Today's Message Index:
----------------------
1. 12:23 AM - Re: Rotax starting - 912S (Nigel Graham)
2. 02:25 AM - Re: Rotax starting - 912S (nigel charles)
3. 02:25 AM - Re: Rotax starting - 912S (nigel charles)
4. 03:25 AM - Re: Rotax starting - 912S (M.J. Gregory)
5. 04:37 AM - Re: Flap Jig Alignment (Kingsley Hurst)
6. 06:41 AM - Rotax starting - 912S (Fergus Kyle)
7. 08:47 AM - Rotax starting - 912S (Graham Singleton)
8. 08:48 AM - Re: Rotax starting - 912S (Leo J. Corbalis)
9. 09:26 AM - ventilation (Paul Stewart)
10. 11:45 AM - Re: Rotax starting - 912S (Ami McFadyean)
11. 12:29 PM - Re: Flap Jig Alignment (Rowland Carson)
12. 12:57 PM - Re: Rotax starting - 912S (Ami McFadyean)
13. 01:02 PM - Re: Rotax starting - 912S (Ami McFadyean)
14. 01:45 PM - Re: Rotax starting - 912S (Ami McFadyean)
15. 02:00 PM - Re: Rotax starting - 912S (Ami McFadyean)
16. 06:09 PM - Wheel Skirts for Tri Gear (Alan Stills)
17. 06:22 PM - Flap Washout (David Simenauer)
Message 1
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Nigel Graham" <nigel_graham@btclick.com>
The clutch is only vulnerable when it is engaged and the engine kicks
back (i.e. during starting). Once the engine is running, the clutch will
be disengaged and the low RPM torsional resonance can't affect it.
The real damage seems to occur if the engine fires at just below the
required cranking speed and kicks the crank back the wrong way. As Paddy
points out, the forces are immense. It looks just as bad from outside
the aircraft as it feels from within.
While the more powerful starter may well alleviate the problem in the
short term by increasing cranking speed, I feel that the problem will
not be truly fixed until Rotax develop (or get Ducati to) an ignition
system with a mapped "starting" ignition retarded to TDC or even
slightly later. This soft-start would get the engine running without
damage, at which point the normal ignition mapping would take over.
This concept is not new. It is employed successfully on the Europa
"primary trainer" that I fly (DH82a) and was developed over seventy
years ago to protect the starting system - your fingers!
Nigel
----- Original Message -----
From: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
Subject: Re: Europa-List: Rotax starting - 912S
--> Europa-List message posted by: "Ami McFadyean"
<ami@mcfadyean.freeserve.co.uk>
That being so, the 'shaking and banging' is likely caused by the low
frequency primary resonance (torsional and/or blade-flap) that is
inevitably
present below normal cranking speeds. In the absence of any damping,
the
forces produced by resonance will build-up towards infinity. The crank
and
gearbox get hit with similar forces too; its just that the sprag is the
weak
link in the chain (and, if it's any consolation, cheaper than a new
crank!).
However, damping of resonance is provided by the friction clutch in the
gearbox; hence Rotax's insistence that this be maintained at the upper
limit. Also anything that accelerates the cranking engine quickly
through
and clear of the resonant band should help (i.e. powerful battery, good
contacts, high torque motor). We have to hope that it is the 'shaking
and
banging' ONLY that causes the problem, not the loads of normal starting.
Last Summer, there was a certain 912S CT that was regularly shaking the
carburettors out of the mounting sockets on start up, possibly
exacerbated
by the big floppy 2-blade prop it had.
Duncan McF.
----- Original Message -----
From: "P.A.D.Clarke" <paddyclarke@lineone.net>
Subject: Re: Europa-List: Rotax starting - 912S
> --> Europa-List message posted by: "P.A.D.Clarke"
<paddyclarke@lineone.net>
>
> Hi All,
> First a word of caution. I'm not an engineer and don't
have
> any specialist knowledge. What I have to say may well be ( and
probably
is )
> a load of old rubbish. Having said that, I'll press on anyway.
