3 busted lugs on one wheel
08-02-2017, 11:51 PM
#31
The nominal stress area for a m14x1.5 thread is about 0.194in^2.
σ=F/A = (16,000/0.194)
σ = 82.5ksi
For a fastener to be certified to grade 10.9, its minimum proof strength needs to be about 136ksi and its tensile strength to be about 150ksi.
This is quick and dirty hand calc that is very conservative, but still proves the scenario you are suggesting is very unlikely.
Last edited by sweet victory; 08-03-2017 at 02:16 AM.
08-03-2017, 12:51 AM
#35
A good torque vs clamping force look up table btw.
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.fastenal.com/content/feds/pdf/Torque-Tension%2520Chart%2520for%2520Metric%2520Fasteners.pdf&ved=0ahUKEwj--63lkrrVAhVK7GMKHbkKB9EQFggxMAE&usg=AFQjCNHQtnuC59iH2tMnGLQSUZ-fT21g_w
https://www.google.com/url?sa=t&source=web&rct=j&url=https://www.fastenal.com/content/feds/pdf/Torque-Tension%2520Chart%2520for%2520Metric%2520Fasteners.pdf&ved=0ahUKEwj--63lkrrVAhVK7GMKHbkKB9EQFggxMAE&usg=AFQjCNHQtnuC59iH2tMnGLQSUZ-fT21g_w
08-03-2017, 02:08 AM
#37
A good torque vs clamping force look up table btw.
https://www.google.com/url?sa=t&sour...GLQSUZ-fT21g_w
https://www.google.com/url?sa=t&sour...GLQSUZ-fT21g_w
In practice, my group uses Abaqus for our FEA. A majority of our systems fall under grade A shock items under MIL-S-901D so all of our torque specs are based on the system meeting customer requirements.
Last edited by sweet victory; 08-03-2017 at 02:30 AM.
08-03-2017, 03:08 AM
#38
Race Director
Thread Starter
After staring at the parts for a while, I think I created or aggravated an issue with my wheel studs when I installed them. This wasn't an issue at the time; the broken studs failed further outboard from the point where the lug nuts were originally snugged. It wouldn't have been an issue, but then...
When I installed 15mm spacers, it seems at least possible that the lug nuts on the affected studs, when torqued, were at or near the flaw/stress/bad juju I caused/exacerbated at install time.
Or, you know, totally not my fault, man.
When I installed 15mm spacers, it seems at least possible that the lug nuts on the affected studs, when torqued, were at or near the flaw/stress/bad juju I caused/exacerbated at install time.
Or, you know, totally not my fault, man.
08-03-2017, 11:41 AM
#39
08-03-2017, 12:09 PM
#40
Race Director
Thread Starter
You and...a small handful of other folks on RL. 
If I hadn't had the car up on jack stands in the driveway just 2 weeks ago, I'd be wondering how long one or two had been broken off like that. I _almost_ waited to check until I got to a more convenient location, but the sensation was REALLY unsettling. Still makes me a little anxious to think about...
For what it's worth: I went back and reviewed the product info for those studs. They are listed as a "wear item," recommending replacement every 2 years or as needed based on examination for wear. I wasn't even close to the 2-year mark yet.
I should have taken the disclaimer included in those instructions a little more seriously.
If I hadn't had the car up on jack stands in the driveway just 2 weeks ago, I'd be wondering how long one or two had been broken off like that. I _almost_ waited to check until I got to a more convenient location, but the sensation was REALLY unsettling. Still makes me a little anxious to think about...
For what it's worth: I went back and reviewed the product info for those studs. They are listed as a "wear item," recommending replacement every 2 years or as needed based on examination for wear. I wasn't even close to the 2-year mark yet.
I should have taken the disclaimer included in those instructions a little more seriously.
Last edited by 5CHN3LL; 08-03-2017 at 12:29 PM.
08-03-2017, 02:06 PM
#42
Race Director
Thread Starter
It turns out that many things are self-tightening, especially when you hear a stud break and feel the wheel wobbling on the hub. One or two items have yet to un-clench.
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Dr. G7 (10-03-2021)
08-03-2017, 04:00 PM
#43
Rennlist Member
You and...a small handful of other folks on RL.
...For what it's worth: I went back and reviewed the product info for those studs. They are listed as a "wear item," recommending replacement every 2 years or as needed based on examination for wear. I wasn't even close to the 2-year mark yet.
I should have taken the disclaimer included in those instructions a little more seriously.
...For what it's worth: I went back and reviewed the product info for those studs. They are listed as a "wear item," recommending replacement every 2 years or as needed based on examination for wear. I wasn't even close to the 2-year mark yet.
I should have taken the disclaimer included in those instructions a little more seriously.
08-03-2017, 04:47 PM
#44
Rennlist Member
How many removal/re-attachment cycles can they endure?
08-03-2017, 05:02 PM
#45
Race Director
Thread Starter
The documentation that came with the studs did not mention any limitations or recommendations beyond the 2-year replacement cycle. For the record, even that's a stretch for my car given the guidelines in the install notes...
Wheels studs used in competition are considered wear items and should be replaced on the following intervals
o Street/DE car with less than 10 events a year – Replace every two years
o Race Car with or DE car with over 10 events a year – Replace every year
o Pro level racing – twice a year
The car is not going to be operated until the replacement bolts are here. I wouldn't let my worst enemy drive the car with the remaining studs installed.
Other than the three that were f****g broken completely off, there were no anomalies during disassembly. The broken studs - and the two remaining good studs - all backed out of the hub with the expected amount of effort given the installation method (30 lb-ft plus Loctite 272). Those suckers were certainly not loose.
Wheels studs used in competition are considered wear items and should be replaced on the following intervals
o Street/DE car with less than 10 events a year – Replace every two years
o Race Car with or DE car with over 10 events a year – Replace every year
o Pro level racing – twice a year
The car is not going to be operated until the replacement bolts are here. I wouldn't let my worst enemy drive the car with the remaining studs installed.
Other than the three that were f****g broken completely off, there were no anomalies during disassembly. The broken studs - and the two remaining good studs - all backed out of the hub with the expected amount of effort given the installation method (30 lb-ft plus Loctite 272). Those suckers were certainly not loose.