Paxton SN92 Preload Setup

[WCP]

Does anyone out there have, or has seen, a procedure to set the ball drive preload for a Paxton SN92. This is the internal drive shim adjustment rather than impeller clearance adjustment. The response I've got so far from those contacted is "send it to me and I'll fix it". I have my own idea on how to proceed but would like some confirmation.

[M15 Trucker]

Have you tried John Myer, of Myer's Studebaker Parts?
Their phone no is 740-674-4897, and he is a Co-opertor
Advisor for TW. Has rebuilt many superchargers and
related parts if you need them.

[grobb284]

If it is like the sn93, you preload the belleville washer with shims to establish a preload on the bearing assembly, in turn the input shaft, ie. the necessary torque to maintain rotation, not the breakaway torque.

You'll find you will have to assemble and disassemble a number of times.

I can't remember the required torque, in the vicinity of 30 inch lbs.

Call Craig at Paradise Wheels for the required torque.


1963 Studebaker Avanti: C4 Corvette narrowed front/rear suspension, C5 13" calipers/rotors adapted to C4, Viper differential with Intrax 3.54 ratio (the snake has been charmed!), coil overs, stainless tubular frame, stainless chambered side exhaust.
Here are two links for some pictures and information.
Slide Show
Magazine Article

[WCP]

Thanks grobb284. Sounds like the SN92 & 93 are pretty similar. There are 3 places to put shims that will increase the load on the balls - behind the belleville washer, behind the rear race, and behind the front race. I've been assuming that the shim behind the belleville washer be adjusted to set the position of the output shaft such that the impeller mounting surface is flush with the case and then to increase the shim behind the front race on a trial and error basis to arrive at the correct preload. I've been told the preload should be 60-65 in.lbs. Any thoughts on this? I'll try calling Craig at Paradise Wheels. Thanks

[WCP]

Talked to Craig. Faulty thinking on my part. A shim under the front race moves the output shaft rearward and the determining factor is the position of the seal on the output shaft. To increase preload any of the 3 locations can be used, but putting the shim under the belleville washer or rear race simply increases the flex of the belleville washer and increases preload. Thanks for putting me on the right path. BTW Craig says the preload should be 20-25 in.lbs. Seems low based on my SN60 experience but I will let KOOL R2 decide on the target.

[grobb284]

quote:I've been told the preload should be 60-65 in.lbs

quote:BTW Craig says the preload should be 20-25 in.lbs.

Craig can be counted on to give you the correct information. Anything over 35-40 in-lbs may accelerate wear. You probably can't easily turn the input shaft by bare hand at 24 in-lbs, this may surprise you.

65 in-lbs may be a recipe for premature bearing failure.

Effectively internally there is not much boost difference between models, just how the force is established to keep the balls from slipping.

Not yet sure how others claim anywhere from 9 to 11 lbs boost with a SN60 or a later variant, unless they are pressurizing a 2 liter coke bottle. Essentially the same speed up ratio, same bearing balls, and essentially the same impellers, with perhaps a "tuning of the vanes." The VR4 is a slightly different animal.

No magic, no major boost performance improvements from one model (SN-60, SN92, SN93) to the next as far as boost output.


1963 Studebaker Avanti: C4 Corvette narrowed front/rear suspension, C5 13" calipers/rotors adapted to C4, Viper differential with Intrax 3.54 ratio (the snake has been charmed!), coil overs, stainless tubular frame, stainless chambered side exhaust.
Here are two links for some pictures and information.
Slide Show
Magazine Article