Date: Thu, 31 Jan 2002 21:48:02 -0500
Reply-To: David Beierl <dbeierl@ATTGLOBAL.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: David Beierl <dbeierl@ATTGLOBAL.NET>
Subject: Re: Red light rev(the Jolly guy from Rhode Island)
In-Reply-To: <20020131231420.36587.qmail@web14706.mail.yahoo.com>
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At 06:14 PM 1/31/2002, gary hradek wrote:
> Might not this deliberate design choice by VW be
>to prevent drag on the starter motor from the
>alternator during start up? Could make the
>difference in those cold Rhode Island winters as you
>crank away? "Better to light a red light than to
>curse a nonstarter" gary
Might very well. Or it might have been they had a huge surplus of 150-ohm
resistors left over from the V-2 program. Or they asked Bosch "what do we
need to excite your alternator?" and Bosch said "100 ma." Or perhaps they
dreamed it. As someone said here lately, I long ago stopped assuming that
their engineering decisions made sense.
david
ps -- I'm reminded of quite some time ago when I was working for one of the
former members of Intereissengruppen (sp?) Farbenindustrie, the Badische
Anilin und Soda Fabrik -- making floppy disk drives. The Germans had a
design using an amazingly wonderful ironless-rotor motor that cost twelve
bucks in volume, driven by a single-source Thompson-CSF control chip that
cost about three. It had a big heat sink on the back, and used back-EMF
from the motor to deduce the speed and control it to the specified 300 rpm
at the drive spindle. They needed +/- three per cent, and were just barely
achieving it with this gold-plated nightmare. Meanwhile the Americans were
beating their pants off with a two-dollar motor developed for eight-track
car players, controlled by a thirty-cent ($1?) Cherry Semiconductor chip
that didn't even run warm, using a tachometer output from the motor to get
+/- one per cent.
It did occur to them that something along the latter lines might be
possible, and they prototyped a drive in Germany and sent the project over
here to finish. I have no idea why, since I was the only electronics guy
there and I was just a tech with aptitude. Anyway, I took it on (and
basically copied the circuit Shugart was using) -- but the torque was just
barely enough to bring the disk up to speed, and sometimes not quite. I
puzzled and researched specs and tried to get hold of a torque tester
(which they had in the plant down the road where they made the floppy
disks, to test them). Never did get hold of it up though, because I soon
figured out that the motor they were using was supposed to be driven by 24
volts. I told the boss who said "Rubbish!" and I had to get the
sales-critters from the motor company to confirm that the glorious German
engineers had spent six months of development with the wrong
motor. Fortunately the right one was mechanically alike, so that part was
ok. And "my" circuit actually did get built by Canon making drives under
license from BASF.
It was still a lousy drive, though. The single thing it had going for it
was that it was only 2/3 the regular height, and it was the only drive that
small on the market -- until somebody at Tandon figured out how to make a
skinny 8-inch drive by using a cam mechanism to engage the drive puck,
operated by a turn-handle on the front of the drive. Six months later the
whole industry was making half-high and 1/3-high drives and that was it for
BASF drives. BTW, they made lousy floppy disks, too, couldn't get their
coating process tweaked.
I won't tell you about their VCR that used a fixed head and a little
cartridge that ran about 60 inches-per-second and took two minutes or so to
get to the end of the tape -- then stop and step the head up one track and
start back in the other direction. No complicated spinning heads, no
Beta-VHS wars. They figured people wouldn't mind a 150-millisecond dropout
every couple minutes...or was it 200 ms? Dunno if they sold any in
Germany; they never brought it over here.
--
David Beierl - Providence, RI
http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage"
'85 GL "Poor Relation"
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