> The problem seems to arise when the engine kicks back
on
> start up. The poor little starter motor turning one way meets the
engine
> violently kicking back the other. The location for this titanic
conflict
is
> the sprag clutch - no wonder it can't cope. The higher output starter
spins
> the engine so fast that there is plenty of inertia to carry it over
the
> compression, whenever ignition takes place. This is how it feels
anyway.
> I agree that the higher power starter will put greater
> torque into the clutch, but I suspect the increased forces are
relatively
> small compared to those involved in meeting a backfiring engine. I
shudder
> to think what it would feel like to have a kick back against the high
power
> starter.
> Cheers, Paddy Clarke
> ps. I hope this message doesn't appear twice - we had a power cut just
as
it
> was being sent!
> ----- Original Message -----
> From: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Rotax starting - 912S
>
>
> > --> Europa-List message posted by: "Ami McFadyean"
> <ami@mcfadyean.freeserve.co.uk>
> >
> > How is it that the higher power starter motor does not put a higher
load
> on
> > the sprag clutch, which would lead to the earlier demise of the
clutch?
> This
> > assumes that the clutch is the victim rather than the cause, which
seems
> to
> > be the case.Or is it that the violent starting (and the 'standard'
but
> less
> > violent stopping) is the sole cause?
>
>
==
==
==
==
Message 2
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "nigel charles" <nigelcharles@tiscali.co.uk>
>Maybe it has something to do with winter MOGAS; other forums have recorded
that these problems are eased by use of AVGAS.<
If winter MOGAS is the culprit your problem should go away as we change to
summer MOGAS. It will be interesting to hear further progress with this
problem.
Nigel Charles
Message 3
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "nigel charles" <nigelcharles@tiscali.co.uk>
>Also anything that accelerates the cranking engine quickly through
and clear of the resonant band should help (i.e. powerful battery, good
contacts, high torque motor). <
This is another good reason for the use of external power for start when
available. I use a car battery rated for diesel use for all my starts from
my base airfield. This gives plenty of current for the starter. I don't
recall having any kickbacks when external power has been used but it has
happened quite often with starts from the internal battery especially on
cold starts when the cranking speed is not quite so high.
For those still building it might be worth considering including a
convenient external power connection point. If your C of G is such that an
aft mounted battery is required mounting a socket just aft of the wing (a
good place for safety) is very straightforward. If you have the battery in
the engine compartment a little more planning is required. For monowheels
aft C of G's are beneficial for take-off and landing as it helps to ensure
directional control with the tail on the ground. It also slightly reduces
drag in the air due to reduced tailplane downforce. The only penalty is the
weight of the extra wire from the battery to the starter (about 1.5lb).
Nigel Charles
Message 4
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| Subject: | Rotax starting - 912S |
--> Europa-List message posted by: "M.J. Gregory" <m.j.gregory@talk21.com>
Could these problems be exacerbated by exceeding the maximum propeller
mass-inertia limit recommended by Rotax? In the case of the 912 this was
6000 kg-cm squared.
Does anyone know what the current recommended limits are for the 912S and
the 914, and how commonly-used propellers such as Warp Drive compare to
them?
Mike
Europa Club Safety Officer
-----Original Message-----
From: owner-europa-list-server@matronics.com
[mailto:owner-europa-list-server@matronics.com]On Behalf Of Ami McFadyean
Subject: Re: Europa-List: Rotax starting - 912S
--> Europa-List message posted by: "Ami McFadyean"
<ami@mcfadyean.freeserve.co.uk>
That being so, the 'shaking and banging' is likely caused by the low
frequency primary resonance (torsional and/or blade-flap) that is inevitably
present below normal cranking speeds. In the absence of any damping, the
forces produced by resonance will build-up towards infinity. The crank and
gearbox get hit with similar forces too; its just that the sprag is the weak
link in the chain (and, if it's any consolation, cheaper than a new crank!).
However, damping of resonance is provided by the friction clutch in the
gearbox; hence Rotax's insistence that this be maintained at the upper
limit. Also anything that accelerates the cranking engine quickly through
and clear of the resonant band should help (i.e. powerful battery, good
contacts, high torque motor). We have to hope that it is the 'shaking and
banging' ONLY that causes the problem, not the loads of normal starting.
