Wing attach bolts in tension

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Hawk81A

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dog

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I .didn't post this before, but now that the conversation has gotten here - and it applies. When I was building my Ultrapup, I was installing hardware - mostly AN-3 and I was tightening with a 1/4 drive ratchet and it "felt right". I saw an article about proper AN torque, got a 1/4 drive torque wrench and was I overtightening. Dennis

which means you threw all of your overtorqued
harware in the dumpster,right
 

Dan Thomas

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In the 1970s I sold wheels and all the hardware, and brakes, for several years. Stuff from 8"trailer wheels up through cars and trucks and heavy trucks and earthmoving equipment. Piloted wheels were rare, and mostly found on some medium-duty trucks using the Motor Wheel design. Those wheels were piloted and the nuts had flat flanges that clamped against flat wheel disc surfaces.

No design had problems with wheel slippage or fretting unless the nut torques were incorrect, or the studs or nuts were lubed, or dirt was between the wheel and hub face. Undertorquing leads to movement and fretting and ultimate failure. Overtorquing either breaks the stud or stretches it beyond its elastic limit (yield point) so that it loses its clamping force. Lubricating the stud is asking for an overtorque situation.

Light-duty wheels have a tapered nut and seat. Big trucks use a spherical face on the nut and seat. Earthmoving stuff had a variety of the three types of nut faces.
 

proppastie

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Lubricating the stud is asking for an overtorque situation.
I have used anti-seize or grease to prevent rust....and be careful not to over torque or torque to the bottom of the spec. I have never had a problem with a lug nut I personally tightened....only those done by tire installers which often are too tight.....early on my fix-it days I did see some LH threads on Dodge which caused me problems. (oh thats what the L means) ......
 

Dan Thomas

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I have used anti-seize or grease to prevent rust....and be careful not to over torque or torque to the bottom of the spec. I have never had a problem with a lug nut I personally tightened....only those done by tire installers which often are too tight.....early on my fix-it days I did see some LH threads on Dodge which caused me problems. (oh thats what the L means) ......
Never-seize can result in bolt tensions 40% higher than intended when torqued to spec. How many people reduce their torque settings by 40% when they use that stuff?

The OEMs tell you do install them dry. They have a reason for that.
 

cvairwerks

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Engineering will dictate whether nuts and bolts are installed with dry or wet threads. We have both cases. We even have instances where bolts are installed with wet primer on both the shank and threads. Torque values are specified for every case.
 

pfarber

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The friction of the wheel being pressed against the hub from the stud tension keeps the wheel from shifting on the hub.
But this is aided by the lug nuts having a chamfer and the wheel having a matching mating surface.

I would not say that the wheel is held in place by friction, but by this interface of the nut and wheel.

Simple test. Use a standard nut with no chamfer and the wheel is no longer held in place.
 

dog

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wheel on a hub or a prop on a hub,both have two
requirements that they get from thier respective bolts,one is to be held on without shifting,the other is to determine exactly WHERE they are not
to shift from.
That they are centered and balanced and stay that way is part due to the friction between the mateing surfaces and clampling and in some
cases a drive lug is needed to deal with sudden
torque reversals,works kind of like a gear with
a ratio of 0 to 1
 
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Bellaire MK

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I .didn't post this before, but now that the conversation has gotten here - and it applies. When I was building my Ultrapup, I was installing hardware - mostly AN-3 and I was tightening with a 1/4 drive ratchet and it "felt right". I saw an article about proper AN torque, got a 1/4 drive torque wrench and was I overtightening. Dennis


wheel on a hub or a prop on a hub,both have two
requirements that they get from thier respective bolts,one is to be held on without shifting,the other is to determine exactly WHERE they are not
to shift from.
That they are centered and balanced and stay that way is part due to the friction between the mateing surfaces and clampling and in some
cases a drive lug is needed to deal with sudden
torque reversals,works kind of like a gear with
a ratio of 0 to 1
All prop flanges require a centering boss for the prop, never rely on the bolts to center the prop assembly. Firewall Forward by Tony Bengelis is an excellent reference.
 

Dan Thomas

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But this is aided by the lug nuts having a chamfer and the wheel having a matching mating surface.

