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Pip pin logic

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asarangan(at)gmail.com
Guest

Posted: Sat Oct 26, 2013 7:58 pm Post subject: Pip pin logic

I am hoping someone can help me understand the logic behind the spar

pip pin. According to a posting by Neville Eyre some time back, the

pin is important for preventing the spar tang from migrating aft and

jamming the aileron crank. This makes sense, especially given how

close the spar is to the cranks. However, in my limited experience, I

have only seen pins used for shear stresses, not longitudinal stress.

The latter would mean the ball at the end the pin has to be load

bearing. This seems a bit odd to me, but I am sure there must be a

logic behind this setup. I am hoping someone can shed some light on

this for me.

ptag.dev(at)tiscali.co.uk
Guest

Posted: Sun Oct 27, 2013 1:22 am Post subject: Pip pin logic

Hi! Andrew,

I don't profess to be an authorised person to pass a professional  comment

but since often I do ......!

It is an established fact that the wings fail forward which means that the

starboard spa tip will tend to want to be loaded towards leaving the port

pin AFT taking the metal socket with it off the port spa. Without the pip

pin the only restraint will be the CUFF which is wrapped round both spa's in

their centre portion and the socket bonded to the aft of the Port spa . So

an additional restraint on the starboard spa tip to keep it clamped to the

aft side of the Port spa when rigged is an obvious bonus.

( Just in passing it would be of prime interest as to the state of all these

items on the William Mills catastrophe aircraft? And surely the

investigators would do us all a big favour to circulate such fine detail for

our consumption?)

However to improve on the pip pin being used for this purpose I think would

need a pin threaded for a nut to be tightened and if you can develop a way

of access to a fully assembled aircraft for applying a bolt and nut I would

be pleased to hear of it !  In the meantime the pip ball rules!

Best regards

Bob Harrison   G-PTAG 



--

craigb(at)onthenet.com.au
Guest

Posted: Sun Oct 27, 2013 2:48 am Post subject: Pip pin logic

However to improve on the pip pin being used for this purpose I think would

need a pin threaded for a nut to be tightened and if you can develop a way

of access to a fully assembled aircraft for applying a bolt and nut I would

be pleased to hear of it !  In the meantime the pip ball rules!



Bob, and all others of course

I like you and no doubt quite a few others have given the threaded bolt

option

You mention quite some thought, spending a lot of time traveling for work

Gives you the luxury of time to ponder such small things, the main issue

I have over switching to some sort of threaded arrangement is the alignment

issues

With the pin now can be troublesome, now say it has the be PERFECTLY aligned

to

Get the thread to start without cross threading it, and it just got a whole

lot

Harder, of course you could use some form of stepped alignment with say a

3/8

Taper stepping up to the 1/2 inch thread and a caged nut that can move to

align

But not rotate, that was my idea anyway, but I don't think there is enough

space

Say 1/2 an inch, for the caged nut, plus then the tapered end of the bolt

sticking through

The nut. One option that did come to mind was something similar to a masonry

anchor

Where you slide the whole thing into a hole, and tighten the bolt(or nut)

depending

On the style and the unit in the hole expands at the end to lock itself into

the

Concrete. If you used an internal thread arrangement to pull a set of jaws

outwards

You could "grab" the back end of the socket where the balls are now, and

pull both spars

Then hard into the seat back, by simply tightening one bolt



HOWEVER



The device mentioned would likely be a custom made part, with springs etc to

ensure the jaws

Retract, I know of no such part at present.



Secondly, no doubt someone will weigh in with and it is a concern of mine

too

It is generally accepted the seat back is NOT contributing to transfer lift

loads etc

To the airframe, and that like most aircraft the wings do flex and move in

flight

If you have the spars firmly bolted to seat back then you remove that

movement potential

Completely and probably make the seat back a major load bearing component,

and who knows

What the result of that might be



Just my thoughts

Make of them what you will, the pin works ok, sure its not perfect, but

would

Something else be any better



Regards

craig

davidjoyce(at)doctors.org
Guest

Posted: Sun Oct 27, 2013 3:27 am Post subject: Pip pin logic

We know that the wings & spars have been proof tested to 

10g and the force on the spar pin is principally one of 

shear with the spar tip trying to depart downwards, and at 

10g MAUW, the actual shear force is likely to be something 

in excess of 3000kg.

