Torque value for seating new hub studs? (1 Viewer)

[mudgudgeon]

Why not replace the stud with a bolt and the cone washers?

A bolt head is typically too large and will protrude post the edge of the hub preventing the wheel from fitting over the hub.
The nuts used have a thinner wall than most.
I have used socket head cap screws previously to get more thread engagement in the hub. They have a small diameter head, so no clearance issues.
Getting the correct thread may be a challenge depending on where you are

 

[izzyandsue]

Holly crap Fred, that was good reading, but bellville washers give me nightmares as I spent a few years post grad researching/writing a thesis using Schnorr washers on clamped surfaces. But yeah, its a mechanical seal in the end, help even out clamp force for a given deformation.

 

[Malleus]

I was bored.

 

[mudgudgeon]

I was bored.

Seeing as your looking to entertain yourself,

Do the cone washers in this scenario add to the clamping force applied to the drive flange with the given fastener torque?
Or are they all about positively locating the flange?

I've read conflicting opinions, and searched for definite info, but don't really know what terms to search for.

What is the purpose of the cone washers?

 

[Malleus]

Seeing as your looking to entertain yourself,

Do the cone washers in this scenario add to the clamping force applied to the drive flange with the given fastener torque?
Or are they all about positively locating the flange?

I've read conflicting opinions, and searched for definite info, but don't really know what terms to search for.

What is the purpose of the cone washers?

In my admittedly personal opinion, both. The angle of the OD acts as a lever (this is really all a wedge is) to apply a force axially along the centerline of the stud. The cone shape is self-centering. This is necessary to a degree because on off-center drive flange would put a bending load on the driveshaft and eventually wear the splines. I suspect it doesn't work as well as the designers hoped. Since the shaft and flange are pretty much stuck axially, there should be about zero wear on the drive splines, unlike the old FJ40 style transfer case shifter, which moved on the splines every time you shifted from high to low, or vice versa.

Interestingly, or not, German machine design philosophy specifically excludes this type of design. They believe that one cone or wedge shaped machine element is sufficient. Adding another, or more, diminishes the centering effect because the cones end up fighting against each other, due to machining inaccuracies in the flange and the washers themselves, to a lesser extent. Without a sufficiently thick face (which it has), the flange would tend to lift off the hub. Having said that, Germans are all about efficiency, or at least their perception of it. They would probably have designed the connection to have a centering washer around the splined shaft, or something like that.

I once had a German friend who was visiting this side of the pond ask me about the sign posted before a bridge explaining the allowable weight limits. I told him what it meant and added that most truckers ignore it, but that it wasn't a problem because the bridges were designed using an additional safety factor. He thought that reflected poorly on American designers because they couldn't design a bridge for exactly the load that was allowed for it. I asked him what would happen in Germany if a truck driver tried to drive over a bridge with a load in excess of the design capacity. He laughed and told me that would never happen.

Perception is everything.

 

[baldilocks]

If you were to use a bolt in place of the hub stud, you would step up to a 7/16 bolt and use a split “lock” washer and no cone. This has been done, documented and filed in the Mud library.

Compare with any American made full floater.

 

[bloc]

I got the impression Toyota used cone washers here and the steering arm to effectively make the stud shorter (and less likely to stretch) than the thickness of the flange.

Also, The properly installed cone washer allows the stud itself to help transmit torque by applying forces to the root of the stud where it exits the hub face, as opposed to purely the friction between the hub flange and hub face (with a paper gasket between them) in shear, which is what would happen with simple holes and nuts or bolts. The cone washers and STUDS
provide something similar to a tightly machined pinned or grooved interface.
(not bolts, where the thing the washer clamps around is spinning inside it while being clamped, I can't believe anyone would consider this a good idea)

 

[LINUS]

I only scanned once things got deep about post ~10-12, so my reason for studs probably was already hit on.

In the refinery, we use studs on all flanges with nuts on either side - reason we do it is once you gather up the slack with studs centered is you get a more accurate torque on critical flanges just torquing a nut than a bolt.

So for the flanges I bet it's so the nut is being torqued rather than resistance inside the cone washer & fastener if you used a bolt.

 

[mudgudgeon]

krazy krauts!

@Malleus I understood the cone to act as a wedge to improve clamping force, but it's been shouted down more than once. Interesting to read your thoughts

transmit torque by applying forces to the root of the stud where it exits the hub face

This is where this system fails. I've seen hub studs sheared of at the thread root, or flush at the face of the hub.

