Wing attach bolts in tension

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wsimpso1

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Of course, your assessment is correct, but you missed the one extremely large load that one must design for in wheel ends - hitting the bump stops. Wish I had some hard numbers to inject, but of course a function of the somewhat randomly chosen jounce velocity, vehicle mass and rubber hysterisis. One way or another, mush greater value than regular deflection within limits, cornering or rotational torques.

I have removed MANY alloy wheels from iron hubs (actually rotors) that I know for certain have been hard onto the travel limiting devices. IF the hub pilot or the stud in bending had actually carried the load, the corrosion product woutd have been fractured and the wheel(s) would just fall off with fastener removal. They don't/didn't. To demonstrate just HOW much I trust the clamping force of wheel bolts, I place a coating of zinc-rich paint ("cold galvanizing) on the face of the hub and rotor - drastically reducing the co-efficient of friction between wheel mounting face and hub/rotor face - and there is never any evidence that movement has taken place (but they DO come off without resorting to a BFH to fracture the bond at the interface).
We are way off of airplanes here. My apologies to all for the thread drift... But 8000 pounds to make my Focus wheel shift on the hub, wouldn't a hit that big also deform the major structures, wreck the spherical joints, and generally consign the car to the boneyard?
 

dog

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wing bolts,paper clips,wheel studs and nuts
are all spring machines,useing the same physics
to get a job done
and in fact the wheel bolts hold the wheels on so that people can drive to offices and create paper
that gets clipped together before bieng sent off
with more wheels and bolts so that other bits of metal can be turned into whatever the numbers and words on the paper say and then there are
AN bolts and friction gets to do its thing with springs on airplanes and some people see that
as one thing and others as just another spring
 

PiperCruisin

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Ahhh... bolted joints. For an intro to bolted joints, see the website Bolt Science (A Tutorial on the Basics of Bolted Joints).

A couple notes off the top of my head:
1. Bathtub fittings at the wing root means that each individual joint sees mainly tension/compression, but also shear and bending moments. Most of the load is carried by the abutment and not the joint. It tends to be a function of the force ratio as defined by the ratio between the abutment and bolt stiffness. The FR calculates the force on the bolt from axial loading, but it roughly estimates how much shear and bending it takes as well. I've never seen this factored in, but have seen it in detailed FE models.
2. Fatigue is a strong consideration for designing bolts in tension. Because there is significant torque to put them in highish tension, fatigue allowables are based on stress range (depends on material strength and thread details).
3. Clamp load is calculated by knowing your torque, friction (head and threads), and setting (joint surface and number), force ratio (joint geometry ...see cone of compression and bolt stretch). Clamp load and joint friction determines if the joint slips under normal operation unless it is a high tolerance fit where the bolt acts more like a threaded rivet/dowel. Not sure how the F-16 is done. Would be curious to know.
4. High clamp loads are desired for joints where high shear resistance is needed (with low tension). High enough clamp load is needed to prevent gapping under normal loads for fatigue and/or resist shear load slip which can lead to wear/egging and/or loosening of the bolt (if some retention mechanism/safety wire is not used).
5. A combination of high load, high clamp load, and inadequate washer geometry/abutment materials, can lead to yielding the abutment causing a loss in clamp load.
 

PiperCruisin

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Lift strut bolts, Kitfox, Avid and Challengers. There was an SB on the latter. I was never keen on this concept and then to see AN-4 studs / bolts welded to the ends of the lift struts, not easy to inspect for cracks, also bending issues are a problem.
Sorry, late to the conversation.

I'm not sure I understand this. I'm pretty familiar with the design. The struts have bushings welded to the ends. Bolts go through the bushings which puts the bolts into double shear (no significant tensile loads that I know of. All the wing bolts act in shear.

There are a couple of bolted joints in tension however. The engine mounts (which is pretty common and subject to fatigue loading) and I think the horizontal stab bolt(s) at the root. The horizontal also has struts which are largely, but not entirely in shear loading (memory is a little fuzzy on that one).
 

