[Land-speed] Fw: Magnesium

Ed Weldon 23.weldon at comcast.net
Sun Jun 15 19:39:59 MDT 2008


Fwd to list with edits
----- Original Message ----- 
From: "Ed Weldon" <23.weldon at comcast.net>
To: "Doug Odom" <dlodom at charter.net>; <sardatech at yahoo.com>;
<land-speed at autox.team.net>
Sent: Sunday, June 15, 2008 6:38 PM
Subject: Re: [Land-speed] Magnesium


> Doug -- You say the Mag QC's grow 3 times as much as the aluminum ones.
> Right out of the handbooks the average thermal expansion coefficient of
> AZ63A is 15, Aluminum 356 is 12.  That's only 25%.  Tom's average
> temperature rise (from say 72F) on the magnesium is about 35% more than
the
> aluminum.  Your 3 times "rule of thumb", which I'm sure comes from a load
of
> experience suggests that something else is going on.  My first guess would
> be that too much heat is going into the magnesium housings either in the
> initial oven heating or in the actual track conditions or both. So the
> magnesium is doing its yield thing.  The real tip off would be to mike the
> pinion bearing bores and record the readings before each assembly.  If
they
> grow you'll know press fits might too much.  But then that might be
> unavoidable.
> Some extra cooling may be in order but for sure the hardware has to be
able
> to live under the track conditions.  Time you add that extra hardware
you'd
> have more weight than the difference between the aluminum and the mag
> housings.  And departing from conventional wisdom on setting up the
preload
> and bearing press fit is a potentially expensive test program. Sounds to
me
> like the easiest answer is to off the mag quick change housing and replace
> it with aluminum.  If the extra weight is a problem put the driver on a
> diet.  Could probably do well with a 10 pound weight loss.
> Yeah, Tom.......I'm not a stakeholder here; just a source of background
> noise....
> Ed
>
> ----- Original Message ----- 
> From: "Doug Odom" <dlodom at charter.net>
> To: <sardatech at yahoo.com>; <land-speed at autox.team.net>
> Sent: Sunday, June 15, 2008 12:11 PM
> Subject: Re: [Land-speed] Magnesium
>
>
> > Tom, What brand are they? Are they Almag or Aluminum? I do know that I
set
> > up the Mag much tighter than the Aluminum ones. The Mag ones grow about
3
> > times as much and need more preload.  Doug Odom in big ditch


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