Center Lock Drive Studs

[Holeshot]

I'm working on designing the hubs for a formula sae vehicle. Our team has opted to go with centerlocking wheels for this year's car. I have a basic design for the hub outlined, however I have some questions regarding the drive studs. I was planning on simply using hardened steel dowel pins cut to the appropriate length and press-fit into the hub body.

In studying some of the reference pictures I have of how other teams have resolved this problem, I noticed many teams use drive studs with a allen key head. Does this mean that they are threaded into the hub? I can see how this would be preferable to a press-fit, but are these studs something that can be purchased or does each team manufacture them to suit their needs?

Also, as far as the material choice for the studs, is it common for them to be hardened? Since the wheels we will be using are aluminum, I can see it being sufficient to use unhardened steel studs. I haven't completed a fea analysis just yet, but I thought I would see what insight others could provide.

[Holeshot]

I'm working on designing the hubs for a formula sae vehicle. Our team has opted to go with centerlocking wheels for this year's car. I have a basic design for the hub outlined, however I have some questions regarding the drive studs. I was planning on simply using hardened steel dowel pins cut to the appropriate length and press-fit into the hub body.

In studying some of the reference pictures I have of how other teams have resolved this problem, I noticed many teams use drive studs with a allen key head. Does this mean that they are threaded into the hub? I can see how this would be preferable to a press-fit, but are these studs something that can be purchased or does each team manufacture them to suit their needs?

Also, as far as the material choice for the studs, is it common for them to be hardened? Since the wheels we will be using are aluminum, I can see it being sufficient to use unhardened steel studs. I haven't completed a fea analysis just yet, but I thought I would see what insight others could provide.

[Jersey Tom]

There are definitely a variety of ways to go about this. Pressed dowel pins could work.

When I was doing this 4 years ago, I did my drive pins from unhardened 1144 steel for machinability, though 416 stainless would be another good option as you wouldn't have to worry about rust. My hubs were drilled and reamed through, and the drive pins had a straight shank through most of the hub and was threaded at the end for a backside nut. In this way, the shear force on the pins is held by that straight shank (tolerance for a slip fit) rather than loading threads. I machined flats on the pins so I could hold them in place with a wrench to tighten the nut on the backside.

Alternatively, it would be easy enough to take some socket head cap screws (with the allen feature) and turn the OD to whatever you need, thread the hubs, and screw them in with some Loctite in there as well.

[EHog]

splines.

[Holeshot]

Jersey Tom,
I've been thinking about what you said with regards to modifying a socket head cap screw and have come up with a related alternative. What do you think about modifying a socket head set screw by eliminating the threads on one end by reducing them to the thread root diameter. The reason I propose this is to eliminate the stress concentration and weakening of the stud at the transition from the threaded to unthreaded section. The type of stud I'm proposing to modify can be seen below:
http : //www . mcmaster.com/#set-screws/=a29rp0

Also, thank you for mentioning corrosion. It was something I hadn't really considered, but is of the utmost importance to ensure proper fitment.

[ibanezplayer]

We've used bullet-nose dowels in the past as well as standard dowels. The bullet nose are definetly better in my opinion, it makes it easier to mount wheels. Ours were tapped on the back side to mount the brake rotors to and also held the dowel captive in addition to the press fit.

Splines are neat a'la Force India, but not the easiest thing to make for either the hub OR wheel.

[Mike Cook]

On our old setup, I made .5" aluminum dowels. The spindle flange had a .0625 deep counterbore for these aluminum dowels to press into (to ensure good position). Then the aluminum dowel itself, had a 1/4 inch shcs inside of it (with the head facing outboard) and then on the inboard side of the spindle flange, I either use a lock nut, or in some cases a threaded brake button to hold it all together. Still pins seems heavy and overkill for fsae.

[Holeshot]

I'm a little confused by your solution. Did the SHCS go all the way through the aluminum dowels? so the dowels were threaded all the way through? Or just bored out?

[Jersey Tom]

Holeshot,

There are a bunch of ways of doing this. Pressed in drive studs, threaded in studs, through-hole studs with a backside nut, even studs that are machined right into the hub. Feel free to go after any of them, and see how they do.

Your note about stress concentrations is a good one btw... but also bear in mind that these things might be so oversized from a shear force perspective that the concentration isn't a big deal.