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Discussion Starter #1 (Edited)
Seems to be alot of discussion lately on Single Shear loads and engineering. Instead of cluttering threads with he said she said, lets have an educated discussion on shear loads. Twisted Customs mounts their upper chassis links in single shear. The 3/4 Grade 8 bolt is run through a .25 wall 2.5 inch DOM tube to support and transfer shear loads. This design has been trail tested in the most extreme situations without fatigueing and stress cracking. So Lets try and keep the information technical and not uneducated opinions. I'm always interested in further education.
 

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I'll play. A link mount is not a place for being a cheap ass with six ounces of steel. "Twisted Customs" needs to hire a new engineer if the current one thinks single shear on a critical connection like a link mount is acceptable :flipoff2:
 

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I haven't followed the recent discussions on single shear vs double shear so I will stick with the basics.

The problem I see with single shear designs is that it puts the bolt in a combination of shear and bending localized at the first thread engagement. The bending stress will lead to fatigue failure. Typically the ultimate strength of a bolt in shear is much greater that of a bolt in bending. But the single shear design typically fails in fatigue, not single load application.

Reasonably designed "double shear" will remove the bending component and double the shear area making the joint substantially stronger in fatigue and ultimate strength.

I also see designs people claim are double shear but the secondary abutment is 1/10 the thickness as the main abutment. That is nothing more than a deflection limiter that will slightly reduce the bending but not reduce it substantially.

That said, most bolted joints are underdesigned in abutment size and bolt stretch. They also put the abutment in shear rather than axial or bending. A bolt has ~10% of it's clamping force in shear before it slips compared to 100% axially.
 

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I'll play. A link mount is not a place for being a cheap ass with six ounces of steel. "Twisted Customs" needs to hire a new engineer if the current one thinks single shear on a critical connection like a link mount is acceptable :flipoff2:
:shaking:
 

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I agree with lt1yj on all points.

it is just bad practice to "skimp" on critical joints whether a single shear is sufficient or not.
 

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You can design a proper single shear joint, and you can design a proper double shear joint. Just because its 'single shear' doesn't mean its BAD.

That said, the double shear joint will be much stronger with the same size fasteners. Since we deal with impact loading, which is difficult to place numbers on, it seems pretty logical to just make that other tab.
 

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Nothing wrong with a single shear application if sized and torqed appropriately. Bolts should not be loaded in any type of shear, single or double. Most people misunderstand the design of a bolted joint. The bolt should be only loaded on tension from the tightening torque, the clamping force of the bolt to the mating surfaces of the parts takes the shear load. Most bolt on steering arms and rod ends on the other end of them are a single shear joint but no one questions that? What about your lug nuts?
 

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I think a properly built single shear link mount is plenty strong on a light weight comp buggy, but its not suitable for a heavy ass full bodied rig.
If its 'properly built' then it should be adequetly sized for the heavier vehicle. The size of the vehicle doesn't mean that single shear is any worse.....
 

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Nothing wrong with a single shear application if sized and torqed appropriately. Bolts should not be loaded in any type of shear, single or double. Most people misunderstand the design of a bolted joint. The bolt should be only loaded on tension from the tightening torque, the clamping force of the bolt to the mating surfaces of the parts takes the shear load. Most bolt on steering arms and rod ends on the other end of them are a single shear joint but no one questions that? What about your lug nuts?

X2 :D
 

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With the number of buggies TC has built over the years I would tend to trust them to know what works in this particular case.

What I think they're underestimating though is the perception of the mob. It's not a question of "is it strong enough" it's more a question of will the mob mentaility take over and will the cry of "TC uses single shear links" cause more harm than it would be worth to add another tab :shaking:
 

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:shaking:
I think a properly built single shear link mount is plenty strong on a light weight comp buggy, but its not suitable for a heavy ass full bodied rig.

Care to back that up with any type of emperical data? Or are you just giving it your "gut feeling"?