In comparison to this, the tendency for the spar tip to 

move backwards and disengage itself from the spar pin must 

be very small and I have no doubt that the clever fellows 

at Europa did their stress calculations and concluded that 

the tension strength of the pip pin system was sufficient. 

I suspect that reinventing that particiular wheel will 

achieve nothing but risking not being able to get your 

wings off somewhere down the line.

Regards, David Joyce, G- XSDJ



On Sun, 27 Oct 2013 20:48:18 +1000

  "craig" <craigb(at)onthenet.com.au> wrote:

 	  Quote: 	
		   

<craigb(at)onthenet.com.au>

 

 

 

 However to improve on the pip pin being used for this 

purpose I think would

 need a pin threaded for a nut to be tightened and if you 

can develop a way

 of access to a fully assembled aircraft for applying a 

bolt and nut I would

 be pleased to hear of it !  In the meantime the pip ball 

rules!

 

 Bob, and all others of course

 I like you and no doubt quite a few others have given 

the threaded bolt

 option

 You mention quite some thought, spending a lot of time 

traveling for work

 Gives you the luxury of time to ponder such small 

things, the main issue

 I have over switching to some sort of threaded 

arrangement is the alignment

 issues

 With the pin now can be troublesome, now say it has the 

be PERFECTLY aligned

 to

 Get the thread to start without cross threading it, and 

it just got a whole

 lot

 Harder, of course you could use some form of stepped 

alignment with say a

 3/8

 Taper stepping up to the 1/2 inch thread and a caged nut 

that can move to

 align

 But not rotate, that was my idea anyway, but I don't 

think there is enough

 space

 Say 1/2 an inch, for the caged nut, plus then the 

tapered end of the bolt

 sticking through

 The nut. One option that did come to mind was something 

similar to a masonry

 anchor

 Where you slide the whole thing into a hole, and tighten 

the bolt(or nut)

 depending

 On the style and the unit in the hole expands at the end 

to lock itself into

 the

 Concrete. If you used an internal thread arrangement to 

pull a set of jaws

 outwards

 You could "grab" the back end of the socket where the 

balls are now, and

 pull both spars

 Then hard into the seat back, by simply tightening one 

bolt

 

 HOWEVER

 

 The device mentioned would likely be a custom made part, 

with springs etc to

 ensure the jaws

 Retract, I know of no such part at present.

 

 Secondly, no doubt someone will weigh in with and it is 

a concern of mine

 too

 It is generally accepted the seat back is NOT 

contributing to transfer lift

 loads etc

 To the airframe, and that like most aircraft the wings 

do flex and move in

 flight

 If you have the spars firmly bolted to seat back then 

you remove that

 movement potential

 Completely and probably make the seat back a major load 

bearing component,

 and who knows

 What the result of that might be

 

 Just my thoughts

 Make of them what you will, the pin works ok, sure its 

not perfect, but

 would

 Something else be any better

 

 Regards

 craig  

 

 

Un/Subscription,

Forums!

Admin.

davidjoyce(at)doctors.org
Guest

Posted: Sun Oct 27, 2013 3:44 am Post subject: Pip pin logic

Bob, The AAIB report on William's plane made it clear that 

the starboard wing broke away from its spar. Although not 

specifically mentioning the pins or the strap system, that 

implies that thy hadnot failed before the forces became 

big enough to break the spar. Regards, David

On Sun, 27 Oct 2013 09:21:26 -0000

  "Bob Harrison" <ptag.dev(at)tiscali.co.uk> wrote:

[quote] 

<ptag.dev(at)tiscali.co.uk>

 

 Hi! Andrew,

 I don't profess to be an authorised person to pass a 

professional  comment

 but since often I do ......!

 It is an established fact that the wings fail forward 

which means that the

 starboard spa tip will tend to want to be loaded towards 

leaving the port

 pin AFT taking the metal socket with it off the port 

spa. Without the pip

 pin the only restraint will be the CUFF which is wrapped 

round both spa's in

 their centre portion and the socket bonded to the aft of 

the Port spa . So

 an additional restraint on the starboard spa tip to keep 

it clamped to the

 aft side of the Port spa when rigged is an obvious 

bonus.

 ( Just in passing it would be of prime interest as to 

the state of all these

 items on the William Mills catastrophe aircraft? And 

surely the

 investigators would do us all a big favour to circulate 

such fine detail for

 our consumption?)

 However to improve on the pip pin being used for this 

purpose I think would

 need a pin threaded for a nut to be tightened and if you 

can develop a way

 of access to a fully assembled aircraft for applying a 

bolt and nut I would

 be pleased to hear of it !  In the meantime the pip ball 

rules!

