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jbhart(at)onlyinternet.ne
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 Posted: Thu Oct 05, 2006 4:25 am Post subject: Propeller Extensions |
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At 06:02 PM 10/4/06 -0700, you wrote:
| Quote: |
David, According to IVO's installation instructions, because of flexure of their brand prop, clearance between the leading edge at the end of the prop (my assumption), can be as much as 5". I'm not sure if the fact thta the prop could be used on a pusher as well as a puller if the 5" clearance is total fore and aft or per side. Thats a lot of movement in my humble opinion. Now if that is only at the ends of the blades (tips), then half way up on each blade half (or 1/3, if three blade) would not flex any where nera that amount.
I really don't want to stick a spacer that long on the back of my gear box. If I am anywhere near correct in my math, the longer a moment is the more foot pounds at distance it has to work with. Even if the clearance is minimal between the bolt shank and the individual mounting holes, it has a larger moment of purchase. I also know that the sheer rating on these bolts is pretty high but man.
Ohio Ralph
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David & Ralph,
If the propeller extension is properly made and the propeller bolts are
properly torqued, the bolts will not experience shear loads. The compressed
surfaces between the extension, the flange and the propeller will take all
the shear loads. The bolts will be in tension.
Jack B. Hart FF004
Winchester, IN
do not archive
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David.Lehman
Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA
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| Posted: Thu Oct 05, 2006 4:39 am Post subject: Propeller Extensions |
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Jack...
Obviously I'm not an engineer, so I'm probably asking obvious questions, but... Doesn't the longer moment/overhang induce shear trauma to the bolts, especially at the head/shank or nut/shank areas, depending on which is at the gearbox flange?...
DVD
On 10/5/06, Jack B. Hart <jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)> wrote: | Quote: | --> Kolb-List message posted by: "Jack B. Hart" < jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)>
At 06:02 PM 10/4/06 -0700, you wrote:
| Quote: | --> Kolb-List message posted by: "Ralph Hoover" <flht99reh(at)Columbus.rr.com (flht99reh(at)Columbus.rr.com) >
David, According to IVO's installation instructions, because of flexure of their brand prop, clearance between the leading edge at the end of the prop (my assumption), can be as much as 5". I'm not sure if the fact thta the prop could be used on a pusher as well as a puller if the 5" clearance is total fore and aft or per side. Thats a lot of movement in my humble opinion. Now if that is only at the ends of the blades (tips), then half way up on each blade half (or 1/3, if three blade) would not flex any where nera that amount.
I really don't want to stick a spacer that long on the back of my gear box. If I am anywhere near correct in my math, the longer a moment is the more foot pounds at distance it has to work with. Even if the clearance is minimal between the bolt shank and the individual mounting holes, it has a larger moment of purchase. I also know that the sheer rating on these bolts is pretty high but man.
Ohio Ralph
|
David & Ralph,
If the propeller extension is properly made and the propeller bolts are
properly torqued, the bolts will not experience shear loads. The compressed
surfaces between the extension, the flange and the propeller will take all
the shear loads. The bolts will be in tension.
Jack B. Hart FF004
Winchester, IN
do not archive
|
--
ô¿ô "Attitude is everything ~ pick a good one"... [quote][b]
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ô¿ô
"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."
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Ralph Hoover
Joined: 09 Jan 2006
Posts: 206
Location: Central Ohio
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| Posted: Thu Oct 05, 2006 6:08 am Post subject: Re: Propeller Extensions |
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David, Though I am also NOT an engineer, many of the equipment pieces I design and build for the plastic blow mold industry do require certain "engineering" formulations to make properly. Probably enough knowledge to make me a danger to thoses around me.
I am not saying that to downgrade Jacks qualifications. No way! I have seen to much of his proof. I am saying that because of sheer, there is added stress, there is induced load problems added when a rotating, vibrating piece of anything is "extended" past its intended design to some degree.
Jack Hart said:"If the propeller extension is properly made and the propeller bolts are properly torqued, the bolts will not experience shear loads. The compressed surfaces between the extension, the flange and the propeller will take all the shear loads. The bolts will be in tension.
I can't disagree with Jack on that one , with my little knowledge, that what he is saying above is "mathematically" correct, in a perfect world. But Jack, you do have a rotating device, however well balanced it may be. And because of its rotation and the law of physics that says something about a body in motion tending to stay in motion until it meets an immovable object, or a force greater or lesser than its energy produced to that point. That prop, that hub and all that mass will want to continue to move in its pleasing direction until something causes it to waver, then get outa the way and Katty bar the doors. Cause now you have a disoriented piece of energy wanting to "give into" the stronger outside force. As long as every bolt is torqued to its specified load, all is well. But you have to admit, Jack, as you add weight and distance to anything you have a longer less forgiving moment of weight.
