The configuration/shape of the bolt head allows it to flex during the torqueing process, causing a spring clamping force that keeps the bolt tight. They are used in places where there is rotation/vibration and you want things to stay tight, especially places that are hard to inspect and get into to check and re-torque the bolts (eg: ring gears, flexplates, etc).
What do you guys thing about drilling holes thru the head for safety wire? Thought about doing that on my truetrac in my Ford 9"... ..
Safety wiring won't keep bolts torqued. It will stop them from winding completely out and chewing things up if they do get loose .
From what I've read for instructions [and done on my assy] Blue loc tite. BowmAlloy is I think one up from grade 8, may have an L9 on the head instead of lines [from Echardt-Finard] but don't know if self locking.
I thought lockwires were to prevent bolts from becoming loose and/or winding completely out due to vibration, but are not relied upon to maintain the correct torque setting of the bolt. The main objective is to keep bolts in place to prevent seperation of parts and so the bolts don't become "foreign object debris" in the machinery assembly. Everything I have been taught or have read says that lockwires are not there to maintain the applied torque specifications of the bolt. Am I wrong? Please shed some light if I am incorrect. Always good to learn new things.
It may just be semantics, but if the bolt is properly torqued and then safetied with, lets say .040 or heavier stainless, which is properly wrapped and tightened like a piano string that bolt is not going to move any. If the bolt doesn't move you're not going to lose any clamping force on the part. You'd be surprised how much torque it takes to break the larger diameter safety wire. This is from a guy that's done a lot of safety wiring over the years...
When I cut bolts, I drill an appropriate hole in a piece of angle iron. Nut it and cut on my band saw.
Was curious, as I’ve seen them before, but had no idea how they worked, or even what they’re called. Looked to see if I could find anything in my Machinery’s Handbook (17th Ed), and nothing, which I thought a bit strange. The AFT link mentions a General Motors Standard AA Hex Lock Bolt. While working at General Motors Diesel Division, they sent us on a “hardware” course, and I kept that material for the longest time, but think I recently ditched it all.
My take is that the FAA is high on safety wire not because it maintains bolt load, but because it provide a quick visual warning that something is awry. Bolts hold components together by preload induced stretch and fastener friction. Safety wires are window dressing.
I’m not sure how or if they maintain torque on a fastener but I can say that working on industrial equipment that was safety wired I never saw a safety wired fastener come loose. Not so for fasteners that weren’t safety wired saw many that were loose or missing. I’m not a big fan of lock washers either, I saw many that were broke or flattened. I’m a fan of safety wire, lock nuts, belville washers and lock tight and now that I know place bolts also. Dan
Speaking of lock washers, we (design engineering group) were told at General Motors Diesel Division (built the LAV/Stryker) not to spec any split ring style lock washer. Instead we were told to spec thread locker.
And you are correct, I had to dig out my old FAA AC 43.13-1B and find the following... Dang it, I hate when that happens. But, safety wire is still one of the best ways to ensure that the fastener doesn't move and lose the torque setting...
Henry used lock wire on rod caps as I recall, flywheel too? Been a day or two since I took a FH V8 apart. But, fast forward from there, never took a SBC apart that anything was safety wired up. For an airplane? I get that. Did Henry really need it, or “it’s a good idea”?
I think a lot has to do with shock and load when it comes to safety wire. Rods and main bolts loads are exerted towards the length of the bolt not with the diameter of the bolt. The crank shaft and flywheel wheel bolts do. I think that's why some crankshaft bolts are so large, to give more bite on the threads. I've been on many race forums and Ford nine's are well known for loosening the ring gear bolts in hard Street and racing situations. Funny some guys will talk about never happening and then there are several shop owners will indeed state that it is a problem that they encounter on a regular basis. I also think this is where the shock comes into play, unlike a motor that is already spinning and then revved up but at a controlled rate (weight, load, drag etc) a rear end, when launching goes from a static rest to full load in a split second along with the chance of traction lose, spin to a high rate of speed very quickly. This is where I see safety wire being a positive, especially after reading many shop owners say it does indeed stop the rear ends from returning to their shops. A couple shop owners refuse to rebuild a 9 inch rear-end for a race car without safety wire. I figure I'd rather heed their warning and experience rather than admit later they were right and knew more than I thought I did. ...
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