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I have installed a new cable in a very original rev counter but as the revs increase the cable obviously fails to grip the female drive and the screaming necessitates removal. Apart from having the complete gauge serviced are their any suggestions as to how I might effect a cure? Araldite perhaps ? 

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That sounds a bit permanent. I would take the unit out of it's case & take a look to see what is going on.

Bob.

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Thank you for your interest chaps --the rev counter works well until the revs increase and then the screaming starts suggesting an imperfect location in the entry to the instrument. I was just wondering how I might effect a  DIY cure on what I believe to be the loose connection. I will remove from the dash and examine the fit.  

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Much more likely to be the bearing inside the rev counter screeching, they do wear. 

Bob.

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Sounds like a dry bearing. A little drop of sowing machine oil may cure it, but don`t flood it.

Ralph.

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On 10/15/2020 at 3:08 PM, Ralph Whitaker said:

Sounds like a dry bearing. A little drop of sowing machine oil may cure it, but don`t flood it.

Ralph.

 

 

I'd like to try this.  How do I remove the chrome trim ring on the tach without damaging it?  I obviously didn't spend enough time with my meccano set as a child.

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It should rotate until the tangs line up with slots in the body, it will then pull off, followed by the glass. You then slacken the two bolts at the rear of the body, & the inside parts will become loose. hold you hand under the dial as you undo the screws, & it will eventually drop into your hand. You will then be able to see the insides, & get a feel for where the noise is coming from. Try not to disturb the hair spring, & be careful when touching the aluminium disk.

Bob.

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5 hours ago, Lebro said:

It should rotate until the tangs line up with slots in the body, it will then pull off, followed by the glass. You then slacken the two bolts at the rear of the body, & the inside parts will become loose. hold you hand under the dial as you undo the screws, & it will eventually drop into your hand. You will then be able to see the insides, & get a feel for where the noise is coming from. Try not to disturb the hair spring, & be careful when touching the aluminium disk.

Bob.

 

 

Thanks Bob.  Here goes nothing! :D

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In my experience it is usually the back bearing that the square end of the cable enters into, and can be oiled with a drop of light oil without dismantling the instrument. I have known inner cables to be slightly too long putting pressure on the bearing. If slackening off the thumb nut holding the cable in a turn stops the noise then put a thin washer between the outer cable and the threaded boss on the rev counter( effectively making the outer cable slightly longer.)

Ralph.

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I don't know if it is recommended practice or not but I took my cordless drill and a robertson bit that matched the tachometer cable end, inserted the drill into the tach and ran it at varying speeds for about 6 minutes.  Highest it went was 3200 but there wasn't any squealing.

 

The drill should be set as if you are undoing a screw, counter clockwise.

Edited by David Owen
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if you push a good fitting rod (screwdriver etc) into the square inner, can you feel, or see any sideways movement to indicate wear ?

It looks as if the whole thing could do with a clean.

Bob.

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2 hours ago, Lebro said:

if you push a good fitting rod (screwdriver etc) into the square inner, can you feel, or see any sideways movement to indicate wear ?

It looks as if the whole thing could do with a clean.

Bob.

 

Compressed air to clean?  Low PSI.

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No. Just carefully wiping with solvent on cotton bud or similar. Compressed air could easily damage the delicate mechanism.

Bob.

Edited by Lebro
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I recently went this this drill. My tacho was screeching intermittently and the needle would swing wildly. Not all the time, just enough to be worrisome. First I removed, cleaned, and lightly lubed the old inner cable. No joy. Then a new cable, which for some reason was hard to find in the proper length. The LHD cars use a cable listed as 31 inches long (actually closer to 32 inches), but the usual suppliers only had them in 36 inches which I think is meant for a Spitfire. At any rate I found one, UK made of the correct length, but still the screech persisted. I then removed and dismantled the instrument as above, using a light drop of gun oil and manually manipulating the square drive in the back of the gauge. It had felt rough before the oiling and now felt much smoother. Reinstalledit, went for a drive, but within ten minutes it was back to its old tricks. Choice words were uttered.

At this point there was nothing much else i could do, so I ordered an exchange unit from Rimmer Brothers which arrived here in CONUS within 5 days. That did the trick. Nice steady needle and quiet as it should be. The refurbished unit had the old rust cleaned away from the back and the inside appears to have been repainted as it is much brighter with the the lights on compared to the old speedo. It even came with a new O-ring to use between the bezel and the dashboard. At around $155 all in, including postage here and postage to return my old unit, I rate it very good value for the money.

A word or two of caution: the threads on the tach drive and the the instrument head are very fine and it is easy to get the cable ends cross threaded unless the cable is carefully aligned and seated. Easy does it.

 

Edited by Andy303
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22 minutes ago, Andy303 said:

I recently went this this drill. My tacho was screeching intermittently and the needle would swing wildly. Not all the time, just enough to be worrisome. First I removed, cleaned, and lightly lubed the old inner cable. No joy. Then a new cable, which for some reason was hard to find in the proper length. The LHD cars use a cable listed as 31 inches long (actually closer to 32 inches), but the usual suppliers only had them in 36 inches which I think is meant for a Spitfire. At any rate I found one, UK made of the correct length, but still the screech persisted. I then removed and dismantled the instrument as above, using a light drop of gun oil and manually manipulating the square drive in the back of the gauge. It had felt rough before the oiling and now felt much smoother. Reinstalledit, went for a drive, but within ten minutes it was back to its old tricks. Choice words were uttered.

At this point there was nothing much else i could do, so I ordered an exchange unit from Rimmer Brothers which arrived here in CONUS within 5 days. That did the trick. Nice steady needle and quiet as it should be. The refurbished unit had the old rust cleaned away from the back and the inside appears to have been repainted as it is much brighter with the the lights on compared to the old speedo. It even came with a new O-ring to use between the bezel and the dashboard. At around $155 all in, including postage here and postage to return my old unit, I rate it very good value for the money.

A word or two of caution: the threads on the tach drive and the the instrument head are very fine and it is easy to get the cable ends cross threaded unless the cable is carefully aligned and seated. Easy does it.

 

 

 

Thanks Andy, especially for the heads up on the cable.  I wouldn't have picked up on that.  Where did you get the correct length cable?

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Team Triumph. I think it was his last one however. TRF, BPNW, and Moss didn't have one.

 

Check Ebay: https://www.ebay.com/itm/Brand-New-Tachometer-Cable-Triumph-TR3-TR3A-TR3B-LHD-Cars-Made-in-UK-/173302063092

 

2 hours ago, David Owen said:

 

 

Thanks Andy, especially for the heads up on the cable.  I wouldn't have picked up on that.  Where did you get the correct length cable?

 

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David:

I have attached some pages extracted from Anthony Rhode's "Repairing Jaeger & Smith's Speedometers"  as might apply to a tachometer. You can easily find a complete copy on-line. The tachometer works on the same principle  as the speedometer, just ignore the bits about the odometer worm drive. The input shaft and the bronze bushing are what need a bit of grease. I only tried oiling the input shaft from the back - I was afraid that I might ruin a good exchange core if I tried to dismantle the thing. Too much oil is bad as it could coat the magnet and cup which would be bad.

interesting article on the chronometric instruments - truly "clocks" and pieces of art. The much simpler, cheaper replacements found on our cars must have saved the car makers a pretty penny.

Pages from Smith-jaeger_speedo_repair.pdf

Edited by Andy303
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