Changing tachometer rotation

I have to admit I'm not really knowledgeable on how an electronic tach works. Would it be possible to change the rotational direction of one? I'm thinking, of course, of a Miata I know there's no spring in there like there is on the speedo.

Learn me!

check here post number #12 is prob the most important http://mazdaroadster.net/showthread.php?8038-reversing-the-Miata-tach-rotation-Anyone-else-ever-thought-about-it

Mmm, like a Fiat X1/9?

Yeah, its called a 1:1 gear drive.

Not a mechanical tach, Kenny

I should have known to ask Adam. I was wondering if it would be as easy as changing polarity. Maybe I'll look into it a bit more and see if there's something that can be done to fix the non-linearity...

In reply to Keith Tanner:

No, you attach a (lightweight) gear to the original tach shaft, and use it to drive another gear with the tach needle mounted to its shaft.

you could possibly mod a reverse rotation speedo to work. like this http://www.autometer.com/cat_gaugedetail.aspx?gid=3368&sid=52

If its an electric tac, couldn't you just flip the positive and negative wires?

According to the link from MrChaos - yes, but it becomes very non-linear for some reason. I'll see if I can figure out why.

i don't get it? why would you want to have the tach move in the other direction?

Either electric or mechanical, if you do successfully reverse the rotation, won't the face of the tach be useless? I'm sure the calibration would be off as well.

Really stupid question: if the shaft for the tach needle can be accessed is there any reason it couldn't have a shaft brought out of the 'wrong' side then have a faceplate put over that? Might be worth gutting an old tach to see.

Nisonger carries reverse sweep aftermarket tachs. Maybe they can give some insight into how to or they can reverse the Miata tach?

http://www.nisonger.com/whats-new.htm

I understand rotating the tach so that redline is at the top.. but I do not get reversing the sweep. I have driven cars that have a reversed sweep on the tach.. was really distracting as it was so "off" and different from the other gages

I would give Redline Gauges a call. They do a lot of custom, one off stuff.

Curmudgeon wrote: Really stupid question: if the shaft for the tach needle can be accessed is there any reason it couldn't have a shaft brought out of the 'wrong' side then have a faceplate put over that? Might be worth gutting an old tach to see.

That would work.

It's for fun. If Cobras and GT40s can have counter-rotating gauges, why not a Miata? Gauge faces are the easy part.

I've already rotated my tach.