[HoosierPE]

Greetings fellow F-body enthusiast!

I've created this new topic to introduce Hoosier Performance Engineering's first new product; a clean sheet approach to a billet front hub and bearing assembly for the 4th Gen F-bodies and C4 Corvettes. Many of the other hub/bearing threads are getting pretty long and don't really end with a sustainable solution, so I thought a new thread was in order.

I won't bore you with the details on HPE, other than to say a group of highly qualified and skilled automotive engineers have gotten together to create performance products for the 4th Gens and modern muscle cars. You can read more about HPE on the General Discussions forum where Kevin introduced HPE as a new sponsor.

I've been contemplating the 4th Gen front hub issues since I returned to Auto-X in the fall of '97 with the purchase of my first TA and began working in earnest on new designs in November of last year. What you see below is the result of two gear-heads' work for the past 7 or 8 months, plus over $6000 worth of invested in prototypes, tooling and CNC programming. Prototypes are installed and accumulating mileage and we will be ready to take orders as soon as the machine shop volume quotation is received and final pricing can is set. (Trying to wrap up pricing yet this week.)

I'll let the pictures do the talking first, and then will follow up with some detailed descriptions of the components. Enjoy.

Finished product:
(IMG:https://fbcdn-sphotos-g-a.akamaihd.net/hphotos-ak-ash3/1014542_375876139190953_1528206097_o.jpg) , (IMG:https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-frc3/976331_375876125857621_1907471607_o.jpg)

Here's a disassembled OEM hub and the new HPE replacement parts. Note the OEM uses ball bearings while the other is tapered roller. On Timken's website, the tapered bearings are rated much higher in every category vs. the ball bearings. Small bearing has a 1.25" ID and the large bearing has an 1.5" ID. For comparison, the old GM RWD cars used like 7/8" and 1" bearings with the front spindle design.
(IMG:https://fbcdn-sphotos-h-a.akamaihd.net/hphotos-ak-frc1/1009411_377277199050847_782089290_o.jpg)
(IMG:https://fbcdn-sphotos-c-a.akamaihd.net/hphotos-ak-ash4/999016_377277289050838_494724905_n.jpg)
(IMG:https://sphotos-b.xx.fbcdn.net/hphotos-ash4/1009351_377277345717499_1374075883_o.jpg)
(IMG:https://sphotos-a.xx.fbcdn.net/hphotos-prn1/1015137_377277329050834_2109600006_o.jpg)

We use an inverted spindle design, much like OEM part, except ours is a two piece design with a wheel mounting flange and pin (spindle) that we shrink fit together. The shrink fit provides three times the push out force of an equivalent press fit. Pin, flange and housing were all coated with a clear zinc treatment. The pin has been case hardened in the two areas where the bearing races will rest. The mounting flange is case hardened where the seal will run. Specs were per the Timken recommendations for the bearings used.
(IMG:https://sphotos-b.xx.fbcdn.net/hphotos-frc1/1008279_375876219190945_1586806985_o.jpg)

Pin with locking washer, nut and small cap screws. The washer engages the key way in the in threaded end of the pin, the nut is added and torqued to desired preload, and when the threaded holes in the nut lines up with the holes in the washer, the cap screws are added as the retention mechanism, basically replacing the cotter pin in similar parts.
(IMG:https://sphotos-a.xx.fbcdn.net/hphotos-prn1/1014577_375876269190940_1184777397_o.jpg)
(IMG:https://fbcdn-sphotos-b-a.akamaihd.net/hphotos-ak-ash3/1015262_375876245857609_442072466_o.jpg)

Sub-assembly shown with dry bearings for clarity.
(IMG:https://sphotos-a.xx.fbcdn.net/hphotos-ash3/1015600_377277409050826_1257648155_o.jpg)

These assemblies are completely rebuildable and repackable. Should be the last set you will ever need.

I will add some more pictures of the prototypes installed on one of our cars.

Please let me know what you think!

[Chevy053]

What was the reason for the design decision to go with a 2 piece flange. Was a single piece considered?

[HoosierPE]

What was the reason for the design decision to go with a 2 piece flange. Was a single piece considered?

Primarily it was a cost & affordability thing, for material, machine time and tooling. Ideally, you'd like to have a one piece forging that is near the final shape and then machine that piece down to the final product. That is how the OEM pieces are done. No way to justify the forging tooling right now, which would probably be $10k or more, with what I believe will be low volumes (hundreds not thousands). We use pre-hard 4140 for both the pin and the flange which is a lot more costly than mild steel, and starting with a 6" diameter billet and whittling it down to 1" diameter in some spots generates quit a bit of waste.

At first we thought we would use a heavy press-fit and then I remembered shrink-fitting from my college days and started researching that process. The Machinery's Handbook goes through the process in great detail. The added bonus was the much higher retention force over a press-fit with the same amount of interference, 3.66 times for an axial pull and 3.2 times in torque or rotation. (This application doesn't see any rotational torque since it is not a driven axle.) An interesting side note; all of the train axles and wheels are a shrink-fit.

Turns out the two piece design might be the better performing design when you consider the stress concentrations and reverse bending cyclic loading of the application. On a one piece design, the transition from the flange to pin diameter becomes critical to avoid stress concentrations and a fatigue failure. If that radius or filet is too small, or there are surface imperfections, it becomes a stress riser and the focal point of crack initiation.

Update: We ran our first Auto-X on Sunday in my son's '95 LT1 (383) Camaro running 315 Khumo's. We had 6 runs on 65 second course with no change in preload on the prototype hubs.

[Chevy053]

What was the reason for the design decision to go with a 2 piece flange. Was a single piece considered?

Turns out the two piece design might be the better performing design when you consider the stress concentrations and reverse bending cyclic loading of the application. On a one piece design, the transition from the flange to pin diameter becomes critical to avoid stress concentrations and a fatigue failure. If that radius or filet is too small, or there are surface imperfections, it becomes a stress riser and the focal point of crack initiation.

Thats what I was getting at. Was just curious if that was by accident or not.