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  1. #1
    Registered User Jim Burghart's Avatar
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    Default Repairing worn pinions. Testing using epoxy?

    I am working on a nice early wood works tall case movement. The maker is Joel Curtis from Cairo, NY. Some of the pinions on the time side are very badly worn. I normally would send them to Don Bruno to have new ones made, but I would like to keep the movement as original as possible.
    I decided to try using epoxy and powdered pigments to fill to groves. Has anyone done this before, I would be curious how well it holds up?


    I am posting a before and after photo. I still need to finish sand the pinion smooth and add a bit of a finish.


    Since the server was down last night, I posted this to the Facebook page too.


    Below are the basic steps I used.


    I used a very similar technique to the one I use for casting new gear teeth. I used 5 minute epoxy and mix in powdered pigment to attempt to match the color. It also helps make the epoxy more like a putty.


    I clamped the gears so the pinion tooth I was filling is flat. Add the epoxy mix and let it set up. For this movement I had to do this on 3 pinions. So 3 clamps, and 3 teeth at a time. A bit tedious, but keeps the epoxy where I wanted it without making a mess.


    The shaping was done with a small file first, then fine sand paper doubled sided taped on a piece of stiff flat brass. You have to be very gentle and take your time. The pinions can easily break. Next I am going to use some thinned linseed oil to finish it off.
    I think making the surface as smooth as possible is important to reduce wear and friction.


    I will post the results once I get the movement in the test stand. The epoxy is set in very well, and was not hard to file. I'll be really happy if this works








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  2. #2
    Registered User tom427cid's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: Jim Burghart)

    Looks as if it will work,but, I think that I would address any wear on the mating wheel. Unless they don't appear worn-then it probably will work.
    Good luck,BTW nice job!
    tom
    "keep 'em runnin' "

  3. #3
    Registered user. roughbarked's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: tom427cid)

    I may have drilled and put in a couple of pins to bond it better to the pinion but otherwise, as said above.

  4. #4
    Registered User Burkhard Rasch's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: roughbarked)

    looks good,and I do whish You the best,but wether it works on the long run we´ll see.I hope the epoxy stuff sticks enough to the wood!
    Best
    Burkhard
    Gigni de nihilo nihil,et nihil in nihilum posse reverti
    (Persius)

  5. #5
    Registered User Jim Burghart's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: Burkhard Rasch)

    Thanks for the comments and ideas. Since I can't move the wheels on the arbors this is my only choice outside of replacing them.

    I like the idea of adding pins as a bonding surface. I have a few more teeth to go, and I'll give it a shot.

    The movement had had bushing work done in the past, and I think there were depthing issues. The movement was temperamental, and the train felt like it had some resistance on the time side. I plan on removing all the old bushings and attempting to relocate them to a better location.

    I have never had to relocate some many pivot holes. I am thinking of starting at the escape wheel and working back?

    The epoxy held up great when filing and sanding, hopefully that's a good sign.

    Jim

  6. #6

    Default Re: Repairing worn pinions. Testing using epoxy? (By: Jim Burghart)

    Quote Originally Posted by Jim Burghart View Post
    ...........I used 5 minute epoxy and mix in powdered pigment to attempt to match the color. It also helps make the epoxy more like a putty.
    ...........I like the idea of adding pins as a bonding surface.
    ...........The movement had had bushing work done in the past, and I think there were depthing issues.
    ...........The movement was temperamental, and the train felt like it had some resistance on the time side.
    .......... I plan on removing all the old bushings and attempting to relocate them to a better location. I have never had to relocate some many pivot holes. I am thinking of starting at the escape wheel and working back?
    ..........Next I am going to use some thinned linseed oil to finish it off.

    The epoxy held up great when filing and sanding, hopefully that's a good sign.

