Yes I finally recevied your response....I will have to disagree with your
assement of the thermal proporties of the metal used.
I have rebuilt several Water Pumps, generators, and altenators over the
years which all required a Press fit of either the Pully, or the impeller.
Machine shops regularly will use heat and cold to aid in the reassembly of the
press fit parts. When Heat is uniformally applied to the part with the hole,
the dimension of the holes diameter "Will" increase. And when you freeze the
shaft part, it's outside diameter will decrease. It's the nature of things.
Very Very few things react the other way, and I can only think of one metal the
does this and it's that "Memory metal" (can't remember the actual name.) But
Cars and engines don't contain any of this material.
Different metals have different expansion rate of course. Aluminum being
one of the most active in this property. The reassembly of the parts is Much
easier when this is done, and they won't slip once their tempratures equalize.
Disassembly can be done this way as well, but it is more dificult. I have
normally submersed the inner parts in Ice cold water, while Applying torch heat
to the out (Hub) part. Makes disassembly much easier, and greatly reduces the
interferenc wear associated with just pressing them in and out, which will wear
the fit eventually causing slip.
When I built my Last Drag Bike years ago. It needed to be bored WAY out,
and new cast iron sleeves installed. Machine shop did the boring the press fit
tollerence for the sleeves. I then put cylender block in the oven at 275
degrees, and the sleeves in the freezer. When it was time, The sleeves droped
right in the machined holes. As the blocked cooled and the sleeves heated up,
it was a Locked tight fit. Bike ran for 11 years with out breaking even once.
Just my thoughts. Sorry so long.
Rich
-----Original Message-----
From: Steve Laifman <Laifman@Flash.Net>
To: Rich Atherton <gumby@connectexpress.com>
Cc: Fraser,Ron <Ron_Fraser@xn.xerox.com>; tigers@autox.team.net
<tigers@autox.team.net>
Date: Sunday, May 24, 1998 4:22 PM
Subject: Re: FW: Aluminum Water Pump
>
>
>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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