[url=https://classicgoldwings.com/forum/viewtopic.php?p=214248#p214248:2xb86xya said:
joedrum » Yesterday, 5:27 am[/url]":2xb86xya]
simple math a spiral wedge made out of whatever doesn’t beat a solid bolt head ever ...using two wedges where all that’s needed is one is flat out stupid ..when your life is on the line ....you know what beats any spiral wedge ...it’s a hot rivet ..that first structures use from the get go ..everything else since then was total downgrade...studs are a complete fabricated over done engineering baloney in my book
Joe... I am an educated and experienced engineer. An engineer is someone who believes they know just-enough-about science, nature, and physics, to dive headling into a battle to fight nature, knowing full well that in the end, they will lose, and the bigger things they do, the more catastrophic it will be when they fail.
As part of my daily responsibilities, I design structures, use weldments and fasteners to hold them together... and unfortunately, I don't get to design them from the GIT-GO, I have to do it POST_FACTO... after someone else overlooked something critical, I have to affect a fix, and predict it's lifespan. Thermodynamics, expansion, heat transfer ALL fall into the materials sciences that I've had to know, and effectively employ, in order to be licensed and insured to do what I do. When I teach, I teach basic physical principles, and explain how they're employed in real life circumstances. When I give you opinion, I will tell you WHY my opinion is that way, and unless it has to do with pets, food, or music, my opinions are pretty much always the result of basic physical science facts. I don't have to wear thick glasses, but girls call me 'boring'.
Yes, there's times when a hot rivet will be a more suitable fastener than a bolt... and there are times when a soft bolt is better than a hardened bolt.
When you thread a 4-1/4" bolt through a 4" casting, into a tapped blind hole, and the bolt head seats after four turns, that means you have :
A) four threads of bolt, binding inside the hole's threads
B) 4" of bolt shank binding in the hole
C) Bolt head underside, binding against the head.
As you twist the bolt, you overcome binding of the threads, hole, and head-to-block... AND you TWIST the bolt... AND you're PULLING on FOUR THREADS... AND, you're applying tension to the bolt.
At this point, you're stepping into the world of STRESS-STRAIN, section modulus, elasticity, and force. Here's a complicated read, but look at the graphs, as they explain it in a quick picture:
https://en.wikipedia.org/wiki/Stress%E2 ... rain_curve
The first stage of tension... is ELASTIC. Consider a situation where you had a bolt that was made of plastic...
PULLING on the bolt causes it to stretch... and when you pull, up to a point, it will spring back to it's original shape. Once you exceed a certain point, the bolt will start to stretch... that's the point where it starts to YIELD... meaning... it will NOT return to original length. In metals, once you get to the yield point, the metal's properties change... they start to work-harden... and at this point, the hardening slightly INCREASES the strength of the bolt, but as you continue to increase the tension, the material 'necks'... it gets thinner... and then it breaks.
If you were to get a destructive-test tensiometer, and broke a thousand quarter-inch bolts, you'd get really, really good at estimating the yield strength of each sample, and when you changed from a Grade 3 to Grade 5 to grade 8, then 10, you'd be able to watch the bolt, and see the stretch, and know when it breaks. I know, because it was part of my job long ago, to qualify fasteners and X-ray weld coupons for cranes. I broke bolts by the thousands.
Now, rather than threading that bolt through a casting, just thread it into the hole and start twisting. Put a big long-a$$ bar on it, and twist 'till the bolt breaks. It had NO tension on it, but it broke. As you pulled on it, it felt springy... that's ELASTIC state. Then you pulled harder, and it gave a little... it went PLASTIC... (you exceeded yield strength), and after that, it hardened a bit, and then it necked, and broke.
Materials stretch, strain, and fail not because of any ONE force, but as a combination of ALL forces... that's called COMPOSITE stress, because while you're turning the bolt in (applying torque to twist it), you're also asking it to STRETCH, and since the casting faces and bolt landing aren't perfectly parallel, you're BENDING it...
And you're binding the threads, and binding the hole, and binding at the block.
And the amount of thread engagement you have in the hole is only 4 threads... oh wait- 3... because to alleviate some of the binding at the top, you've added a washer.
Now, realize that a thread is not a spiral... it's a scratch... what's leftover after a cutting tool RIPPED through a hole in the material, leaving a ramp (good term, BTW... 'ramp' is a 'simple machine'!) that a SUPPOSEDLY MATCHING bolt fits into. The amount of strength in the bolted assembly is first-and-foremost limited by the amount of 'thread meat'... and the threads' strength is a function of engagement surface, quality, and ancillary tension (torque).
Always remember: strength is not determined by the strongest element, but rather, the limitation of the weakest element.
Thread a stud in the same hole. Run it all the way to the bottom... don't apply force, just thread it 'till it's fully bottomed. At that point, there is NO force on the threads. Slip the casting over the stud. Drop on the washer, then thread on the nut. At this point, there is zero tension, and zero torque on the stud.
With the nut spun down by hand... with no torque, the bolt and threads' available strength is at maximum.
Start applying torque. The stud is placed under a SLIGHT amount of torque, but there's only TWO forces resisting- first is friction against the washer, the second, is friction against the threads in the nut. There's only so many threads in that nut, BUT... the nut's threads are all totally engaged, all the time... and the material of the nut is substantially stronger than the casting which the stud is seated in. This not only means the nut's grip is stronger, it means the surfaces will present substantially less friction. This means that as you apply force to the nut, MORE of it goes to generating clamping pressure, LESS of it goes to ancillary drag.
If you're still thinking that a stud is inferior to a bolt in terms of fastener capacity in a cylinder head, look at any extreme-power drag race engine, and count the number of head bolts used. The answer is none, ever.
Studs, stretch-bolts, and those stupid plastic buttons that hold the bumper cover on my son's Accord are not my opinion, they are fact- engineering design, and manufacture based on material science and physics. I don't write the laws of physics, I just spend quality time being punished after I've broken them.
