I've just removed the 120m/h speedo from my car in order to repair it as the milage counter is not working. When the face of the gauge was removed, I noticed a number stamped on it (46630) in purple ink.

Is there any significance to this number, such as an individual serial number or could it be a model number?

must be one of the mysteries of the universe - I've seen the purple numbers, but never taken any real notice of them

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did I tell you that I won a trophy?

Possibly a production quality stamp...

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"Show me the Mini!"

A couple of questions
What is the build date/ year etc of your, presumably, Cooper S?
Is the speedo ratchet arm metal or plastic?

Why do I ask?
I recently had cause to take my speedo apart, 68 build MK1 S, to fix the odometer which wasn't fixed properly by a speedo repairer.
When I dismantled it I found the plastic ratchet arm and a quite different odometer mechanism to that described in John Rhodes Smiths speedo pdf.
I'm interested in getting an idea of when Smiths started using plastic arms and the different odometer mechanism.
It took me a week to work out how to get the odometer mechanism apart, and then only after I had examined it in great detail under a magnifying glass.
Australian built Smiths speedos for the MK2 S, Mini K etc still used the metal ratchet arm.
I had a very S/H Mini K speedo which I used to get the locking clip from that holds the ratchet arm to the eccentric shaft which had been replaced with an E clip by said speedo repairer and which was too big and kept falling off.
Needless to say I was not happy and decided to pull it apart myself to try and fix it.

RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

G'day miniron,

Thanks for your response.

My car is listed as a December '67 Cooper S and is on the register from this site. Plus the unique identifying body parts (i.e.: spot welds where spot welds are meant to be, etc....it still has the original sound deadening on the under side of the parcel shelf in the boot) match how a genuine Cooper S is supposed to be put together. I state this that whilst I have the matching engine and car numbers, the body number has been unrecoverable from the radiator shroud.

The speedo itself has a plastic ratchet arm running against a plastic cog.

My reason for my post was I am trying to establish if the 35,073 miles are genuine for the vehicle or is this a replacement speedo. So any information you might be able to provide will be helpful.

Here are a couple of photo's:

People in the trade call Ratchet Arms "Pawls"...

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"Show me the Mini!"

The number might mean the mileage that the speedo craps itself...

Could be a qc stamp from the manufacturer.

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Rob Forsyth
Miniot!!

