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Re: FW: Aluminum Water Pump

To: Rich Atherton <gumby@connectexpress.com>
Subject: Re: FW: Aluminum Water Pump
From: Steve Laifman <Laifman@Flash.Net>
Date: Sun, 24 May 1998 16:53:28 +0100

Rich Atherton wrote:

> Couldn't you heat the hub and cool the shaft to retain the friction fit.  if 
>you
> go far enough, they should just slip together, or apart with a little effort.
> Its how they put in cylinder sleeves!
>
> Rich

Rich,

This is the third time I've tried to rply to your question.  Every time the
computer freezes and I've got to reboot, losing the message.  Maybe this 
message is
not meant to be delivered, and I'm just not listening.

Anyway,  The "friction" fit (or intereference fit) is a standard industrial
practice to join a shaft to a hole without resorting to woodruff keys, set 
screws,
locking nuts, drive pines, and other more costly solutions.  The shaft diameter
gets smaller and the hole gets larger as a function of their themal expansion
material properties.  0.005 to 0.007 interefernece is comon for light torque
applictations.

Problem is that after many, or poor, rebuilding this interference gets less as 
the
shaft wears, and/or the hub wears.  A single room temperature movement of a new
pump to a new location, providing you don't over-shoot and have to back up, 
usually
does not cause a problem with a good part.  A few rebuilds, or pump swaps later 
may
be a different story.

Re-builders are known to use larger shafts for re-builds for the impeller fit.
Sometimes they are good enough to change the bearings and seals too match.
Sometimes they are not.

I've experienced all variations on this theme, so make sure you know who you are
dealing with.  A hard chrome plating on the shaft will increase it's diameter a 
few
thousandths, and make it almost impervious to wear on the sealing surfaces, and
bearing surfaces, as well as the hub.

If you want increased flow performance, and can stand the cost, look at that
aluminum Hi-Po Edelbrock makes for the 289 "K" Hi-Po
motor.  It is very close to the factory specs, and close enough to the TE/AE
numbers to make adjustment a simple matter.  Using their hub and a new 6 blade 
Ford
Canadian fan is a bolt on (with a diameter change for the steering rack), or you
can use your own hub pressed on by a pro (after measuring), or you can use the
lawnmower blade idea - very clever. I'm not so sure that the four bolts can't
center the fan accurately, with some post-assembly verification.

Steve

Let's see if it gets through this time.
{8->

--
Steve Laifman         < One first kiss,       >
B9472289              < one first love, and   >
                      < one first win, is all >
                      < you get in this life. >


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