Last Summer, there was a certain 912S CT that was regularly shaking the
carburettors out of the mounting sockets on start up, possibly exacerbated
by the big floppy 2-blade prop it had.
Duncan McF.
----- Original Message -----
From: "P.A.D.Clarke" <paddyclarke@lineone.net>
Subject: Re: Europa-List: Rotax starting - 912S
Message 5
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| Subject: | Re: Flap Jig Alignment |
--> Europa-List message posted by: "Kingsley Hurst" <hurstkr@growzone.com.au>
"David Simenauer" wrote
I have just started on the flaps. On both sides, when the flap cores are
set upside down in the jigs, the jig for the outboard piece is slightly
thicker, maybe by 2 or 3 mm, than the jig for the outboard piece.
David,
The heights of the two jigs should be exactly the same when butted together.
One of the handiest things I have found during my build is MDF (Medium
Density Fibreboard). It comes in varying thicknesses one of which is 3mm.
It is exactly true to size.
If the difference in height of your two jigs is 3mm, I would suggest you put
a piece of 3mm MDF (at least as big as the jig) under the lower jig to
elevate it and as Stephan suggested, ensure the profiles are straight using
a long straight edge. If the 3mm MDF is too thick, try purchasing a sheet
or two of cardboard or use newsprint paper or the like to obtain the correct
thickness. If I remember correctly, I think I also laid a piece of plastic
film in the area of the flap join in order to prevent the flap being glued
to the jig if any micro happened to seep out.
I have also found MDF to be invaluable for making templates, jigs, feeler
gauges etc.
Regards
Kingsley Hurst
Mono Classic 281 in Oz
Message 6
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| Subject: | Rotax starting - 912S |
--> Europa-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
--> Europa-List message posted by: "Nigel Graham" <nigel_graham@btclick.com>
The clutch is only vulnerable when it is engaged and the engine kicks
back (i.e. during starting). Once the engine is running, the clutch will
be disengaged and the low RPM torsional resonance can't affect it.
The real damage seems to occur if the engine fires at just below the
required cranking speed and kicks the crank back the wrong way. As Paddy
points out, the forces are immense. It looks just as bad from outside
the aircraft as it feels from within.
While the more powerful starter may well alleviate the problem in the
short term by increasing cranking speed, I feel that the problem will
not be truly fixed until Rotax develop (or get Ducati to) an ignition
system with a mapped "starting" ignition retarded to TDC or even
slightly later. This soft-start would get the engine running without
damage, at which point the normal ignition mapping would take over.
This concept is not new. It is employed successfully on the Europa
"primary trainer" that I fly (DH82a) and was developed over seventy
years ago to protect the starting system - your fingers!
Nigel
----- Original Message -----
From: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
Subject: Re: Europa-List: Rotax starting - 912S
--> Europa-List message posted by: "Ami McFadyean"
<ami@mcfadyean.freeserve.co.uk>
That being so, the 'shaking and banging' is likely caused by the low
frequency primary resonance (torsional and/or blade-flap) that is
inevitably present below normal cranking speeds. In the absence of
any damping,the forces produced by resonance will build-up towards
infinity. The crank and gearbox get hit with similar forces too; its just
that the sprag is the weak link in the chain (and, if it's any consolation,
cheaper than a new crank!).
However, damping of resonance is provided by the friction clutch in the
gearbox; hence Rotax's insistence that this be maintained at the upper
limit. Also anything that accelerates the cranking engine quickly
through and clear of the resonant band should help (i.e. powerful battery,
good contacts, high torque motor). We have to hope that it is the 'shaking
and banging' ONLY that causes the problem, not the loads of normal starting.
Last Summer, there was a certain 912S CT that was regularly shaking the
carburettors out of the mounting sockets on start up, possibly
exacerbated by the big floppy 2-blade prop it had. Duncan
McF.
I've been thinking (sorry).
We used to take precautions when starting big radials in the following
manner:
While cranking up the engine, we pumped the fuel into the intake manifold
by which time the engine was at proper rev, so turned on the ignition and
she fired. There was no premature popping to damage starter mechanism,
and there was insufficient time for fuel to pool in the intake.
Why does there have to be sparking before its time?
