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Can anyone help me with a measurement?

Discussion in 'General Talk' started by Tashadra, Apr 5, 2018.

  1. Tashadra

    Tashadra Well-Known
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    Hi all

    I would just like to know what the distance is between the mini V wheels inside a C-beam setup.
    If anyone can help me with that measurement, that'll be great.

    I don't have any parts to measure it myself.

    Basically I want to know if a TR12 lead screw would fit/work between the wheels instead of using a TR8.
    Want to know if there would be enough clearance or would it be a very close fit.

    c-beam space.jpg
     
  2. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Due to slight variations in the extrusion runs, it would be hard to say if in any other assembly will be exactly dead on to the tolerances that exist in your assembly. A better suggestion would be simply to cut a strip of cardboard 12mm wide and see if it fits and if so how much is left over. If it turns out that you have say 12.2mm in there, do you think you can perfectly split the difference? You might consider a TR10 instead as it will leave you plenty of room to spare. 10x16 bearings that will fit the end pockets are also readily available.
     
  3. Tashadra

    Tashadra Well-Known
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    Thanks for the reply

    The problem is I'm still in the drawing/designing phase. I'm basically beefing up the sphinx design. I don't have any parts on hand. On CAD it looks like there would be enough gap, close but enough. I just wanted to confirm with a real world measurement.

    I was thinking of going 1200mm on the Y axis and 800mm on the X axis (lead screw lenghts). At those lenghts I'm scared that TR10 would have too much whipping.
     
  4. Scotty Orr

    Scotty Orr Master
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    I don't have a Sphinx, but I am using a TR8 on a 1000mm axis and have eliminated whipping. I think a TR10 should work fine.
     
  5. Tashadra

    Tashadra Well-Known
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    Scotty could you perhaps explain how you eliminated whipping?
     
  6. Scotty Orr

    Scotty Orr Master
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    The best way is to have enough length to put the lead screw under tension (instead of compression). I didn't have that extra length, and didn't want to cut down my C-beam. So what I did is illustrated in the following video. Some may disagree, but it worked (and is working) for me.

    [I tried to set the video to start at 12 minutes in. If it didn't, skip ahead to 12 minutes.]

     
    #6 Scotty Orr, Apr 5, 2018
    Last edited: Apr 5, 2018
    Mark Carew and MaryD like this.
  7. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Knocked a plate together and came up with 12.9mm clear between the wheels so even accounting for minor dimensional variations you should be fine with a TR12 screw. You will need to give some thought to the anti-backlash nut and how to install bearings at the end plates. If you have the shop capacity available you may want to turn the ends of the lead screws down to 8mm. This will simplify the build due to the readily available 8mm bearings already sized to work with the C-Beam end plate holes.
     
    Mark Carew and MaryD like this.
  8. Tashadra

    Tashadra Well-Known
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    Thanks guys, really helped alot.

    I was planning to machine all plates myself so bearing sizes are not an issue.

    Holding thumbs haha
     
  9. MaryD

    MaryD OpenBuilds Team
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    I only know one other person that uses that phrase and he lives in South Africa. :) Here in the states, we'd say "cross your fingers".

    Gesture_-_Holding_Thumbs (Small).JPG crossed-fingers (Small).jpg
     
  10. Tashadra

    Tashadra Well-Known
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    Hahaha, well I'm from South Africa ;)
     
    MaryD likes this.
  11. Mark Carew

    Mark Carew OpenBuilds Team
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    Great explanation and demonstration @Scotty Orr thank you for sharing this tip :thumbsup:
     
    Anthony Bolgar likes this.

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