Standard Electric Standard Electric Time clock problem

Discussion in 'Electric Horology' started by tsmith, Feb 13, 2015.

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  1. tsmith

    tsmith Registered User

    Nov 5, 2008
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    I have a 40's vintage Standard Electric synchronous master clock with a GE motor. The clock is in very good original condition but has a problem. There is a fiber gear (approximate 1/2" diameter and 20 teeth) that the motor drives via a steel gear. The fiber gear is missing 2 teeth and of course when it reaches that point every thing comes to a complete and immediate stop.

    The fiber gear is a press fit on a knurled shaft and can be replaced. I'm guessing there are not a lot of those gears available. Besides cutting another out of something a bit more durable such as brass, is there another solution to fix this problem?

    I've pulled the motor and clock down, cleaned out the dried grease and oiled and greased where appropriate. It all seems to work as it should except nothing works because of the gear problem.

    Any help would be greatly appreciated.

    Thanks,
    Tom
     
  2. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    I would suppose one could use layers of
    cotton fiber ( old T shirt maybe ) and fiberglass resin
    to reconstruct the missing teeth.
    One could cut into the disk to give it strength.
    It would be interesting to try, don't you think?
    Tinker Dwight
     
  3. eskmill

    eskmill Registered User
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    Aug 24, 2000
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    The "composition fiber" gear wheels are preferred when ordinary spur gear drives would be annoyingly noisy. The material is "resilient" and runs with minimal tooth-to-tooth clearances. The down side is that they require lubrication and are prone to be weak if overloaded. Very large ones were used in automobile engines as cam-shaft gears because they are quiet in operation.

    I don't know of a substitute material to reproduce small fiber gear wheels for a clock. Some have replaced the with brass gear wheels but at the sacrifice of a noisy whine sound.

    I suppose there are some modern plastics that would serve well with the same desirable characteristics.
     
  4. tsmith

    tsmith Registered User

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    Thanks for the replies. The rotational speed of the gears is 1 rpm (I think). There shouldn't be any gear noise at that speed but I'm sure they made the gear of fiber material for some reason. There is not a lot of load on the gear or they wouldn't have used plastic.

    Best case situation would be finding a original gear off a parts unit. Next I guess would be to find a spur gear from Boston Gear or ?? and modify it to work. Last would be to make one from scratch out of bronze.

    I have a few pics in the event anyone is interested in them.

    Tom
     
  5. David S

    David S Registered User
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    Dec 18, 2011
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    Building on Tinker's idea, perhaps you could locate some FR-2 printed wiring board material. It is an impregnated paper product. Since I assume the original probably has oils in it now you would have to find a way to insert the patch and secure it. If there is enough room on either side of the wheel perhaps sister strips pinned in place, then hand cut the teeth.

    Just thinking without seeing what you have.

    David
     
  6. Jeffrey R. Wood

    Jeffrey R. Wood Registered User
    Old Timer

    I scrapped some of these movements way back when they were considered virtually worthless except for parts. But today I know of none still in service at their original locations. If you can provide a better picture of your broken gear I hopefully can help. But the earliest type was extremely prone to this kind of failure. They ended up replacing the motor with a smaller type using a special adapter plate and different gears. I may have some of these!

    Jeffrey R. Wood
     
  7. Tinker Dwight

    Tinker Dwight Registered User

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    That would be pretty abrasive, David. FR is made from fiber
    glass. The ends of the strands would be like little chisels.
    If just replacing a section, just cloth and resin is OK. If making
    an entire wheel, you might want to soak the cloth in paraffin
    wax first and then resin to a disk. When hardened, turn it
    to expose the fibers. Then bake it to remove the wax and
    while still hot drop it in oil.
    Then machine the teeth.
    I'm not sure what fiber they originally used but I doubt it
    was glass fibers. It was more likely cotton or such.
    Tinker Dwight
     
  8. David S

    David S Registered User
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    Tinker you are thinking of FR-4. To the best of my knowledge the FR-2 we used did not contain any fiberglass.

    David
     
  9. Tinker Dwight

    Tinker Dwight Registered User

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    Aah Yes, you're right. I think is might be too weak for the job then.
    Tinker Dwight
     
  10. tsmith

    tsmith Registered User

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    Ok, I guess the bronze gear is out?? I can't imagine the spur to spur causing much noise with the very low rpm involved. Is there some other reason to use fiber versus bronze?

    The spur gear on the motor is steel and drives the fiber spur gear on the shaft for the time and circuit control cams/switches.
    One of the pictures I posted shows the fiber gear with the two missing teeth. I removed the motor prior to taking the picture which mounts to the other side of the plate with the drive gear protruding through and below the fiber gear.

    The gear is 1/2" OD and about 1/4" thick with 22 teeth and is pressed on the knurled shaft.

    I suppose I could cut a dovetail slot on the gear and epoxy some material in the slot but there isn't a lot of room between the teeth and the hole for the shaft.

    Thanks for the help,
    Tom
     
  11. harold bain

    harold bain Registered User
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    Tom, I suspect you missed post # 7. Contact Mr Wood to see if he might have a part for you.
     
  12. David S

    David S Registered User
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    Tom, I have been struggling to find the name of the stuff we used to use that had similar properties to the fiber gears. Here is a link to the types of material that I think would be suitable. If you could find some material or get a sample you could try to make a complete new gear.

    http://www.sdplastics.com/phenolic.html

    David
     
  13. tsmith

    tsmith Registered User

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    Thanks David. I do have some phenolic but don't know if it has the fiber material in it.

    The clock cases used in many of the WW2 deck and boat clocks used something like this. I'll have to cut some and see if it might work.

    Thanks again,
    Tom
     

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