Hi ShortRedHead,
Your speedo internals are the same as mine.
The diamond shaped washer with the keyhole slot holding the ratchet arm/pawl on the eccentric is what was replaced on mine with an E clip.
So much for the "speedo expert".
The odometer problem with my speedo, apart from the E clip, was that the ratchet arm/pawl kept sliding off to the side of the ratchet wheel as the odometer wheels were not moving freely due to dust and corrosion on the shaft the odometer wheels run on.
I see you have already removed the speedo needle.
Did you mark the needle position on the side of the driving cup/disc?
If not then you need to replace it on the shaft using the alignment dot marked on the speedo face near the needle stop.
Put the needle on the shaft with the cup/disc in its natural position ie: with the disc/cup coil spring untensioned. This will be between the needle stop and the fuel gauge. You will need to manoeuvre the needle past the stop when you are fitting the outer ring part of the speedo dial.
On the speedo dial you will see the RPM - revs per mile number which for an S should be 1280 with a 3.44 diff ratio.
This number is the number of revolutions of the speedo cable for each mile travelled. This is then transferred to the odometer via the worm drive and ratchet wheel and pawl.
The revs per mile is also the road speed at 60 MPH so the needle should point to 60 MPH when the cable is turning at 1280 RPM.
You can check this by driving the speedo cable at 1280 RPM using an electric drill.
Unfortunately this is not as easy as it seems as the cable has to be driven anti clockwise and most electric drills don't run that fast in reverse.
There are drills that run at the same speed range in both directions.
Now how to take the odometer apart.
The odometer drive shaft consists of a grooved shaft that runs inside a tube that the odometer wheels run on.
On the LH end of the odometer wheels, opposite end to the ratchet wheel, you will see a spring around the shaft.
Inside this spring is a plastic circlip that looks like a plastic washer.
You will need a magnifying glass to see this.
(The LH end of the grooved shaft has a tapered section which the plastic circlip slides over when you are re assembling things).
You will need a couple of tiny jeweller's type screwdrivers to lever the circlip off the shaft and this has to be done inside the spring and then retrieve the circlip from inside the spring.
Once you have done this you can withdraw the grooved shaft from the odometer assembly from the RH end after removing the pawl arm.
This can be another "Jesus Clip" moment as there is a spring at the RH end as well along with the ratchet wheel, odometer wheel drive etc.
Best to do this in a plastic bag so that if it does not go well you will still have all the bits in the bag.
Photograph your way in to make sure you get everything back correctly.
Once you have removed the shaft and RH drive bits you will be left with the odometer wheels on a tube.
The odometer wheels are driven by tiny yellow pinion gears that run on the inside edges of the wheels.
You can just see these between the wheels along with the thin metal disc between each wheel.
Once you get it all apart you will probably find lots of dirt inside (from the large rotodip hole in the bulkhead) and the surface of the wheel tube will have some light black corrosion.
Clean this off with scotchbrite, clean everything else carefully and reassemble.
As they say re-assembly is the reverse of dis-assembly.
Well the person that said this didn't have to re-assemble a Smiths speedo.
Get a block of wood and drill a hole that the end where the cable attaches will fit into so that the odometer section is facing up.
This is your assembly jig, well a sort of bush mechanic equivalent.
Drill a second hole that the hollow brass tube will fit into and this is your assembly jig to hold the wheels as you assemble them onto the tube.
If you look closely at each odometer wheel you will see a small hole towards the outer edge of each wheel. This is used to align the wheels and pinions and a piece of wire through the holes keeps it all in alignment.
Once you have all the wheels assembled on the tube put the grooved shaft in the tube and continue to assemble the ratchet wheel end bits and you are then ready to refit the assembly into the diecast base.
You will need five arms and the patience of a saint to do this.
At the LH end put the plastic circlip inside the LH spring and insert the grooved shaft through the circlip and into the base.
This is where the tapered LH end of the grooved shaft comes into play as it expands the circlip and then allows it to fit into the circular groove in the shaft.
You may have to do this several times as you need to check that all the wheels align properly as each wheel completes one revolution. You can turn the ratchet wheel by hand before fitting the pawl to check this.

How the odometer mechanism works.
Each inside edge of the odometer wheel is different.
One side has teeth all around the inner edge and the other side has only, IIRC 3 teeth.
This gear mechanism turns each adjacent wheel one digit for each revolution of the preceding wheel.
When you get to 99999.9 miles it starts from 00000.0 again and this is when most odometer problems occur.
After 10 years or more the dust and corrosion causes too much drag on the odometer wheels and the pawl just keeps sliding off the ratchet wheel.
The end of the pawl where it contacts the ratchet wheel can also wear with a slight taper which also assists the sliding off action.
A slight dressing with a very fine file helps here but only if necessary.
This, apparently, occurs on speedos with the metal pawls as well.

It was some time ago when I did this but it will give you info on how to go about dismantling and re-assembling the odometer.

As to your original query it's probably a serial number or type number.

Hope this helps.
RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

Thanks for all that info, Although I'm not sure where I get the extra arms from ("You will need five arms and the patience of a saint to do this"). LOL

Sean

Sean,
I have some pics I took during the dismantle and I will try and post them.
My speedo also has 466 30 on it but it isn't printed.
It looks as though it was hand written with a Texta pen.
Its probably a type number as there where many different Cooper S speedos depending on diff ratio and engine size.
Australian built MK1 cars would probably all have this number, whereas UK import cars may be different.
The diamond shaped retaining circlip on your speedo looks correct.
I had to modify a metal pawl arm circlip to fit when I replaced the E clip.

RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

Helps??
Surely this post deserves the highest commendation from the host-masters.
Ron has ventured into realms rarely dreamt of by mere wheel bearing changers.
And he has done it in sequence and without a single reference to a service tool part number!
This is the nearest most of us will ever get to brain surgery for beginners.
Well done.

(Genuinely) Well done.