Tachometer seize?

[Boink]

The other day my tachometer (1959 Bugeye) suddenly made a serious ticking and it stopped working. I assumed it might be the cable or even the generator gear-drive. Pulled all that out and verified all was well. Never thought it might be the tach itself. Pulled the tach and, yes, it seems to be seized at least a little bit. I put a small screwdriver in the output (where the cable goes in) and it is very hard to turn. Odd that the cable didn't snap with all the resistance.

I've since put in some "Deep Creep" to the outer part that the cable goes into, hoping to loosen it all up and get it lubricated. Maybe it just developed some rust in there (and it did look a tiny bit rusty). After it has set for a bit (and I've manually turned it with a screwdriver), it will move some, but there is more resistance than I would have ever thought there should be.

So, my question to the community is:
a) does this happen much? I've never experienced it.
b) should the output turn VERY freely (when normal)? I presume it should be effortless.
c) am I nuts to open this up and try to salvage it (as I'm trying)?
d) can I take this even further apart?
e) should I just start looking for a replacement?
See attached pic where I've taken the cover off and removed the guts.
Thanks for any replies.

 

[dklawson]

Yes, it happens to both Smiths/Jaeger mechanical tachs and speedometers. The speedometers are functionally the same as mechanical tachs with the addition of the odometer drive components. Since mechanical tachs were more-or-less phased out by the mid-1960s you are much more likely to hear of this problem with speedometers.

Your approach is correct. Some penetrating oil on the input where the square hole is will soften the old grease given a little time. Don't rush it and don't flood the assembly. There is a needle bearing support for the spindle the needle is on. You don't want to get that gummed up with grease or oil.

Since you have already taken the movement out, I suggest you download and read through Anthony Rhodes' PDF about repairing speedometers. It has some good advice on cleaning and things to watch for in disassembly and assembly.

https://www.lotus-europa.com/manuals/misc/electrical/Smith-jaeger_speedo_repair.pdf

 

[Boink]

Thanks Doug! Yes, I went easy with the penetrating stuff... and then I've since added some graphite. I then put a square drive on my drill and took it up to 3000rpm (on the tach) and it is much better. There is still a point where it catches just a bit. So, I hope a little time will help. Might have to finally add a little machine oil (?).
Thankfully, the rest of the tach works smoothly/freely. It's just that input collar part.

BTW, I think the ticking was the cable jumping out of the square hole. The end of the cable was bent a little, so I think that when the tach seized it jumped out and was bend a bit (which I straightened).

Anyway, this might be able to go back in the car by tomorrow. Hope hope...

P.S. - thanks for the speedo PDF. I've seen this one a few years ago. My main odometer has never worked, but the trip one does. I've been meaning to take that all apart and give it a go as well. As for the tach, it looks like the main input/output shaft is a similar mechanism. Too bad there isn't an easy-to-replace bushing.

 

[Boink]

Just to make this a bit of reference thread (with this pic). The clockwork-like portion of mine, that is very delicate, works smoothly. Of course, it should all work smoothly.

 

[Billm]

Just to carry this conversation a little further-
Bill Mayer had his tach gearbox die a few weeks ago on his Bugeye so we replaced it only to hear a horrible howling from the rear of the generator. Turns out that the rear bushing was burned up since neither he nor I had remembered to oil/grease that rear bearing for a few years.
Now with a new generator and gearbox we will try to remember to check and oil that rear bushing once per year- it was an expensive mistake!
BillM

 

[Boink]

Good advice Bill. Thankfully, that end of my tach system is good. I also have a spare tach-drive and cable if it comes to that.

 

[Boink]

And additional reference photos. The first shows the very delicate spring mechanism that returns the needle. The second is a side view that shows the spinning disk. The final one is the output socket (that was sticky with mine); the cable inserts here.

Carpe tachometer! Or rather, non-carpe tachomerundum?!!!

 

[Jim_Gruber]

And tahere is always Speedhuts GPS Speedo and Electronic Tach. Looks pretty darn nice in the box. Dash gets rebuilt next Wi re when it all comes apart for paint. Soon Bugsy you'll get to drive. 78 today in Dayton. Hopefully beginning of May.

 

[59diamond]

There are these two fellows in San Diego who have a little hole in the wall shop called I think "Speedo Shop" who fix old tachs and spedos. If I were you I would try to find a similar place near you and take the tach to them for inspection. I had problems with my Tach on my other Bugeye and they fixed it. One thing I learned from them is that graphite is taboo for a tach. the tach has a very delicate spring mechanism and graphite can really gum it up.

 

[59diamond]

Generators with the tach drive are out of stock at Moss and Victoria British, but Pacific Northwest had one in stock and now i see that they don't have any in stock either. so if it turns out that you need a new generator this company is in Oregon.

https://www.bpnorthwest.com/generator-w-tach-drive.html

 

[Boink]

Thanks all. I am aware of graphite and tiny mechanisms so I didn't put any graphite in the actual mechanism itself (which was working well). We do have a speedometer shop right nearby, but it seems that my penetrating oil and re-oil have resolved the problem. I've never been shy about going into gauges. I remember repairing an early Mini fuel gauge which had electromagnets fed by extremely tiny wires. Next up will be to fix my main odometer.

Thankfully I don't need the generator or the tach-drive gearbox. Yes, British Parts Northwest is very close to me (though, oddly, they do no counter sales, so one has to pay shipping here in Portland).

 

[Boink]

VICTORY, she is mine.

After using the penetrating oil and waiting... adding some graphite, getting it all over me... cleaning up... running it with a drill with a square-head tip... waiting a few hours... and finally adding some fine machine oil... waiting a little longer, then a tiny bit more oil, and BOB'S-YOUR-UNCLE! It works very nicely.
So, I put it all back in the car (after some additional cable lubrication), and I'm back in the business of measuring revs mechanically!!!!!!!!!!!!


Bring on the Sprite-driving weather.