I'm no 912S specialist, but couldn't that preclude some of the problem?
Ferg
Message 7
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| Subject: | Rotax starting - 912S |
--> Europa-List message posted by: Graham Singleton <graham@gflight.f9.co.uk>
At 23:56 14/04/2004 -0700, you wrote:
>--> Europa-List message posted by: "Ami McFadyean"
><ami@mcfadyean.freeserve.co.uk>
>
>That being so, the 'shaking and banging' is likely caused by the low
>frequency primary resonance (torsional and/or blade-flap) that is inevitably
>present below normal cranking speeds. In the absence of any damping, the
>forces produced by resonance will build-up towards infinity.
I have always believed that the shaking and banging on start up was due to
the fact that at low cranking speeds the ignition timing is too advanced,
hence the regular kick backs. The rough stopping may well be due to high
compression/ small flywheel effect.
just a thought or two
Graham
Message 8
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Leo J. Corbalis" <leocorbalis@sbcglobal.net>
Re wire the start/ignition system separating the the starting so the starter
motor can get the engine rotating and then turn on the ignition modules. As
I recall we used to turn the big fat radials thru one revolution of the prop
and then turn on the ignition.
Leo Corbalis>
Message 9
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--> Europa-List message posted by: Paul Stewart <europa@pstewart.f2s.com>
Many offered very helpful advice about ventilation and eyeball vents
> some time ago. What I have come up with is posted in the builders album
> section of the owners forum http://forum.okhuijsen.org/ (Have not yet
> worked out how to title the group of pictures. )
>
> Regards
>
> Paul Stewart
> G-GIDY
Message 10
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
Does anyone know when or by what criteria the fuel companies change their
formulations?
In the UK we can expect snow up to the end of April. Does that mean no
'summer' fuel until May+?
Duncan McF.
----- Original Message -----
From: "nigel charles" <nigelcharles@tiscali.co.uk>
Subject: Re: Europa-List: Rotax starting - 912S
> --> Europa-List message posted by: "nigel charles"
<nigelcharles@tiscali.co.uk>
>
> >Maybe it has something to do with winter MOGAS; other forums have
recorded
> that these problems are eased by use of AVGAS.<
>
> If winter MOGAS is the culprit your problem should go away as we change to
> summer MOGAS. It will be interesting to hear further progress with this
> problem.
>
> Nigel Charles
>
>
Message 11
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| Subject: | Re: Flap Jig Alignment |
--> Europa-List message posted by: Rowland Carson <rowil@clara.net>
At 2004 04 14 16:55 -0400 David Simenauer wrote:
>when the flap cores are set upside down in the jigs, the jig for the
>outboard piece is slightly thicke
David - this is, I believe, a common problem. The blocks of foam that
the control surfaces are cut from are not themselves very
dimensionally accurate. I had to shim mine in various places to get
both LE & TE straight, and to achieve the specified washout. Remember
that the object of the exercise is to make a nice straight-looking
control surface, and don't worry if you have to adjust the
underpinnings to get that end result. You'll be throwing away the jig
blocks - the aeroplane parts are what you keep!
Incidentally the method in my manual for setting washout using shims
was based on incorrect trigonometry - I told the factory but I don't
think they've changed it yet. A digital level is very handy for
getting the washout correct, although you _can_ do it without one.
[blatant advert]
From the number you quote in your signature, I assume you bought your
already-started kit from Jim Graham, who has been a Europa Cub
member. I hope that he passed on to you the Europa Club information,
and that you might consider joining the Club yourself. If so, please
contact me direct for more info.
regards
Rowland
--
| Rowland Carson Europa Club Membership Secretary - email for info!
| Europa 435 G-ROWI (670 hours building) PFA #16532
| e-mail <memsec@europaclub.org.uk> website <www.europaclub.org.uk>
Message 12
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
The clutch is engaged any time that the engine is kicking back (including at
shut-down) and the immense forces that are felt to be at play are actually a
manifestation of the interaction of the prop., crank and dog clutch in the
gearbox (the latter in particular as the dogs bounce from face to face). No
doubt the sprag and starter is suffering too, but that would not be
discernable from outside.
