18 replies to this topic

[Whatty]

~~~~~Please delete this text before posting the topic~~~~~~
Please give your topic a title that quickly describes your problem. Just putting 'Help my Mini doesn't work' is useless to anyone trying to help.
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Morris Mini Mark 2
1969
Neg earth conversion.

Fitted new Smiths RVC stepper tachometer from Minispares to my Morris. Started car and needle goes straight to 5-6K rpm. On turning off ignition the needle drops and stays at 3K rpm!!! Double checked all connections and earth. Set correctly to 4cyl setting. Tried again - same result.

Product faulty?

[dklawson]

They call the new Smiths gauges RVC????

New Smiths are produced by Caerbont. You said this was a stepper tach. If it really is a stepper, it won't behave like the traditional 1970s type RVC tachs. There are a bunch of dip switches to set and at least 2-3 ways to hook it up.

Go through any documentation supplied with the gauge and double-check the settings. Some additional information may be online at Caerbont. Emails to them may or may not be responded to. However, they may have a phone number on their web site.
http://www.caigauge.com/

[Whatty]

Hi DKL

This is the one I ordered: http://www.minispare...itle=TACHOMETER GAUGE SMITHS 0...

And here the box it came in.



As you can see from the box its labelled as a Stepper. Personally I thought the 'stepper' type were the old chronometric ones as seen on vintage race cars that flicked up and down.

As you say there are settings on the back for 4/6/8 cyl and they were correctly set for 4cyl.

I checked the wiring using a known tach and it was good. The Smiths one made an odd clicking noise when switching the ignition on so maybe damaged in transit

I've now sent this one back to Minispares who will return it to Caerbont for inspection .

[dklawson]

Yes indeed, the label surely says "stepper". However, the traditional Smiths RVC tachs are voltage pulse sensing, not stepper driven. The Mini Spares description and your comment about the limited number of switch settings indicates this is not realy a stepper tach.

I have yet to work on a chronometric gauge as you mention. I know their movements are quite different from other Smiths instruments. Of particular importance in this case... chronometrics are cable driven so they are not related to what the Mini can use.

The reference to "stepper" means that a gauge is driven by a motor ( a stepper motor) instead of a traditional D'Arsonval movement. The D'Arsonval movement uses an electro-magnetic coil moving around a "c-shaped" permanent magnet. These are analog gauges. The stepper motor by comparison is VERY different. A PC board with a microprocessor tells the motor moving the needle to move through a certain number of degrees of rotation to position indicate RPM. The PC board sends a number of digital pulses to the motor. For each pulse the motor will "step" a certain number of degrees forward. They are VERY stable gauges. VDO sells a fair number of them for tachs and speedometers. Defi also makes a lot of them.

Just to give you an idea how different the more modern tachs are... see these two pages at Caerbont discussing their switch settings and installation:
http://www.caigauge.com/page29.html
http://www.caigauge.com/page30.html
(Multiple dip switch settings to match the gauge to the number of cylinders and the type of ignition system.)

Regardless, I'm sorry you had to send this back. If all you had were switches for 4/6/8 cylinder, then this was not a real stepper tach (in spite of what the box says). You're quite right... nothing should have made noise when you installed this or applied power to it.

[Whatty]

Doug - you're a mine of infomation, I learn something new every time you post.

So the chronometric tachs are cable driven - from the cam/crank?

Many thanks
Rob

[guru_1071]

the smiths type will click when the ignition is switched on, and the needle will flick up, then return to zero.

the gauge is just self calibrating

[Whatty]

Potters Bar to New Jersey is a long way so I'd imagine that some cargo handler has dropped it en route

Hopefully a replacement will be along shortly.

[Paul Wiginton]

I use one of these Smiths counters, there is a potentiometer inside it which is adjustable with a small screwdriver. It comes un callibrated

Paul

[Whatty]

I use one of these Smiths counters, there is a potentiometer inside it which is adjustable with a small screwdriver. It comes un callibrated

Paul

Paul, When you say it comes uncalibrated I assume you're referring to the 4/6/8 cyl setting behind the rubber plug?
