Mk1 cooper s speedometer

[LKE]

Hi guys
I'm always pleasantly surprised by all knowledge in here.

So - I have this SN4479/20 1408 Speedometer, and have learned here that's is might be the right one to have in a 970.
Can you please help me judge if it's a complete, standard unit or a "street mix" of everything?

If anyone really pay the amount mentioned herein, I might sell or P/X for race parts App K.





If will dismantle (from the Mini Marcos FIA racecar it's in) and take more pics if needed.

Best regards
Lars, Norway

[1071 S]

[quote="Spider"]I'm just right now going through the process of checking the calibration of a couple of speedos, not that I can do much with them if they are out, other then tweek the needle a little one way or the other!.."

Spider, the speedo is easily calibrated/adjusted. Mine was originally for a 3.76 but now suits the 3.1 diff. The odometer is a different kettle of fish and requires gears (either a different gearbox speedo gear or an intermediate box.

Cheers, Ian

[Spider]

I'm just right now going through the process of checking the calibration of a couple of speedos, not that I can do much with them if they are out, other then tweek the needle a little one way or the other!.."

Spider, the speedo is easily calibrated/adjusted. Mine was originally for a 3.76 but now suits the 3.1 diff. The odometer is a different kettle of fish and requires gears (either a different gearbox speedo gear or an intermediate box.

Cheers, Ian

Hey 1071 S, so what / how did you do it?

[rich@minispares.com]

Hey 1071 S, so what / how did you do it?

you can get the speedo internally recalibrated or fit an external 'cheater' gearbox.

http://www.speedograph-richfield.com/ht ... arbox.html

in one of my cars the speedo has been 'recalibrated' with red nail varnish to go up to 120 mph - they have been into the rev counter as well to give it a bit more as well............

[Spider]

Hey 1071 S, so what / how did you do it?

you can get the speedo internally recalibrated or fit an external 'cheater' gearbox.

http://www.speedograph-richfield.com/ht ... arbox.html

in one of my cars the speedo has been 'recalibrated' with red nail varnish to go up to 120 mph - they have been into the rev counter as well to give it a bit more as well............

Bhahaha,,,, yeah, I recon Red or even Pink Nail Polish would suit you nicely there Rich and at any speed!!

Yeah, ta on the gearboxes, I have used them before and they do keep everything working as they should, but soulds like 1071 S did a recalibration on the speedometer function. Curious as to what he did as I maybe able to use that to correct a few I've here that appear to have lost magnetism.

[1071 S]

well I didn't actually do it - rather I paid a local instrument shop to do so....... I believe the technique involves changing the distance between the speedo needle drive and driven plates....

Also, wiping the volume between the plates with a suitably sized hacksaw blade will stop the dreaded Mini speedo wobbly needle syndrome.

Can't be too difficult or convoluted as it didn't cost that much.

Cheers, Ian

[ianh1968]

edit> Forgot I had this! Here's a page from one of the ST Manuals which maybe of help;-

... I have this book as well and fell into the trap regarding the 12" wheels...

I am fairly sure that the 12" tyres here are fairly tall profile ones which may
not fit a Mini. For a while I used the 960WRPM figure in my calculations as this
gave me a higher road speed - I was deluding myself.

When I investigated this properly for a set of 145x70x12 tyres, I found that
these were specified at 1555cm circumference. This translates to 1035
wheel revs per mile which is about an 8% error...

All of a sudden, my top speed was reduced by about 8mph on what I had
previously thought it was - bummer!

My latest Yokohama 165x60x12 tyres are 1045 wheel revs per mile...
A set of Yoko 165x70x10's worked out at about 1080...

I have made a calculator for road speeds which can handle all the
gearbox/diff and tyre permutations known to man (well, me anyway...)
It does MPH and Km/h, so it should appeal to a global audience.

It's an Open Document type spreadsheet, a .ods file...

Ian

[Spider]

I have made a calculator for road speeds which can handle all the
gearbox/diff and tyre permutations known to man (well, me anyway...)
It does MPH and Km/h, so it should appeal to a global audience.

It's an Open Document type spreadsheet, a .ods file...

Ian

Handy gadget Cheers for that

[69k1100]

Once you remove the needle and faceplate there is a couple of screws that bend a bar (the seat for the speedo needle) this changes the distance between the fixed magnet plate and the drag cup (eddy current setup)

Closer increases the torque applied to the fixed magnet plate/drag cup increasing the torque applied to the hair spring resisting the needle moving around.

