Mechanical Tach install

PostPost by: brettengelaz » Tue Jul 13, 1999 6:08 pm

I'm considering fitting a period (1968) Jones chronometric tach, but where
is the best location for the tach-drive? I've heard that the Titan dry-sump
pump
has anoption for a tach drive, but it's very far from the dash (Left-hook
car).
The Pegasus Racing catalog has a tach drive that can be fitted to the back
of the cam, after appropriate machining, but I'm not too keen on modifying
the head if I don't have to..They also have a crank shaft pick-up that might
work too...So, who out there has fitted a mechanical tach, and how did
you do it?
----------------------------------------------------------------------------
--------
Brett Engel PSO Engineer
Cisco Professional Services
(602)-912-1852 [email protected]
Cisco Systems Suite 120
2390 E Camelback Rd Phoenix, AZ 85284
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PostPost by: paul_adamson » Tue Jul 13, 1999 8:07 pm

The main question is .... why?
I'm sure there must be ways of improving the accuracy of the original tach?

----- Original Message -----
From: bengel <[email protected]>
Sent: 13 July 1999 19:08
Subject: [lotuselan] Mechanical Tach install on S3 Elan








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PostPost by: abstamaria » Wed Jul 14, 1999 6:51 pm

Brett,

I considered the same option before but gave up because of the complexity.
Why not install one of the "period-style" electronic tachometers. Stack
makes one.

Regards,

Andres
Manila







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PostPost by: ozone.breath » Wed Jul 14, 1999 8:02 pm

Brett,
I didn't realize that the Jones/Motorola tachs are chronos.
Are they all like that, or just the "vintage" ones? I've
never had one.

That is very Interesting. Do they have the "ratcheting"
motion, similar to a Smiths chrono?

My vote goes with the Titan oil pump location, if you are
going dry sump. Sounds like a clean installation.

Regards,
Erik Berg
Los Angeles






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PostPost by: brettengelaz » Thu Jul 15, 1999 10:49 pm

Thanks for all the input on the Tach install. The reason I am leaning
toward the mechanical tach is due to the high accuracy, simplicity
(no electrical req's). Yeah, I use mechanical water temp, oil temp/press.
gagues too.....

Plus, I have one, off my old Datsun 2000 race car, that's been carefully
packed away for the last 15 years...If I didn't have one already, I'd
likely go for a high-end electrical tach with a vintage look.

The Jones tach is very similar in operation to the Smiths and StewartWarner
chrono's, rachets, but, does not overshoot or bounce when rev'ed, and seem
to be very reliable. I have always liked the positive needle movement of a
chrono
much better than a electical or a magnetic/mechanical tach. Besides,
this one has the "Moon Eyes" logo for Moon racing products on the face,
definitely a "60's" look.

I'm going to investigate the oil-pump drive; while the cable will be rather
long, it
is the simplest and most likely the cheapest too...

Thanks for all the advice


----------------------------------------------------------------------------
--------
Brett Engel PSO Engineer
Cisco Professional Services
(602)-912-1852 [email protected]
Cisco Systems Suite 120
2390 E Camelback Rd Phoenix, AZ 85284
----------------------------------------------------------------------------
---------





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PostPost by: rodbean » Fri Jul 16, 1999 11:39 am

"Erik V. Berg" wrote:


The Smiths mechanical I had in my Elan race car didn't ratchet or ever do
anything other than give me reliable indications throughout my ownership of
the car. I suspect that the Jones mechanical tachs are as good.

By the way, the problem with electric tachs for 8500-10000 rpm engines is
that they are only accurate on an average reading basis (if they're in good
repair) .... not good enough when a few rpm can make a difference to the
longevity of your engine. I used to shift at 8750 rpm which was
appropriate for the cams I had. I would have been a bit nervous if the
tach had been moving around in that range.

Rod






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PostPost by: ozone.breath » Fri Jul 16, 1999 5:33 pm

Howdy, all.
I wrote:

Rod replied:

Hi, Rod. Isn't this list great?

Ratcheting was probably a poor choice of words. Chronos make sort of
a clicking motion, eh? I don't consider that a negative characteristic...
I was just trying to verify that the Jones tachs are indeed chronos,
by asking Brett if they have a similar motion.

I did not mean to imply in any way that a Smiths chrono might not
be reliable or accurate. If I could afford it, I'd already have
installed one in my '65 Elan by now. The Jones on the other hand,
appears to be available new from Pegasus, for pretty reasonable
money... hmmmm...

Regards,
Erik






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PostPost by: abstamaria » Fri Jul 16, 1999 11:23 pm

Hello Rod,

I understand that the electronic tachometers by Stack (which I think makes
the instruments installed on the Elise) are very good. They have models
that go into very high rev ranges. They have a classic range, but
unfortunately have only two sizes -- one too small and the other too large
for the Elan.

Regards,,

Andres
Manila
S4 SE 45/8439






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PostPost by: rodbean » Sat Jul 17, 1999 4:21 am

"Erik V. Berg" wrote:


YES!!!


I've always heard that the Jones tachs were very good. I wonder if the one
from Pegasus has the right interfaces for the Elan engine. How much money are
we talking about?

Rod






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PostPost by: sprinterdave » Mon Jul 19, 1999 7:38 am

Most people fit the tacho drive to the jackshaft ( ie the cam) which
drives the fuel and oil pumps. The front tining chain coverneeds a hole
drilling into it and the appropriate drive atatchment fitting.


--
David Shiers





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PostPost by: abstamaria » Mon Jul 19, 1999 11:23 am

Hello Erik and Rod,

Erik wrote:


"Ratcheting" was descriptive, I thought. The Smiths mechanical tach I have
on the other Lotus has that clicking motion as well -- actually a little
difficult to get used to, but it provides a very period feel. It reminds me
of the opening scenes in "Grand Prix" (the older guys might remember that
movie), which had close-ups on tachs and exhausts as the F1s blipped on the
starting line.

As a historical note, I replaced the tachometer on my 1948 MG TC about a
year ago, because the tach then installed on the car was an aftermarket,
less expensive replacement from Moss Motors. The Moss tach's needle moved
across the dial smoothly -- a telltale sign that said it wasn't
"chronometric." Just to be sure, the cognoscenti could also check the
clock's hands (on the tach in the TC): it was painted on in the Moss tach!
Accurate twice a day, the MG joke goes. The newly refurbished genuine MG
tach (with mechanical clock) is "chronometric," and now has the ratcheting,
clicking motion. The ratcheting is not as abrupt as on the Lotus's Smiths
tach (but then the twincam does rev more quickly and much higher than the
prewar MG XPAG engine).

The irony of all of this is that you can tell a fake Rolex chronometer from
the real thing by observing at the second hand. The quartz movement in the
fake causes the second hand to jump from second to second. The mechanical,
genuine Rolex's second hand sweeps smoothly across the dial. (The quartz
movement is more accurate, but that's beside the point).

I apologize for the non-Elan content, but thought a general perspective
might be interesting.

Regards to all on the List,

Andres
Manila
45/8439 DHC







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PostPost by: rodbean » Mon Jul 19, 1999 6:24 pm

"A. Sta. Maria" wrote:


Hello Andres,

As one who learned to drive on a 1950 TD, I remember the ratcheting of the
mechanical tach well. Later, when I drove someone's 1953 TD, which had an
electric tach that swept smoothly all over the place (now and then arriving at
an indication of probable true revs), I decided I liked the accuracy of the
mechanical tach and I'd live with the nervousness of the movement.

Still later, when I raced the Elan with the Smiths mechanical tach, I was
grateful for that accuracy.

Rod






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