Today's Message Index:
----------------------
1. 06:35 AM - Re: pitch? (Stuart Harner)
2. 01:40 PM - Prop inertia & the B box (Richard Pike)
3. 02:39 PM - Re: pitch? (Jack B. Hart)
4. 03:19 PM - Rudder Failure on my Xtra. (Brad Nation)
5. 05:47 PM - Re: Rudder Failure on my Xtra. (John Hauck)
6. 07:47 PM - Re: Rudder Failure on my Xtra. (Rick Neilsen)
Message 1
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Thanks Rick, that helps.
This list once again proves what a great bunch of guys make it up.
I have sent an email to WD about this and will wait for a reply.
Holiday weekend and all, plus I am on the road for work next week, so it
may be a while before I find out what they say.
I will let you know what comes of this.
Thanks again to everyone!
Stuart
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of Richard
Girard
Sent: Saturday, August 30, 2014 8:20 PM
Subject: Re: Kolb-List: pitch?
Stuart, I'm re-posting this response just in case it didn't come
through. And I'm going to add something after.
Before you get rid of your WD prop, know this. Most of the MOI problems
on "B" gearboxes come from trying to make the engine idle at too low an
RPM. Doing this beats up the dogs and wears out the spring washers in
the gearbox. Just keep the RPM at idle at 2000 or more and you'll be
just fine.
You have one more option before you dump the prop. Have the blades
tapered. It's going to mean putting another $200 or so dollars into the
prop but tapering the blades gets rid of mass on the blade tips where
you get some good out of it.
My 2 cents, your $200 bucks if you decide to do it.
Rick Girard
In the winter of 2006, hot out of LSARM training I built a rig and did
the rotational inertia per Rotax Service Instruction 11 UL 91E published
December of 1992 (attached). At the time I had six props for various
aircraft in the shop. As I recall only the wood two blade that came with
my Firestar passed and being of multi-laminate constuction only did
barely. Jimmy Young also did tests on two props, a WD and an IVO if
memory serves. Both were three blade props.
Anyway, I stand by the recommendations above.
I know I'm not alone in recommending WD props for one simple reason.
They are great at holding up to the trials and tribulations of the
pusher configuration. I put an AN 6 bolt through a Warp and didn't even
know it until I landed. I put a cheap pair of bifocals through the Power
Fin on my trike and it cost me two new blades.
Rick
On Sat, Aug 30, 2014 at 7:47 PM, Stuart Harner <stuart@harnerfarm.net>
wrote:
John,
That was the exact impression I had, and the reason I did not question
it
any further. Seemed like he knew the plane, the engine and the gearbox.
I
did not get the "used car salesman" red flag.
I really did not give it much extra thought until some replies to my
starting pitch angle came back, indicating that this combo would not
work.
The numbers back this up, Rotax did not put the limits in the book just
for
the heck of it.
However, no one has replied that Yes, they are running this combination
and
it is fine. The flip side of that is no one has said "I tried that and
it
tore up my gearbox", only some have warned that it would not work,
according
to the numbers.
So, it would seem that it all comes down to whether I want to try it or
not.
I have been doing some research on this subject today, some of it I did
not
understand. I like physics, but am not very good at it.
To me, a heavier prop (flywheel) would help smooth out the pulses of
combustion, at the expense of quick throttle response. It seems to me
that
a lighter prop would speed up and slow down "faster" so that it would
"hammer" the gears more. More rotational mass (MOI) would be slower to
reach a set speed, but would also tend to continue rotating at that
speed
(minus the drag of producing thrust) therefore carrying the inertia into
the
next combustion pulse. To me this should dampen the "hammering of the
gears
effect". Maybe I just don't "get it".
Something else I find interesting is that the Rotax manual warns never
to
run the engine without a prop (load) as it will damage the gearbox.
They
give a max MOI, but wouldn't there also be a minimum MOI?
Maybe I am fretting over nothing. Maybe I should bolt it on and fly!
I value EVERYONE's input, and thank you one and all.
Stuart
P.S. I still haven't heard a suggested starting pitch angle....
-----Original Message-----
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck
Sent: Saturday, August 30, 2014 3:00 PM
Subject: RE: Kolb-List: pitch?
Daryl Heineman, President of Warp Drive, is probably the salesman you
are
referring to that sold you the prop. Normally, he is the only one
selling
them. Good man. Knowledgeable when it comes to Warp Drive Props and
engine
combos.
