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Fasteners and the Art of Keeping Your S*#@ Together

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captdistraction

GrumpyRacer
1,954
1,697
Phoenix, Az
Preface: I'm a huge believer in witness marking every important bolt in the car and using a good quality torque wrench when setting it, and only occasionally use German Values to set something where a torque wrench won't go. Also inspecting the car before and during each event (typically at EOD for the next day).

That all said, I've had a recent incident where a inexpensive lock nut cost me a few thousand dollars:

a watts link retaining bolt walked its nut loose (which was a standard nyloc, but had no additional loctite or secondary retaining method), one I had previously set and marked. During a long enduro race it worked itself loose until it was off, and the bolt moved enough to allow the watts-rod end to come loose and the lateral control of the axle was lost, while the car was at 10/10ths race pace.

The short of it was that both sides of the car's rear tub were hit by the wheels and tires, puncturing a tire at 94mph, heavily scoring a shock casing, lightly rubbing the driveshaft, damaging two wheels, and scaring the -redacted- out of me. There's no reason this bolt should have come loose, but somehow, it did. I think once it was the least bit loose, the cycle of the car being worked at an extreme level just quickly moved the bolt until it was gone.

As I put everything back together, I want to revisit how I set this up. Much of my suspension does not call for loctite (though brake fasteners, and many factory or factory-style fastener positions use it). I'm considering using something for ALL bolts and wanted to get some opinions on the experiences of others.

Which should I use for this stuff? Blue? Red? I want to ensure every critical bolt has a locknut/nyloc (or double nut if possible), some form of secondary locking material, and fresh witness marks.

Should I consider something even further like a nordlock or drilling and safety wiring critical fasteners? While I think my cautious approach previously worked in a HPDE scenario, in a race scenario where the hardware is pushed far past its design limits on the regular requires even more careful consideration. I don't take this stuff apart often, so I don't care about it being somewhat more difficult to service.

For fun, here's a few pictures:

what we found after the incident (the car had to be ditched behind a tire wall and eventually recovered at the end of the event)
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BS1DUzzl.jpg
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also before anyone questions the hardware in place, this wasn't something provided by the part manufacturer, but a bolt I put in place of what they provided. They used a fine thread 10.9 bolt, and I had changed to this coarse 12.9 bolt which may have contributed to the failure.
 
492
387
DFW, TX
Being in shear, I would have not thought a nyloc nut would have be able to back out unless it got hot and the nylon disappeared. An all-metal stop-nut would not have that issue.

Were there no spacers on either side of the rod end inside that bracket or did they fall out?
 

Grant 302

basic and well known psychic
They used a fine thread 10.9 bolt, and I had changed to this coarse 12.9 bolt which may have contributed to the failure.

This. Scratch the 'may have' part. Did you lookup or raise the torque spec to match the clamping force to the original fastener? I'm going to guess that it would need a bump of ~+20% torque to match the clamping force. What are both of the fastener sizes/specs?

I'm not sure safety wire would have prevented this issue.
 

captdistraction

GrumpyRacer
1,954
1,697
Phoenix, Az
Being in shear, I would have not thought a nyloc nut would have be able to back out unless it got hot and the nylon disappeared. An all-metal stop-nut would not have that issue.

Were there no spacers on either side of the rod end inside that bracket or did they fall out?

They were ejected when the bolt pushed far enough out (shocking that I was able to recover the bolt).

Also yes I stuck with the original torque spec which sounds like the root of the problem.

I imagine heat comes into play, it’s only a small distance away from the exhaust and going through 30 minute+ cycles at race pace.


The thread is more generalized in what types of solutions I should consider for extreme duty to reduce the chances of this happening again


Sent from my iPhone using Tapatalk
 
492
387
DFW, TX
Then my statement about an all-metal stop nut applies, and as mentioned increasing the torque for a coarse thread vs fine thread.

While I had to use bolts/nuts on exhaust at one point, I used all metal stop nuts. But they would also be prone to galling. Eventually I changed things to v-band clamps.

