Repairing a Tachometer

[harper6t]

Re: Tachometer

I have a friend that restores instruments, i have seen lots of bezels removed and I can tell you that is an excellent job of taking off the bezel.
Check the spindle to see if there is excess wear - if it flops about too much it may need rebushing, this could throw out the whole of he spindle to the point where its rubbing somewhere it shouldn't.
You might want out check out the velobanjogent site (http://velobanjogent.blogspot.com.au/search?q=magnetic)- another friend - he spent many years repairing instruments - apart from being a very interesting site for Velocette, he does have a lot of info on smiths instruments, you might find info on how to roll the bezel back on, the site shows the smiths special tool but if you have a lathe it can be easily done as long as you can make the holders for the instrument top and bottom. basically instrument is mounted in lathe between 2 holders and a bearing in a holder is pressed against the bezel as the instrument is turned (by hand).

 

[Jkilla71]

The link is great, a lot of gooddetails about Smiths.

Thanks for the compliment but even ablind squirrel finds a nut once in awhile. I have to admit that I usually getlucky with first time projects because I will stop and walk away when I getfrustrated and chances are you can find the best solutions to any projectissues on the internet. ​

 

[CarlS]

Re: Tachometer

I have a friend that restores instruments, i have seen lots of bezels removed and I can tell you that is an excellent job of taking off the bezel.
Check the spindle to see if there is excess wear - if it flops about too much it may need rebushing, this could throw out the whole of he spindle to the point where its rubbing somewhere it shouldn't.
You might want out check out the velobanjogent site (http://velobanjogent.blogspot.com.au/search?q=magnetic)- another friend - he spent many years repairing instruments - apart from being a very interesting site for Velocette, he does have a lot of info on smiths instruments, you might find info on how to roll the bezel back on, the site shows the smiths special tool but if you have a lathe it can be easily done as long as you can make the holders for the instrument top and bottom. basically instrument is mounted in lathe between 2 holders and a bearing in a holder is pressed against the bezel as the instrument is turned (by hand).

Good post and good link. Thanks for information.

 

[Jkilla71]

Re: Tachometer

I had gone to my old man’s house yesterday and the shaft is now spinning free. Turns out the needle comes right off with your fingers, I was going to cut a piece of paper to protect the tachometer face and pry on opposite sides with some small screw drivers but my dad told me that this is type you can just wiggle off with your fingers and he gently lifted the needle right off at the hub, Then the 2 fasteners on the face, the centers just pop out from the rear with a tiny punch. The brass plate also has the same plastic fasteners that pop out from the rear with the same tiny punch. Then the adjustment screw is taken out from the rear and the 2 plates lift out on the adjustment screw side first because it is held in with 2 forks in slots on the other side. The drive hole for the cable has a small cup that can be pulled off with little force and then we took a punch down the center of the magnet and tapped the shaft and the shaft slide out a little and my dad just stopped me there and just started soaking with penetrating oil on both sides of the shaft, he got it free in a couple seconds and then when it could be easily spun with my fingers he hooked it up to the drill and with the drive shaft underneath, he ran the drill and bathed the shaft from the inside with penetrating oil and when he was done it spun just like the new replica does. He wouldn’t let me put it back together because he wants me to bring the replica with me over Christmas so he can calibrate the Smiths with it using an electric drill. I counted how many turns it was to remove the adjustment screw but he said it wouldn’t be correct and I am in no hurry anyway.







I did take a picture of it with the brass plate removed but I think my thumb got in the way because it was just darkness.

 

[Rocky]

Very nice update

 

[CarlS]

Very nice update. Thanks.

 

[Jkilla71]

I had decided to try and finish putting the tachometer back together today.
I had bought some 6mm grommets that turned out to be too big but I was able to cut the hat brim off and chop off the stovepipe part and what remains fit in good, not great but good. I am thinking the 4mm grommet might be the right size. 6mm is the inner diameter of the hole.

I wasn't happy with the way the bends in the bezel looked so I bought a new one.

My old man told me to use epxoy to put the bezel on instead of crimping he wanted me to be able to take it off again if I needed to since the bezel was new and undamaged. I didn't want to use epoxy so I made him give black silcone a try first then see if it cures and seals and holds it on. If not I will give the epoxy a try and crimp it as a last resort.

In the last picture you can see the bead silcone inside the bezel, it is kind of hard to see because of the black paint on the cup but there is a good amount in the channel. I guess time will tell if it holds.

My old man made a board with a round cutout for the tach sit in so it could be clamped in place in case we were going to climp it. However, we used heavy rubber bands to compress the cup against the bezel so we could fill the channel with black silcone instead. I will take the rubber bands off in 3 or 4 days and see if it holds




The grommets don't look much different than the stock ones with the screws back in the tach cup.

 

[devo]

nice one Joel
I hope it was a neutral cure silicone.

 

[Jkilla71]

nice one Joel
I hope it was a neutral cure silicone.

Is there a third choice? it says "non-chemically cureing" and I believe it is water based. It's intended uses is for flashing/siding/windows...etc. indoor/outdoor

 

[Jkilla71]

I forgot to mention the calibration part before we put it back together. After putting the needle back on below the stop then once it is on you push the stop in and move the needle to the proper side. We used my Replica smiths tach as a reference and hooked it up to an electric drill and spun it up to full power, which ended up being a hair over 6000 rpm on the replica tach. Then hooked the Smiths tach up to the drill and it read about 5100 rpm at full power, so a couple turns of the adjustment screw we got it right to what the replica tach was reading.

 

[CarlS]

Good work. Thanks for the post.

 

[devo]

Is there a third choice? it says "non-chemically cureing" and I believe it is water based. It's intended uses is for flashing/siding/windows...etc. indoor/outdoor

Yup, the main thing is dont use the acid cure type (smells like vinegar ) as the fumes will corrode metal and electronics