Technical 12 volt small tach

Is it off at a consistent difference though the RPM range? If it is, it just needs the needle moved to compensate for the error.

 

Yes, I would say at the 6 cylinder setting the error is consistent





I will see if I can reposition the needle as you two have suggested and retest
Who knows, maybe I can get this 12 dollar tach to actually work.

 

Got back on this project

Went with a 0 to 6 k autometer, instead of the 0 to 8 k I tried earlier
My wife adapted the gauge face using photos shop.








This auto meter is more accurate than the tach I tried earlier.
The bottom middle scale is 6 cylinder

I still need to make a back housing for it but that should be easy. This gauge is a little bigger in diameter.

She was able to copy the GM font (numbers and R.P.M.) and place it on the auto meter gauge face used in the center.
Did a pretty good job matching the center color.

 

nice job, very classy!

 

She did a very good job, it appears. If you don't tell, some people will think it was factory.

 

Tell wife really nice job on the tach face. Glad you got it to work. Nice find on the hypo needle shafts. Didn't think of that. Did you super-glue or epoxy the needle to the motor shaft? I'd think road vibration would work it loose quickly. Maybe not... .

You might find you need to make some adjustment on the resistance that the 4/6/8 circuit uses. I'd suggest a potentiometer for trial & error testing. Then check the pots' resistance, & get the correct resistor & solder it in. If you can see the resistors by the #-of-cylinders switch, & can read them, that'll get you close to start. As far as electronic "stuff" goes, beyond this, I'd need help. FWIW, I've found that the OEM tachs aren't very accurate, either. A couple of Ford tachs I pulled from the boneyard, were only close, at best. Didn't think about using a pot back then. Would appreciate you keeping on posting results. TIA. Marcus...

 

Very cool. Your forethought made the job turn out well, and low dollar to boot! A lot more involved than buying a tach and using the supplied hose clamp on the column. Looks like it's been there since 1950.

 

Wow what a good idea....I have my og gauges waiting for their turn to one day go back into the truck. I wanted to convert them to electronic to get rid of the hard lines but still look factory. Didnt take the time yet so just threw in some dolphins. I have never even thought of incorporating a tach the way you did....

Also cool to get the wife involved, mine loves the truck but hasnt really had an opportunity to offer any help (other than the "here hold this a second").

 

thanks for the feed back, I appreciate it

for this test the needle is just pressed on. when its finally done ill use some adhesive for the needle.
The shaft extension can be glued on with super glue, but the needle will have to be able to pop off for any work needed in the cluster.

I don't think ill be able to make any fine adjustments, but thanks for the tips.

Luckily for me my wife knows how to use Photoshop, but if I didn't have that option a guy could just use dry transfers.

 

Have not been able to install the new cluster in the truck yet


Here is some info on an even smaller tach in case someone wants to try something similar


It's 12 volt 0 to 7 k
Once disassembled its just over a inch deep and about 2 inch in diameter




Something like that might be able it fit inside some clusters without having to extend the needle



The tack I decided to use is 0-6 k, and a wider sweep, although its a bit bulky the range and sweep fits better for my stovebolt.