1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

rigging up old tachometer

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Old Oct 15, 2006 | 09:05 PM
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From: un. k
rigging up old tachometer

I was going through all of my grandfather's old stuff in the garage at my grandma's and I managed to find a still intact Smiths Tachometer. Sure it only goes up to 60 x100 RPM, but its ******' old school pimp.

I think it might've come off of one of his MG's or Sprites, I dunno.

How would I go about installing this tachometer? I measured and it has a 12mm threaded input on the back. Could I use another tach's cable?

Anyone know anything about Smith Tachs? Google says they're electric.. huh
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Old Oct 15, 2006 | 09:13 PM
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From: Behind a workbench, repairing FC Electronics.
12mm threaded? That's gotta be mechanical then. Similar to the speedometer cable.

There're adapters where you can get the speed off of the Metering Oil Pump driveline, but that means you have to premix.
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Old Oct 15, 2006 | 09:14 PM
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make a clock out of it
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Old Oct 15, 2006 | 09:19 PM
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From: un. k
Originally Posted by Pele
12mm threaded? That's gotta be mechanical then. Similar to the speedometer cable.

There're adapters where you can get the speed off of the Metering Oil Pump driveline, but that means you have to premix.
I do already premix. I was planning on blocking off my OMP, but.. what is this you speak of?
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Old Oct 15, 2006 | 10:04 PM
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just to check here, it's not coax is it? it could have an electric pulse input.
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Old Oct 16, 2006 | 07:23 AM
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It's almost certainly mechanical...will require a cable being driven off a gear on the camshaft...oh wait a minute, we don't have a camshaft. Post pictures.

Rich
Attached Thumbnails rigging up old tachometer-64mgb_20020120_03.jpg  
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Old Oct 16, 2006 | 10:07 AM
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From: un. k
hmmm, actually, thinking about it

it might be coaxial

I'll post up some pics when I get home from class
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Old Oct 16, 2006 | 02:07 PM
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From: un. k
Nope, its definately mechanical.

1. How do I go about using the OMP to hook it up to see if its accurate for use?

or

2. Should I try putting the innards of a cheap electric tach in it?

pics will be scanned shortly (yeah, I'm just placing it on a scanner)
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Old Oct 16, 2006 | 04:46 PM
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The best way to go about this is to just discard the tach. To get a mechanical tach to work right would take a lot of work, and hardly be worth the time and money. As for putting the workings of a cheap electrical tach into it, you might as well just use the cheap tach you buy. The scale the new tach would use is likely different than the ones on the tach you have, meaning it wouldn't read right.
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Old Oct 16, 2006 | 04:59 PM
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haha dude, why bother? always trying to be innovative just get a tach thatll actually work
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Old Oct 16, 2006 | 05:03 PM
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From: un. k
You'll see!

You'll ALL SEE!

I found a website that actually takes INTERNET SERIOUSLY!

No really, I'm taking up the mechanical to electric conversion: http://www.britishcarforum.com/lore/...ment.php?id=12

And I've already found a donor tach with the same 270* sweep and 6k RPM range. AWESOME!
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Old Oct 18, 2006 | 07:10 PM
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From: un. k
Here is a pic of the tach I managed to hunt down with the part number.

Apparently its from a Bugeye Sprite I. So its almost 50 years old. Yes I have no problems converting a $200 historical tachometer for use in my RX-7.

And its getting the guts from this tach: An ISSPRO I managed to get new on ebay for $30 as opposed to $120 from http://egauges.com/vdo_ind.asp?Type=...EVA-R&PN=R5591

Yes I have no problems ripping apart a brand new tachometer.

And its going on the passenger side of the dashboard, near the a-pillar. I think the passengers should have a tach to watch, too! It'll be fun freaking them out.
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Old Oct 18, 2006 | 07:24 PM
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From: Wheeling WV
That thing looks really nice, will you mount it in the usual dash location or someplace more showy, like above the clock?
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Old Oct 18, 2006 | 07:34 PM
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From: un. k
read the line right above your post, Zephy
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Old Oct 18, 2006 | 07:43 PM
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From: Wheeling WV
I'm sorry wasn't paying attention to anything under the picture, doesnt sound like a bad idea, I have yet to see that done on another car.
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Old Oct 18, 2006 | 07:44 PM
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From: un. k
If I don't screw up the conversion, its going to be pretty badass.
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