I've flown with Warp, and done business with them, for 21 years. Tested
them, unintentionally, to the max. They always come through and get me
back
home.
I don't know what kind of flying you will be doing, but doubt you will
ever
be able to over stress your gear box with this prop and a FS????
Daryl was not trying to fool you, I am sure.
I'd fly that combo.
My experience and opinion only. Don't try this at home.
john h
mkIII
Titus, Alabama
-----Original Message-----
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner
Sent: Saturday, August 30, 2014 11:04 AM
Subject: RE: Kolb-List: pitch?
Jack,
Some others have raised that issue. I was aware of the MOI limits on
gearboxes and quizzed Darrell at Warp Drive before I ordered the prop.
He
assured me it would be OK, but had no hard numbers for me.
Now I am beginning to wonder if I was fooled by a salesman. :(
I can easily set up and run the MOI tests myself to get the true answer,
but
I suspect I am not going to like it.
Options are buy a new milled aluminum hub, but that is saving all the
weight
at the center, which won't help the MOI much. I could convert to a two
blade hub, but the 60" is probably not able to put enough load on the
engine
at any kind of a reasonable pitch.
I wanted to check out the Power Fin props at OSH, but could not find
them on
the field nor in the list of vendors.
Now what I am going to say next is strictly personal and is NOT meant to
start any flame wars over props:
I know Travis recommends the IVO, but for me they are not an option due
to
other's experiences. End of story, no more gas for the flames.
I have a good regard for the Warp Drives, related to the above sentence,
again, no more gas.
I am completely open to any other prop that gets the job done that is
reasonably priced.
I don't care about looks, but am concerned about vibration, price and
noise,
but of course they have to take a back seat to proper application.
Some things I have read and conversations I have had led me to think
that
the 3 blade would be a better choice as it would be smoother and quieter
than a 2 blade. I also liked the idea of a lower overall folded size
(my
hanger/trailer situation came into play here).
Anybody want to buy a new prop that has not even had the bolts torqued
down?
Not the first stupid thing I have done, probably not the last
either.....
Stuart
-----Original Message-----
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of Jack B. Hart
Sent: Saturday, August 30, 2014 9:02 AM
Subject: RE: Kolb-List: pitch?
--> <jbhart@onlyinternet.net>
>
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com]
Sent: Thursday, August 28, 2014 3:41 PM
Hi,
My Warp Drive prop (3 blade- 60) arrived yesterday and I am getting
ready to
set it up. It is going on my Firefly with a Rotax 447 (single carb),
B-Gearbox with 2.58 ratio.
........................
>
Stuart,
I hope you have considered the following:
The B gearbox is rated for a max moment of inertia of 1025 lb-in squared
or
3000 kg-cm squared.
Ultralight News of Canada found the three blade Warp prop exceeded these
numbers.
See: http://www.ultralightnews.ca/articles/driveselection.htm
Warp Drive should be able to tell you the moment of inertia of your
propeller.
Or, the above site can direct you to a Rotax Service Bulletin that
explains
how to determine the moment of inertia of your prop.
Jack B. Hart FF004
Winchester, IN
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Zulu Delta
Mk IIIC
Thanks, Homer GBYM
It isn't necessary to have relatives in Kansas City in order to be
unhappy.
- Groucho Marx
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Subject: | Prop inertia & the B box |
Years ago CPS had a complete series of tech articles in their catalog on Rotax
engines and gearboxes and one of those articles was on prop inertia and how much
the B box could handle. CPS currently has a number of those tech articles online
but not all of them. I still have an old CPS catalog that includes all the
old articles and this is the article on prop inertia, so I scanned it, perhaps
it will be useful.
Also, since I am the list curmudgeon who gripes about ridiculously oversize pictures,
and since I am not sure how big these pictures will turn out to be, I thought
I better put it in a separate thread... [Wink]
--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0
My soul shall be joyful in the LORD; It shall rejoice in His salvation. Psalm 35:9
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=429705#429705
Attachments:
http://forums.matronics.com//files/prop1_176.jpg
http://forums.matronics.com//files/prop2_417.jpg
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From: "Stuart Harner" <stuart@harnerfarm.net>
>>>>>>>>>>>>>>>>>>>>>>>
..................
I have been doing some research on this subject today, some of it I did not
understand. I like physics, but am not very good at it.