    Jim
    There's a lot going on here and one cannot argue with success but I do have a few concerns. I believe the relevant points are in the quote above. You are correct to be concerned about the epoxy bonding to the teeth which are usually worn very smooth. One would usually 'rough up' the surface for a better bond but in this case I'm afraid that would remove additional material may make it more difficult to preserve the original shape of the teeth. I'm not sure what sort of 'pins' are proposed, metal or wood pegs? in either case I'm afraid that making holes in the teeth for the pegs, while slightly increasing the bonding surface, may actually weaken the original structure. I'm also concerned that contaminating the epoxy with "powdered pigment" to the extent that it renders the epoxy "like a putty" will reduce the strength of the bond and the hardness and durability of the bond and finished wearing surface. I have tried this repair using epoxy and very fine wood sawdust which is similar to the original material, but have come to the conclusion that unless the wear on the teeth is extreme, that it is often best to leave it alone. Old parts that have run together for going on 200 years often seem to have 'mated'.

    You said that you felt there were depthing issues and previous bushing work that is suspect. If this clock were on my bench I would begin by correcting the depthing and bushing issues first, and then evaluate whether the worn pinions are actually causing a problem. There are a couple of things to look for here. First, old wooden wheels tend to shrink in one direction more than the other and are often found to be somewhat oval. So when evaluating the depthing be sure to check it all the way around the wheel. Usually an average works OK. (Trueing an oval wheel involves a bit more than just turning it round, but that's another story). The second thing to watch for (perhaps it should be the first) is once you have the bushings properly centered and the pivot holes sized correctly, if any of the wheels are closer to the worn pinion than they were when the pinion was worn you may find that the tip of the tooth will jamb against the 'rut' in the pinion. As the pivot holes and pinions wore together over the years that wasn't a problem but it often can be an issue once the pivot holes are 'tightened up'. Replacing the pinion or 'filling in' the ruts as you propose may be the only solution.

    You said "the train felt like it had some resistance on the time side." I suggest that you specifically identify the source of that friction before using the 'shotgun' approach of replacing all the bushings and filling all the rutted pinions. I'm sure you already know that poorly shaped replacement teeth are a common cause of friction hang-ups so if any are present they should be suspect.

    Finally, I would avoid the linseed oil. The last thing you need is something like this penetrating the wood around your epoxy patch and interfering with the wood bond.

    I hope you can report back in a few years that everything held up and is running great.

    RC

  7. #7

    Default Re: Repairing worn pinions. Testing using epoxy? (By: R. Croswell)

    Here is a rather badly worn pinion in my Seth Thomas wooden works. I resurrected this clock from a damp basement about 2 or 3 years ago. I decided that the best way to 'fix' this worn pinion was to just leave it alone. One of the best running clocks I have and I run it all the time. Sometimes a problem really isn't a problem. I suspect I'll be dead and gone for decades before this pinion actually needs to be replaced.

    RC
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  8. #8
    Registered User George Nelson's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: R. Croswell)

    RC and All,

    RC, thanks for your most thoughtful comments! I have been sitting back, quietly reading these posts and realized that I had a lot of questions about things. You thorough post, presenting your thoughts and concerns, addressed ALL of my questions completely!

    I am just beginning to delve into the wood works repair facet of our hobby, and am amassing a notebook of hints and helps to get started. Your always most helpful comments are so very much appreciated!

    Best to all,

    George Nelson

  9. #9
    Registered User Jim Burghart's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: George Nelson)

    Thank you RC.

    I agree there are a number of concerns. The resistance seemed to be directly related to the gears not meshing smoothly. There are no replaced teeth on the time side.

    Your concern about the linseed oil is well noted, and I will avoid using it. Maybe a light coating of wax to help smooth the surface?

    The powdered pigment I use does not seem to create an issue for the epoxy. It doesn't take much. The 5 minute epoxy is much more like putty all ready, and the powder really just adds color. I have been using it along time to color epoxy for repairing missing teeth and before that for repairing damage to model airplanes. I have never had the epoxy fail, but this may have more stress on it.

