Over 20 years ago I purchased a brand new power steering pump, so now with this discussion occuring the time has arrived to bring it out from its resting place and have a good look at it. The first thing that you notice is just how heavy it is, given its size. The housing is composed of three parts, with no pulley or brackets attached.
A pump which features a bearing only at one end of the shaft is known to have a cantilever shaft. This design is to aid assembly and after servicing, reassembly. As I detailed above, the vane carrier is not pressed onto the shaft, but is located by a pin. This allows the shaft to be withdrawn from the carrier with ease once the pump body is separated. Correct location of the carrier following reassembly is also assured. This explains most of the thinking behind why the carrier is not pressed onto the shaft, but it does not explain shaft end float.
I earlier thought that the bearing would demonstrate axial movement within the housing, and this would thus explain the end float. By inspecting my new pump, I can now see that this theory is flawed. The bearing which is of a sealed design, is pressed onto the shaft being preceeded by an oil seal, both to the limit of their travel. This assembly is then placed into the pump body, the outer circumference of the bearing being pressed into the pump housing until fully seated.
By inspection, the shaft of my new power steering pump displayed no end float at all. It turned smoothly and with purpose, but there was no end float, not even a hint. Therefore the end float is not designed into the pump, rather it is a consequence of something else. Given that the bearing is pressed fully home onto the shaft, end float cannot occur unless the bearing's outer circumference is allowed to move with respect to the pump housing in which it resides. Considerable wear within the bearing surfaces could also see shaft end float being exhibited.
So, given that the new pump that I possess exhibits no axial movement of the shaft (end float), does that mean that pumps with end float do so through wear or from manufacturing tolerances and if so where is the movement located? The way that I see it, the shaft cannot move unless there is axial movement at one point or another with the bearing. I don't see the bearing moving with respect to the housing, but wear once it occurs within the bearing will certainly allow a degree of movement to exist. Given that the design of the bearing precludes any adjustment, I am inclined to suggest that the axial movement is located within the bearing, either possibly at the time of manufacture, or more likely through wear. To add weight to this argument, the sealed bearings within certain types of bicycle headsets feature a tapered split sleeve which is tightened against to remove play within the bearing as it occurs. Here there is no such adjustment allowed.
I will also note that the pulley locates on the shaft via a key, and is thus secured into the shaft by a bolt. The pulley is assumed not to be moving independent of the shaft.
Therefore the axial movement (end float) within the shaft is directly attributable to the bearing, its design, manufacturing tolerance and or wear. In addition, the means of retention of the vane carrier on the shaft means that shaft axial movement and the efficient operation of the vane carrier and as such the pump are entirely independent.
Ron.
So it stands to reason that when I get around to fitting power steering to one of my TCs, I could use a V8 pump with a flipped vane and mount it the other way 'round, possibly in a similar manner to the AC compressor with a separate tensioner pulley. That just leaves the question of where to stick the reservoir.