My point was that the whole system must have (by law of nature) a primary
resonant frequency somewhere; it's usually engineered to be below cranking
speed, before the point where combustion loads can commence and below the
speed that the engine will normally run. So, as you say, once the engine is
running it is beyond the speed range that can produce kickback Of interest,
some two-stroke set-ups can be seen with a resonance well above cranking
speed to the extent that the engine struggles to power-up through this
resonant speed once the engine is running
I can't think that Rotax would have been so thoughtless as to have provided
too much advance at cranking speed (4 degrees) and others have confirmed
that trying to start on one ignition only (which would crudely "halve" the
rate of advance of the combustion flame-front, effectively retarding the
ignition) makes no difference to the shaking. However, if the cranking speed
is below par for whatever reason and the engine fires whilst at or close to
the resonant frequency, then the combustion loads will massively antagonise
the shaking.
I had the same problem on the BMW (the BIG starting problem on that was
similar to that of the Rotax and was the last straw for this project) which
of course had mapped ignition and a flywheel. What helped resolve the
problem was adjustment of the gearbox preload, which moved the engine-prop
resonant frequency away from cranking-speed frequency. Problem then was that
the preload was then wrong for operation.
Its also worth noting that the BMW starting was eased by leaving the
ignition switched off until the starter had run up to cranking speed.
Maybe this is just another way of looking at the same problem, but I think
it more accurately reflects the dynamics at play.
Duncan McF.
antagonise the whole regime.----- Original Message -----
From: "Fergus Kyle" <VE3LVO@rac.ca>
Subject: Europa-List: Rotax starting - 912S
> --> Europa-List message posted by: "Fergus Kyle" <VE3LVO@rac.ca>
>
> --> Europa-List message posted by: "Nigel Graham"
<nigel_graham@btclick.com>
>
> The clutch is only vulnerable when it is engaged and the engine kicks
> back (i.e. during starting). Once the engine is running, the clutch will
> be disengaged and the low RPM torsional resonance can't affect it.
>
> The real damage seems to occur if the engine fires at just below the
> required cranking speed and kicks the crank back the wrong way. As Paddy
> points out, the forces are immense. It looks just as bad from outside
> the aircraft as it feels from within.
>
> While the more powerful starter may well alleviate the problem in the
> short term by increasing cranking speed, I feel that the problem will
> not be truly fixed until Rotax develop (or get Ducati to) an ignition
> system with a mapped "starting" ignition retarded to TDC or even
> slightly later. This soft-start would get the engine running without
> damage, at which point the normal ignition mapping would take over.
>
> This concept is not new. It is employed successfully on the Europa
> "primary trainer" that I fly (DH82a) and was developed over seventy
> years ago to protect the starting system - your fingers!
>
> Nigel
>
> ----- Original Message -----
> From: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Rotax starting - 912S
>
>
> --> Europa-List message posted by: "Ami McFadyean"
> <ami@mcfadyean.freeserve.co.uk>
>
> That being so, the 'shaking and banging' is likely caused by the low
> frequency primary resonance (torsional and/or blade-flap) that is
> inevitably present below normal cranking speeds. In the absence of
> any damping,the forces produced by resonance will build-up towards
> infinity. The crank and gearbox get hit with similar forces too; its just
> that the sprag is the weak link in the chain (and, if it's any
consolation,
> cheaper than a new crank!).
> However, damping of resonance is provided by the friction clutch in the
> gearbox; hence Rotax's insistence that this be maintained at the upper
> limit. Also anything that accelerates the cranking engine quickly
> through and clear of the resonant band should help (i.e. powerful battery,
> good contacts, high torque motor). We have to hope that it is the 'shaking
> and banging' ONLY that causes the problem, not the loads of normal
starting.
>
> Last Summer, there was a certain 912S CT that was regularly shaking the
> carburettors out of the mounting sockets on start up, possibly
> exacerbated by the big floppy 2-blade prop it had. Duncan
> McF.
>
> I've been thinking (sorry).
> We used to take precautions when starting big radials in the following
> manner:
> While cranking up the engine, we pumped the fuel into the intake manifold
> by which time the engine was at proper rev, so turned on the ignition and
> she fired. There was no premature popping to damage starter mechanism,
> and there was insufficient time for fuel to pool in the intake.
