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Thread: Making plans to build a concrete bowl lathe - opinions welcome.

  1. #91
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    Feb 2009
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    Slowly but surely



    The big (3/4") nuts will be recessed on the back side to keep it clean looking. I accomplished this with short pieces of pvc pipe. The washers will be embeded in the concrete.









    I used gate hinges for the motor mount, many configurations are possible.:


  2. #92
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    Mar 2007
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    Mark,
    I am in awe of your ingenuity.
    This thread is packed with slick ideas and will likely spawn a bunch of 'me, too' projects.
    Thanks for the inspiration.

    BobV

  3. #93
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    Thanks for the kind words Bob. I cant wait to be mixing the concrete!

    There is more to come...stay tuned

  4. #94
    Looking good!

    Are you planning a way to steady the motor while running/hold belt tension?
    My motor on my home built wobbled until I made it rigid.

  5. #95
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    Yeah Steve, I plan on having a turnbuckle, Haven't decided where to mount it just yet, above the motor or below?

  6. #96
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    Nov 2008
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    Redford, MI
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    Mark,
    Your motor mount is too flimsy for a three horse motor, should be a solid plate 1/4" min to hold the motor and there is probably too much slop in the hinge joint. Under load the motor will dance.

  7. #97
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    Quote Originally Posted by Ron Lynch View Post
    Mark,
    Your motor mount is too flimsy for a three horse motor, should be a solid plate 1/4" min to hold the motor and there is probably too much slop in the hinge joint. Under load the motor will dance.
    I agree, I'm not real happy with it Ron. It won't remain as it is, the round bar is just a piece of 1/2 aluminum I had hanging around the shop and used for a mock-up. I would like to find a bronze bushing that will fit the hinges and be tight on a 1/2 steel dowell or something. btw, I cheaped out and went with a two horse motor and figgure I could allways go bigger later if needed but I think two will do just fine.
    I've stared at it for about an hour this morning...lol lol

  8. #98
    Mark, this is great, like everyone else I can hardly wait to see it run! Sure looks like you're doing a fine job.

  9. #99
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    Looking for some investment capitol....

    Thnk you Skip,
    It realy has been a lot of fun. If it turns out and works well I just might market the lathe. I would invite known turners (or anyone from the creekfor that matter) to come up for a free test drive just for the reviews.
    I'm thinking a web site is in order and I could even sell it in kit form.

    Yes, that is an open invitation for the fine folks here, If yer ever in my neck of the woods feel free to stop by for beer and a test drive on the Monolathe

  10. #100
    Mark,

    Its coming together nicely! I didn't think of building it with an unbonded post tensioned system. Are you using standard threaded rod or did you locate some stronger material?

    Ray

  11. #101
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    Quote Originally Posted by Ray Pena View Post
    Mark,

    Its coming together nicely!
    Thanks Ray...
    Are you using standard threaded rod or did you locate some stronger material?

    Ray
    I thought about it...briefly..
    Carbon structural steel A-36 (standard threaded rod) has a yield strength of 250 MPa and ultimate strength of 400 MPa (or more).
    250 x 145.037738 pounds-force per square inch or 63,260 yield strength per square inch.
    a 1/2" diameter rod has a sectional surface area of 0.2^2"
    Therefor 63,260 x .2 x 4 (#of rods) = 29,000 pounds yield strength.
    or 46,400 pounds ultimate strength.

    I don't think the machine will ever see 30k pounds of tensile forces acting on it do you?


    I did follow up on the special order sheaves and they are due in Wednesday...Woot Woot!! I can finally get the spindle machined. With any luck the shop can have it done by the end of the week and I'll be mixing concrete next weekend.

    I also stopped by OSH and picked up a few bronze bushings for the strap hinges today as well.. It will take a little work to make them fit the hinges but I'm capable. As well I have some steel stock to reinforce the motor mount.

    Stay tuned...

  12. #102
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    Feb 2008
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    torrance, Ca
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    2 HP should be enough unless you get REALLY serious. Until you starting turning stuff over 100 pounds regularly you should be fine.

  13. #103
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    Quote Originally Posted by alex carey View Post
    2 HP should be enough unless you get REALLY serious. Until you starting turning stuff over 100 pounds regularly you should be fine.
    Thats what I was thinking Alex. I can always upgrade later...

    I've been fiddlin with the motor mounts tonight, ground down the bronze bushings and pressed em in the hinges. Nice precision fit Not 100% sure I like it but it will work till I come up with something beter. (should have got pics but its gettin late)

  14. #104
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    Quote Originally Posted by Mark Norman View Post
    I agree, I'm not real happy with it Ron. It won't remain as it is, the round bar is just a piece of 1/2 aluminum I had hanging around the shop and used for a mock-up. I would like to find a bronze bushing that will fit the hinges and be tight on a 1/2 steel dowell or something. btw, I cheaped out and went with a two horse motor and figgure I could allways go bigger later if needed but I think two will do just fine.
    I've stared at it for about an hour this morning...lol lol

    I think its more than just the hinge play should be considered; on my rockwell, (embarrassingly modified, but now a memory to the 3520B....) it would jump up about one-two inches when I turned it on, no matter what speed pulley I had the belt on, and very slightly when I was turning heavy blanks. I hadn't designed any way to completely lock the motor in a single plane; it was mounted on 1.5" x 12" stainless piano hinge. I had originally planned to figure something to keep it from moving, and to keep more tension on the belt than just the weight of the motor, but I never got around to it. This was really annoying, and I think contributed to some serious chatter when shear scraping. I don't have the same problems now; granted the stand on the 3520 is incomparably more stable, but I think the motor mount also contributes somewhat significantly as well.

  15. #105
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    Did You have a soft start programed on the VFD Nathan?
    I am working on a tensioning devise for the motor....Pondering...

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