Today's Message Index:
----------------------
1. 12:08 AM - Re: Re: 912 with low RPM--- new vibration problem (Les Goldner)
2. 12:51 AM - Re: 912 with low RPM--- new vibration problem (jetboy)
3. 05:44 AM - Re: 912 with low RPM--- new vibration problem (rampil)
4. 06:38 AM - Re: Re: 912 with low RPM--- new vibration problem (Dave Austin)
5. 06:57 AM - Hesitation (george.mueller@aurora.org)
6. 08:16 AM - Re: 912 with low RPM--- new vibration problem (Roger Lee)
7. 08:32 AM - Re: Hesitation (Roger Lee)
8. 10:35 AM - Re: Re: Re: 912 with low RPM--- new vibration problem (Guy Buchanan)
9. 10:35 AM - Re: Re: Re: 912 with low RPM--- new vibration problem (Guy Buchanan)
10. 01:43 PM - Re: 912 with low RPM--- new vibration problem (Roger Lee)
11. 03:00 PM - Wedding Gifts (Rich & Sandy Schultz)
12. 03:20 PM - Re: Wedding Gifts (John W. Cox)
13. 03:48 PM - Re: Re: 912 with low RPM--- new vibration problem (Noel Loveys)
14. 04:18 PM - Re: Wedding Gifts (Robert Taylor)
15. 09:17 PM - Re: Re: 912 with low RPM--- new vibration problem (Guy Buchanan)
16. 10:23 PM - Re: 912 with low RPM--- new vibration problem (Roger Lee)
Message 1
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| Subject: | Re: 912 with low RPM--- new vibration problem |
Roger,
The engine seems to be mounted properly, but I will take your advice and
recheck the mounts. (but remember, the plane only has 20 hours TT and there
was no vibration before changing the pitch).
No, I have never exceeded 5800 RPM. The highest static RPM I got yesterday
was about 5600.
Its not easy to static and dynamic balance a 3-blade Warpdrive and I
question the need to do it for a new plane that was balanced just fine
2-days ago.
I spoke to a Rotax 912/914 mechanic today. He says he has seen Warpdrive
props that will vibrate once the pitch goes below some level. Tomorrow I am
going to set the pitch back up to where it was originally (to where I only
get 5100 static RPM) and see if the vibration goes away. If it does, I will
be having a long talk with Warpdrive.
Les
> -----Original Message-----
> From: owner-rotaxengines-list-server@matronics.com
> [mailto:owner-rotaxengines-list-server@matronics.com] On
> Behalf Of Roger Lee
> Sent: Sunday, March 09, 2008 5:31 PM
> To: rotaxengines-list@matronics.com
> Subject: RotaxEngines-List: Re: 912 with low RPM--- new
> vibration problem
>
> --> <ssadiver1@yahoo.com>
>
> Les,
>
> Take a really good look at your engine mounts. Don't be
> gentle. Try and move them with the engine and see if they
> show any signs of separation or cracking.
> Has the rpm ever been over 5800?
> The other big item is you should really get a static and
> dynamic balance. This is where I would put my money right
> now. This could easily be the problem. I might be willing to
> bet money on this one.
>
> A static and dynamic balance's should be done by everyone.
> More people have this problem and don't even know it. If it
> is out of balance a little you may not feel it in the stick
> or frame. If it's out quite a bit then you really feel it.
> This issue is hard on gearboxes engine mounts and all the
> related components and this is the hardest thing to get
> people to do. If they can't see it it must be ok or not
> broken. Wrong!
>
> --------
> Roger Lee
> Tucson, Az.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=168667#168667
>
>
>
>
>
>
>
> Photoshare, and much much more:
>
>
Message 2
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| Subject: | Re: 912 with low RPM--- new vibration problem |
You do need to be sure static and dynamic and pitch balance is satisfactory.
with warpdrives the piitch balance can be checked by marking each blade tip with
a piece of tape, different colours or number of strips to identify them.
Then run up to cruise or full power with an observer a safe distance viewing from
the side of the disc. All blade tips should cone out equally, if one is out
of line the pitch should be adjusted accordingly.
I have done this for a set of new warpdrives that were so far out static that I
had to remove 1/2" of blade to match them, and increase that blade pitch around
0.2 deg. to compensate. Vibration gone.
Another tip - when setting the pitch, a very accurate way is to hold a laser pointer
across the rear surface of each blade in turn, at the same chord distance
position, with the blade set horizontal and laser shining onto the floor. resolution
is around 1" beam displacement per degree of misalignment - more accurate
than the bubble level.You may find making a special clamp to correctly locate
the pointer necessary on some props.
