Today's Message Index:
----------------------
1. 03:56 AM - Re: XC Photo (icrashrc)
2. 04:47 AM - Re: harmonics (Thom Riddle)
3. 05:21 AM - Re: Re: XC Photo (John Hauck)
4. 05:50 AM - Re: harmonics (JetPilot)
5. 08:24 AM - Re: V.W.conversion (Rick Lewis)
6. 08:42 AM - Re: Stits (DAquaNut@aol.com)
7. 08:58 AM - Re: Re: harmonics (Herb)
8. 09:31 AM - Re: Re: V.W.conversion (frank.goodnight)
9. 01:42 PM - Re: Re: V.W.conversion (Richard & Martha Neilsen)
10. 06:41 PM - Re: Re: harmonics (Jack B. Hart)
Message 1
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John,
That is a great picture! Any chance you could send me the full size version of
this pic via email?
Thanks,
John Hauck wrote:
> Bumped into this old photo while looking for something else.
>
> I believe this was taken on Bonneville Salt Flats, Utah, May 2007.
>
> The black line used for speed runs on the flats, is visible in the photo,
> running right below John W's Kolbra.
>
> john h
> mkIII
--------
Scott
www.ill-EagleAviation.com
do not archive
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=238688#238688
Message 2
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If the harmonic is coming from some airframe part and is a result of engine/prop
vibrations, then the engine/prop vibrations being transmitted to this airframe
part would be lessened if the mounts were a little softer. In any case a change
in mount stiffness would change the natural harmonic frequency which might
make the current troubling sound go away, go to a different pitch, go to a different
part of the airframe or get worse. Difficult to predict.
Assuming the prop is statically balanced, blades pitched equally, and tracked properly,
the next step I would consider is dynamic engine/prop balancing. Doing
so may solve your problem at the source, which would be the best solution. Many
class D and bigger airports with reasonably complete maintenance shops have
the capability to do dynamic engine/prop balancing. Last time I checked local
prices it was about $250.
--------
Thom Riddle
Buffalo, NY
http://riddletr.googlepages.com/sportpilot-cfi
http://riddletr.googlepages.com/a%26pmechanix
A complex system that works is invariably found to have evolved from a simple system
that works.
- John Gaule
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=238690#238690
Message 3
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> That is a great picture! Any chance you could send me the full size
version of this pic via email?
> Thanks,
Scott:
If I can find my original file, it will be on the way.
If John W took this photo, then we are out of luck.
john h
mkIII
Message 4
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You mentioned that John H. mentioned the gear box spacers, this makes several different
people that I have heard mention this. The others were not on the Kolb
list, but it seems to be something important with the 912. I am not sure
what the symptom is if the spacing is out of tolerance, but I will ask. The SS
seems like an interesting plane, it would probably leave all of us behind.
What speed and and RPM 's do you use for both long range and high speed cruise
? What are you approach and landing speeds ?
Mike
--------
"NO FEAR" - If you have no fear you did not go as fast as you could
have !!!
Kolb MK-III Xtra, 912-S
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=238698#238698
Message 5
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Subject: | Re: V.W.conversion |
The engine Great Plains offers is probably the way to go. The owner, Steve, has
a good background on these engines and can offer most anything you'll need to
make the engine perform. He is also presently working on his own version of
the water cooled heads. Attached is a picture of my engine that I'm fitting
up on my MXIII. The re-drive is a must for good performance and is well made.
It cost around $1600.00. You will engine up with a good engine that should
perform on your Kolb at only 1/3 the price of a Rotax, especially if you go with
the water cooled heads.
Rick Lewis
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=238708#238708
Attachments:
http://forums.matronics.com//files/misc_pics_050_185.jpg
http://forums.matronics.com//files/vw_engine_036_677.jpg
Message 6
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In a message dated 4/10/2009 8:20:23 P.M. Central Daylight Time,
herbgh@nctc.com writes:
A Firefly needs its fabric treated with a 50-50 mix of brush
and spray...after the first coat of poly brush is applied in the
normal way...and use 50-50 til you are satisfied that the uv
protection is good... Two cross coats is good enough IMHO
... you are trying to make weight after all... and this stuff does add
wt...
the cost difference is because of the paper trail that certified
fabric must have I think...mainly... Herb
Herb,
That sounds like a great idea! I wish I had heard that idea
before I covered My Firefly! Has this process been tested for longevity in the
sunlight ? How long has this process been proven to hold up in sunlight
compared to the 3 full cross-coats Stits recommends ?
Ed FF #62 ( In Houston )
**************Feeling the pinch at the grocery store? Make dinner for $10
or less. (http://food.aol.com/frugal-feasts?ncid=emlcntusfood00000001)
Message 7
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I am Rebuilding a C box...I notice that the input shaft and prop
shaft both have spacers/shims ...They are important such that too
much clearance will allow hammering with throttle changes...This
will result in an accelerated wear factor which will gradually affect
the case...or enclosure.and bearings and gear lash.......Herb
At 07:50 AM 4/11/2009, you wrote:
>
>You mentioned that John H. mentioned the gear box spacers, this
>makes several different people that I have heard mention this. The
>others were not on the Kolb list, but it seems to be something
>important with the 912. I am not sure what the symptom is if the
>spacing is out of tolerance, but I will ask. The SS seems like an
>interesting plane, it would probably leave all of us behind. What
>speed and and RPM 's do you use for both long range and high speed
>cruise ? What are you approach and landing speeds ?