To me, a heavier prop (flywheel) would help smooth out the pulses of
combustion, at the expense of quick throttle response. It seems to me that
a lighter prop would speed up and slow down "faster" so that it would
"hammer" the gears more. More rotational mass (MOI) would be slower to
reach a set speed, but would also tend to continue rotating at that speed
(minus the drag of producing thrust) therefore carrying the inertia into the
next combustion pulse. To me this should dampen the "hammering of the gears
effect". Maybe I just don't "get it".
>>>>>>>>>>>>>>>>>>>>>
Stuart,
May be I can help you "get it".
The moment of inertia is the spread of the mass about the center of rotation
times the radius of gyration squared.
Take a large hex nut and tie to the end of a string.
Give it a whirl in the horizontal plane with a short
radius and notice the tension in the string and the
revolution count.
Double string length and try to keep the rotation
speed the same as before.
You will find that the string tension more than doubles and the energy you
have to exert to swing the whole thing goes way up. In this case the system
mass "the nut" is constant but as the mass is moved out from the center of
rotation more torque is required to keep rpm constant.
These represent the loads as seen by the gear box and the crank. It is
desirable to have a low inertia propeller so that the propeller can
accelerate and de accelerate and absorb some of the firing impulse exerted
on the crank by the piston and connecting rod. This reduces the peak
oscillatory torque loads in the crank and on the face of the gear
teeth.
It is some what counter intuitive. With a lower inert propeller, the
engine and gearbox will jump around a little more on the mounts. But
internally the gear box and crank and piston rod bearing assemblies will be
operating under lower peak loads while the system is delivering the same hp
as it would with a higher inertia propeller.
Jack B. Hart FF004
Winchester, IN
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Subject: | Rudder Failure on my Xtra. |
Kolbers,
The good news is that no one was ingured and the aircraft damage was
relatively minor. It could have been a lot worse if it happened in the
air.
Recently we had a taxi test in my Xtra with a once around the pattern
and shortly after landing the right rudder failed! Atfter a sharp left
turn to exit off the runway, without the benefit of a taxiway, the Xtra
ending up off the runway with both axels sheered off at the wheel and a
bent right wing tip.
After getting the plane back to the hanger I found that the rudder
failure was caused by the weld failing between the upright square bar
that connects the rudder to the cables. I also noticed that the axel is
hollow. Should the axel be solid?
Have any of the Kolbers experienced this before and if so, any
suggestions as to the cause of the failure and the best course of
action, repair or replace the failed part?
I have attached the photos of the failed part and the sheered axel.
Brad Nation
MK III Xtra
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Subject: | Rudder Failure on my Xtra. |
Not rudder failure, but what looks like a rudder crank that failed, not
because the weld failed, but the round tube wall stressed cracked over time
and failed. I had a similar aileron crank failure on a Ultrastar in 1985.
Weld was good but the rotating tube wall stress cracked and failed.
First I have heard of this type failure in a rudder crank. That doesn't
mean much.
Axles are normally tubular. Looks like yours are the popular 5/8" OD axles
that use little ball bearings which cannot be adjusted. I upgraded to 3/4"
OD axles with tapered roller bearings after I lost a wheel at Muncho Lake,
BC, in 2000. Never had another problem with wheels, axles, and gear legs.
Our MKIII aircraft are heavy when we strap in a couple husky guys, a full
load of fuel, and anything else we can stick in there. I think MATCO
advertises the 5/8" axles as 600 lbs static and 2000 lbs max. Most of us
exceed that number a great deal. If you land at 3 g's, that's 1980 lbs. 4
g's is 2400 lbs. See what I mean. That is if you and your airplane weigh
600 lbs. 900 to 1000-1200 lbs is more like it.
I guarantee those wheels, axles, and bearings have been constantly
overstressed. I didn't realize that 14 years ago when I broke mine.
Sorry it happened. It always hurts to break our airplane.
john h
mkIII
Titus, Alabama
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of Brad Nation
Sent: Sunday, August 31, 2014 5:19 PM
Subject: Kolb-List: Rudder Failure on my Xtra.
Kolbers,
The good news is that no one was ingured and the aircraft damage was
relatively minor. It could have been a lot worse if it happened in the air.
Recently we had a taxi test in my Xtra with a once around the pattern and
shortly after landing the right rudder failed! Atfter a sharp left turn to
exit off the runway, without the benefit of a taxiway, the Xtra ending up
off the runway with both axels sheered off at the wheel and a bent right
wing tip.
