller
turning. When the propeller turned fast enough the shot would "fling out"
and the propeller would be fully engaged. You had to advance the throttle
slowly or the engine would over-rev a bit. It worked very well!!
--
Roger Mellema
BD-4 Builder Newsletter Ford V-6 powered BD-4, N76VR
Ford 351 Windsor powered 2/3 P-51 Wickham Twin to go
Tobus
I gather you could not stop the propeller by doing this in reverse?