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

  1. #76
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    I spent a hunnerd bucks on some parts today..Got the bearings and intermediate (jack-shaft)...



    Close up pic with the cell phone:



    The intermediate shaft is 1" and will carry the 18" pulley as well as a 6" pulley and I will need to have a key-way cut in it and then I'll cut the shaft to length when I determine the apropriate length.

    The 7/16" all-thread will go all the way through the headstock and hold both flange bearings.

    I also picked up the 3/4" all-thread that will hold the ways.

    Still waiting on the sheave and bushing for the primary drive on the headstock so I can have the 1-3/4" shaft made.

    More to come
    Last edited by Mark Norman; 04-09-2009 at 1:25 AM.

  2. #77
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    Quote Originally Posted by Dave Bryan View Post
    Mark,
    I really like your idea about a concrete lathe base. I built a wood lathe base and am pretty pleased with it. I wanted to build the most out of wood instead of metal, since I'm a woodworker. The three main metal parts are the headstock spindle, tailstock spindle and bed. See the attached picture.

    I did learn several things the hard way. First, the alignment of the headstock parallel to the bed both vertically and horizontally is critical. Second, alignment of the tailstock to the headstock is just as critical. Without these, spindle turning or even using the tailstock to support a bown in the initial stages of turning will be a problem, and drilling using the tailstock almost impossible. I used a 16" long 2" dia round bar turned down to a 1 1/2" dia headstock spindle with 1 1/4X8 threads. It is supported by two deep groove bal bearings in spherical mounts, which I think is the critical part. This allows you to align the spindle regardless of how mis-aligned the vertical bearing supports are (within reason). Do you plan to have a hole down the center of the headstock spindle for a knockout bar or vacuum chucking? I found machinists not very interested in drilling this long of a hole.

    There are a lot of other lessons learned that would be too long for this thread. If you are interested, please send me an e-mail through the forum and I'll be glad to share.

    Good luck. It's not just the destination, but also the journey...
    Dave, Very nice job on the wood lathe! It is very good looking and the construction looks perfect. Mak is having a blast building his monster and we all can't wait to see it completed!

    Mark, Keep plugging along and you will win the battle soon!

    Jeff
    To turn or not to turn that is the question: ........Of course the answer is...........TURN ,TURN,TURN!!!!
    Anyone "Fool" can know, The important thing is to Understand................Albert Einstein
    To follow blindly, is to never become a leader............................................ .....Unknown

  3. #78
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    You are absolutely correct Jeff

    On both accounts. Dave did do an awesome job on his and I am greatly enjoying the design-build process.

    I hate waiting for parts though

  4. #79
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    you need to paint it. im thinkin binford colors.
    14x48 custom 2hp 9gear lathe
    9 inch pre 1940 craftsman lathe
    36 inch 1914 Sydney bandsaw (BEAST)
    Wood in every shelf and nook and cranny,,, seriously too much wood!

  5. #80
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    Quote Originally Posted by curtis rosche View Post
    you need to paint it. im thinkin binford colors.
    Would that be like Chevy orange? I'm thinking Big Block LOL LOL LOL

  6. #81
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    If ya havent figgured it out yet....I like pics;)

    Made a little progress...I am going slow because it is uncharted teritory for me. .... Measure twice...and then do it again...

    I'll let the pics tell the story of todays progress...



















  7. #82
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    torrance, Ca
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    looking good. im getting giddy.

  8. #83
    Looks great!
    When is the concrete truck coming?
    I like the idea of casting the sleeves in place for everything.
    Good job! I'm getting inspired!

    P.S. Did I miss it? What are you using to make the outer curves of the form?
    Last edited by Steve Frederick; 04-10-2009 at 7:25 AM. Reason: Added a question

  9. #84
    Hi,

    I have been following this thread for about two weeks now and have been interested in posting the following comment before you got too far. Unfortunately the forum moderators rejected all previous attempts to register an account. Luckily, fourth time’s the charm!!!

    My background is in architecture. Architects in general do not design structure, but we have a basic understanding of the forces involved. I may be wrong but the diagram below shows my concerns. But first, Have you planned any reinforcement? I think there may be quite a bit of moment acting on the concrete, and without proper reinforcement you may be in for a nasty and dangerous surprise. At the very least the reinforcement will hold things together if there is a failure.

