Conference vmsnet::car$note:carbuffs

    Has anyone actually taken an old AC Speedometer apart?  I have gotten
    quotes of $100.+ to rebuild mine.  Sounds like a lot.  I was surprised
    when I removed it from the dash what a simple little thing it is.  I
    believe the only problem is the 30 year old grease has turned to dust. 
    The bushing on the input does not feel sloppy or anything, so I'm
    figuring if I just take it apart, clean it, and relube it, all should
    be fine.  The problem is, the needle has to come out to remove the face
    to get at the screws in the head, but there is no apparent way to
    remove the needle!  There has got to be some little trick to this that
    I'm missing.  Does anyone know what that might be?
    
    Dave

    
    	I seem to recall reading the procedure in a magazine recently.
    
    	Darn, what was the name of it?  If I remember I'll let you know
    	and you can pick up a copy.
    

    I found the trick.  The needle is fastened (permanantly) to a little
    sleeve, which is then press fit onto the shaft.  It comes apart with a
    little careful work.  I got the whole unit apart.  I never realized
    what a simple device a speedometer is.  The problem was just as I
    thought, the lube was all dried out.  I cleaned everything in alcohol
    then put it back together with some molybdenum disulfide grease, and it
    looks great.  I bench tested it using an electric drill to spin it.  It
    is now nice and quiet, and the needle moves smoothly like it should.  
    Looks like I just saved myself $100.00.
    
    Dave

    The real test will be to see if it is still calibrated....
    
    Make sure you test it before you hit the next speed trap.
    
    Chris
    

Re: <<< Note 302.128 by LEFTY::CWILLIAMS "CD or not CD, that's the question" >>>

>>    The real test will be to see if it is still calibrated....

The easiest way to do this is with a GPS (Global Positioning System) that shows
speed; it will show your speed accurately within a couple of miles per hour...

                             Roger

>>                      <<< Note 302.129 by PEAKS::OAKEY >>>

>>Re: <<< Note 302.128 by LEFTY::CWILLIAMS "CD or not CD, that's the question" >>>

>> >>    The real test will be to see if it is still calibrated....

>>The easiest way to do this is with a GPS (Global Positioning System) that
>>shows speed; it will show your speed accurately within a couple of miles
>>per hour...

>>                             Roger

	Or even simpler, zip by an officer and his trusty radar. He will
 write down your speed on a little piece of paper so you do not forget. ;-) ;-)

	Norm

 

    Actually, I still need a speedometer drive.  The one that is in the car
    now is the wrong one for the gears in the rear end.  I figured after I
    change the drive, I can do a quick calibration check by comparing the
    speedo and the tach.  I calculated that the engine should be turning
    3341 RPM at 65 MPH.  If the two guages are close to being in
    calibration, I should know right away by whether or not these numbers
    match up.
    
    Dave

A speedometer is calibrated by degaussing the assembly then re-magnetizing 
the pole piece to a specific strength.

The air gap and return spring tension are checked/adjusted and the assembly 
is bench tested.

1000 rpm should indicate 60 mph, 500 rpm = 30 mph, etc.