Technical 12 volt small tach

I would like to try to incorporate a small tach in the center of my gauge cluster
1950 Chevy 3100

I have approx 1 3/8 space to fit something in the center

Is there a tach with guts small enough to fit?

I can open up the back of the housing so depth is not an issue,
just need a small diameter.







It would look something like this

I would color the faceplate and dial to match the existing gauges

This was. 2 inch amazon tach I tried but the guts were to big

 

Sorry, I can't help - but that's a cool idea. Hope you find one.

 

smallest aftermarket tach I've seen is about 2". Equus gauges. Or disassemble the tach, extend the shaft and install a short needle and renumber to fit your space

 

Modifying the shaft is an idea

I doubt kits are availiable for that?

 

That's such a good idea, but the smallest I have seen is 2"

 

i wonder if you could extend the shaft so the tach could be mounted behind those gauges and the face mount in front. just an idea.

 

Harbor Freight Tools has some really small gauges, a tach is one of them. Not anything I've bought, just something I've seen and looked at while there. I am Butch/56sedandelivery.

 

this is the tach I disassembled and tried last night
unfortunately I destroyed the spring coil while prying up the needle

A needle shaft extension should work, Just trying to figure out how to accomplish that.

The guts of that gauge were about 1/4 too big.

 

Before I'd try to modify a tach to be smaller I would quarter the original truck gauges. You can see they are just 4 gauges mounted in a cup which is already "Quartered" for you just enlarge the cup it won't be seen anyway. By the way, nice idea!

 

Ill check that out

But the gap on the outer edge provided the light

 

Made a little progress

I could not figure a way to to fit my trial tach in the housing so I mounted it to the back of the gauge cluster housing













Now just need to figure a way to extend the shaft of the tach
Not quite sure how to accomplish that.


I'm testing the fit up with a spare housing I have.

If I get this figured out I redo it with a better tach

 

Not sure iffen this would help, but a really good hobby shop (like, say, one catering to R/C planes, R/C cars, + especially HO cars - &/or maybe 1/32 & 1/24 th scale slot cars. Model trains might get you close, too. It's been awhile since I've been in one...) should have both brass & alum tubing. (One possibility is Auto World near South Bend IN. AFAIK, their main display-shop closed, but the guy is still in business, & may have a smaller store by now again. I think HO stuff, esp for scratch-building, may be your best bet.) That tubing could be soldered, epoxied, or maybe crimped (I don't like that idea) to extend the pointer shaft. Hmmm, maybe even a friend w/a hobby lathe could turn one out w/the needed threads (?) on each end. Or a serious watch repair guy, or maybe a decent jeweler? Kinda hard to guess, as I don't have the pieces in front of me. Another possibility would be some OEM tach. Big face, but some of the "innards" are pretty thin & kinda small - I think. This could have some interesting results. Long ago I pondered split-shafts for multi-level gauges, but never took it far enough to find out if it was practical.
FWIW, & good luck. .
Marcus...

 

Thanks
A small OEM tach would probably be best.
Google not much help



Your comments on the tube is interesting
I measured the shaft with a micrometer and ordered some stainless round tube.
http://www.amazon.com/Stainless-Steel-Hypodermic-Round-Tubing/dp/B003TFFC9M/ref=pd_rhf_eetyp_p_img_1

10 buck. Worth a try.

Even if I'm successful extending the needle shaft, I'm still not sure it will work. Might be to much drag on the little coil springs in the tach.

Thanks for the ideas

 

if extending it does not work, it looks like the "guts" are now small enough to fit if the center of the housing was cut out. just need to mount the face.

 

Great thinking outside the box.

 

Thank you
____________________


After the tach was broken down it still did not fit inside , but it was close

As I mentioned earlier this was a cheap tach I got off amazon, it was about 12 dollars and probably not very accurate. I thought I would use it as a test to see if it was possible to modify it to the AD gauge. If it doesn't work I'm not a lot of money, just time.

Here's a pic of the small coil springs mentioned earlier




A little help from my wife on the tach face. Matching the color,

 

I've had this idea for years and never took action . GOOD ON YOU MAN!!!!! Go for it! Be the Man. Congratulations on a great start!

Regards,

Cosmo

 

Thanks Cosmo
_______________________

I was able to extend the needle with the tubes I purchased.
Still mocking it up







Ran into a little snag on the first mock up
The needle would not return to zero, not sure what the hang up is

 

Cool project, looking good.

 

I love it!
Here's what I did, maybe it'll help you with your idea.

Technical - Gauges: How to make a "Vintage" Tachometer for a '47-53 Chevy Truck | The H.A.M.B.

 

Thanks for posting your tach
You did a great job, I may have to consider blowing out the back of the housing if this needle extension won't work.

 

finished the mock up

 

Nice job, have you tried it out yet?

 

Your video is one of the best ever posted on the H.A.M.B. Three generations of family and great music. Love it.

 

thanks for your comments on my video, I appreciate it

__________________________________________________

finished a bench test
the tach worked, I did this test with a cheap tach I got off amazon just to see if it was possible.
here is the test


The tach is not very accurate as I suspected, My idle is set at 450 rpm.
but I can take what I learned here and incorporate it to a better tach maybe a
Sunpro CP7906 Mini Super Tachometer II

I also added some turn signals lights

 

the tach calibration might be off from the added weight of extension for needle. i'm sure it's light but any weight could change it. killer idea!

 

Strangely it seems to be more accurate on the 4 cylinder setting


But still off

Ill apply what a learned here to a better tach. Maybe a 0 to 6 k mini will be better suited.

 

does the needle just need to be rotated?

 

Looks like 0 has a positive stop, you can see the coil resting against it in this pic


But there is a lock collar, I'm not sure if there is any adjustment there. Seem like the needle needs to be loaded more


The needle does move at idle, just dose not register correctly.