On older Windsor based motors I had issues with header bolts loosening until I switched to Fel-Pro metal gaskets. Reused them plenty of times with no issues. When I had a motor with aluminum heads with thread inserts, i had to stop using ARP stainless bolts and reverted to cheapo black oxide header bolts to prevent galling between the ARP bolts and the stainless thread inserts.

The starter would always want to fall off... On this particular application I was able to put in a longer bolt and use a nyloc as added insurance as one bolt hole was not blind.

Things that had to be removed often, I didn't use loctite and relied on safety wire. I've broke plenty of 1/16" cobalt bits drilling bolt heads for safety wire. Standard stuff was easier to find than metric.

A good source for fancy metric stuff are specialty motorcycle fasteners. Owning a Ducati introduced me to to a whole world of blingy Ti and stainless stuff. I have plenty of stuff safety wired on the bike.
 

TymeSlayer

Tramps like us, Baby we were born to run...
3,786
2,738
Exp. Type
HPDE
Exp. Level
3-5 Years
Brighton, Colorado
You should never use a nylon insert locknut in any critical application. It has limited amount of use and reuse. They use them because their cheap but there are more expensive all metal and deformed locking nuts out there, similar to what's used on aircraft.

http://www.fastenerexperts.com/lock-nuts/

The use of Loctite is great and the main difference between blue and red is how often will you be putting them on and taking them off. Blue is great for most application whereas red is considered more permanent and may require high heat to remove.

A relatively new product is LockOne which works great but you'll need extra threads on the end of the bolt as it is a compliment to a regular nut. There's a video in the link below.

http://www.katonet.com/lockone.html

Using a castellated nut and lock wire or a cotter pin is not only a pain in the ass but tends to get expensive and tyme consuming.
 
Last edited:

steveespo

Lord knows I'm a Voodoo Child
Moderator
4,007
1,924
Exp. Type
W2W Racing
Exp. Level
10-20 Years
Cookeville TN
Deformed metal nuts are used by Ford in many applications. They are meant to be single use but they don’t come loose. Typical application is the cat pipe to header nuts and the strut top nuts to the spring perch. A dab of locktite with nylon nuts or lock washers works well too.


Sent from my iPhone using Tapatalk
 

cobrarob

11 Shelby GT500
555
130
new york
image.php

Have not used this but came across it the other day.?
 

drano38

Wayne
1,130
318
I've got most of my suspension hardware witness marked and inspect it prior to every HDPE event. But looks like checking every day is even better.
Might have to change out some hardware next spring with some form of lock nuts.
Capt - Glad the car didn't get any more damage - but any is too much.
 

302 Hi Pro

Boss 302 - Racing Legend to Modern Muscle Car
2,009
441
Southeast
Sorry to see this happen to you.

My question is with picture 1: Is this a pic of what you found during your initial failure inspection? Or, did you reinstall a bolt in the mounting bracket and rod end for illustration purposes?
 
I have been in the process of doing a full build on a Jeep and have put a ton of thought into this exact issue. I am going the way of fine thread bolts with the metal lock nuts. This is due to my experience with nylock Vs. Metal lock fasteners. Nothing scientific, but it always seemed that the nylocks where much easier to disassemble after the fact, so my logic is that they are much easier to "rattle" apart...

My $0.02, FWIW.

Also, glad you came out of it "unscathed."
 
492
387
DFW, TX
I would never expect a nyloc nut to rattle off unless it's been melted. Most nylocs you buy are junk material however. Hardened nylocs are not very common at your run of the mill hardware store. Even then, it's not to big a problem if the bolt is in shear and in a good bracket.

But... is your bolt a close tolerance fit to the hole? Are you putting the threaded part of the bolt in shear or the much stronger shank? The shank should pass all the way through the bracket. Ideally, no threads should be within the bracket. If not, buy a longer bolt and cut off the extra thread.

If things are not a tight fit, you are just going to elongate the bracket's hole the bolt passes through, probably remove the torque setting on the bolt, and then things start rattling around.

The bracket in the first picture is not ideal because the one end is basically unsupported. A bit of a gusset on one or both sides of the bracket would strengthen it quite a bit.

Maybe not in print any more, but the Carroll Smith books like "Prepare to Win" were informative.
 

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