> Why does there have to be sparking before its time?
> I'm no 912S specialist, but couldn't that preclude some of the problem?
> Ferg
>
>
Message 13
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
>>I shudder
> to think what it would feel like to have a kick back against the high
power
> starter.
<<
Actually, no difference other than the small additional torque of the
starter and small additional inertia of the rotor (if indeed it is any
heavier or faster). The dynamics of the problem (whilst it is occurring) are
not controlled directly by the characteristics of the starter motor.
Duncan McF
PS Terrible pun!
----- Original Message -----
From: "P.A.D.Clarke" <paddyclarke@lineone.net>
Subject: Re: Europa-List: Rotax starting - 912S
> --> Europa-List message posted by: "P.A.D.Clarke"
<paddyclarke@lineone.net>
>
> Hi All,
> First a word of caution. I'm not an engineer and don't
have
> any specialist knowledge. What I have to say may well be ( and probably
is )
> a load of old rubbish. Having said that, I'll press on anyway.
> The problem seems to arise when the engine kicks back on
> start up. The poor little starter motor turning one way meets the engine
> violently kicking back the other. The location for this titanic conflict
is
> the sprag clutch - no wonder it can't cope. The higher output starter
spins
> the engine so fast that there is plenty of inertia to carry it over the
> compression, whenever ignition takes place. This is how it feels anyway.
> I agree that the higher power starter will put greater
> torque into the clutch, but I suspect the increased forces are relatively
> small compared to those involved in meeting a backfiring engine. I shudder
> to think what it would feel like to have a kick back against the high
power
> starter.
> Cheers, Paddy Clarke
> ps. I hope this message doesn't appear twice - we had a power cut just as
it
> was being sent!
> ----- Original Message -----
> From: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Rotax starting - 912S
>
>
> > --> Europa-List message posted by: "Ami McFadyean"
> <ami@mcfadyean.freeserve.co.uk>
> >
> > How is it that the higher power starter motor does not put a higher load
> on
> > the sprag clutch, which would lead to the earlier demise of the clutch?
> This
> > assumes that the clutch is the victim rather than the cause, which seems
> to
> > be the case.Or is it that the violent starting (and the 'standard' but
> less
> > violent stopping) is the sole cause?
>
>
Message 14
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
4806 kg.cm2 for a 62" wide chord HP Warp Drive (including bolts and
faceplate, but not spinner, all of which would be negligible at such a small
radius of gyration).
The benefit of the small diameter props that Europas run should favour being
well within the Rotax gearbox inertial load limits (which I don't think were
changed for the 912S or 914, even though the higher gearing ratios of these
would suggest that they might).
So it should be other users of 912s that are suffering more than us.
Duncan Mcf.
PS Will Bob Harrison please stop sniggering at all this!
----- Original Message -----
From: "M.J. Gregory" <m.j.gregory@talk21.com>
Subject: RE: Europa-List: Rotax starting - 912S
> --> Europa-List message posted by: "M.J. Gregory" <m.j.gregory@talk21.com>
>
> Could these problems be exacerbated by exceeding the maximum propeller
> mass-inertia limit recommended by Rotax? In the case of the 912 this was
> 6000 kg-cm squared.
> Does anyone know what the current recommended limits are for the 912S and
> the 914, and how commonly-used propellers such as Warp Drive compare to
> them?
>
> Mike
> Europa Club Safety Officer
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com]On Behalf Of Ami McFadyean
> To: europa-list@matronics.com
> Subject: Re: Europa-List: Rotax starting - 912S
>
> --> Europa-List message posted by: "Ami McFadyean"
> <ami@mcfadyean.freeserve.co.uk>
>
> That being so, the 'shaking and banging' is likely caused by the low
> frequency primary resonance (torsional and/or blade-flap) that is
inevitably
> present below normal cranking speeds. In the absence of any damping, the
> forces produced by resonance will build-up towards infinity. The crank and
> gearbox get hit with similar forces too; its just that the sprag is the
weak
> link in the chain (and, if it's any consolation, cheaper than a new
crank!).
