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prop hub extentions
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Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Fri Feb 23, 2007 4:47 pm Post subject: prop hub extentions

Hey gang,



I seldom look at barnstormers but did today and noticed this photo of a prop hub extention. It is the same type I bought 3 of before learning that it's not the one of choice. It is tapered and uses the 1/2" bolts into the gearbox flange. and has no lugs on the prop side. After many phone calls and my good friend at TNK sending me the latest hub extentions they are selling, we wound up making our own. It uses the 912 lugs on the gearbox flange and the prop side and the 8mm bolts. I also learned that the tapered extention was used on earlier 2 cycle engines and 2 blade props. I have one of those if anyone needs one. The extention that TNK is sending out as of late is good with one exception. on the prop side the 912 lugs fit lose in the holes. Meaning that you would have to hold the back of the lug with vice grips or pliers. We made ours so it is the same press fit as the prop flange on the engine. Worked out real nice. We can offer the aboved extention if anyone wants one for $300.00 labor is 200.00 for machine work material is about 40 bucks. 



Is anyone running one of these tapered hubs without the lugs and have the warp hub mounted backwards useing the smaller bolt circle? If so do you think it is safe? Darryl at warp said he would rather not see the 68"+ 3 blade used in this configueration .



for what is worth.....



ps. I didnt try and use spell check or attach the photo to this post, the last time the bbs vaporized my message! so what you see is what you get sorry!

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Fri Feb 23, 2007 4:56 pm Post subject: Re: prop hub extentions

here is the hub in question

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Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Fri Feb 23, 2007 5:24 pm Post subject: Re: prop hub extentions

here is the one i found on barn stormers

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Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sat Feb 24, 2007 2:40 pm Post subject: Re: prop hub extentions

here is the one we made with the 912 lugs pressed in

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Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

MKIIIX040

Joined: 31 Mar 2006
Posts: 123
Location: Millinocket, Maine

Posted: Sun Feb 25, 2007 6:42 am Post subject: prop hub extentions

Now thats a nice ah!

 Vic 

 Extra 912

 Maine

 Archive this hall monitors

   [quote][b]

_________________
MKIIIX040
912UL

planecrazzzy
Guest

Posted: Sun Feb 25, 2007 7:18 am Post subject: Re: prop hub extentions

Hey Paul,

              What grade of aluminum was used ?  7075 ?

  Gotta Fly...

Mike & "Jaz" in MN

 PS ...Vic.... Archive what ??? ( are you grabbing something ? ) He he he

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sun Feb 25, 2007 7:30 am Post subject: Re: prop hub extentions

Mike,



I used 6061. Here is a before shot.

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Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Dennis.Kirby(at)kirtland.
Guest

Posted: Tue Feb 27, 2007 7:09 pm Post subject: prop hub extentions

"Paul Petty" wrote: < here is the one we made with the 912 lugs pressed

in >



Beautiful piece of work, Paul!



Which causes me to wonder: Do I need one of these for my Mark-III?



With this recent thread about prop hub extenders, I still do no know if

the specific advantage is:  1) noise reduction, by moving the spinning

prop tips further away from the trailing edge, or 2) improved

performance.



Can anyone answer this?



Thanks in advance,

Dennis Kirby

912ul, Powerfin-72

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Mon Mar 05, 2007 4:06 pm Post subject: Re: prop hub extentions

Dennis,

I thought the extention was needed to have proper clearance. Without one on my kolbra the prop would be vert close to the flaps. The reason for this thread was to find out what everyone is useing. I bought/made 3 before I found the one closest to what TNK sends out. The problem with the "black" one was it uses the smaller diamater bolt circle and no lugs (rotax). Daryel at warp was not happy with this combo. The one Travis sent me for comparison did not have the holes on the prop side properly sized for the lugs to be "pressed" or "pulled" into the hub. This has been a real adventure finding out what is used out there. I have seen it all however I think what we landed on is the closest to right. If there is such of thing.



p.s. send me a off list e-mail at paupetty(at)myway.com if you need more photos



p.s.s. call me anytime (at) 601-480-9979

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Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Tue Mar 06, 2007 5:07 pm Post subject: Re: prop hub extentions

I had some of the same questions about my Prop Extension on my 912-s.  I am not concerned about having lugs or not where it bolts down to the 912's, those bolts are huge, and the diameter of the pattern is large, meaning the will be lightly stressed.  I have one of the RED extensions you posted in some of your pictures.  I have two concerns about this, first is the taper in the extension itself down to 2 inches before the flange to attach it to the prop.  Second, using the smaller bolt pattern on the warp puts a LOT more stress on the small bolts that attach the prop to the spacer itself, these bolts are pretty small and do break sometimes.  The stress on those bolts increases almost exponentially as the bolt pattern diameter gets smaller.   Its just plain dumb using the smaller pattern when the larger one could be used.   Attached is a picture of my spacer...



I like two things about your hub, first is has no super thin taper in it sressing the aluminum neck itself.  Second is the larger bolt pattern on the prop side takes a lot of load off the thin prop bolts.   ( I also like the cool black color    it matches my prop ).  One thing I have to ask though is why use 6061 aluminum instead of 7075 ?  Isnt 7075 a lot stronger ?  If memory serves me right, isnt the red spacer made out of 7075 ?



