How the right fastener can prevent hardware failure on track

J.G.
By J.G. Pasterjak
Apr 20, 2024 | Shop Work, fasteners, Washers | Posted in Shop Work | Never miss an article

A few years ago, the SCCA Solo Nationals week started off rather promisingly. A third-place trophy in the CAM Invitational gave us high hopes heading into the SCCA Championship event. But our excitement dropped to the ground when our inattention to a single bolt cost us a strong finish. We want you to learn from our misfortune, so we put …

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Comments
Satch_Carlson
Satch_Carlson New Reader
5/9/18 5:16 p.m.

The jam nuts I've used (bulkhead nuts?) are thinner than the nuts they're jamming.

With safety wire, note the excellent photo in this piece, which shows that there is actually some thought involved; the wire should go in the direction of tightness. (This seems obvious, but I've seen it wound the other way a surprising number of times.)

wlkelley3
wlkelley3 UltraDork
5/9/18 8:49 p.m.

So us helicopter mechanics may be useful after all. cheeky

te72
te72 Reader
5/9/18 10:23 p.m.

Saw the painting method (where you mark the bolt and nut, or bolt and area near where bolt engages the surface) used on a friend's car. Really smart way of making sure fasteners that are supposed to retain tension are in fact, doing just that. If you're gonna mark things in more than one place, for ease of quick viewing, just make sure you don't mark them 180 degrees opposite of each other. if the fastener spins 180 degrees, you'd never know. If the marks are uneven intervals, the only way it can be correct is if the fastener has held its tension, or spun a full circle to the exact same spot, which would be somewhat unlikely.

 

Most important thing, I've discovered, in regards to bolts and other things in the engine bay, is environmental consideration. Is the fastener you're using made of an appropriate material for the job you're asking it to perform? Consider:

 

-Temperature

-Vibration resistance

-Pressure

-Tensile strength

 

Example that most comes to mind in my case have been related to my turbo system. The guy who put my engine together at the machine shop used grade 5 bolts between my head and exhaust manifold, and exhaust manifold and turbo. Had to re-clock the bearing section of the turbo (because it was sitting with the oil drain about 45 to 50 degrees from vertical, which is less than ideal and causing me some nasty issues), when I attempted to remove these grade 5 bolts... disaster.

 

Ended up breaking a bolt off in the manifold, as the threads had effectively welded themselves to the manifold flange. That was NOT a fun job to fix, and ended up requiring the manifold to be sent off to a machine shop to repair. The solution? Stainless ARP studs in my case. Meets the temperature requirements for such a hot area of the engine bay, plenty of tensile strength, and should prevent any unexpected funkiness from using typical hardware store bolts...

 

More recently, had the line from the turbo compressor housing to the wastegate develop a hole. It was Parker nylon air line, good for 150psi, which meets the pressure requirement, BUT... a quick look at their spec sheet revealed that it's max operating temperature was only 200 degrees F. The coolant running through my engine, used to cool the other parts down runs nearly that hot... how warm do you suspect the actual components themselves, and the air around them is? Little surprised this one failed.

 

What's the danger with a blown wastegate line, you ask? Well, in simple terms, if that line blows, it keeps your wastegate from opening. Two things then tend to happen. You have a LOT of fun, briefly, before realizing you're running much more boost than usual, and secondly, things get expensive, because you're running much more boost than usual. Fortunately my ECU has a very fast reacting overboost protection circuit, so no harm was done. Potential for a blown engine though...

 

Sorry for the really long post, but I'm a big proponent of proper material selection, it makes all the difference! Thanks for posting this article online, was a good read on paper, hopefully this is one of those threads that gets a long life and good exposure. =)

Scargod
Scargod GRM+ Memberand New Reader
5/11/18 7:01 a.m.

Quite good writeup. I'd never thought that the tabbed washers would be failure prone. Does seem to work to keep some Harleys from falling apart.
Also that dirty/oily bolts, nuts, holes don't benefit much from a thread-locker.
In general, and especially with a race car, you cannot pay enough attention to having the right grade of fastening hardware, proper torque and good techniques. I'm still scratching my head about why I lost a bolt and had a catastrophic failure on the track, totaling my almost new car. Stock, it relies solely on tension. Now they have wedge-lock washers and thread locker.

te72
te72 Reader
5/11/18 10:15 p.m.
Scargod said:

In general, and especially with a race car, you cannot pay enough attention to having the right grade of fastening hardware, proper torque and good techniques. I'm still scratching my head about why I lost a bolt and had a catastrophic failure on the track, totaling my almost new car. Stock, it relies solely on tension. Now they have wedge-lock washers and thread locker.

Poor engineering, or is this a car that might not be expected to be used on a track? I'm curious for more details, if you're willing to share. Failure analysis is something that's always interested me, and I find it a good way of learning.

fidelity101 (Forum Supporter)
fidelity101 (Forum Supporter) UltraDork
6/17/20 9:49 a.m.

you forgot cross threading!

Appleseed
Appleseed MegaDork
6/17/20 10:13 a.m.

Remember,  cross threading is nature's Loc-Tite.

Colin Wood
Colin Wood Associate Editor
6/17/20 10:47 a.m.

In reply to Appleseed :

I think that deserves to go on a bumper sticker or a t-shirt.

Woody
Woody GRM+ Memberand MegaDork
6/17/20 11:03 a.m.

In reply to Satch_Carlson :

 

^^Satch!!

Apexcarver
Apexcarver UltimaDork
6/17/20 11:03 a.m.

Something to think about, in cases where you have a rod end, turnbuckle adjuster, etc. The jamb nut serves more than one purpose. You have prevention of turning, so that it doesnt lengthen and eventually separate. But then you also have the preload keeping the threads from lashing back and forth and fretting/eroding themselves and causing a sudden pullout/failure if ignored long enough. 

 

Loose threaded fittings dont only fail by backing out. 

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