Wheel Train not working.

Discussion in 'Clock Construction' started by dandydude, Apr 18, 2015.

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  1. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Hello,

    Iam building a clock. It has four wheels including the great wheel. The fourth wheel is supposed to indicate the seconds. It would be turning the escape wheel as per my design.
    The wheels currently are 3D printed plastic. The arbors are aluminium that i turned on my lathe. The bearing are all ball bearings.
    I can turn the 4th wheel with my finger, and all the wheels turn in their respective ratios. However, iam not able to turn the wheel from bottom up. I mean when i try turning the great wheel, it simply wouldnt move.
    The 4th wheel is A 0.6 module. The great wheel 2nd and 3rd are 0.7 module. All are cycloidal gears.
    The photograph shows my test stand. I have in fact used my water bottle as the weight so that i can adjust the weight with the amount of water. The bottle is full at the moment and hasnt made a difference.

    Thanks
    Dilip WP_20150418_005.jpg WP_20150418_006.jpg
     
  2. David S

    David S Registered User
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    Dec 18, 2011
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    Have you tried just trying them in pairs. I.e. 1st and 2nd wheels in place and see if they turn, the 2nd and 3rd and so forth? It is going to take quite a bit of force anyway, and I don't think a small water bottle with do it.

    David
     
  3. MartinM

    MartinM Registered User

    Jun 24, 2011
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    Because of the additive factors of working with so many variables. I'd look at trying to diagnose it by using Plastigauge. Just run a strip through each gear pair with no other gears in the train. The amount of flattening will tell you where the tight spots are.
     
  4. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Hello,

    I trust the drawings and 3D printing to such an extent that i hadnt even looked closely at the gears. The quality of the prints arent great. I had a look at it with the loupe. The wheels are not meshing well with the pinions. Not much space between the pinion leaves. I guess i will have to have it done precisely in metal and test it again.

    Regards
    Dilip
     
  5. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    You are also, kind of, pushing the envelop with plastic
    gears. The pinions should be made of metal or,
    use less ratio change at each step. ( meaning,
    use two gear sets in place of one )
    Also, remember, in a clock, the gears only need
    one face. You can make the back side thinner, reducing
    the need to make high quality gears on your 3D printer.
    Tinker Dwight
     
  6. Jim DuBois

    Jim DuBois Registered User
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    Jun 14, 2008
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    I notice you have the mechanism suspended by the back plate of the clock I think? Many movements sit on a seatboard so the frame doesn't try to go trapezoidal when the weight is hung. Even the slightest flex in the frame can cause serious loss of energy/binding/non running etc. Also, even in ball bearings the arbors need a bit of end shake, just a few thousandths of an inch is sufficient, the arbors need to slip on the bearings freely also. Otherwise the endshake will not be available to the arbors....finally, there is a tendency for people to fit a clock train according to specifications developed for non clock applications. Clocks have very little power available to power the escapement, and the gear train speeds up motion while most gear trains reduce take a higher RPM power source and reduce it. As a result of all this most first clock efforts by engineers and the like are fit too tight in several ways....
     
  7. Burkhard Rasch

    Burkhard Rasch Registered User
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    Jun 1, 2007
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    agreed to all what has been said the "drum" seems to be quiet small (to my eyes) in relation to the first wheel causing additional load needed to move the train .Maybe a bigger drum would be the solution?
    Just my 2cts..
    Burkhard
     
  8. tok-tokkie

    tok-tokkie Registered User

    Nov 25, 2010
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    I must agree with what Jim posted. I made a wall clock using a thick stainless wall plate with four 'pillars' poking out horizontally with the gear train on plates fitted to those pillars. The train worked ok under hand power but the sag caused by the weight made the train jam up. I added a wooden prop down to the floor to support the front plate and the train then worked ok.
    I remade the clock using a seatboard and it worked ok. Initial seatboard was two planks on top of a fridge. When I made the proper wall mounted seatboard I was able to reduce the drive weight quite a bit. The more rigid seatboard made the same train work better.
     
  9. dandydude

    dandydude Registered User

    Nov 30, 2014
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    Dear Burkhard,

    All my pinions are minimum 12 leaved. With a 144 teeth great wheel i need 16 rotations of the drum to last me 8 days. I am making a wall clock. I have a certain height in mind. The cord would become too long if i used a larger drum. To take a care of the extra weight requirement i am trying to reduce friction as much as i can. Iam using ball bearings for all wheels including escapement.

    You are right the drum is quite tiny. However i tried pushing the wheel with my hand and it would still not budge. I figured, 3d printing is just not been precise.the teeth dont mesh. the pinion leaved are blotched and dont have the space between the leaves to accomodate the gear teeth.

    Iam getting the wheels cut in metal and will update you about how it goes.

    Thanks
    Dilip
     
  10. Tinker Dwight

    Tinker Dwight Registered User

    Oct 11, 2010
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    A pulley on the weight makes the drop 1/2.
    Take a file to the back sides of the teeth. I suspect
    a clearance issue.
    Tinker Dwight
     

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