[Healeys] Bouncing Speedometer

[Bob Spidell]

It so happens I've been studying/working on/swearing at my BJ8's speedometer extensively for the last few years (got 
tired of dropping $200 at the speedo shop).  I'm not a hexpert, but I've learned a lot.

If the bounce is 'rhythmic;' that is, the needle is steady then pops at an even period--particularly when the odometer 
or tripmeter increments--it's probably a cracked or stripped odometer or tripmeter drive gear, respectively.

If it's more or less random--and since you have a fresh cable and angle drive--it's probably due to some resistance in 
the mechanism.  There is a surprising (to me) amount of resistance to the cable even in a properly functioning speedo.  
Anything that adds to that resistance will cause the cable to wind up slightly, then when you're past the resistance the 
cable snaps back and bingo--a bounce.

Remove the cable at the back of the speedo, insert a small screwdriver and turn it (you can do this with the speedo in 
the car if you're a contortionist).  It should turn smoothly through 360deg--if it binds at all you'll need to pull it 
out and inspect the guts.  There's no mystery--no 'jeweled bearings' etc.--just a small shaft that looks like a 
miniature camshaft that drives the magnet carrier.  The magnet pulls the drag cup, which turns the needle.  The odometer 
and tripmeter are driven by two gears off a large spiral gear on the shaft.

I don't want to start a debate on the best lube for the cable--I use silicone oil; graphite is good but messy, and light 
grease is OK but might gunk up over time.  Dry is probably just fine, too.

I've attached a doc that might help.

Bob


On 5/1/2011 6:51 AM, Ron Ray wrote: ..

-- 
*******************************************************************
Bob Spidell           San Jose, CA            bspidell at comcast.net

*******************************************************************

[demime 1.01d removed an attachment of type application/pdf which had a name of Repairing Speedo-2002.pdf]