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  1. #25
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    Quote Originally Posted by widgitmaster View Post
    .....In my honest opinion, my design will gain tremendous efficiency due to perfect alignment, and any friction caused by using ball bearings at the pivot point will be negligible! Gravity causes the friction, but Gravity also perpetuates the motion!

    Eric
    Come on Eric, nobody is perfect.

    But I do think you come closer to it than most people when it comes to machine work.

    On source of friction that may remain in your design is the lubricant in the bearings and the seals. Have you considered open bearings running dry; they are going to be very lightly loaded.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  2. #26
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    LOL
    Thanks Geof!

    Because the bearings are already in house, I don't think I'll be changing them. They were not too expensive, but seals can be removed and lubricants washed off!

    This morning I placed an order in McMaster-Carr for a "Bulls-Eye" level, and four stainless adjustable feet! With all this concern for friction, we would not want this puppy sitting on an incline would we?

    Eric
    Attached Thumbnails Attached Thumbnails Buls-Eye_level.gif   Leveling_feet.gif  

  3. #27
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    This is going to be very cool. Can't wait to see it.

    Watching the videos, I do agree the other systems were losing a lot from all the twisting and misalignment.

    I have to give you another crazy thought though. Two in fact.

    First, since you're swinging your balls (hmmm, that didn't sound good) with rigid arms, you wouldn't have to start the mechanism by grabbing a ball and pulling it away. There is no harm in that if you do, I'm just saying you wouldn't have to. You could, for example, grab a lever at the top of the arm.

    That brings me to my second remark. As soon as I saw the guy in the video trying to "push the swing" to keep it going, it made me wonder what sort of mechanism could do that automatically. I'm imagining a circuit that waits for a photo interrupter to tell us that the arm has swung to a certain position and then some sort of fast acting actuator (air? solenoid? starter solenoid from a car?) to give it a shove at that point. This mechanism could be mounted above to act on a lever that is part of the rigid arm per point #1.

    These are not serious suggestions to change your design at all. As I said, they're just crazy thoughts.

    I'll be quiet now and enjoy the show.

    Cheers,

    BW

  4. #28
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    Quote Originally Posted by BobWarfield View Post
    This is going to be very cool. Can't wait to see it.
    .... "push the swing" to keep it going, it made me wonder what sort of mechanism could do that automatically....BW
    Cool is a conservative description.

    Regarding the pushing I have seen 'perpetual' pendulum toys which had an electromagnet at the bottom of the swing to give it a little kick every time it went past. I guess there must have been a Hall sensor to activate the kick just before bottom dead center and turn it off right at the bottom.

    Something like this could possibly be incorporated but I think part of the charm in Eric's project is the goal of very low friction and very precise alignment for very slow dissipation of the starting energy.

    Maybe we can start a sweepstake to guess the running time for a given angular displacement of the ball. My guess for a starting angle of 30 degrees from the vertical is 5 minutes.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  5. #29
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    Well, I started out good by cleaning up the shop removing everything from the mill table. With an open table I placed one of the plates on paper, to keep the nice finish from getting scratched. Then I use an end mill to bring two sides parallel and to print.

    Next I setup the vise in the long direction. Along with some soft jaws mounted on the outside of the vise, I milled a nice step in both jaws to hole the thick plates. Then I milled the length of both plates.

    Now I setup a stop on the vise, and used a 3/4" dia ball end mill to make the fancy radius on the top edges of the base plate! All was looking really pristine, until my slippery coolant soaked hands dropped the FLIPPING PLATE

    Now all four corners and edges are badly damaged, I have to either order another plate, or shrink the whole assembly in CAD and start over again!

    I bet everyone in the UK heard me blow off steem about an hour ago
    Attached Thumbnails Attached Thumbnails 100_4703.JPG   100_4705.JPG   100_4706.JPG   100_4707.JPG   100_4708.JPG  

    100_4709.JPG   100_4710.jpg   100_4711.JPG   100_4712.JPG  

  6. #30
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    I think I can fix it!

    After I calmed down, I brought the plate into the house and washed the oil & dirt off it. Then I measured some of the damaged corners and edges ...

    I will need to expand the .375 radius to .438, and mill a .094 radius on all other 90 deg corners. By doing this, 99% of the damage will be removed!
    But I have to order a 7/8" dia ball end mill!

    :banana:

    Eric
    Attached Thumbnails Attached Thumbnails 100_4713.JPG   100_4714.JPG  

  7. #31
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    This morning I calculated the centers for the pockets, and placed the part in the vise bottom side up. Then I set the DRO to x,y zero in the center of the plate. With this setup, I can drill & countersink all the holes, drill & tap the four holes of the adjustable feet, and mill out all the pockets without removing the plate from the vise!

    First I finished all the larger pockets, as they all have the same distance from their centers. After lunch, I'll finish the remaining pockets, With a little luck, I should be able to get the whole bottom view finished in one day!

    The .875 dia. ball end mill is on order, should be here in a day or two. That will erase the blunder from yesterday !
    Attached Thumbnails Attached Thumbnails 100_4715.JPG   100_4716.JPG   100_4717.JPG   100_4718.JPG   100_4719.JPG  


  8. #32
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    Eric, do you hand crank these? What depth of cut per pass are you using? Man, you have a lot of patience.

  9. #33
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    Yes, but I do have a power x-axis feed!
    I made them .625 deep, and first cut was .300 deep
    And yes, my back is tired! Maybe its time for one of those thick pork chop dinners

    Didn't feel like drilling & tapping, so I stopped and deburred the pockets!
    Attached Thumbnails Attached Thumbnails 100_4720.JPG   100_4723.jpg  

  10. #34
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    ill bet we're all thinking the same thing....about the hand cranking...

    "just use that cnc ya built"

    then when a tool path was wrong..and it tried to rapid across the plate at a diagonal .....

    we would have really heard some disapproval ..very much like the plate dropping

    ,....am i right?
    "witty comment"

  11. #35
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    Ah yes, but remember it was people cranking handles who made all the parts that landed us on the moon! I like it, I've been doing it for over 39 years! CNC has its strong points, but people cranking handles made them too!

  12. #36
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    Quote Originally Posted by .xXACEXx. View Post
    ....then when a tool path was wrong..and it tried to rapid across the plate at a diagonal .....
    I have a feeling that if Eric did do CNC the probability of something like this happening would be very low; not zero because perfection is not possible but a lot closer to zero than a lot of us.
    An open mind is a virtue...so long as all the common sense has not leaked out.

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