Mike Bigelow

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"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Wed Mar 07, 2007 4:10 pm Post subject: Re: prop hub extentions

Mike,



I still have the black tapered hub if you want it. Dont know if the prop side is the same bolt circle as the Kleiv but your welcome to it. Two things I noticed about your photo are 1. your prop hub doesn't seam to be completly sandwiched. Is this normal? 2. Why did you go with castel nuts and cotter pins? Just curious.... One more question does the Kleiv hub have the larger diamater bolt circle with the bored holes for the rotax lugs? From evey one i have talked to the rotax lugs and 8mm bolts are the strongest combo for what it's worth.

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Fri Mar 09, 2007 11:47 am Post subject: Re: prop hub extentions

Hi Paul,



What do you mean by sandwiched ?  I am including another picture so you can get a better look at it, if you see something that does not look right please let me know !



I used cotter pins because they are easy, and I had the cotter pins.  Is there a reason not to use them on the extension ?   The Kiev prop is VERY light, and uses the smaller bolt pattern only.   It performs well, is smooth, and quiet, but the hub and blades are so light that is scares me.   It would probably be fine for a smaller 2 stroke engine, but it does not seem strong enough for a 912-s.   The other problem is that if something came off the engine and went into the prop, the Kiev would surely explode into a million peices 



I have a Warp drive prop with the larger bolt pattern sitting in the box just waiting to bolted on      After seeing how light the Kiev prop is, the small bolt pattern, and the small neck in the spacer, im just not willing to be the test case for this setup....



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Fri Mar 09, 2007 11:54 am Post subject: Re: prop hub extentions

Pictures

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Fri Mar 09, 2007 11:57 am Post subject: Re: prop hub extentions

Here are a couple pictures..

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_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sat Mar 10, 2007 10:50 am Post subject: Re: prop hub extentions

Mike,



Look at the side view of your prop hub. Notice how the 2 "Halfs" dont completely touch at the top but almost touch at the bottom. The warp is completely closed when torqued to spec. Yours might be fine. Just a thought.

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sat Mar 10, 2007 11:00 am Post subject: Re: prop hub extentions

Mike,



As for the cotter pins and castle nuts. I dont know if they pose a problem or not. I was just curious why you used them over nylocks. Some told me this rule of thumb when it comes to AN hardware. "If the bolt goes through a rotating part i.e. control stick or any part that moves use drilled bolts castle nuts and cotter pins. IF the part is to be bolted tight or torqed to spec use undrilled bolts and nylock nuts" Cant remember who told me that. But is on this fine list. Question, what is the torque on the prop hub on the Kleiv?

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

Paul Petty

Joined: 11 Jan 2006
Posts: 226
Location: Mississippi

Posted: Sat Mar 10, 2007 11:09 am Post subject: Re: prop hub extentions

By the way gang. In case any of you are wondering, the photo of my prop hub and prop is NOT tightend down nor is the prop pitched in that photo. Just to clear that up in case any of you thought I had completly lost my mind over. Getting close to losing it but not yet!   

do not archive

_________________
Paul Petty
Kolbra #12
Ms Dixie
912 UL 70" warp

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sat Mar 10, 2007 3:12 pm Post subject: Re: prop hub extentions

Hi Paul,



The torque on the prop bolts is 14.5 foot-lb, for both the 6 that holds the prop to the spacer, and also 14.5 foot-lb for the bolts that clamp the blades down ( 2 each for a total of 6 ).   I used a very accurate torque wrench and was very careful to get the torque perfect on each bolt.  I also used the sequential pattern to attach the prop to the spacer.  The picture you see is a fully tightened and adjusted prop...  I never really paid attention, but looking at the picture I have no idea why the space varies a bit between the hub halves.  The 2 halves never touch together anywhere, there is a space along the enitre hub.



Do most people use Nylock on the prop bolts ?  It would have certianly been easier and I would like to change them if that is the way to go.  I had to file washers, or add them to get the correct torque so that the cotter pin grooves lined up with the holes.  It was a pain in the arse !!!



Every time I look at your spacer, I like it more     Nice, thick, strong, and a cool black color that matches my prop.   



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

JetPilot

Joined: 10 Jan 2006
Posts: 1246

Posted: Sat Mar 10, 2007 3:19 pm Post subject: Re: prop hub extentions

Looking agian, yours is silver, but it could be anadozied.    I do like the thick neck of yours.   The taper to a very thin 2 inches on my spacer and the black spacer you have in your pictures one scares me on the Kiev Prop, I really would not trust it on the much heavier warp drive prop.



Mike

_________________
"NO FEAR" - If you have no fear you did not go as fast as you could have !!!

Kolb MK-III Xtra, 912-S

NeilsenRM(at)comcast.net
Guest

Posted: Sun Mar 11, 2007 9:08 am Post subject: prop hub extentions

Mike



There is no problem using castle nuts with cotter pins on prop bolts. There 

is a concern with nylocks in that the torque on the bolt may not be just 

right. Most torque specs are given using regular dry nuts or bolts.



Also I see a few props with metal hubs using crush plates. Crush plates are 

mostly for wood props. You may not be need to use them on metal or medal hub 

props. Check with your prop manufacturer. Powerfin doesn't need them. My 

general rule is if it doesn't serve a purpose, I take it off my airplane. 

Light planes fly better.



Rick Neilsen

Redrive VW powered MKIIIc



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