A buddy repeatedly sheared hub studs off. The fix used was to drill and tap deeper into the hub 6mm thread, and counter bore the start of the hole in the hub for a snug fit on the straight shank of 8mm SHSC.
75mm SHSC was used with the cone washer and flat washer, and torqued to 75ft/lb (I think)
This was done so shear load was taken on the full thickness shank of the SHSC, not at the thread root. The counter bore for the SHSC was done to provide minimal clearance for the shank so the 6 SHSC were effectively acting as dowels.

AFAIK, my buddy had no failures after doing this

 

[Malleus]

I only scanned once things got deep about post ~10-12, so my reason for studs probably was already hit on.

In the refinery, we use studs on all flanges with nuts on either side - reason we do it is once you gather up the slack with studs centered is you get a more accurate torque on critical flanges just torquing a nut than a bolt.

So for the flanges I bet it's so the nut is being torqued rather than resistance inside the cone washer & fastener if you used a bolt.

I'd say you were pretty close to the truth there. The difference between a stud here and a screw is that point exactly. The thread into the hub serves to anchor the stud so that the nut can bind it, creating the clamping force. You'd only (at best) get a partial approximation of this with a headed fastener.

 

[JeepinPete]

Sorry, but I disagree. First, your assumption that torque stretches the bolt, in this case, is incorrect. The torque applied in this case isn't sufficient to do that. Maybe deform the threads, but that's what happens anytime you tighten a bolt. Second, if the cone washer clamps the threads, you have a problem. The bore in the cone washer is a clearance fit for the thread diameter. Third, clamping the fastener OD will not result in greater torque, since the cone washer OD is free to turn. If the OD taper was less than 1.5° per side, it would be a locking taper, and then your argument might hold water.

- Of course the bolt/stud stretches. No stretch = no axial load on the fastener.
- The cone washers are split. When you tighten down the nut, the taper of the cone washer is driven into the taper in the flange. The ID will close up around the stud/bolt. This is the means to which the clearances are removed in this type of connection.
- The cone washer OD will experience friction with the taper bore in the flange. This friction will increase the torque required to tighten the bolt compared to a stud, as the stud is not being rotated relative to the cone washer during tightening.
- Lastly, a cone washer cannot increase clamping force, no more than a belleville washer or split washer can.

 

[bloc]

This is where this system fails. I've seen hub studs sheared of at the thread root, or flush at the face of the hub.

A buddy repeatedly sheared hub studs off. The fix used was to drill and tap deeper into the hub 6mm thread, and counter bore the start of the hole in the hub for a snug fit on the straight shank of 8mm SHSC.
75mm SHSC was used with the cone washer and flat washer, and torqued to 75ft/lb (I think)
This was done so shear load was taken on the full thickness shank of the SHSC, not at the thread root. The counter bore for the SHSC was done to provide minimal clearance for the shank so the 6 SHSC were effectively acting as dowels.

AFAIK, my buddy had no failures after doing this

A very good solution.. though 75 sounds like a LOT for a stud that small.

also it should be pointed out how few people are shearing studs with stock size tires, and even 315s. We don't hear about it too often. For toyota's purposes it is a great system given the limited space they had to work with.

 

[mudgudgeon]

A very good solution.. though 75 sounds like a LOT for a stud that small.

also it should be pointed out how few people are shearing studs with stock size tires, and even 315s. We don't hear about it too often. For toyota's purposes it is a great system given the limited space they had to work with.

It may have been 50mm. Can't remember.
But I'm fairly sure 75mm was used to get a fastener with a long enough straight shank to pass through the flange, and embed in the hub. The thread may have been cut short.

This solution was on a rig running 37s, being raced occasionally and shown very little mercy with the loud pedal.

 

[blkprj80]

The ID will close up around the stud/bolt. This is the means to which the clearances are removed in this type of connection.

That's it right there for me. The inside of the cone contacts the smooth section of the stud, thus pulling things to center on all 6 studs.

The centerline is perfectly aligned (enough), and you compress a gasket. Done.

I wouldn't want the inside of the cone to pull up on threads of a bolt; I'd rather the smooth part of the stud.

 

[Mr Cimarron]

Never had issues with 35’s and a Cummins. I don’t beat on my rig but I do chirp the tires downshifting sometimes and have done a few burn outs in gravel.

 

[bloc]

It may have been 50mm. Can't remember.
But I'm fairly sure 75mm was used to get a fastener with a long enough straight shank to pass through the flange, and embed in the hub. The thread may have been cut short.

Sorry, I meant 75ft-lb of torque. On an 8mm stud it HAS to be significantly less than that.

 

[mudgudgeon]

Sorry, I meant 75ft-lb of torque. On an 8mm stud it HAS to be significantly less than that.

Gotcha. Right you are, my bad.

Max torque on a grade 12.9 SHCS should be around 33ft/lb