After getting the plane back to the hanger I found that the rudder failure
was caused by the weld failing between the upright square bar that connects
the rudder to the cables. I also noticed that the axel is hollow. Should
the axel be solid?
Have any of the Kolbers experienced this before and if so, any suggestions
as to the cause of the failure and the best course of action, repair or
replace the failed part?
I have attached the photos of the failed part and the sheered axel.
Brad Nation
MK III Xtra
Message 6
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Subject: | Re: Rudder Failure on my Xtra. |
The kolb list is very valuable in spreading the word if there is an issue.
Thanks for reporting it.
I think the issue might be that the rudder control system wasn't designed
to handle the load that toe brakes put on the rudder control system. Flight
loads and ground control steering just doesn't put that much load on it.
Like so many things when a seemingly small change is made it can effect a
bunch of other things. Those of us that have the old heal brakes shouldn't
have a issue. For those that have toe brakes check for stress in the area
described. Also check the rudder control horn on the rudder and the rudder
hinges. It would seem that some beefing up of the rudder system is in order
when using the newer toe brake setup. Seems like there was one toe brake
installation that increased the leverage to the master cylinders for this
very reason. Maybe both areas need to be looked at. In the mean time don't
stand on those toe brakes.
As always worth what you paid for it and refunds anytime.
Rick Neilsen
Redrive VW Powered MKIIIC
On Sun, Aug 31, 2014 at 8:47 PM, John Hauck <jhauck@elmore.rr.com> wrote:
> Not rudder failure, but what looks like a rudder crank that failed, not
> because the weld failed, but the round tube wall stressed cracked over ti
me
> and failed. I had a similar aileron crank failure on a Ultrastar in 1985
.
> Weld was good but the rotating tube wall stress cracked and failed.
>
>
> First I have heard of this type failure in a rudder crank. That doesn't
> mean much.
>
>
> Axles are normally tubular. Looks like yours are the popular 5/8" OD
> axles that use little ball bearings which cannot be adjusted. I upgraded
> to 3/4" OD axles with tapered roller bearings after I lost a wheel at
> Muncho Lake, BC, in 2000. Never had another problem with wheels, axles,
> and gear legs.
>
>
> Our MKIII aircraft are heavy when we strap in a couple husky guys, a full
> load of fuel, and anything else we can stick in there. I think MATCO
> advertises the 5/8" axles as 600 lbs static and 2000 lbs max. Most of us
> exceed that number a great deal. If you land at 3 g's, that=99s 19
80 lbs. 4
> g's is 2400 lbs. See what I mean. That is if you and your airplane
> weigh 600 lbs. 900 to 1000-1200 lbs is more like it.
>
>
> I guarantee those wheels, axles, and bearings have been constantly
> overstressed. I didn't realize that 14 years ago when I broke mine.
>
>
> Sorry it happened. It always hurts to break our airplane.
>
>
> john h
>
> mkIII
>
> Titus, Alabama
>
>
> *From:* owner-kolb-list-server@matronics.com [mailto:
> owner-kolb-list-server@matronics.com] *On Behalf Of *Brad Nation
> *Sent:* Sunday, August 31, 2014 5:19 PM
> *To:* Kolb-list
> *Subject:* Kolb-List: Rudder Failure on my Xtra.
>
>
> Kolbers,
>
> The good news is that no one was ingured and the aircraft damage was
> relatively minor. It could have been a lot worse if it happened in the ai
r.
>
>
> Recently we had a taxi test in my Xtra with a once around the pattern and
> shortly after landing the right rudder failed! Atfter a sharp left turn
to
> exit off the runway, without the benefit of a taxiway, the Xtra ending up
> off the runway with both axels sheered off at the wheel and a bent right
> wing tip.
>
>
> After getting the plane back to the hanger I found that the rudder failur
e
> was caused by the weld failing between the upright square bar that connec
ts
> the rudder to the cables. I also noticed that the axel is hollow. Should
> the axel be solid?
>
>
> Have any of the Kolbers experienced this before and if so, any suggestion
s
> as to the cause of the failure and the best course of action, repair or
> replace the failed part?
>
>
> I have attached the photos of the failed part and the sheered axel.
>
>
> Brad Nation
>
> MK III Xtra
>
>
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