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Re: Speedo revs/mile

To: jeyerman@ix.netcom.com
Subject: Re: Speedo revs/mile
From: Larry Paulick <larry.p@erols.com>
Date: Wed, 18 Oct 2000 10:06:15 -0400
Jan, if the price is right, sign me up for one.  Sounds neat.  About
time we bring the Tigers into the 21 century.

Larry

jeyerman@ix.netcom.com wrote:
> 
> Larry,
> 
> I am talking about a device that is completely independent of the 
>transmission-no cables, connections etc.  Technically it would be possible to 
>build such a device based solely on electronics.  Today you can buy a laser 
>tachometer-you simply aim it at anything spinning and you get an electronic 
>read out of the RPM.  That is the type of device I am talking about.  It would 
>actually be universal-it would fit any vehicle with a driveshaft.
> 
> Jan
> 
> Larry Paulick <larry.p@erols.com> wrote:
> > Jan, they do make a device that either reduces or advances the revs of
> the speedo, and is adjustable.  Many hot rods also have odd combinations
> of tires, trans, rear ends, and this allows for the adjustment.  With
> the toploader and T-5, you just go to your Ford dealer, and ask for a
> different gear for the end of the speedo cable.  They are usually
> identified by color, as in I want a blue one.
> 
> Larry
> 
> jeyerman@ix.netcom.com wrote:
> >
> > It would seem to me that this a very big market for an electronic 
>speedometer- a small magnet glued to the driveshaft and a pickup somewhere 
>near it-then an electronic speedo inside a Smith's case.  An adjustment 
>somewhere for rear axle ratio.  To bad I don't know how to do this!
> >
> > Jan
> >
> > Jay_Laifman@countrywide.com wrote:
> > > >Jay, after you give them the info from the speedo, what
> > >do they do, and is the speedo accurate over the entire
> > >range, and is so to what plus or minus mph?
> >
> > I just spoke to Mo-Ma.  She told me that if she used to 1040 gauge I have
> > (from a SIV Automatic), she could use a 41 tooth gear and get pretty close,
> > but not exact.  I may have to go to an external converter to get closer to
> > exact.
> >
> > The speedo is a completely different issue.  It is not fixed by gears.  I
> > know I am going to get corrected on this one.  But, this is as close as I
> > know - and as always, I'm willing to be corrected.  Attached to the head of
> > the cable is a flat disk with a magnet.  This disc fits in a flat metal
> > dish to which the needle is attached.  There is nothing connecting the dish
> > to the disk.  When the magnet on the cable spins, it creates a magnetic
> > force that lifts/turns the dish and the needle.  As the dish spins faster,
> > the force increases and turns the disc further.  In order to calibrate the
> > speedo then, they don't change gears, but change the amount of magnetism in
> > the dish or the plate or both.  There is also, I think, and adjustment to
> > the resistance against the plate.
> >
> > That being said, I believe there is an inherent inaccuracy in the speedo
> > needle such that it cannot be 100% accurate at all speeds.  You need to
> > pick what range you want to be most accurate, and live with the other
> > zones.  My driving takes me through a very long 45 mph speed trap.  But,
> > then 65 is always a concern.  I don't know how wide the band is of
> > accuracy.  I'll probably shoot for right in the middle of those two.
> >
> > Jay

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