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Re: Speedometer calibration

To: Joseph.DeLuca@wl.com
Subject: Re: Speedometer calibration
From: harris_simmons@juno.com (Charles A Harris)
Date: Tue, 21 Jul 1998 10:05:49 -0500
Having thought about all this interesting and exciting worry about the
accuracy of our speedometers, I think that I might fix Matilda's.  I
remember it breaking its drive cable in '82 on the way to Washington D.
C.  As the speedometer is primarily a social device, and not monitoring
any engine function, so it is not really that important.  In serious
rallying you would not rely on it, and in most club rally situations a
good navigator can certainly overcome the need for it.  Now the oil gage
is important, but a working speedometer would be cute.
Chuck Harris
Waltzing with Matilda at light speed
On Tue, 21 Jul 1998 08:07:49 -0400 "DeLuca, Joseph"
<Joseph.DeLuca@wl.com> writes:
>
>
>I agree with getting a second opinion about the speedo calibration,
>but as a old-time rallyist I wouldn't trust anything other than a 
>stopwatch and a measured mile.
>
>My favorite method is to find a fresh stretch of highway.  One that
>hasn't been torn up too much, because they tend to rearrange the 
>mileage markers when they do construction.
>
>Motor along at exactly 60 mph which translates to one minute per mile.
>Measure the time.  If it takes you 66 seconds to travel one mile
>(which ideally should be traversed in 60 seconds) then calculate 
>66/60 x 100 = 110% (as an example).
>
>Try this at several different mileposts to get an average because,
>as I said, the highway dept (and intoxicated drivers) move the markers
>around a bit.   
>
>For the best accuracy I prefer to visit the local cop shop and ask
>where THEY calibrate the police car speedos.  
>They usually have a measured mile somewhere in town.  The only 
>downside is that they often start to ask you a lot of questions. 
>They think you want to organize drag racing there or something, and 
>if you let slip that you have a "sports car" you're in for it.  
>Tell them you're training for the Olympics (although with my frame 
>that's a stretch).
>
>If the measured mile is in town and you can't do 60 mph conveniently, 
>the factor for 30 mph is 120 seconds per mile, and for 45 mph it's 
>90 seconds.
>
>Happy Motoring
>
>Joe DeLuca
>Sparta, NJ
>'62 yellow 4/4
>
> 
>
>-----Original Message-----
>From: John T. Blair [mailto:jblair@exis.net]
>Sent: Monday, July 20, 1998 5:23 PM
>To: morgans@Autox.Team.Net
>Subject: Re: Speedometer calibration
>
>
>At 06:05 PM 7/19/98 EDT, you wrote:
>
>>My neighbour and I were exercising our Morgans on the highway last 
>week
>>at what seemed to me to be a legitimate speed when we came upon a 
>>gendarme parked on the median.  My friend slowed dramatically.  
>>Afterwards I asked why he had slowed when we were doing only 65.  "We 
>
>>were going close to 80" he replied. I had always thought my speedo 
>was 
>>reasonably accurate.....
>
>John,
>
>  Are you sure that it was your speedo that was off?  Before you go 
>nuts
>trying to get your guage calibrated, take another, late model car, out 
>
>and chase it.  Instruct the driver of the late model car to signal you 
>
>with 5 fingers and then a fist at 50 mph.  Then when you wave back at 
>him, have him move up to 55.  Again signal you with 5 fingers flashed 
>2
>times.  Repeat this procedure for 60 - 1 finger held horizontally and 
>a
>fist, and 65.  
>
>This will let you know that it was YOUR speed o that was off and not
>the other Morgan you were chasing.
>
>John
>
>John T. Blair  WA4OHZ          email:  jblair@exis.net
>Va. Beach, Va                  Phone:  (757) 495-8229
>
>              48 TR1800    65 Morgan 4/4 Series V
>71 Saab Sonett III     75 Bricklin SV1     77 Spitfire
>
>


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