    Concrete is only useful in compression (typically 2500 to 3000 psi for store bought mix), in this case the compression (C) side is shown on the left side of the centerline (neutral axis). The opposite side is in tension (T), for which concrete has a value of zero. The amount of moment acting on the spindle will be based on the weight, velocity and distance of the load (a lot when unbalanced).the load acting on the spindle will create a larger moment on the uprights; the further away the load is from a support, the greater the moment. Here, shear may play a more significant role than in buildings, so it may be something to consider.

    Whichever reinforcement you use (you only need it for tension but an unbalanced load will put tension on both sides) you need to keep in mind that in order to build tension in the rebar, the bar needs to extend the minimum “development length” on either side of the moment point. This length depends on the tension force, compressive strength of the concrete and the size of the bar (larger diameter, longer development length). This may require you to make the foot of your lathe longer on both sides. Also for formed concrete you will need about 1.5 inches of cover over the rebar.

    I am sorry, it seems that this has become a lesson in structural design. I would hate for you to go through the expense and time to build this beautiful machine only to find out that a small item was missed and it can’t be fixed; or worse. If you know an engineer, have them take a look

    Good luck, Can’t wait to see it finished and the first bowl to be turned!!
    Attached Images Attached Images

  10. #85
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    I appreciate your input Ray,

    I have extensive experience in structural concrete and am familiar with the benifits of the compressive forces for concrete as well as the moment forces acting on the column, (10 years as public works inspector)

    As for reinforcing,,, you will love this,,,It will be post-tensioned, The anchors for the pillow block bearings will extend all the way to the floor and be sleeved so when the bearing is attached it will effectively compress the whole column in the vertical axis.

    You can see in the above pics I have the same thing going on for the horizontal axis by way of the 3/4 rods that will hold on the ways and 90 degrees from that I will have two rows of rods for the motor mount attachment. I will also have some steel rebar in it, hoops and stirrups. You may have noticed in the pics that I got 5000psi concrete for the project.

    Just wait, You will fall off your chair when you see the steel I plan on using to hold the horizontal member to the upright. Just some left over bridge rebar thats been on the side yard for a few years... #11's lol..

    I plan on casting it in three seperate pours, first is what you see here, and will be done "on its head" so to say, then I will lay it on its side after stripping the forms and cast the horizontal (the water main pipe), Then I will bring it upright and the last pour will be the small vertical support on the right end of the machine.

    I called my supplier that supposed to be getting me the sheave and bushing for the headstock and apparently he is having difficulty getting a five inch sheave with a 1-3/4 bore so I told him I could have the spindle turned down to any size and to see if he could find one that is 1-1/2" or even 1" would work.

    Lunch time is up, back to work...

    Steve, you didnt miss nuthin, I havent disclosed it yet tease tease tease....
    Last edited by Mark Norman; 04-10-2009 at 2:04 PM.

  11. #86
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    Tonights progress...More hardware...

    I'll let the pictures speak for me



    Just so happens you can get aluminum flashin in 14" at the BORG..



    Just right!!




    I picked up a few acorn nuts for a more finished look.



    Rusty steel could use sandblasting...







    Thinking....

    Mock-up:


  12. #87
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    That is going to be one SWEET lathe.

  13. #88
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    Wimberley, Texas
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    As the man who fell off the 20 story building was heard to say on the way down, "So far, so good". You have indeed considered many things (post #3) and provided much vicarious enjoyment for your readers. We can hardly wait for each new update.

    Have been told (years ago) that rusty rebar actually bonds better with concrete than clean rebar. Assume you have access to more recent actual test data that may dispel this myth(?).

    Looking good so far, and wish you continuing success.
    Richard in Wimberley

  14. #89
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    Thanks Alex.
    It's turned out to be a lot more work than I thought it would be in the begining.
    It's working out well though.

    I am pleased with the progress

  15. #90
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    Quote Originally Posted by Richard Madison View Post
    As the man who fell off the 20 story building was heard to say on the way down, "So far, so good". You have indeed considered many things (post #3) and provided much vicarious enjoyment for your readers. We can hardly wait for each new update.

    Have been told (years ago) that rusty rebar actually bonds better with concrete than clean rebar. Assume you have access to more recent actual test data that may dispel this myth(?).

    Looking good so far, and wish you continuing success.
    Thanks Richard.. you make me laugh...

    I think too much sometimes...then I sleep on it. then Hopefully it comes together. If I can entertain along the way....all the better
    Thanks again

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