froggy47

That is pretty good.

The thing about some really great high performance parts companies, including all the F1 teams - for example, is they value lightness over durability. We autox/hpde guys don't replace/throw away bits like they do every race. So actually having a "metric" as to how long something will last helps us make a rational decision on whether to pay more for a part or not.

Katech_Zach

We have been torturing a lug nut with an impact for the last hour. I don't think we have anything to worry about.

We will post more scientific information later.

Katech_Zach

c5racr1

Awsome

Poor-sha

So your saying that with the Ti nuts you couldn't break the incredibly craptastic stock C7 studs? I wouldn't have guessed that to be the case. No issues with the nuts rounding off?

doublec4

If you guys would like, I have access to a "Skidmore-Wilhelm" bolt tension measuring device at my work.

Essentially it uses two plates compressing hydraulic fluid to register a pressure on the gauge to relate torque and bolt tension.

This way you can see how friction with the different materials and coatings is affecting your clamping force.

I can run the test for you (for free) if you want to send me one of each style lug. Give me a torque value and I will set up the experiment and send you the results.

PM if interested. I am a professional engineer for what it's worth

Katech_Zach

Sure. Email me your address and I'll send you some.
jason@katechengines.com

doublec4

Email sent.

MR Turco

Great data, thanks for the analysis Jason! Can't wait to get them

froggy47

Please test with ARP studs.

dapopa9

Why does the steel stud break off with the steel nut but not with the titanium nut? Just trying to learn why/how this works.

Thanks for the great test data!

froggy47

Me too, we are testing lug nut vs lug nut right. If studs are breaking get better studs. Makes sense yes/no?

Katech_Zach

Honestly, we don't have an explanation for that.

StreetSpeed

That seems bizarre. Only thing I can think (from working with titanium a fair amount) is that titanium while indeed has a higher tensile strength than many steels, is still a fairly "gushy" material. Could be when the titanium lug nut is slamming into the seat, the titanium nut is absorbing some shock, while the steel but is transferring all the force right back into the stud? Just thinking out loud.

Bad_AX

Likely has to do with thread loading with the steel nuts putting a more concentrated stress on the stud.

The is a bit dated, but a good reference. From pg. 13
https://ntrs.nasa.gov/archive/nasa/c...9900009424.pdf
If a bolt is cycled in tension, it will normally break near
the end of the threaded portion because this is the area of
maximum stress concentration. In order to lessen the stress
concentration factor, the bolt shank can be machined down
to the root diameter of the threads. Then it will survive tensile
cyclic loading much longer than a standard bolt with the shank
diameter equal to the thread outside diameter.

This will add some insight to Katech's test results.
https://www.highpowermedia.com/blog/...tener-material
The use of nuts with lower modulus than the male fastener is known to reduce the stress concentration effect at the first thread, and improves the distribution of load over the length of the engaged threads.

A good failure analysis paper.
http://products.asminternational.org...d=2039&search=

I expect the superior performance that Katech observed is due to the difference in tensile properties of the stud and nut as noted in the Race Engine Technology article linked above.

-Scott

454z06

I believe its from the steel nut collapsing around the stud, then twisting the stud till it fails. Happens all then time when you overtorque conical nuts against steel wheels.

JimMueller

Were these test results published?

doublec4

Just got the email notification that this thread got bumped back up.

I sort of let this fall to the back burner for a while.. Katech shipped me a few nuts to play around with but I needed a conical seat machined for the testing device I have here. Our shop was extremely busy for a few months and I wasn't able to get the seats machined for a long time. Then things got crazy in the office and I didn't have time but eventually I did get around to testing a few of them. I'll have to try and find the test data when I get home tonight.

I did my best to control the variables affecting friction (thoroughly cleaned all components with de-greaser and checked everything over for any burrs or imperfections on surfaces and threads).

The bad news is that I ran into one problem... the conical seat adapters (steel) machined to interface with the lug nuts were spinning while being torqued. Therefore, the effect of the "nut face friction" was lost, which I have read, can make up 50% of the torque distribution.

The good news is that this happened for both the Ti and steel lug nuts. Therefore, the resulting clamping force may not be accurate, but a direct comparison should still be possible between steel and Ti as only the thread interfaces were at play during the experiment. (Nut face friction was the same for both types of lug nuts as the material was both steel.)

The results of preload / bolt tension for a specific torque were very similar to the regular steel lug nuts (again, I'll have to try and find the numbers when I get home). Therefore, the coefficient of friction between some generic steel lugs (I believe some looked like zinc chromate finish) and bare steel test surface vs. Ti DLC and bare steel test surface must be reasonably similar. I would conclude that no drastic change to torque values should be necessary.

This doesn't offer any insight to the inability for Katech to break a steal stud while torquing them in their fixture. That part I still haven't spent too much time thinking about.

dclafleur

I think the link Bad_AX shared really nails why this likely occurred

https://www.highpowermedia.com/blog/...tener-material


The Young's Modulus of 8740 is 205 GPa
The Young's Modulus of Ti-6Al-4V Titanium is 113.8 GPa

In a nutshell, the Titanium does a better job of distributing stress across the threads given its lower modulus of elasticity.

tyho

Are the Ti nuts make in the US or overseas? I read somewhere they are from China?