I would not say that the wheel is held in place by friction, but by this interface of the nut and wheel.

Simple test. Use a standard nut with no chamfer and the wheel is no longer held in place.
And I just posted yesterday about the Motor Wheel design that uses flanged nuts with flat faces against a flat wheel face. No chamfers no nothing. The wheel is piloted to locate it, and the nuts are torqued. The studs fit through holes in the wheels and have clearance so that the studs are only in tension. No radial loads. All weight and driving and braking loads are reacted through friction between the wheel and hub. The pilot is not tight enough to carry weight without slippage.

Chamfered nut systems work the same way. The chamfer locates the wheel until things are tight, then friction takes over. If the wheel slips even the tiniest bit the stud bends and fatigues and breaks, or its splines come loose in the hub.

I will remind you that I sold this stuff and was trained in its principles.
 
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dog

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All prop flanges require a centering boss for the prop, never rely on the bolts to center the prop assembly. Firewall Forward by Tony Bengelis is an excellent reference.
you made me run out to the shop
the prop for my a-65 is metal,on a taper crank hub
and there is clearance between the prop and hub
of 1/8 ",AND now that I looked realy close for the first time,the gap is not even around the hub,but when I was checking out the prop on another crank and case,the prop is the same length on each blade as it came assembled and is now
looks a lot like there is nothing but friction and clamping holding it in place
 

Hawk81A

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what did you do when you had rusty studs? My tractor is 1949
While I choose to not get any further into the "wheel / lug nut thing" because it's off topic, this may be a fellow enthusiast I CAN help from my experience. I usually hit any exposed threads with a small wire wheel in a drill motor. Then I lubricate with oil, if it loosens and comes off, fine. If it's difficult, I try turning a few threads, lubricate the INSIDE threads, tighten, and then try loosening again. if necessary, repeat. I get most of them off this way. Sometimes you loose and the threads gall or pull off, or the lug snaps off. I have done a LOT of them this way. Dennis
Back to WING ATTACH FITTINGS ABD BOLTS.
 

Hawk81A

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which means you threw all of your overtorqued
harware in the dumpster,right
No. I really didn't overtighten it THAT much. I definitely don't feel I tightened them enough to stretch the bolts. Besides, this was years ago. Dennis
 

Dan Thomas

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you made me run out to the shop
the prop for my a-65 is metal,on a taper crank hub
and there is clearance between the prop and hub
of 1/8 ",AND now that I looked realy close for the first time,the gap is not even around the hub,but when I was checking out the prop on another crank and case,the prop is the same length on each blade as it came assembled and is now
looks a lot like there is nothing but friction and clamping holding it in place
That system was fine for 65 hp. In some, the centering isn't by the pilot but by dowelled nuts pressed into the hub. The prop has recesses that fit over the nuts.
 

PiperCruisin

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Loss of preload comes from:
Inadequate assembly/tightening process;
Poor design/assembly specifications;
Inadequate knowledge of loads/vibe/thermal situation;
Inadequate fastener design knowledge;
Improper parts/material substitution,
Good info from Billski.

Here is an example of loss of preload in form of a joint diagram from "Bolt Science". In this case yielding of abutment, threads or settling. There is a lot of variation involved. So one looks at max bolt preload (low friction side) so you don't overload the abutment. You look at min preload if you have higher friction when tightening to see the minimum clamp load. Minimum clamp load is then reduced according to number of interfaces (a high number of washers and/or shims can cause a "soft" joint and excess relaxation). The final clamp load times the surface friction coefficient is used to compare to joint load to see if it will slip or not. This is also variable and somewhat load dependent. Tools to evaluate bolted joints can get very detailed and surprisingly complicated, but you have to know your loads.

MITCalc has a bolt calculation app that looks fairly complete, but I'm not endorsing it. However, it gives you an idea about some of the details.

1661295191241.png
 

Dan Thomas

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IO-360 has rod bolts that you measure for the proper stretch rather than torque them.....lubricant does not matter
That's one Lycoming type. Others use a torque spec. Page 7-14 of the Lycoming Direct Drive Overhaul Manual.
 
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