Wing attach bolts in tension

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Bellaire MK

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Looks like the wheel was not correctly matched to the hub. Was the wheel made in China?
 

Bellaire MK

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We may be somewhat off topic, but one can surely learn quite a bit through experience. There was no evidence of hub centricity in that photo!
 

TFF

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With the photo, I think anything your Pakistani or Indian neighbors do to help make it feel like home doesn’t count as a real example.
 

Hawk81A

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Started on this topic. My point was that the HUB carries the load of the vehicle. This was from an RV (recreational vehicle) forum and the lug nuts WERE tight. Wheels are to a car as wings are to an airplane.
NOW to get back on track - a wing attach bolt question: On an aircraft such as KR 1/2, the wing attach points (bolts / fittings) is it shear, or is it clamping force? I always figured it was shear (IIRC, Rand suggested a possible option of taper pins instead of bolts). If it's shear, I imagine it would call for close tolerance bolts. Dennis
 

wsimpso1

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Pops

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The largest auto stamping presses weigh about 500 ton ( Guess). Know the top part is 200 tons. 200 ton was the load limit of the bridge crane. I usually spend several days inspecting and and adjusting everything on the crane for the lift to limits. There are 4 tie rods that hold the 3 sections together. Rods about 8" in dia. and 35' long. Has large nuts on each end. The center of the rods are heated to a certain temp and then the nuts are torqued to specs while holding the temp. Then left to cool. Don't remember the torque.
 

PiperCruisin

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NOW to get back on track - a wing attach bolt question: On an aircraft such as KR 1/2, the wing attach points (bolts / fittings) is it shear, or is it clamping force? I always figured it was shear (IIRC, Rand suggested a possible option of taper pins instead of bolts). If it's shear, I imagine it would call for close tolerance bolts. Dennis
If the holes are reamed and you have a tight fit, I'm guessing the bolts are being used as threaded dowels. Wing root connection for the Avid is reamed for a pin. The torque may also be limited so you don't crush the wood. I don't know what the plans say, but I would limit the torque.

I worked on big yellow machines. Most of the bolted joints used a relatively high torque to get good clamp load to prevent joint slippage. Some even used a torque turn to yield the bolt. One reason is there is no match drilling and reaming like you find on aircraft.

It really depends on the joint and what you are trying to accomplish. If you are relying on clamp load, but the gorilla behind the wrench ends up crushing your abutment, you have a bad design.

Yes, I like to avoid bolts in tension, but it happens and the design is usually becomes a question of fatigue and loosening considerations.
 

challenger_II

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Ah! It finally came around the loop in my muddled brain! An excellent example of the wing being mounted with the fasteners in tension...

Bell UH-1 (205), AH-1 (209), and OH-58 (206). One fastener. And it is called, appropriately, a "Jesus Nut".
 

PMD

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Just a thought about fitted and tensioned "shear" bolts: when one does this, IMHO it would be important to make an interference fit with steel fasteners in aluminum holes. Why? throughout the range of temperatures, AL has much higher co-efficient of thermal expansion to if one was relying on genuine shear (or double shear) loading, fastener tension will vary as the inverse of temperature. I might even be possible a extremely low temps to overtension fasteners and worse yet exceed the brittle transition point for carbon steel alloy bolts. Similarly, when such a joint is placed under high stress (from bolt tensioning) the fastener will reduce a bit in diameter (thus why should be a lubricated interference fit). Now you know why in days long gone by RR built their chassis with tapered bolts individually reamed to leave an interference press fit when nuts were tightened. Those were some of the few genuinely shear loaded fasteners I can think of. Most of the rest rely on part interface friction to keep the (relatively) sloppy fit of a hand inserted shear bolt from smashing back and fourth (i.e. actual wing spar loading conditions).
 

Hawk81A

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On building my KR-2 , I reamed and hand fit each hole for each bolt. Labeled each bolt for the hole.
So, was that a separate nut and bolt for each fitting pair (4 per side per pair - main spar) or one longer bolt and nut going through front fittings and rear fittings (2 per side main spar)? It would seem that the shorter bolts going only through the center spar fitting and outboard spar fitting would be stronger. Dennis
 

rv7charlie

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Most of the rest rely on part interface friction to keep the (relatively) sloppy fit of a hand inserted shear bolt from smashing back and fourth (i.e. actual wing spar loading conditions).
References/examples?
All the cantilever wings with attach bolts in shear that I'm aware of use close tolerance bolts, with zero 'slop'; clamping force of the bolts is more to keep the 'stack' from opening and allowing bending loads on the bolts, than to create friction. Every engineering doc I've ever seen related to aircraft says that joint friction is ignored by the designer of structural shear joints. The few strut braced attachments I've seen use clevis pin type attachments; in some cases using a literal clevis pin & clip, with zero clamping force.
 

PMD

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When I wrote "most of the rest" I was referring to general fastener use in bolted shear loading. I said "like airplane wing" as a general comment, as I am not aware of specific airframe designs so constructed. But, yes, a genuine double shear can (and in some cases SHOULD) be done with nothing but a plain piece of round stock - but IMHO preferrable fitted to zero tolerance or even light interference fit. None IMHO nearly as nice as a tapered pin. IIRC some Euro gliders do just that.
 
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