    As it turns out, Mother Nature has given me a day in the workshop. Hopefully I can get more done today.

    Time will tell.

  10. #10

    Default Re: Repairing worn pinions. Testing using epoxy? (By: Jim Burghart)

    Quote Originally Posted by Jim Burghart View Post
    .........The resistance seemed to be directly related to the gears not meshing smoothly. There are no replaced teeth on the time side.
    I find it helpful to assemble the plates with just two 'gears' at a time when looking for meshing issues. maintaining slight loading on the driven arbor helps. Also check for rotation in both directions. Sometimes the asymmetrical teeth will bind in one direction and not the other which can help identify the bad guy. Turning the wheels using an artist brush or very light spring wire (like a guitar string) can help locate the 'tight spot' as indicated by the brush bristles or spring wire flexing more when the tight tooth passes the pinion.

    Good Luck

    RC

  11. #11
    Registered user. roughbarked's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy?

    Quote Originally Posted by R. Croswell View Post
    I find it helpful to assemble the plates with just two 'gears' at a time when looking for meshing issues. maintaining slight loading on the driven arbor helps. Also check for rotation in both directions. Sometimes the asymmetrical teeth will bind in one direction and not the other which can help identify the bad guy. Turning the wheels using an artist brush or very light spring wire (like a guitar string) can help locate the 'tight spot' as indicated by the brush bristles or spring wire flexing more when the tight tooth passes the pinion.

    Good Luck

    RC
    Yes. It is indeed all about the relationship between each wheel. The watchmaker's air puffer teaches me a lot about such relationships.

    Now I've not tried any of this with wood. If it was me, I'd have likely cut a bit of wood with self attached dowels and drilled fine holes, thinned the dowels to fit the holes if necessary and used wood glue, PVA. I'd then tie it all up with string for a day a week a month or a year, depending on the urgency and then come back and thin the wood into the shape of the other teeth.

    but bear with me, has anyone tested the difference between the epoxy and plastibond? I know it is also an epoxy but I need to realise which epoxy compound you are using to be able to either visualize or test what you are doing, in order to be able to corroborate your findiings.
    Last edited by roughbarked; 03-14-2017 at 09:43 AM.

  12. #12
    Registered User Jim Burghart's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: roughbarked)

    Great info. I like that it will remove the subjective feel from the process.

  13. #13

    Default Re: Repairing worn pinions. Testing using epoxy? (By: roughbarked)

    Quote Originally Posted by roughbarked View Post
    ..........has anyone tested the difference between the epoxy and plastibond? ......
    Which Plastibond product did you have in mind? The only ones I could find are single component glue for plastic moldings and artificial wood. Couldn't find any Plastibond epoxy. Perhaps it's only sold down under?

    RC

  14. #14
    Registered User Jim Burghart's Avatar
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    Default Re: Repairing worn pinions. Testing using epoxy? (By: R. Croswell)

    I am using the fast cure Loctite brand 5 Minute epoxy. I live in a rural area, and this is the brand they carry at the hardware store.

    I have been using the 60 minute version fro tooth replacement with very good results, and not a single failure in years. Sets up slower than would work for the pinions since there is no real way to keep it from running. The 5 minute stuff was easy to get in place, and file and sand after. Just take patience.

    I did practice on some odd bits I had in the shop to make sure it would work. Once I get it running time will tell.
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  15. #15

    Default Re: Repairing worn pinions. Testing using epoxy? (By: Jim Burghart)

    Loctite 5-minute is good for lots of stuff. That's what I used with fine hardwood sanding dust to repair a wooden pinion. Had to do it because I replaced a broken and missing tooth and needed the worn teeth to match the same profile. I also like JB-Weld clear epoxy. My question was Which Plastibond product roughbarked was proposing to use. Also didn't quite understand how he proposed to use dowels in a repair like this.

    RC

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