We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?

Some good info he
http://www.theultralightplace.com/torque_values.htm

Do you mean you are using an 8.8 grade fastener? If the studs are
breaking perhaps you should substitute 10.9 or 12.9. Here is a decent
table with some good info on strengths and applications

http://euler9.tripod.com/bolt-database/22.html

Pete
RoyJ wrote:
We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?


--
Pete Snell
Department of Physics
Royal Military College
Kingston, Ontario,
Canada
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RoyJ wrote:

We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?


You generally run those in once. 8.2 has been addressed. Why are you not using a thread
locker to set the stud?

Put a nut on one side of stud, put stud though a drilled plate and torque other side using
a proper nut and ramp up testing to destruction to see at what torque value it fails at.

We recently had some studs fail in product we make when torqued to values we have used for
years.

Wes

On Mon, 22 Jun 2009 10:18:15 -0500, RoyJ
wrote:

We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?

Are you saying that the stud broke, or that the stud pulled out of the
aluminum hub?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

The stud broke because it was over torqued. Given how the gang changes
tires with wanton use of impact gun with no limiter, assume all studs
are trashed. Plan is to pull all of them, replace with new ones. Suspect
that the new ones are 8.8 (not 8.2, duh.....) My question is what torque
to install the new ones to? The hubs will have had one set of them
installed, run down to the unthreaded section and set hard, then
removed. There has to be some balance between enough torque to set the
stud, not too much to strip the stud out of the aluminum hub, and enough
torque to not unscrew when changing wheels.

Bruce In Bangkok wrote:
On Mon, 22 Jun 2009 10:18:15 -0500, RoyJ
wrote:

We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?

Are you saying that the stud broke, or that the stud pulled out of the
aluminum hub?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Mon, 22 Jun 2009 20:04:00 -0500, RoyJ
wrote:

The stud broke because it was over torqued. Given how the gang changes
tires with wanton use of impact gun with no limiter, assume all studs
are trashed. Plan is to pull all of them, replace with new ones. Suspect
that the new ones are 8.8 (not 8.2, duh.....) My question is what torque
to install the new ones to? The hubs will have had one set of them
installed, run down to the unthreaded section and set hard, then
removed. There has to be some balance between enough torque to set the
stud, not too much to strip the stud out of the aluminum hub, and enough
torque to not unscrew when changing wheels.

Essentially studs are not installed the way you seem to be planning.
Studs use an over size thread on the end to be installed into the
parent metal and are simply driven to the designed depth.

If you are concerned about the security of the installed stud you
could use one of the various locking substances which are made for
various services - easy to remove, never to be removed, etc.

I wonder why you are using an impact wrench? Speed? But if the impact
wrench is causing the problem why not try limiting the torque that the
wrench can produce?

Cheers,

Bruce
(bruceinbangkokatgmaildotcom)

On Mon, 22 Jun 2009 10:18:15 -0500, RoyJ
wrote:

We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?

If this is the stud between two halves of the two piece wheel, I'd
countersink a recess in the rear section and use bolts, with red
Loctite if you want to leave the threads alone. The clamping force
would be more reliable. Make them more like the headed and knurled
studs on car hubs that they are used to, that can't pull out. KISS.

Threaded studs like you describe have this annoying habit of coming
out at the threads instead of the nut if the nut has rusted or stuck
on a bit, and you are depending on the softer aluminum alloy as a
critical stressed member.

And if they don't notice the stick-out of the studs getting longer
than the others (or they all start backing out at the same time) you
could have a failure during a race.

You can't stop them from using rattle guns,"that's Real Racing!" But
if you supply the guns and lock-out the torque adjustment settings you
can limit the torque applied. Might be the better route, even if you
have to pay more for guns that can limit the torque to where you want
it. Tell them a tall tale if you have to, "These are the Real
High-Speed Guns like they use in NASCAR!"

That, or take away the 1/2" full-size impact guns and hand them 1/4"
air ratchets (on a restricted air line at 30 PSI so they can't go much
past snugged down) and a Clicker torque wrench.

-- Bruce --

On 2009-06-23, Bruce L Bergman wrote:
On Mon, 22 Jun 2009 10:18:15 -0500, RoyJ
wrote:

We are having issues with over torquing wheels on racing karts. Results
in snapped studs that are threaded into aluminum hubs. Anyone got some
guidance or links to the torque spec for running an 8mm 8.2 stud into a
high grade aluminum casting/forging?

If this is the stud between two halves of the two piece wheel, I'd
countersink a recess in the rear section and use bolts, with red
Loctite if you want to leave the threads alone. The clamping force
would be more reliable. Make them more like the headed and knurled
studs on car hubs that they are used to, that can't pull out. KISS.

Given that the 8mm size he specifies is essentially 5/16", it
won't take much to over-torque the studs with an air driven impact
wrench.

Threaded studs like you describe have this annoying habit of coming
out at the threads instead of the nut if the nut has rusted or stuck
on a bit, and you are depending on the softer aluminum alloy as a
critical stressed member.

And if they don't notice the stick-out of the studs getting longer
than the others (or they all start backing out at the same time) you
could have a failure during a race.

I *think* that what he was saying was that the studs were being
broken off from excess torque, and the headed and knurled ones won't do
any better in the face of a 1/2" impact wrench.

You can't stop them from using rattle guns,"that's Real Racing!" But
if you supply the guns and lock-out the torque adjustment settings you
can limit the torque applied. Might be the better route, even if you
have to pay more for guns that can limit the torque to where you want
it. Tell them a tall tale if you have to, "These are the Real
High-Speed Guns like they use in NASCAR!"

That, or take away the 1/2" full-size impact guns and hand them 1/4"
air ratchets (on a restricted air line at 30 PSI so they can't go much
past snugged down) and a Clicker torque wrench.

The 1/4" ones might be a good choice -- about the same drive to
stud diameter ratio as with normal automotive studs and 1/2" drive guns.

Enjoy,
DoN.

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