Re-torque rod and crank fasteners

What the rationale on checking and re-torquing these vital fasteners? Just see if can move tighter or break free to run back to full torque. Its said never re-use rod nuts, so does finding them loose or breaking them free to re-torque count as used to replace? Anyone ever find theirs loose after proper + a tad more torque to get correct stretch + red loctite? I have in past on Trixie which is the one I'm concerned with soon.

I've re-used them many times on the race bikes. Torqued to factory specs, and with red Loctite, and never had any come loose.

Ken

lcrken said:

I've re-used them many times on the race bikes. Torqued to factory specs, and with red Loctite, and never had any come loose.

Ken

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+1
They want you to replace them because they loose there self locking feature after one use. Red Locktite fixes that. Jim

Thanks for the reviews which makes sense to me unless maybe the rod bolts went through a known trauma. Some of Trixie's crank nuts were too easy to turn after comma slot pistol cracked there and went in again d/t a rod bolt corrosion fracture. I broke a jaw off an end wrench torquing w red loctite so I don't have much respect for loctite anywhere in my Commandos but for mudguard stays.

hobot said:

Thanks for the reviews which makes sense to me unless maybe the rod bolts went through a known trauma. Some of Trixie's crank nuts were too easy to turn after comma slot pistol cracked there and went in again d/t a rod bolt corrosion fracture. I broke a jaw off an end wrench torquing w red loctite so I don't have much respect for loctite anywhere in my Commandos but for mudguard stays.

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Well FFS.... if they have gone thru known trauma then being "loose" should not be a suprise... No way would reusing those crank fasteners ever again be a good idea.. And if you break a jaw off a wrench w red loctiting prior ( :roll: :roll: ) then thats good. Just proves how good it is or you have too many chinese spanners in the workshop...

Yep I reused old rod bolts with new nuts when Trixie;s sotted piston stuck engine near BDC on a low power low speed failure a couple years after the deer strike hurt everying but the engine and gear box, No other damage found so just new pistons and rod nuts to recover. It was not an assian wrench that broke on a crank stud nut. I was not sure of why the 2nd engine siezure also at slow easy pace until Doug MacRae blow up found one of his rod bolts with half its dia showing darker area of corrossion working its way metal grain by metal grain till popped. So your chidding advise applies to Herb Becker's bad practice too. After this I tried to break Trixie on 5-6 occassions getting expected disappointment of mere Combat power barely able to lift front in red zone but still left behind by the eager sports bikers Especially in turns. Then carb boots cracked and ate the rings which lead to my question of checking fasteners while apart to reseal cases. Btw I stretch rod and crank fasteners to .0065''.

I should add that I inspect the rod bolts and nuts carefully before re-using them. I used to have the rod bolts magnafluxed at every rebuild, along with pretty much all the moving parts, but my local magnaflux/zyglo guy retired years ago, and now I settle for just a close look under a magnifying lens. About the only parts I still check for cracks with a dye penetrant kit are stock alloy rods and the high stress areas of stock crankshafts. That still leaves some risk, but I'm comfortable with that.

Ken

Ugh just close vision inspection for obvious fault or counterfeit, ain't enough, to detect the microscopic fissure that may only be the width of interface of metal grains. DynoDave born about blind so extra effort to close examine, can see that fine, amazing once shown what's possible to see - after its pointed out to you... Trixie has not been through engine traumas with current crank and rod fasteners so just checking I wasn't messing up if just nipping up as can, & still don't know if I even can. The lawn mower extremists say they go by the parts temperature when setting a torque value to use that day > as pure destructive testing guided them. Poor women don't know what attention they miss out on not being issued with chrome or threads.

Years ago when I was in the fastener industry we used a device to show what happens when reusing nuts and bolts. Basically it was a device that showed the pressure applied when a nut and bolt were torqued to a value, in this case 3/8/unf which reached 9000 lbs. The fasteners were then loosened and retorqued to the same value where the pressure was now 6000 lbs. The lower value attributed to deformation of the threads in the nut leading to more of the torque being used to overcome the now higher friction . The nut was then removed and flipped so that the opposite face was against the device and again retorqued and was back to 9000 lbs. This would point to measuring stretch as the better bet. Red loctite might still be holding the nut tight to the bolt but there may be insufficient stretch which could lead to fatiguing of the bolt.

triumph2 said:

The nut was then removed and flipped so that the opposite face was against the device and again retorqued and was back to 9000 lbs. This would point to measuring stretch as the better bet. Red loctite might still be holding the nut tight to the bolt but there may be insufficient stretch which could lead to fatiguing of the bolt.