I say the latter part because I don't feel that "I" should need to correct "else ware" for the "flexure" issue of a prop design.
Ohio Ralph
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jbhart(at)onlyinternet.ne
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| Posted: Thu Oct 05, 2006 6:29 am Post subject: Propeller Extensions |
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Date: Thu, 5 Oct 2006 05:38:27 -0700
From: "David Lehman" <david(at)davidlehman.net>
Jack...
Obviously I'm not an engineer, so I'm probably asking obvious questions,
but... Doesn't the longer moment/overhang induce shear trauma to the bolts,
especially at the head/shank or nut/shank areas, depending on which is at
the gearbox flange?...
DVD
David,
You are correct on your concept of shear at the head end of the bolt. But
the added shear stress due to moving the propeller weight out on the spacer
is minor compared to the shear stress induced from torquing the bolts to the
propeller manufacturer's spec.
You can check this out for your self. Take an old propeller bolt and some
flat washers and insert it inside a piece of pipe cut to length. Thread on
a nut and clamp the pipe in a vice. The using one wrench to prevent the nut
from turning, put your torque wench on the head and start torquing. How far
beyond the propeller manufacturer's limit will you be able to go before
there is a failure? Did the bolt pop off at the head, or did it fail at the
first thread, or some where in the middle?
Jack B. Hart FF004
Winchester, IN
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David.Lehman
Joined: 10 Jan 2006
Posts: 265
Location: "Lovely" Fresno CA
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| Posted: Thu Oct 05, 2006 6:40 am Post subject: Propeller Extensions |
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Good morning Jack...
Good visual, thanx...
David
On 10/5/06, Jack B. Hart <jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)> wrote: | Quote: | --> Kolb-List message posted by: "Jack B. Hart" < jbhart(at)onlyinternet.net (jbhart(at)onlyinternet.net)>
Date: Thu, 5 Oct 2006 05:38:27 -0700
From: "David Lehman" <david(at)davidlehman.net (david(at)davidlehman.net)>
Jack...
Obviously I'm not an engineer, so I'm probably asking obvious questions,
but... Doesn't the longer moment/overhang induce shear trauma to the bolts,
especially at the head/shank or nut/shank areas, depending on which is at
the gearbox flange?...
DVD
David,
You are correct on your concept of shear at the head end of the bolt. But
the added shear stress due to moving the propeller weight out on the spacer
is minor compared to the shear stress induced from torquing the bolts to the
propeller manufacturer's spec.
You can check this out for your self. Take an old propeller bolt and some
flat washers and insert it inside a piece of pipe cut to length. Thread on
a nut and clamp the pipe in a vice. The using one wrench to prevent the nut
from turning, put your torque wench on the head and start torquing. How far
beyond the propeller manufacturer's limit will you be able to go before
there is a failure? Did the bolt pop off at the head, or did it fail at the
first thread, or some where in the middle?
Jack B. Hart FF004
Winchester, IN |
--
ô¿ô "Attitude is everything ~ pick a good one"... [quote][b]
| | - The Matronics Kolb-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Kolb-List |
|
_________________
ô¿ô
"Both optimists and pessimists contribute to the society. The optimist invents the aeroplane, the pessimist the parachute."
--- George Bernard Shaw |
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John Hauck
Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)
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| Posted: Thu Oct 05, 2006 6:45 am Post subject: Propeller Extensions |
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| How far
| beyond the propeller manufacturer's limit will you be able to go
before
| there is a failure? Did the bolt pop off at the head, or did it
fail at the
| first thread, or some where in the middle?
|
| Jack B. Hart FF004
Jack:
Probably pull the threads before it breaks.
Aircraft grade hardware is mass produced. Each piece is not
inspected. Easy for a prop bolt that is not properly heat treated and
produced to slip by. I have gotten bolts without heads, or heads that
were mushroomed rather than hexagonal.
Take care,
john h
mkIII
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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama |
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planecrazydld(at)yahoo.co
Guest
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| Posted: Thu Oct 05, 2006 9:15 am Post subject: Propeller Extensions |
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..and I have received mil spec hardware that had no threads.
John Hauck <jhauck(at)elmore.rr.com> wrote: [quote]--> Kolb-List message posted by: "John Hauck"
| How far
| beyond the propeller manufacturer's limit will you be able to go
before
| there is a failure? Did the bolt pop off at the head, or did it
fail at the
| first thread, or some where in the middle?
|
| Jack B. Hart FF004
Jack:
Probably pull the threads before it breaks.
Aircraft grade hardware is mass produced. Each piece is not
inspected. Easy for a prop bolt that is not properly heat treated and
produced to slip by. I have gotten bolts without heads, or heads that
were mushroomed rather than hexagonal.
Take care,
john h
mkIII [quote][b]
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