If so I had that set for 4cyl as per the instructions.

[dklawson]

I've never worked with a "new" Smiths tach, only dinosaurs that have seen years of use. I'm very surprised that one fresh out of the box would need calibration. It's easy enough to bench calibrate them if you've got the equipment... which I'm sure Caerbont does.

The chronometric were not used on the A-series cars as far as I know. They are much more common on cars from the 1950s and on motorcycles. I have been told that there were cable tach adapters for cars like the Mini but I cannot imagine a more difficult to install accessory. You would need a hole through the front timing cover which would allow attaching the cable to some adapter on the end of the cam. As I said, not an easy proposition. The only cable driven tachs I know of for the A-series were used on the 948 engines in cars like the A-H Sprite. However, those tachs were driven off the back of the dynamo, not directly by the engine. Cars like my Triumphs use a unique distributor with a cable drive output on the body.

More info:
http://archives.jamp...restoration.pdf

[Paul Wiginton]

I use one of these Smiths counters, there is a potentiometer inside it which is adjustable with a small screwdriver. It comes un callibrated

Paul

Paul, When you say it comes uncalibrated I assume you're referring to the 4/6/8 cyl setting behind the rubber plug?
If so I had that set for 4cyl as per the instructions.

You need to callibrate it via the potentiometer. Run the engine with a timing strobe light on it that shows RPM. Adjust the tach to match it.

Paul

[Whatty]

UPDATE:

Thought I'd update this topic and don't I feel stupid

I sent the tach back to Minispares who in turn returned it to Caerbont. They checked it out, all OK and returned it to me via MS.

I wired it back in and got the same result as before - it went nuts, reading 5K rpm with the engine at idle. Rechecked the wiring and hooked my old TIM tach up - worked a treat , Hmmm........

Rechecked the calibration settings on the Smiths unit and that concurred with the instructions.....

Much head scratching, got my science teacher geek neighbour round for a second opinion - same result.

Then a moment of clarity!

My 1968 car was converted by the previous owner to neg earth and at the same time was fitted with a Pertronix style electronic ignition - no points etc.

Therefore I'd been using the wrong wire (choice of two depending on ignition type) from the tach to the coil.......... DOH!

So my tach enjoyed a 7000 mile round trip for nothing and I feel like a complete $#@%

Have a nice day!

[dklawson]

Thanks for taking the time to post an update.

Sorry it was all down to a "DOH!" moment but at least it's working.

[Whatty]

UPDATE:

Thought I'd update this topic and don't I feel stupid

I sent the tach back to Minispares who in turn returned it to Caerbont. They checked it out, all OK and returned it to me via MS.

I wired it back in and got the same result as before - it went nuts, reading 5K rpm with the engine at idle. Rechecked the wiring and hooked my old TIM tach up - worked a treat , Hmmm........

Rechecked the calibration settings on the Smiths unit and that concurred with the instructions.....

Much head scratching, got my science teacher geek neighbour round for a second opinion - same result.

Then a moment of clarity!

My 1968 car was converted by the previous owner to neg earth and at the same time was fitted with a Pertronix style electronic ignition - no points etc.

Therefore I'd been using the wrong wire (choice of two depending on ignition type) from the tach to the coil.......... DOH!

So my tach enjoyed a 7000 mile round trip for nothing and I feel like a complete $#@%

Have a nice day!

Update to the update.

I wrote the above yesterday after speaking with Smiths US Agent BUT before actually trying the new wiring.

So after work dived into the garage and with renewed enthusiasm and high expectations wired the guage back in and ..........drum roll........ NOTHING.... it don't work

Triple checked everything - same result. Can't understand how my cheapo TIM one works perfectly and this Smiths one (Which has the programmable function for both points style ignition and Pertronix type) fails to work at all.

*drunk* off beyond belief.

[dklawson]

Out of curiosity, where are you and where is Smiths U.S. rep? Was it a place like Nisonger or APT?