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Speedo Internals

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jjbunn

jjbunn

Jedi Knight
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Taking apart the gauges for cleaning and rim-repainting.

The speedo has loose parts inside, but I can't tell what they are or where they go. Here's a photo:

1804231467_7213b1d7cf.jpg


Large version: https://farm3.static.flickr.com/2316/1804231467_986ab008e8_o.jpg

There are the two bolts for attaching the cover. There is a small metal spring clip and a moulded plastic part, that looks as if the spring clip screws to. There is no sign of the screw. At the back of the speedo, you can just see that there is a pad of folded paper that has been added behind the rubber insulation, perhaps so as to push against the clip/plastic piece in some way?

Does anyone know what I have here? I really don't want to find a replacement speedo as this one is the original and is labelled in km/h which is rather cool.
 
Julian,
That piece looks to me like the 'crank' that moves the odometer wheel. There should be a small gear driven by the speedo cable, with a pin sticking out that the plastic part goes over. In fact, that may be the gear it goes on that is visible towards the lower left of your photo.

Although the details will be a little different for the TR6, try downloading Tony Rhodes' speedo article at
https://mywebpages.comcast.net/rhodes/speedo.html
 
TR3driver said:
Julian,
That piece looks to me like the 'crank' that moves the odometer wheel. There should be a small gear driven by the speedo cable, with a pin sticking out that the plastic part goes over. In fact, that may be the gear it goes on that is visible towards the lower left of your photo.

Although the details will be a little different for the TR6, try downloading Tony Rhodes' speedo article at
https://mywebpages.comcast.net/rhodes/speedo.html
Click to expand...

Randall: you are gifted! That piece is immediately recognisable in Figure 1 of the document you pointed me to, and it is indeed the crank, as far as I can see.

Perhaps all I need is a screw to reattach it ... we shall see.
 
jjbunn said:
...Perhaps all I need is a screw to reattach it ... we shall see.
Click to expand...

No screw required... it goes over a shaft/peg then that springy bit of blue steel (also in the picture) slips over the peg and slides down to lock it in place.
 
Geo Hahn said:
jjbunn said:
...Perhaps all I need is a screw to reattach it ... we shall see.
Click to expand...

No screw required... it goes over a shaft/peg then that springy bit of blue steel (also in the picture) slips over the peg and slides down to lock it in place.
Click to expand...

Quite right ... But I think I do have something else missing: a spring. Please see the photo below:
1806005803_bf15b16152_o.jpg


As the speedo cable rotates it moves a worm gear which rotates the cog pointed to by the blue arrow. This then rotates the shaft with the peg, as Geo says, which I call a reciprocating cam, pointed to by the red arrow. This motion is transferred to the pawl, pointed to by the yellow arrow, which moves the ratchet (the pink wheel), which turns the odomoter counter. I think!

The trouble is, there appears to be a spring needed, attached at the place pointed to by the green arrow, to keep the pawl engaged with the ratchet, otherwise it's free to float off.

I can't see where such a spring would be secured at its other end. Nor can I find the spring!

Advice most welcome /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
It looks like a reverse lock. Wouldn't use a spring. Get something to turn the gear like the cable was attached and see if it moves back and forth on its own when turned forward and then reverse. It should move in to lock it from reversing the odometer miles. No spring needed.
 
Stirkle said:
It looks like a reverse lock. Wouldn't use a spring. Get something to turn the gear like the cable was attached and see if it moves back and forth on its own when turned forward and then reverse. It should move in to lock it from reversing the odometer miles. No spring needed.
Click to expand...

I like this theory! Question: when rotating the cable socket, should I go clockwise or anticlockwise, looking at the back of the speedo? I'm a bit confused /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
Anticlockwise ... and I confirmed that no spring is required. So it looks like I am in business. I do wonder why it became detached, though.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]I do wonder why it became detached, though. [/QUOTE]

Prior to you getting the car, perhaps someone who didn't know what they were doing, tried to roll back the mileage?
 
jjbunn said:
Anticlockwise ... and I confirmed that no spring is required. So it looks like I am in business. I do wonder why it became detached, though.
Click to expand...