This supposed to be the educated discussion of shear loads...not uneducated opinions.
Seems to be alot of discussion lately on Single Shear loads and engineering. Instead of cluttering threads with he said she said, lets have an educated discussion on shear loads. So Lets try and keep the information technical and not uneducated opinions. I'm always interested in further education.
:stirthepot:
 

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Nothing wrong with a single shear application if sized and torqed appropriately. Bolts should not be loaded in any type of shear, single or double. Most people misunderstand the design of a bolted joint. The bolt should be only loaded on tension from the tightening torque, the clamping force of the bolt to the mating surfaces of the parts takes the shear load. Most bolt on steering arms and rod ends on the other end of them are a single shear joint but no one questions that? What about your lug nuts?
Agreed! But 99.9% of rig builders and garage tinker...ers dont use a torque their bolts. The clamping force is one thing and the diameter of the bolt is another. So many variables to consider its amazing the physics has been soo kind to so many. :laughing:
 

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Nothing wrong with a single shear application if sized and torqed appropriately. Bolts should not be loaded in any type of shear, single or double. Most people misunderstand the design of a bolted joint. The bolt should be only loaded on tension from the tightening torque, the clamping force of the bolt to the mating surfaces of the parts takes the shear load. Most bolt on steering arms and rod ends on the other end of them are a single shear joint but no one questions that? What about your lug nuts?
Is a TRE or tapered lug nut technically in single shear?
 

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Univeral law - if one is good, two is better.
What's better than one woman? Two women.
What's better than one beer? Two beer.
so on...

I did learn today that the tensile strength of a bolt (material strength X cross sectional area) is not the same strength that the bolt has in shear. Shear is about .6 times the tensile strength. In other words - Kula's 3/4 bolt should be in double shear to be at least as strong as the heim.

Thanks Chris...

It's not about what works and will or will not fail, yadayadayada - it's about the fact that for link mounts, specifically, it'a almost always feasible to put things in double shear with very little extra work and material. Why not do it?????
 

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I haven't followed the recent discussions on single shear vs double shear so I will stick with the basics.

The problem I see with single shear designs is that it puts the bolt in a combination of shear and bending localized at the first thread engagement. The bending stress will lead to fatigue failure. Typically the ultimate strength of a bolt in shear is much greater that of a bolt in bending. But the single shear design typically fails in fatigue, not single load application.

Reasonably designed "double shear" will remove the bending component and double the shear area making the joint substantially stronger in fatigue and ultimate strength.

I also see designs people claim are double shear but the secondary abutment is 1/10 the thickness as the main abutment. That is nothing more than a deflection limiter that will slightly reduce the bending but not reduce it substantially.

That said, most bolted joints are underdesigned in abutment size and bolt stretch. They also put the abutment in shear rather than axial or bending. A bolt has ~10% of it's clamping force in shear before it slips compared to 100% axially.

Not much more to say after that - you summed it up very well. There's no question that double shear is stronger than single shear if all else is equal - the question is "Is it strong enough?". Elegant engineering practices make everything only as strong as it needs to be in order to save weight/cost/etc.

Farm engineering (or Russian engineering) overbuilds everything regardless of weight. :flipoff2:

That being said - I lean toward farm engineering practices myself (I may be an engineer but I'm not usually very "elegant":D).....
 

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Agreed! But 99.9% of rig builders and garage tinker...ers dont use a torque their bolts. The clamping force is one thing and the diameter of the bolt is another. So many variables to consider its amazing the physics has been soo kind to so many. :laughing:
I think most people here over build so there is not too many problems.

I think most of the trail plugs are caused by lack of prep and maintenance, not from a bad design. I have full confidence that this application will work fine if that bolt is torqued properly. Do you know what the torque required for a 3/4 gr 8 to 75% of proof load is? about 320 ft-lbs. How many torque their 3/4" bolt to that?
 

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Do you know what the torque required for a 3/4 gr 8 to 75% of proof load is? about 320 ft-lbs. How many torque their 3/4" bolt to that?
not a damn one of em!! :eek:
 

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Is a TRE or tapered lug nut technically in single shear?
A TRE is but a lug nut should never be in single shear, when you tighten the lug nuts, it puts a clamping force between the wheel and hub, that clamping force takes all the load. The bolts are only loaded in tension. When the lug nut are loose, that's when the studs are loaded in shear and fail.
 
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