Ferrari Mailing List: Re: Vintage LM Race vintage tachymeters

[LS (lashdeep]

On older cars, I've only seen tachs that read a signal off of a rotating/timed 
engine component. Typically, this would be a distributor or a camshaft. If the 
tach jumps, it would have to mean a voltage problem with either the "generator" 
on the engine or in the actual gauge itself. 

I did ask a friend who restores old Jags to add thoughts. Apparently, the old 
XK140s used a cable that ran off of the camshaft. This cable led to the gauge 
which contained a plastic hub that positioned the needle. He's seen these 
cables get contaminated with oil leaking from the cam seal. This oil creates a 
problem in the hub mechanism at the gauge and can cause those erratic tach 
movements.

So, in short...who knows!?!

It would have to depend on the car and what type of tach it uses...

What car were we talking about here?

LS 

----- Original Message ----
From: Doug and Terri Anderson <dnt [at] dock.net>
To: LS <lashdeep [at] yahoo.com>
Cc: The FerrariList <ferrari [at] ferrarilist.com>
Sent: Thursday, January 4, 2007 9:10:39 AM
Subject: Re: [Ferrari] Vintage LM Race vintage tachymeters


Done on purpose and hard to duplicate by instrument restorers.  Perhaps the 
old smooth tachs had a tendency to fly way past the actual rpm and those 
that stuttered were closer to actual engine rpm.  Just a guess.  Built in 
damper.
DOUG

----- Original Message ----- 
From: "Paul Bennett" <pbennett [at] macnet.com>
To: "DOUG" <dnt [at] dock.net>
Cc: "The FerrariList" <ferrari [at] ferrarilist.com>
Sent: Wednesday, January 03, 2007 10:03 PM
Subject: [Ferrari] Vintage LM Race vintage tachymeters


>I noticed in many cockpit shots of the older cars, the tachymeters
> didn't increase smoothly as now, but stepped up and down in
> large rpm increments.  Like perhaps 3.0k > 3.5k > 4.0k >4.5k
>
> Any idea of why the jerkiness?
>
>
>
> Great show...18 different race start/finish and view of the
> 'control room' which I'd not seen or heard of before.
>
>
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