 Best regards

 Bob Harrison   G-PTAG 

 

 --

peterz(at)zutrasoft.com
Guest

Posted: Sun Oct 27, 2013 3:48 am Post subject: Pip pin logic

Under extreme load the spar pin is being twisted downwards (at the rear end). So it is no longer purely in shear, thus the tendency for the rear spar to slide off and the need for a pip pin and strap.



If the spar arrangement was a fork type (in many gliders) instead of the scissors that we currently have this twisting load would not exist.



Cheers,

Pete



 



 	  Quote: 	
		   On Oct 27, 2013, at 7:27 AM, "David Joyce" <davidjoyce(at)doctors.org.uk> wrote:

 

 

 

 We know that the wings & spars have been proof tested to 10g and the force on the spar pin is principally one of shear with the spar tip trying to depart downwards, and at 10g MAUW, the actual shear force is likely to be something in excess of 3000kg.

 In comparison to this, the tendency for the spar tip to move backwards and disengage itself from the spar pin must be very small and I have no doubt that the clever fellows at Europa did their stress calculations and concluded that the tension strength of the pip pin system was sufficient. I suspect that reinventing that particiular wheel will achieve nothing but risking not being able to get your wings off somewhere down the line.

 Regards, David Joyce, G- XSDJ

 

 On Sun, 27 Oct 2013 20:48:18 +1000

 "craig" <craigb(at)onthenet.com.au> wrote:

> 

> However to improve on the pip pin being used for this purpose I think would

> need a pin threaded for a nut to be tightened and if you can develop a way

> of access to a fully assembled aircraft for applying a bolt and nut I would

> be pleased to hear of it !  In the meantime the pip ball rules!

> Bob, and all others of course

> I like you and no doubt quite a few others have given the threaded bolt

> option

> You mention quite some thought, spending a lot of time traveling for work

> Gives you the luxury of time to ponder such small things, the main issue

> I have over switching to some sort of threaded arrangement is the alignment

> issues

> With the pin now can be troublesome, now say it has the be PERFECTLY aligned

> to

> Get the thread to start without cross threading it, and it just got a whole

> lot

> Harder, of course you could use some form of stepped alignment with say a

> 3/8

> Taper stepping up to the 1/2 inch thread and a caged nut that can move to

> align

> But not rotate, that was my idea anyway, but I don't think there is enough

> space

> Say 1/2 an inch, for the caged nut, plus then the tapered end of the bolt

> sticking through

> The nut. One option that did come to mind was something similar to a masonry

> anchor

> Where you slide the whole thing into a hole, and tighten the bolt(or nut)

> depending

> On the style and the unit in the hole expands at the end to lock itself into

> the

> Concrete. If you used an internal thread arrangement to pull a set of jaws

> outwards

> You could "grab" the back end of the socket where the balls are now, and

> pull both spars

> Then hard into the seat back, by simply tightening one bolt

> HOWEVER

> The device mentioned would likely be a custom made part, with springs etc to

> ensure the jaws

> Retract, I know of no such part at present.

> Secondly, no doubt someone will weigh in with and it is a concern of mine

> too

> It is generally accepted the seat back is NOT contributing to transfer lift

> loads etc

> To the airframe, and that like most aircraft the wings do flex and move in

> flight

> If you have the spars firmly bolted to seat back then you remove that

> movement potential

> Completely and probably make the seat back a major load bearing component,

> and who knows

> What the result of that might be

> Just my thoughts

> Make of them what you will, the pin works ok, sure its not perfect, but

> would

> Something else be any better

> Regards

> craig  Un/Subscription,

> Forums!

> Admin.

ptag.dev(at)tiscali.co.uk
Guest

Posted: Sun Oct 27, 2013 3:58 am Post subject: Pip pin logic

Thanks for that David but as ever photos speak thousands of words painful so looking would be to some.

Regards

Bob H G-PTAG



--

kingsnjan(at)westnet.com.
Guest

Posted: Sun Oct 27, 2013 4:18 am Post subject: Pip pin logic

 	  Quote: 	
		  

 If the spar arrangement was a fork type (in many gliders) instead of the 

 scissors that we currently have this twisting load would not exist.




	


I fully agree Pete and remember being shocked myself when I learnt how 

Europa set up the spars.  However, I would not like to try to redesign it 

myself given the constraints within that small area.  Europa made that 

decision at the time and the set-up DOES work Ok.