Pretty elegant, though you have to make sure you mark the needle resting location prior to dismantling to apply the correct preload to the needle.

Could also increase the number of magnets if you can't get any closer without touching the drag cup. The standard ones have probably suffered a bit anyway (40 odd years).

[Spider]

Once you remove the needle and faceplate there is a couple of screws that bend a bar (the seat for the speedo needle) this changes the distance between the fixed magnet plate and the drag cup (eddy current setup)

Closer increases the torque applied to the fixed magnet plate/drag cup increasing the torque applied to the hair spring resisting the needle moving around.

Pretty elegant, though you have to make sure you mark the needle resting location prior to dismantling to apply the correct preload to the needle.

Could also increase the number of magnets if you can't get any closer without touching the drag cup. The standard ones have probably suffered a bit anyway (40 odd years).

Well, I'll be a ding-dong-dang! Yeap, I know the bar and the screws, and that makes sence. Thanks for that

[Tim]

The needle resting position is normally marked on the face just below the stop pin. It will be a faint line or a small dot like a full stop.

Tim

[dklawson]

Once you remove the needle and faceplate there is a couple of screws that bend a bar (the seat for the speedo needle) this changes the distance between the fixed magnet plate and the drag cup (eddy current setup)

Could also increase the number of magnets if you can't get any closer without touching the drag cup. The standard ones have probably suffered a bit anyway (40 odd years).

Be cautious with adjustments to the top spindle support. It really is not meant to make adjustments to the inductive coupling. The lower end of the spindle, below the drag cup, is supported by a dry needle bearing. A little too tight on that top support adjustment and the bearing can stop slipping and the needle will go all the way around the face (bad).

Anthony Rhodes wrote a 27 page PDF that discusses repairing and calibrating Jaeger and Smiths speedometers. I have used the additional rare earth magnets mentioned in the Rhodes document (and mentioned by 69k1100 above) to "speed up" a gauge that is reading slow. It's a trial and error thing requiring a fair amount of patience. An acquaintance of mine on another board experimented and found a totally different method works better. He bought a couple of powerful, large, rare earth magnets. He used one of them (dragged across the original Smiths speedo magnet arms) to increase their strength so the gauge would read high. Then he operated the speedo at a known RPM. While watching the needle he brought one of the magnets close to the back of the speedometer (outside of the case) and the rare earth magnet started to de-magnetize the Smiths magnet arms. He said he quickly developed a technique that allowed him to get the magnet strength where it needed to be for proper calibration. I have not had a gauge to try this on yet but find it an interesting alternative to applying new magnets to the inside of the gauge.

Of course, this calibration is only for the analog portion of the gauge and will not correct odometer errors.

If you are interested in calibrating mechanical speedometers and tachs yourself, read through part of this lengthy thread on The British Car Forum.
http://www.britishcarforum.com/bcf/show ... aces/page6
Spindle support adjustment, Post 56, page 6
Calibration discussion, Post 60, page 6

[rogerotto66s]

Bringing this topic back to life!

1966 Austin Cooper S is finally back together!
Only problem is …

… Odometer seems to work just fine.
….Speedometer needle does not move off zero.

This would seem to indicate cable is OK.

What is recommended fix?

Smiths speedo SN 4417/18a 1280

[Peter Laidler]

If the odometer is working that indicates that the cable is rotating and that the magnetic 'driver' is also rotating as it should. So far, so good......

It is likely that the driven plate that responds to the magnetic driver plate s sticking (and not responding to the magnetic will of the driver if you get my drift.....) The problem now is that to clear this you've got to remove the speedo bezel, glass and support ring then remove the screen and mechanism from the rear case (2x 2BA screws at the rear). Try just flicking the indicator/pointer or manually and/or carefully take it round to 120 and back a couple of times to free off any clag.

Easy to test whether you've been successful. Jack up the front of the car, connect speedo to cable inside/under the bonnet and ask someone to start the car and engage gear and drive off - while stationary of course! If the pointer is working then you've done it....., easy as that.

Clear any dust etc etc from the instrument screen, clean te support ring, glass and bezel and re-assemble.

But a word of advice for the unwary. Some glass was held in the bezel by a tar like substance that will have gone hard and caused the glass to stick to the bezel like shxx to a blanket. Don't force anything....., put both into a bowl of hot water and carefully separate the two and then clean off with thinners and hot soapy water. Replace the old tar with a 4mm dia ring of O ring material x 15" or so long, cut to length. Job done