: All about your Snout, Pulley, and Barrings.



topend22
03-17-13, 12:42 PM
Hi Guys, I dont know who p[osted this to give credit too but the information is GOLD...

Here's a post from the other site that sheds some light. I might have a sleeve machined like this other guy.

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Take a look inside the LSA snout before you begin modifications

In the jpeg the screen shot shows a sectioned view of the LSA snout.
Left to right there is the drive pulley (green); a double row angular contact bearing (wide); a single row deep groove ball bearing (narrow); the hub (blue) with drive pins (gray). Down thru it all is the shaft (green).

The installation of the angular contact bearing is the first and most important step. It is must be seated against the shoulder in the housing bore, pressed in with pressure on the outer race only. A quick check to verify that it is seated is the outer bearing race should be 2 mm (+/- 0.1) from the face of the housing. This bearing handles the axial as well the radial loads and (with the pulley installed) maintains the position of the shaft assembly. If the position is not correct the rest of the shaft assembly will be off.

The next step is to press the shaft assembly into the housing and bearing in the same operation. The inner race of the angular contact bearing must be supported during this operation if not it can be damaged, moved or the bearings (wide and narrow) can be preloaded. The shaft assembly is pressed to seat the shoulder of the shaft against the inner race of the angular contact bearing. You can verify this by checking the 22.9 dimension (below). Or by the length of shaft protruding from the angular contact bearing, this should measure 29 (+/- 0.5).

The last operation is pressing the drive pulley onto the shaft. The (blue) hub face must be supported when pressing the pulley on, if not the angular contact bearing will be damaged. A machined tube works best (14.1 ID x 28 OD x 28 L ) it clears the drive pins and protruding shaft. You can use a bearing heater to warm the hub, it will help reduce the press force required. Don't remove material from the shaft diameter or pulley bore to make it easier to press on.

Quick check things after work has been done by someone else:
*If you want to do a quick check if the work has been done correctly. Even if the pulley is installed and the snout is mounted on the SC you can see if this part is OK. And it's easy, if it is still there remove the plastic cap from the hub of the SC drive pulley. The end of the shaft (the pulley is pressed onto) should be flush to slightly shy of the pulley hub face. If the shaft face is more than 1 mm down from the hub face it's likely care was not taken during the swap.

*If you got the snout assembly back from a shop with the pulley installed you can check as above and check another dimension. Another point to measure is from the coupling hub face (blue, far right) to the face of the housing that mates to the SC. This is the most important dimension to check. This should measure 22. 9 mm (+/- 0.5). Less than 22.4 is a little to be concerned with but if it's more than 23.4 be sure it pressed in all the way. When this hub sticks out more than designed it will leave less room between the face of the mating hub in the SC. The coupling that is in between can be pinched between the two hubs. The result is high bearing preload, excessive heat, premature bearing failure, and (worst case) the rotors are pushed back into the SC housing.



A word of caution regarding after market couplings and pulleys:
Yes the OEM couplings may be noisy and the spring tends to wear into the center shaft.
(Mine has never been noisy but it was worn. I machined mine and installed a needle bearing race over the shaft. (they're heat treated) I have a shiny spot on the race and on the spring coils but no grooves after 10K miles.
Keep in mind they are designed to handle radial and axial misalignment between the snout hub and pins to the SC hub and pins. The tolerances can and do stack up and the thermal expansion/contraction of the entire assembly has to be considered. Something has to be compliant. It's the coupling!
Check out couplings available, Google "shaft couplings", there's a bazillion of them. The majority are designed for a little or a lot of shaft misalignment. And they are speed rated and de-rated based on misalignment. Yes there are a boat load of solid coupling as well. Read the requirements for shaft alignment for a solid couple. It's tight and tighter as the speeds increase and the (shaft) supporting bearings get closer to the coupling points. Keep all this in mind as you continue to increase the overdrive percentage of the SC.

My point......Be very careful if you decide to switch to a solid coupling there is more to be concerned with than just the fit on the (6) drive pins!


Drive pulleys:
IMO drive pulleys that have been pinned to the shaft are reason for concern. The OEM pulley/shaft combinations are ALL interference fitted they don't need to be pinned. Any shop that uses or recommends pins either can't hold the tolerances and/or doesn't trust their own work. Beyond that an 1/8" dowel pin will not help if the fit is not correct.