Reminds me of an old mate of mine now deceased unfortunately . . . . . . 

whenever I used to say "IF", he would always reply  . . . . . "Yes, and IF 

the dog didn't stop to shit, it would have caught the hare!"



In jest



Kingsley from Oz



do not archive.

peterz(at)zutrasoft.com
Guest

Posted: Sun Oct 27, 2013 4:44 am Post subject: Pip pin logic

I also agree, don't redesign something that has been proven..... Everything is an engineering compromise, and I assume tank capacity and simplicity was the original design intent.

Cheers,

Pete

 	  Quote: 	
		   On Oct 27, 2013, at 8:17 AM, "Kingsley Hurst" <kingsnjan(at)westnet.com.au> wrote:

> 

> If the spar arrangement was a fork type (in many gliders) instead of the scissors that we currently have this twisting load would not exist.

 I fully agree Pete and remember being shocked myself when I learnt how Europa set up the spars.  However, I would not like to try to redesign it myself given the constraints within that small area.  Europa made that decision at the time and the set-up DOES work Ok.

 Reminds me of an old mate of mine now deceased unfortunately . . . . . . whenever I used to say "IF", he would always reply  . . . . . "Yes, and IF the dog didn't stop to shit, it would have caught the hare!"

 In jest

 Kingsley from Oz

 do not archive.

asarangan(at)gmail.com
Guest

Posted: Sun Oct 27, 2013 12:25 pm Post subject: Pip pin logic

I did speak to one manufacturer of "quick release pins" (on an

unrelated matter) who said that the load rating only applies to the

main shaft and not to the retaining mechanism (i.e. ball). This was

the reason for my original question.



In addition, I also recall seeing an email in this group who said

something was rattling around the belly, which turned out to be the

spar socket. There was no conclusion on why it had come off, but it

could be due to the pip pin ball slipping, allowing the spar to pull

the socket off.



The spacing between the spar and the aileron crank is just a few

millimeters. So if there is enough force to pull a socket off its

araldite bond, that same force can easily flex the spar enough to

interfere with the cranks, especially since the spars have a lot of

flex in the lateral direction.





On Sun, Oct 27, 2013 at 6:48 AM, craig <craigb(at)onthenet.com.au> wrote:

 	  Quote: 	
		   



 However to improve on the pip pin being used for this purpose I think would

 need a pin threaded for a nut to be tightened and if you can develop a way

 of access to a fully assembled aircraft for applying a bolt and nut I would

 be pleased to hear of it !  In the meantime the pip ball rules!



 Bob, and all others of course

 I like you and no doubt quite a few others have given the threaded bolt

 option

 You mention quite some thought, spending a lot of time traveling for work

 Gives you the luxury of time to ponder such small things, the main issue

 I have over switching to some sort of threaded arrangement is the alignment

 issues

 With the pin now can be troublesome, now say it has the be PERFECTLY aligned

 to

 Get the thread to start without cross threading it, and it just got a whole

 lot

 Harder, of course you could use some form of stepped alignment with say a

 3/8

 Taper stepping up to the 1/2 inch thread and a caged nut that can move to

 align

 But not rotate, that was my idea anyway, but I don't think there is enough

 space

 Say 1/2 an inch, for the caged nut, plus then the tapered end of the bolt

 sticking through

 The nut. One option that did come to mind was something similar to a masonry

 anchor

 Where you slide the whole thing into a hole, and tighten the bolt(or nut)

 depending

 On the style and the unit in the hole expands at the end to lock itself into

 the

 Concrete. If you used an internal thread arrangement to pull a set of jaws

 outwards

 You could "grab" the back end of the socket where the balls are now, and

 pull both spars

 Then hard into the seat back, by simply tightening one bolt



 HOWEVER



 The device mentioned would likely be a custom made part, with springs etc to

 ensure the jaws

 Retract, I know of no such part at present.



 Secondly, no doubt someone will weigh in with and it is a concern of mine

 too

 It is generally accepted the seat back is NOT contributing to transfer lift

 loads etc

 To the airframe, and that like most aircraft the wings do flex and move in

 flight

 If you have the spars firmly bolted to seat back then you remove that

 movement potential

 Completely and probably make the seat back a major load bearing component,

 and who knows

 What the result of that might be



 Just my thoughts

 Make of them what you will, the pin works ok, sure its not perfect, but

 would

 Something else be any better



 Regards

 craig

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