Two reasons come to mind:

The first is that it is over 30 years old.

The second is that it's British made.
 
As opposed to the fine quality of some modern American cars. See my previous post on 2 GM window mechanism failures within 4 days and the p**s poor customer service that came with it, which caused me to vow never to buy their cars again.
 
Yes, I'm with you on GM. I hate my Chevy Blazer with 381K miles on the original untouched Vortec. Had to put a new coil on it at 379K miles. Pi**ed me off.

My Triumph's are my toys. My GM is my workhorse.
 
Why would you roll back the mileage on a 36 year old car that nobody believes any of the mileage any way.
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]Why would you roll back the mileage on a 36 year old car that nobody believes any of the mileage any way. [/QUOTE]

Don,

First of all, no one residing here would for obvious reasons.

Secondly, for those who are not here, an answer in a word: EBAY
 
DNK said:
Why would you roll back the mileage on a 36 year old car
Click to expand...
Who said it was 36 years old when it was rolled back ?

I once bought an older "low miles" Dodge camper van (from a Dodge dealer). Found an oil change sticker that gave a mileage almost 20K higher than the odo showed ... dated less than a year previously.

Not to mention the Triumph shop that was trying to pass off a TR250 as a LHD TR5 a few years back ...
 
I recall a place in Long Beach with a sign advertising 'Used Cars and Speedometer Repair'. I guessing they were all 'one-owner low miles'.
 
Stirkle said:
Yes, I'm with you on GM. I hate my Chevy Blazer with 381K miles on the original untouched Vortec. Had to put a new coil on it at 379K miles. Pi**ed me off.

My Triumph's are my toys. My GM is my workhorse.
Click to expand...

I have solely had GM cars since 1982 and until last year I would never have believed that I would dump them. Sure it didn't matter which model you had as the front brake rotors would always warp after a short while, but it was the recent models that drove me away from them.

The wife's 99 Malibu (bought at 6 months old) which experienced every problem that you can find on the internet listings and yet for which they never issued recalls. The inlet plenum leaking for instance; it did the same on my 01 Bonneville and they did do a recall on that, but not the more common problem on the Malibu.

The heater fan resistor block that failed on the Malibu and my son's Cavalier - very common problem no recalls.

The straw that broke the camels back was when the Bonneville (also bought at 6 months old) rear right window actuator failed (a piece of plastic broke). Sure it was due as it must have been up and down at least 200 times in 5 years. Can you replace the plastic bit? No, you have to buy the whole assembly including a new motor - list price in the hundreds. I bite the bullet and get a new one, fit it, test it and all is OK - phew. 4 hours later, the wife takes the car out and it doesn't even reach the end of the driveway before the other one fails in exactly the same way. She didn't even operate it, the window just fell down - that's what I call high quality engineering. I call GM and they are as useless as !!!s on a bull - no interest whatsoever.

Perhaps the factory that built the Blazer should build them all. My company provided me with a Trailblazer, which so far is OK and if it fails at least I don't have to pay for it.

My wife drives a Subaru (built in the US and excellent so far); my daughter has a Toyota (also excellent).

I would much rather support domestic industries rather than China and I always buy local when I can, but if the quality isn't there then I am going to go looking for as much of it as I can afford. There is a cost to quality, but it pays off in the long run.
 
Back to the missing spring issue...

Yes, that hook you pointed the arrow to is for a spring. If you don't have that spring the pawl will not be pulled against the drive gear for the odo wheels. There should be two similar springs, one for the odometer and one for the trip meter (2 pawls, 2 springs).

EDIT:
See my 11/05/07 post for supplemental information.
 
dklawson said:
Back to the missing spring issue...

Yes, that hook you pointed the arrow to is for a spring. If you don't have that spring the pawl will not be pulled against the drive gear for the odo wheels. There should be two similar springs, one for the odometer and one for the trip meter (2 pawls, 2 springs).
Click to expand...

Sorry, only just spotted this reply (how does one get email notification of posts to a topic?).

It seems to work without a spring. As I think stirkle said, it's a reverse lock. But you have me worried now!
 
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