Re: Aluminum battery racks?

["Tom Peterson" <topper@infowest.com>]

How come the DC-3 (C-47) has lasted so long?
----- Original Message -----
From: "Peter VanDerWal" <peterv@peoplepc.com>
To: <ev@listproc.sjsu.edu>
Sent: Thursday, March 28, 2002 11:28 PM
Subject: Re: Aluminum battery racks?


> > >I'm working on a Bradley GT (not GTE) conversion and I'm getting
> > >ready to do the detail design of my battery rack. I've looked at the
> > >rack on the GTE which is basically a subframe running under the
> > >entire pan. That has to be heavy. I've never heard of anyone making
> > >racks out of anything but steel. Is there a reason Aluminum can't be
> > >used? There's an Aluminum scrap place close to me that sells it for
> > >$3/lb. What about the acid? These will be flooded batteries not
> > >sealed. Steel would be easier as far as the welding goes but if I
> > >can loose some weight...
> > >
> > >thanks for the advice,
> > >Steve
> >
> > There's nothing that makes it inherently a bad material, but it's a
> > b*tch to weld and rivet holes can loosen through vibration over time.
> > It can also stress fracture if the stresses are not distributed
> > evenly. Acid has less effect on aluminum than it does on steel, IIRC.
>
> The main problem with aluminum is that by the time you over-engineer it
> enough to overcome it's short falls, it ends up weighing as much or more
> than steel (in this application).
>
> Remember you are probably support 1/2 ton of lead here.  Aluminum does not
> handle repetitive stress (like bumps in the road) very well.  With steel
as
> long as the stress is below the bending force it can handle it
indefinitely
> (it's springy) aluminum on the other had fatigues and will eventually
break.
>
> There is no way to avoid this, the only solution is to use enough aluminum
> that the stress levels will be comparatively low enough that the battery
box
> will outlast the rest of the vehicle.  Or you can use steel supports to
> handle the stress and only use the aluminum as a container (not a battery
> support), but this complicated AND heavy.
>
> If your goal is light weight, use steel sheet metal that is thick enough
to
> be self supporting and weld it into the pan.  This way the battery box
will
> help stiffen the pan and the pan will help support the battery box.
Win/Win
> situation.
>
>