> However, damping of resonance is provided by the friction clutch in the
> gearbox; hence Rotax's insistence that this be maintained at the upper
> limit. Also anything that accelerates the cranking engine quickly through
> and clear of the resonant band should help (i.e. powerful battery, good
> contacts, high torque motor). We have to hope that it is the 'shaking and
> banging' ONLY that causes the problem, not the loads of normal starting.
>
> Last Summer, there was a certain 912S CT that was regularly shaking the
> carburettors out of the mounting sockets on start up, possibly exacerbated
> by the big floppy 2-blade prop it had.
>
> Duncan McF.
> ----- Original Message -----
> From: "P.A.D.Clarke" <paddyclarke@lineone.net>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Rotax starting - 912S
>
>
Message 15
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| Subject: | Re: Rotax starting - 912S |
--> Europa-List message posted by: "Ami McFadyean" <ami@mcfadyean.freeserve.co.uk>
Actually, the starting problem should be reduced by approaching or exceeding
the prop inertia limits as more prop inertia means lower resonant frequency,
which is further displaced from cranking speed.
Maybe the small, low inertia Europa props are contributory and it's not just
our relatively high utilisation that seem to be favouring us being victims.
Another aspect is prop material, the high modulus/low hyteresis Warp Drive
being hard on gearboxes. But then William Mills runs an Arplast (but did
once run a Warp Drive).
Duncan McF.
----- Original Message -----
From: "M.J. Gregory" <m.j.gregory@talk21.com>
Subject: RE: Europa-List: Rotax starting - 912S
> --> Europa-List message posted by: "M.J. Gregory" <m.j.gregory@talk21.com>
>
> Could these problems be exacerbated by exceeding the maximum propeller
> mass-inertia limit recommended by Rotax? In the case of the 912 this was
> 6000 kg-cm squared.
> Does anyone know what the current recommended limits are for the 912S and
> the 914, and how commonly-used propellers such as Warp Drive compare to
> them?
>
> Mike
> Europa Club Safety Officer
>
> -----Original Message-----
> From: owner-europa-list-server@matronics.com
> [mailto:owner-europa-list-server@matronics.com]On Behalf Of Ami McFadyean
> To: europa-list@matronics.com
> Subject: Re: Europa-List: Rotax starting - 912S
>
> --> Europa-List message posted by: "Ami McFadyean"
> <ami@mcfadyean.freeserve.co.uk>
>
> That being so, the 'shaking and banging' is likely caused by the low
> frequency primary resonance (torsional and/or blade-flap) that is
inevitably
> present below normal cranking speeds. In the absence of any damping, the
> forces produced by resonance will build-up towards infinity. The crank and
> gearbox get hit with similar forces too; its just that the sprag is the
weak
> link in the chain (and, if it's any consolation, cheaper than a new
crank!).
> However, damping of resonance is provided by the friction clutch in the
> gearbox; hence Rotax's insistence that this be maintained at the upper
> limit. Also anything that accelerates the cranking engine quickly through
> and clear of the resonant band should help (i.e. powerful battery, good
> contacts, high torque motor). We have to hope that it is the 'shaking and
> banging' ONLY that causes the problem, not the loads of normal starting.
>
> Last Summer, there was a certain 912S CT that was regularly shaking the
> carburettors out of the mounting sockets on start up, possibly exacerbated
> by the big floppy 2-blade prop it had.
>
> Duncan McF.
> ----- Original Message -----
> From: "P.A.D.Clarke" <paddyclarke@lineone.net>
> To: <europa-list@matronics.com>
> Subject: Re: Europa-List: Rotax starting - 912S
>
>
Message 16
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| Subject: | Wheel Skirts for Tri Gear |
--> Europa-List message posted by: "Alan Stills" <astills785@earthlink.net>
Would someone who has a tri gear please give me the length of the skirt. I'm having
decals made up and haven't got the speed kit yet.
Al Stills
A095
Message 17
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--> Europa-List message posted by: "David Simenauer" <dsimenauer@cox.net>
I've got my jigs shimmed and my flap cores aligned properly. But I have to admit
I'm not completely certain how to make sure the washout is correct. Any help
with this would be appreciated.
Thanks,
Dave Simenauer
A101
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