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No doubt measurement of bolt stretch is the definitive way to indicate tension or load. Your scenario above suggests only the nut deforms and not the bolt - interesting.

No question. Measuring stretch is the only way to torque them with locktite on the threads instead of the specified lube. New or old nuts. Jim

I already knew I'd wasted money on Norton torque wrenches. Ancient Norton lore I was nursed on said if renewing rod shells in intact engine just new nuts is ok. So - with triumph2's test report - that once a full torqued nut is loose its lost its full re-clamp potential and should be flipped or replaced. That implies if I find a rod or crank nut loose enough to twist below factory torque - it should be replaced not re-tightened? ?? Norton rod nuts and others are not the same on both faces.

Some nuts are bevel relieved a tread depth around hole on one side but not the other. I put these type nuts bevel side down, is the right?

hobot said:

I already knew I'd wasted money on Norton torque wrenches. Ancient Norton lore I was nursed on said if renewing rod shells in intact engine just new nuts is ok. So - with triumph2's test report - that once a full torqued nut is loose its lost its full re-clamp potential and should be flipped or replaced. That implies if I find a rod or crank nut loose enough to twist below factory torque - it should be replaced not re-tightened? ?? Norton rod nuts and others are not the same on both faces.

Some nuts are bevel relieved a tread depth around hole on one side but not the other. I put these type nuts bevel side down, is the right?

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If you find something loose you better replace bolt and nut. And maybe the part too. Jim

Well JIm your brief summary is as seemingly sensible as first impressions of saying we need to use a torque wrench, so what you state means we should not be re-torquing head and cylinder fasteners but replacing when any found below initial torque used to seat. Triumph2 report made too dam much sense and backs up your advice comnoz to replace so not over straining em for re-use. Is speed of torque application in cold or hot temps beyond need to know here?

A few pages of fudge factors for re-torquing T-wrench setting dependents.
https://www.fastenal.com/content/feds/p ... teners.pdf

Re-use of Fasteners and Torque In the event that a fastener is reused, attention must be given to the method of reinstalling the fastener. Upon reuse, a nut and bolt combination will require an increased torque value to reach the desired clamp load. This results from the deformation of the nut threads.

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On a demonstration with a ½-13 zinc plated SAE J429 Grade 5 hex cap screw and zinc plated SAE J995 Grade 5 hex nut with an installation torque of 70 ft-lbs to obtain a clamp load of 9000 lbs (without any added lubrication). On the second installation, this torque had increased to 95 ft-lbs to obtain 9000 lbs. By the fourth installation, we required 145 ft-lbs to reach a clamp load of 9000 lbs .

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Cylinder head bolts are going to get loose because the gasket compresses. No need to replace them.

If crank or rod bolts are loose it is because the bolt has stretched beyond it's elastic point. A rod bolt should return to very close to it's pre-stretched length when the nut is loosened. If it doesn't then it is damaged.

And running them loose means they have been fatigued.
If it is a rod bolt that has been loose then the rod is likely damaged also. Jim

So far only a crank nut or two found too easy to re-tighten after Peel's over rev and Trixie's rod bolt corrosion so don't really know if I goofed up or excess shock jerk loads backed em off. I could not measure stretch of deeper crank nuts so mimiced grunt of the ones I could. Learning another years worth of Combat lore I now think Trixies leak all over issue [only when operated in 2S zone or over 70 mph] [and dry floor - once exterior drained] is a combo of 3 things 1. internal factory sump passage retaining a piece swarf I could not clear finally piled up enough grit to wet sump at lower rpm, 2. past ring blow by sealant integrity, 3. Re- using head and barrel nuts a few too many times. Before I gave in to expose crank again, poor ole Trixie was one tightly fastened gal. Trix's rod nuts and bolts were all new 7ish000 m's ago so will use a Twrench set to mere factory spec and hope for the best. My like new expensive T-wrench read ~28+ lb on them to get almost .0065" tension from cheap dial micrometer. Why would I do that?

Skip the shop pep talk - scroll past text to linger awhile
http://www.lightningmotorsports.com/arp_tech.htm