Ralph
--------
Ralph - CH701 / 2200a
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| Subject: | Re: 912 with low RPM--- new vibration problem |
The other possibility is simply that changing pitch and thus the RPM
simply plopped you right into an engine-airframe resonance. This
scenario wold imply nothing wrong with your engine. Did you try other
RPM settings and find that the vibration reduced on either side of 5100?
--------
Ira N224XS
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| Subject: | Re: 912 with low RPM--- new vibration problem |
You didn't mention if you had checked the tracking of the prop.
Dave Austin 601HDS - 912, Spitfire Mk VIII
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I am having a hesitation when I put the throttle in on my 912UL powered
Zenith 701. The RPMs come up smoothly as I put the throttle in, but when
I get close to full power, I get a hesitation for about 1 or 2 seconds at
around 4800 RPM. Then, after this hesitation, the RPM continues on to
5200, which is what I am currently getting at wide open throttle on
takeoff. I am thinking there is something about the geometry of my
throttle cables that might be causing this but when I take the cowl off
and watch the cables move the throttle it seems pretty smooth all the way
to full power. Does anyone have any idea what might be causing this?
George in Milwaukee
CH 701 912UL
Message 6
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| Subject: | Re: 912 with low RPM--- new vibration problem |
Les,
A few things here.
Changing the prop pitch can indeed change a vibration from a fine frequency vibration
into either a rougher one or a finer frequency vibration. The fact of the
matter is it is there and still is.
Setting the Warp Drive or any prop should give you no vibration in the normal rpm
ranges. Go fly your plane where the pitch is at and see if you can get 5500rpm
or there about. If you have a vibration correct that. It isn't the rpm's fault.
Changing the pitch to give a finer vibration will still cause you problems
in the future. That vibration goes right into your gearbox and engine. It just
shouldn't be there at all, fix the cause and don't mask it.
One item the guys are talking about is blade tracking, making sure each blade is
flying in the same plane of reference. This can be done by putting something
like a cardboard box up under the tip of the low blade pointing down and drawing
a line at exactly where it crosses. the box should be only 1/4" away from
the tip. Each blade there after should cross the line when turned by hand across
that line.
The next item is to do a static balance. This is done with the prop off the plane
and to make sure when put on a balancer of some type that no side of the prop
is heavier than the other. This should be done with all hardware attached.
The blades may be equal from the factory, but all the nuts, bolts and washers
are not.
Third is a dynamic balance. This is done on the plane and tested at cruise rpm
with a balancer.
I have a 3 blade Warp Drive. With the hardware it was out of balance on static.
The Warp Drive factory claimed each blade was within a few grams of each other.
I put it on my Flight Design CT for a static balance and it was out by .33
IPS a third of an inch.That's alot. I couldn't feel it in the stick, but I new
I should balance my prop. I had to ad 24 grams of weight (washers) to the prop
hub to bring it back down with in spec. Everyone wants one that will read out
at.000, but mine got as close as .02, a whole lot better.
Unless you do a track, static balance and a dynamic balance you may just chase
you tail and make the vibration a fine vibration over a courser vibration, but
it will still be there.
None of these items are hard to do and you could do it all in 2-3 hours. The dynamic
balance will probably take the longest at 1-2 hours with a tech and his
tester.
--------
Roger Lee
Tucson, Az.
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Hi George,
Just a couple of thoughts.
When was the last time you did a full carb sync? A carb sync will help rule out
a cable length issue. Until you do a sync and know everything is working equally
on both sides then doing anything else is just a guess.
You may want to check the float control arm. You need to pull the carb off. Pull
the bowl off and measure the float arm. It should be 10.5mm from the side edge
of the bowl to the top of the main jet shoulder with the arm resting at it's
bottom position. Not the top of the main jet itself, but where you screw it
in.
One way to check to see if you have a carb issue is to run your engine up to 3500-4000
rpm on the ground. Apply the choke, very little if anything should happen.
The enricher doesn't have an affect after this rpm. If you notice a drop
(more than 25rpm) or an increase then you have a carb/fuel issue.
I'm leaning towards the sync and float side of this so far. If you have done a
sync in the not very distant past (less than 25 hrs) then check the float and
needle.
--------
Roger Lee
Tucson, Az.
Read this topic online here:
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| Subject: | Re: 912 with low RPM--- new vibration problem |
At 12:04 AM 3/10/2008, you wrote:
>I spoke to a Rotax 912/914 mechanic today. He says he has seen Warpdrive
>props that will vibrate once the pitch goes below some level.