>
>Mike
>
>--------
>"NO FEAR" - If you have no fear you did not go as fast as
>you could have !!!
>
>Kolb MK-III Xtra, 912-S
>
>
>Read this topic online here:
>
>http://forums.matronics.com/viewtopic.php?p=238698#238698
>
>
>Checked by AVG - www.avg.com
>04/11/09 10:51:00
Message 8
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Subject: | Re: V.W.conversion |
Hi Rick.
good pictures . Who makes your redrive? Thanks for answering my
question.
Frank Goodnight
Firestar2
HKS power
On Apr 11, 2009, at 10:23 AM, Rick Lewis wrote:
>
> The engine Great Plains offers is probably the way to go. The
> owner, Steve, has a good background on these engines and can offer
> most anything you'll need to make the engine perform. He is also
> presently working on his own version of the water cooled heads.
> Attached is a picture of my engine that I'm fitting up on my MXIII.
> The re-drive is a must for good performance and is well made. It
> cost around $1600.00. You will engine up with a good engine that
> should perform on your Kolb at only 1/3 the price of a Rotax,
> especially if you go with the water cooled heads.
>
> Rick Lewis
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=238708#238708
>
>
> Attachments:
>
> http://forums.matronics.com//files/misc_pics_050_185.jpg
> http://forums.matronics.com//files/vw_engine_036_677.jpg
>
>
Message 9
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Subject: | Re: V.W.conversion |
Rick
That is good news on the GP water-cooled heads. Do you have any details? Are
they like yours?
Do not archive
Rick Neilsen
Redrive VW powered MKIIIC
----- Original Message -----
From: "Rick Lewis" <cktman@hughes.net>
Sent: Saturday, April 11, 2009 11:23 AM
Subject: Kolb-List: Re: V.W.conversion
>
> The engine Great Plains offers is probably the way to go. The owner,
> Steve, has a good background on these engines and can offer most anything
> you'll need to make the engine perform. He is also presently working on
> his own version of the water cooled heads. Attached is a picture of my
> engine that I'm fitting up on my MXIII. The re-drive is a must for good
> performance and is well made. It cost around $1600.00. You will engine
> up with a good engine that should perform on your Kolb at only 1/3 the
> price of a Rotax, especially if you go with the water cooled heads.
>
> Rick Lewis
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=238708#238708
>
>
> Attachments:
>
> http://forums.matronics.com//files/misc_pics_050_185.jpg
> http://forums.matronics.com//files/vw_engine_036_677.jpg
>
>
>
Message 10
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At 04:46 AM 4/11/09 -0700, you wrote:
>
>If the harmonic is coming from some airframe part and is a result of
engine/prop vibrations, then the engine/prop vibrations being transmitted to
this airframe part would be lessened if the mounts were a little softer. In
any case a change in mount stiffness would change the natural harmonic
frequency which might make the current troubling sound go away, go to a
different pitch, go to a different part of the airframe or get worse.
Difficult to predict.
>
..........................
Just to add a few thoughts. It all has to do with energy inputs. The
greater the HP and the lighter (less stiff) the air frame the greater the
chance is for harmonic vibrations to develop. Every air frame and or
components will have some natural frequency. But there is an energy input
threshold that must be passed before the frame will resonate that is related
to structural stiffness. It is similar to unbalanced aileron flutter where
a certain speed (energy level) must be reached before there is an onset of
flutter.
So what is the driving energy force? Well it is the engine and the
propeller. They cause a twisting in the mounts directly proportional to the
average torque being developed. Superimposed on top of the average torque
is periodic torque variation that is caused by engine cylinder firing
impulse. The amplitude variation is dependent upon torque resistance
(springiness) of the crank shaft and crankshaft load. This load will be the
gear box or propeller. As one increases crankshaft load more and more of
the torque variation must be transferred to the engine mounts and dissapated
though the supporting structure.
So what are the choices? One could add more cylinders for a given average
torque, and this would reduce the torque variation component magnitude so
that will not exceed the airframe threshold. One can de couple the engine
and propeller by moving to softer mounts. One can back off the throttle a
little and reduce the torque variation amplitude, and in doing so miss match
frequencies. This may also be accomplished by changing gear box ratios or
changing the number of propeller blades.
Another way to reduce the torque variation amplitude transmitted to the
airframe is to add some kind of dampening in between the engine and the
propeller. Also one can reduce inertial load seen by the crankshaft (less
twisting). Just because an engine gear box or reduction unit can tolerate a
certain level of propeller inertia does not mean that it is the correct or
desired combination for all airframes. By lowering propeller inertia for
the same power output means lower energy dissipation to the air frame. A
more flexible the propeller will give further improvement, by absorbing some
of the crank torque variation amplitude from the crank and there by not being
passed on to the airframe.
One last comment. On the FireFly, I had some noise problems. Streamlining
the struts removed a constant bass strumming noise. The Victor 1+ being a
one cylinder engine, it shakes things a bit. I found that it really excited
the inboard aileron hinges. When I took all the play from the aileron
hinges and control system, things became quieter. Also, I discovered the
soft wing gap seal fluttered. Tube stiffeners in the front and rear cross
seams to care of it.
FWIW
Jack B. Hart FF004
Winchester, IN
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