2-groove pulley for power steering conversion: why is it needed?

[S11A]

Going the P38 route and collecting the parts needed. Have a Saginaw canned ham type PS pump on the way.

I saw on TeriAnn's page that a 2-groove engine main pulley is needed but could not figure out why. Is it because the existing pulleys would not line up with the new PS one? Is it possible to align them since the bracket for the PS pump needs to be custom built any way? There is a lot of room above the alternator so I am guessing a custom bracket could be fabbed to position it on the same plane with the others.

Or or is it because you can't find a long enough belt to wrap all of the engine pulley, water pump pulley, alternator pulley, plus the PS pump pulley? So need to leave the existing pulleys and belt alone and just do a separate belt for the PS pump only?

Or other reason?

[SafeAirOne]

I saw on TeriAnn's page that a 2-groove engine main pulley is needed but could not figure out why. Is it because the existing pulleys would not line up with the new PS one?

Or or is it because you can't find a long enough belt to wrap all of the engine pulley, water pump pulley, alternator pulley, plus the PS pump pulley?

Or other reason?

As you noted, you can mount the PS pump so the pulley is in line with the other pulleys, and they can manufacture a v-belt 2 miles long if they want.

The more likely reason for a 2nd pulley is because the more you wrap the v belt around a pulley, the more torque the belt can apply to the pulley before it begins to slip. If your belt contact angle on a pulley is small (the belt just barely bends around the pulley before moving on to the next pulley), that lightly-engaged pulley will readily slip. In a multiple accessory arrangement, such as when you add a PS pump, you might not be able to get the belt to wrap around the pulley(s) sufficiently to drive the accessory(ies), hence the 2nd pulley.


If you really want to know the math:


From www.learneasy.com:

...There is a further complication with belts - they might slip if there is too much torque on a small pulley and not enough friction. This needs to be checked.



Where:
Ft = tension on tight side
Fs = Tension on slack side
e = 2.71828
mu = Coefficient of friction
theta = angle of contact between belt and pulley
beta = half the wedge angle (typical wedge angle is 40 degs, so use 20 degs)

[S11A]

Great explanation, thanks Mark.

If Les is reading, I am now in the market for a 2-groove main pulley ;-)

[Les Parker]

Thanks for the thought !
NLA from Landrover, though Ike is showing stock, Landrover # is ERC5348.

[S11A]

Thanks Les. Ordered from Ike.

[S11A]

What size socket is needed? Googling turned up 1-5/8 and 1-11/16 as the most common answers but I did see others...

Also, I should probably replace the key - what size is that and do our hosts stock?

Edit: yes- http://www.roversnorth.com/ProductDesc.aspx?code=235770

The engine is a 2.25 diesel, 3 main.