This is very suspect. I use the same Warp as a 912 on a 582,
just with 3 degrees less pitch. No problem.
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
Message 9
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| Subject: | Re: 912 with low RPM--- new vibration problem |
At 03:21 PM 3/9/2008, you wrote:
>Although I very carefully changed the pitch of the 3-blade warp drive prop
>about 3/4ths of a degree, and the maximum RPM is now within the range you
>suggested, the plane now vibrated a lot more than it did at all but idle
>setting. Yes I double checked the uniformity of prop pitch and made certain
>that the blades were seating right..
Where, on the blade, did you check the pitch? My Warp has
3/4 degree variation at the tips so what I do is equalize them at 75%
span after getting the RPM close. I use 75% because that's
approximately the "max force" position on the blade.
The other thing to check is that one blade didn't accidently
recede slightly when you were changing pitch. Even a tiny difference
in radius will result in a huge imbalance. Make sure they're seated.
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
Message 10
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| Subject: | Re: 912 with low RPM--- new vibration problem |
So long as each blade was measured and checked at exactly the same point it should
not matter. You aren't actually setting it for the first time to get close
for a first time run, so the actual degrees at this time should not make a difference.
You are only fine tuning it. So long as each blade was checked at the
same point and the same amount + or - was done to each then they should be equal.
You could put the prop protractor at the square tip if you wanted. You are
only trying to get them all equal. I agree with guy just double check to make
sure they are all the same.
--------
Roger Lee
Tucson, Az.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=168872#168872
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Hi Deb and Lisa,
I went to Bed Bath and Beyond today. I bought everything we had talked
about, Deb, but there were a couple of things that had already been bought.
This is what I bought: hand held mixer, Pyrex baking pans, vegetable
peeler, grater, measuring spoons, measuring cups, oven mitt, pot holder,
canisters, spatula, and tongs. The total came to $98.55 with tax. We still
have $21.45. Do you want me to go back and pick up a couple more things
from the kitchen list? Bed Bath and Beyond has a complimentary gift
wrapping service, so I let them wrap everything. There are four silver
boxes with the store sticker on them and one box is wrapped in silver/white
paper. We can sign the little gift tags with each family name and still get
a wedding card. I thought about going to Borders and picking up a cookbook
to go along with all of their new kitchen equipment.
Let me know what you guys think.
Sandy
Message 12
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I think the aviation department at BB&B has a long way to go to help our
Rotax but it is always wise to keep the wife happy.
John
________________________________
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Rich
& Sandy Schultz
Sent: Monday, March 10, 2008 2:57 PM
Subject: RotaxEngines-List: Wedding Gifts
Hi Deb and Lisa,
I went to Bed Bath and Beyond today. I bought everything we had talked
about, Deb, but there were a couple of things that had already been
bought. This is what I bought: hand held mixer, Pyrex baking pans,
vegetable peeler, grater, measuring spoons, measuring cups, oven mitt,
pot holder, canisters, spatula, and tongs. The total came to $98.55
with tax. We still have $21.45. Do you want me to go back and pick up
a couple more things from the kitchen list? Bed Bath and Beyond has a
complimentary gift wrapping service, so I let them wrap everything.
There are four silver boxes with the store sticker on them and one box
is wrapped in silver/white paper. We can sign the little gift tags with
each family name and still get a wedding card. I thought about going to
Borders and picking up a cookbook to go along with all of their new
kitchen equipment.
Let me know what you guys think.
Sandy
Message 13
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| Subject: | Re: 912 with low RPM--- new vibration problem |
Actually I think the installation instructions that come with Warp props
specify to use the tip for setting pitch. Yes, it goes against convention
but the convention is only with the OEM specs which is not the case with
Warp.
Noel
-----Original Message-----
From: owner-rotaxengines-list-server@matronics.com
[mailto:owner-rotaxengines-list-server@matronics.com] On Behalf Of Roger Lee
Sent: Monday, March 10, 2008 6:11 PM
Subject: RotaxEngines-List: Re: 912 with low RPM--- new vibration problem
So long as each blade was measured and checked at exactly the same point it
should not matter. You aren't actually setting it for the first time to get
close for a first time run, so the actual degrees at this time should not
make a difference. You are only fine tuning it. So long as each blade was
checked at the same point and the same amount + or - was done to each then
they should be equal. You could put the prop protractor at the square tip if
you wanted. You are only trying to get them all equal. I agree with guy just
double check to make sure they are all the same.
--------
Roger Lee
Tucson, Az.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=168872#168872
Message 14
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| Subject: | Re: Wedding Gifts |
The cookbook sounds like a real good idea, given your other choices.
