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MG TD TF 1500 - TD speedometer reset knob

Hello,

After having recalibrated my TD speedometer and hopefully fixed the bouncing tendency of the needle, I am ready for installing it back onto the dash. Until now, the odometer trip reset knob was detached on the glove box.

When is the right moment for attaching the reset knob to the shaft on the speedometer? Before installing the speedo on the dash?
This is the only way I see to insert the cotter pin, but perhaps I am wrong…

Thanks for your comments.

Jesús
J Benajes


I dont think there is another way.

Jim B.
JA Benjamin

Let us know if you fixed the bouncing and how you did it.
Christopher Couper

Jim, thanks for the confirmation.

Christopher, for testing and calibrating the speedo I built a bench with a variable speed motor for driving directly the speedo input.

During the first tests, the needle bounced like mad, the same as it did on the car, so the cause should be inside the speedo. After taking apart the mechanism I found that it had been greased too liberally (perhaps in 1962, according to an inscription in the inside) and the grease had dried up. I cleaned all the gum and put everything together with very little lubricant.

On the bench, the needle still wobbles a little at medium speeds, but now one can read the indicated value. I hope than the improvement will remain whit the speedo back on the dash.

Jesús
J Benajes

Jesús: I am in the same place and the last time my speedo and tach were oiled was 20 years ago so they are probably ready.

I pulled my speedo cable today and the fitting that fits into the transmission was bent and it was even wearing the shaft a bit. I doubt that this would cause it to bounce but I did my best to straighten it out and will test it in a few minutes.

The next step is to pull the gauges and oil them.

For that I guess I need to pull off the needles. What's the trick to get them back on again in just the right position since mine have been calibrated?
Christopher Couper

Chris, I wrote up a bit about doing that in a recent thread for D. Lamb. I think it's titled something like TF Speedometer connections. Bud
Bud Krueger

Bud: I will search it out.

I did my best to straighten it but it was not perfect. But it did improve the bouncing a lot. Before it would swing about 30 to 40 mph at 3500 rpm in 4th (55 mph?) every second. Now it just jumps 5 mph every 5 seconds which I can live with. Probably the result of the little bit I could not get out of the bent fitting.

Next task is oil.
Christopher Couper

Chris, aside from the thread mentioned by Bud, you might look at an extensive thread in a Triumph forum (speedo internals are pretty much the same as in TDs) with excellent description and recommendations of how to disassemble, calibrate and put together again tachometer, speedo and other gauges (the fun starts around the mid of the thread):
http://www.britishcarforum.com/bcf/showthread.php?94885-Instrument-Faces&highlight=speedometer

For relocating the needle in the initial position, and aside from the “standard” procedure to bend the needle over the stop peg and let it “float” to the natural rest position, I have found a more robust way, which however involves removing the mechanism from the casing (what probably needs to be done in any case). It is described in detail below (excuse if my English is not very good).

As far as the internal causes for needle bouncing I have found the ratchet mechanism used in the odometers. If the odometer spindle is not properly lubed, each time one of the arms pushes on the teeth of the number wheel (in the trip odometer with more frequency), there is a momentary deceleration of the spindle and a perturbation on the needle position.

Jesus

How to remove and re-locate the needle

(This method cannot be applied with the mechanism inside the casing)

1. Remove the two small screws holding the face to the mechanism. Leave the needle in its place. The face will stay loose, blocked by the needle.
2. Remove the two screws at the back of the speedo holding the mechanism to the casing.
3. Move carefully the face to clear the lower edge of the case and push on the spindle input at the back of the casing to remove the mechanism tilting it towards the front. The spindle input will tend to jam on the back of the casing wall. Take care in not putting force on the face and needle. The trip reset shaft will stay in its hole and come out last, after the mechanism has cleared the casing edge.
4. Now, with the usual precautions to avoid dropping the mechanism or forcing the sensible parts, attach again the face with the two tiny screws.
5. Move the needle to some relevant position around mid-scale in the dial (for instance at 50 mph) and keep it there steady by carefully gripping the drag cup.
6. Now, using a permanent felt pen, draw a line mark on the rim of the drag cup so that you can recover later the same position.
7. Remove the needle.
8. For re-positioning the needle, you only have to recover the position of the drag cup and insert the needle.
I even put marks on the cup rim for every 10 mph, so that I could follow the needle indication by looking at the cup position (see attached photo). This is very useful during the calibration procedure when the stator has to be disassembled (and the needle and face) for magnetizing the rotor.


J Benajes

Thanks Jesus. I just have to get up the nerve to do this.

Because my trip odometer is not moving (the regular one does) I suspect that my last bounce maybe as you stated above. Getting some lube in there hopefully will get it moving again and get rid of the bounce.
Christopher Couper

I had issues with the reset knob as well. It just did not fit though the dash hole without problems and was a little bit too short anyway (don´t know why, it came that way).
I built some sort of a bayonet lock for it that locks in the reset direction and can be twisted off in the other. Works fine so far and makes taking out the speedo a lot easier.

I cleaned and oiled the speedo as well, left the needle on, though. Improved a lot, but it is still bouncy at higher speeds. I think the cable has a lot to do with it, since with a bench drill it was a lot smoother.

Rgds, Mike
Mike Fritsch

Not sure if this is the same issue [Short reset knob]
I had the same issue with my current TD and just made a new longer one that matched the speedo reset of my first TD.
I used a piece of outer cable from the choke or starter cable. Soldered a small piece of copper tube at one end, that fit the reset shaft. Used a screw that fit the ID for support and drilled it for the split pin.
Used the original knob that fit the flexible cable just fine [Force fit] I covered it in heat shrink to make it look better.
Now I can install or remove the speedo with ease and the reset just bends to allow the removal and install of the speedo with the dash in place.

Rod

R. D. Jones

Great, Rod. I've been looking for that idea for a long time. Thanks. Bud
Bud Krueger

This thread was discussed between 21/06/2015 and 23/06/2015

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