Date:         Tue, 31 Jan 2006 13:48:28 -0500
Reply-To:     Phil Zimmerman <philzimm1@OBERON.ARK.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Phil Zimmerman <philzimm1@OBERON.ARK.COM>
Subject:      Re: 6 broken alternator in 3 yrs - possible root cause

On Sun, 29 Jan 2006 09:45:34 -0700, Larry Chase <roadguy@ROADHAUS.COM> wrote:

>Volks,
>
>Alernator Brackets and Alernators.
>
>Yesterday when I installed a new alternator ... I found that I also had
>another "broken alternator
>bracket".

>
>I'm wondering if perhaps this is what may have caused 6 brackets to break in
>3 years.
>
>What are your thoughts?


 From:    philzimm1@oberon.ark.com
 Subject:  Re: 6 broken alternator in 3 yrs - possible root cause
 Date:  January 31, 2006 10:41:39 AM PST
 To:    roadguy@roadhaus.com

Lar,

I believe Ben, the mechanic I rented shop-space from can provide some or partial explanation to
your reoccurring broken alt. bracket problem.

First, assuming that the six brackets have broken on at least three 'different' engine blocks,
eliminating an uneven mounting surface on the engine block. VW had problems with this on the
1.9 and diesel engine blocks...

Your obs. and hypoth. for the most recent breakage certainly would contribute to a bracket failure.
Were the other five brackets and alternator pivot-bosses similarly miss-matched?

Now my speculation: This is the roadhaus.... each day, drawing mega-amps from the batteries and
requiring mega-charging each and every day she is/was used. Charging two 55 amp/hr deep-
cycle batteries from 10.5-11.5 volts up to capacity takes mega-horsepower! How much Hp?

Ben (the mech mentioned above) built an alternator test-bench. Initially, he used a 1-1/2 Hp
electric motor to drive the alternators. With a 1-1/2 Hp motor turning the alternator under test, he
could only get about 20 amps out of a typical alternator before the electric drive motor stalled. He
then put a 5 Hp electric motor on the test-bench. Got about 40-50 amps out out this. Found a
three phase 10 Hp motor (we are talking some real Hp here). Was finally able to get 60-70 amps
charging out of a typical alternator with this set-up. FWIW I had my rig tested a few years ago. The
tech turned up the load on the alternator, as I kept the RPM's up at about 2,000. At 110 amps
out-put, the alternator was groaning, the drive-belt taught as a violin-string trying to turn the
darn thing. Scared the hell out of me! But, these alternators will out-put some serious amps!!

My point here: I assume you are utilizing the 90 Amp rated Bosch Alternator on your rig. The
amount of horsepower the alternator draws on start-up and during the initial phase of charging
the batteries is very significant. The bracket is put under extreme stress each time this takes
place. Done on a daily basis, I can see where the bracket would finally fail over time.

Not uncommon for high-out-put charging systems to have double or even triple drive-belts. Very
large mounting brackets and the like. Ever notice the "size" of the VW Air-conditioning
compressor mounting bracket? Yes, I know you have seen this bracket more times than you
wanted to! (but that is another story in itself) My point, that AC bracket is a major piece of metal
designed to take the long-term stresses that it sees in use. Now, "if only" the alternator bracket
was as substantial in size as the AC bracket.....

My best guess is you are using the charging system under 'sever-service' conditions and have
seen the results of this over time.

my 2 cents (CANADIAN)