The new bride should be very happy!
:)
----- Original Message -----
From: Rich & Sandy Schultz
To: 'Deb Garetson' ; rotaxengines-list@matronics.com
Sent: Monday, March 10, 2008 5:57 PM
Subject: RotaxEngines-List: Wedding Gifts
Hi Deb and Lisa,
I went to Bed Bath and Beyond today. I bought everything we had
talked about, Deb, but there were a couple of things that had already
been bought. This is what I bought: hand held mixer, Pyrex baking
pans, vegetable peeler, grater, measuring spoons, measuring cups, oven
mitt, pot holder, canisters, spatula, and tongs. The total came to
$98.55 with tax. We still have $21.45. Do you want me to go back and
pick up a couple more things from the kitchen list? Bed Bath and Beyond
has a complimentary gift wrapping service, so I let them wrap
everything. There are four silver boxes with the store sticker on them
and one box is wrapped in silver/white paper. We can sign the little
gift tags with each family name and still get a wedding card. I thought
about going to Borders and picking up a cookbook to go along with all of
their new kitchen equipment.
Let me know what you guys think.
Sandy
-------------------------------------------------------------------------
-----
Checked by AVG.
3/9/2008 12:17 PM
Message 15
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| Subject: | Re: 912 with low RPM--- new vibration problem |
At 01:41 PM 3/10/2008, you wrote:
>So long as each blade was measured and checked at exactly the same
>point it should not matter.
I'm not sure I understand you, Roger. Are you saying that
you'll get the right pitch later using the dynamic tracking method
with the colored tape? Or are you saying that the blades have exactly
the same twist? What I found on mine was that they had different
twist, by as much as 3/4 degree. Thus if you set equal at the tip,
they were 3/4 degree off at 75%. This makes a difference, since the
bulk of the force is generated around 75% span. Thus I set mine equal
at 75% and let the tips fall where they would.
I'm not positive the dynamic tracking method is more
accurate than the geometric method. These blades are solid carbon
laminates and subject to some variation in flexural properties. Also,
the tips are HAND GROUND, yes you heard that correctly. (If you want
a shock, measure the thickness / chord ratio throughout your blades.
Very scary.) This means the tip flexure will probably be somewhat
different, blade to blade.
Guy Buchanan
San Diego, CA
K-IV 1200 / 582-C / Warp / 100% done, thanks mostly to Bob Ducar.
Message 16
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| Subject: | Re: 912 with low RPM--- new vibration problem |
Hi Guy,
Tracking the blades are different than a balance. Tracking is done with the engine
off and just rotating the blades to make sure each crosses the line you have
made at the same place. One blade should not be off the line you marked on
the box. Each blade should cross the line at the exact same point and angle.
A dynamic balance is done for vibration only looking for an off set of a weight
imbalance and it is done at cruise rpm while tied down and under a cruise rpm
load. Any one of the three, tracking, static or dynamic balance can cause a vibration
if out very far. On the setting of the blade pitch it won't matter where
you take a measurement so long as you do it at the exact same spot on each
blade. I do mine at the tip of my squared off Warp Drive prop. Some of the other
props I do I can't do it that way so I measure in 3" on each blade to mount
the protractor. I can set any prop dead on for a 2 blade or a three and I always
triple check my work. Your blades should be exact matches as far as twist.
If they are really off 3/4 degree then you have found the vibration problem.
If they are off 3/4 degree then they can not be set to for each blade to perform
equally at the same rpm under a load. They will all be different at different
rpms. 3/4 degree is a lot. My blades are equal from the hub to the tips. The
warp drive blades should be identical and you should be able to measure back
2"-3" and set the protractor there. When you set the pitch on the ground and
not under a load you can make the fine tuning adjustment anywhere on the blade
because they are or should be all equal at that point and not flexing. We aren't
trying to set up a course pitch for the first time. Just trying to add or
subtract a small amount for a fine tuning.
A dynamic balance can only be done when the tracking, blade pitch and static balance
are all done or you may never get a decent dynamic balance. A dynamic balance
measures vibration in the engine, gearbox and prop and then instructs you
to as how much weight to add and where to add it so as to offset the weight
imbalance in the prop hub assembly with all the hardware attached.
The tips can be used even if they are hand ground because you are going to put
the flat side of the protractor against the flat side of the prop.
I hope this helps. You can call me if you have any further questions. Sometimes
that's easier than long emails. 520-574-1080 Tucson, Az.
--------
Roger Lee
Tucson, Az.
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http://forums.matronics.com/viewtopic.php?p=168956#168956
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