PMD

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We are way off of airplanes here. My apologies to all for the thread drift... But 8000 pounds to make my Focus wheel shift on the hub, wouldn't a hit that big also deform the major structures, wreck the spherical joints, and generally consign the car to the boneyard?
were the load to be applied directly, maybe so, but when you hit a bump stop the inertia of the unsprung mass can probably put that much instantaneous stress onto the bump stop rubber and bracketry - all of which can deform elastically to absorb that energy. Of course, all depends on the nature of the impact - if the road surface (pothole?) managed to still be pressing the wheel upward when the bump stop was involved, the whole 3,000 lbs of car will accelerate enough to cause an easily sensed displacement that could also reach that amount. Automotive suspension is usually a pretty tough bit of kit.

Old guy story: I once lived at the North end of a rather well known 760 kms of remote, paved but quite rough (built on muskeg) roaad. I had a crack at setting an all time record when we got the first fuel injected Sciroccos (77). I was pretty cocky and proud of the accomplishment, until our shop foreman came into the office and asked why the top of the struts had dented the hood on both sides!!!! Some of that bottoming can go from elastic well into the plastic range (yes, the top of the strut towers were punched up almost an inch and the rubber mount in the strut bearings allowed the studs to poke into the hood skin)_.
 
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proppastie

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Since Whataboutism is somewhat popular these days......when looking at sheet bearing for riveted sheets the bearing numbers correspond to Fbru of the respective material....and friction is not considered. ....So is the riveted joint much stronger than the standard calculations for bearing and rivet shear of the riveted assembly?
 

Bellaire MK

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Sorry, late to the conversation.

I'm not sure I understand this. I'm pretty familiar with the design. The struts have bushings welded to the ends. Bolts go through the bushings which puts the bolts into double shear (no significant tensile loads that I know of. All the wing bolts act in shear.

There are a couple of bolted joints in tension however. The engine mounts (which is pretty common and subject to fatigue loading) and I think the horizontal stab bolt(s) at the root. The horizontal also has struts which are largely, but not entirely in shear loading (memory is a little fuzzy on that one).
Hi PC,

There are spherical rod ends on the studs. The good question or concern is the bending loads imposed when the aircraft is pulled or pushed on the struts when ground handling the aircraft. I have been working on a KF-7 and am aware of the design details. This is why Piper has increased the strut forks to 5/8dia. on the J-3 and all others.
Designing with bolts in shear is optimum for light aircraft. As for the North American AT-6 cantilever wing attach of the outer panels is at the outer most surface of the airfoil, a multitude of bolts in tension on the flanges.
We are currently designing and building a new and more conventional wing for the Aircam that will create an alternative to the factory wing. Here are some photos. Best regards, Rick Berstling
 

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Bellaire MK

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We are way off of airplanes here. My apologies to all for the thread drift... But 8000 pounds to make my Focus wheel shift on the hub, wouldn't a hit that big also deform the major structures, wreck the spherical joints, and generally consign the car to the boneyard?
Hub centric and or Lug centric is the automotive terminology.
 

dog

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Were you under tension when you typed that?
you have no idea,ha
business has blown up
spent more hours at a desk than ever in my life
doing quotes with more digits than I ever imagined
cozy little life style,gone
but should I hold up I will have the funds to build a plane or two
and so thinking about how a bolt can apply force to a joint,and exploit friction to our benifit,is a welcome change and a new understanding for me
and highlights just how important having clean,flat surfaces in a bolted joint are,and that those torques settings are to make sure the
surfaces are clamped EVENLY,or maybe they dont
do there job
 

PMD

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I work a lot with bolted high voltage and high amperage electrical connections. You want to believe the need to flat surfaces and properly distributed clamping forces can become a complete art and science all on its own. What I find is that the EEs that design and manufacture such connections are really not very good at it and even some MEs just don't understand the materials forming processes well enough to get it right. For me: this all goes back to trying to make good sheet metal riveted joints in aircraft and boats (and thus why today I would not buy and fly a E/AB a/c unless I knew and respected the builder or built it myself).
 

BJC

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Is this one yours? That's the link I intended to put in the quoted post about biplanes (now corrected).

I would consider the wire ends to be bolts, in the context of 'bolts in tension'. The wings are flying on the threaded ends of the flying wires, right?
Yup, that is my airplane.

And the threaded wires (long, skinny, streamlined bolts?) are definitely in tension.


BJC
 
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