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Thread: Leg Press Question

  1. #1
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    Leg Press Question

    I have been asked to make a replica of the vertical leg press below. My only question is about the portion that moves up and down along the round bar runner. I plan to use cold rolled round for the stationary portion and a DOM tubing for the portion that moves up and down. What material should I use to act as a bearing between the cold rolled and DOM. I have seen a dense plastic with holes drilled in the center but I'm not sure what the plastic is called. Or the type of bearing needed.
    Thank youName:  Vertical-Leg-Press-Machine-D7X-1.jpg
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  2. #2
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    Re: Leg Press Question

    I have seen Linear ball bearings but gettthat OD to match my pipe or DOM ID will be tough

  3. #3
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    Re: Leg Press Question

    Look at IGUS bushings. And linear motion "Thompson" shafting for the shiny shaft. McMaster-Carr has both.
    https://www.mcmaster.com/precision-s...tion-shafts-5/
    https://www.mcmaster.com/bushings/li...ng-type~plain/

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    Re: Leg Press Question

    The plastic is called UHMW for Ultra High Molecular Weight. It is a machinable plastic and is used as a bearing quite a bit in industrial applications. It comes in different thicknesses that I've seen up to 1" and more down to 1/32".
    Last edited by HotRodTroy; 09-15-2020 at 06:43 PM.
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    Re: Leg Press Question

    I found this at Mcmaster carr Oil-Filled Easy-to-Machine
    Wear-Resistant Cast Nylon Tubes https://www.mcmaster.com/84755K414.

    Hot Rod Troy I have used that plastic in strips for squat racks in strip form. People like it because it does not wear the bar down (A section no one touches under 6"5")
    I did not know it was in round form. I will have to check that out

  6. #6
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    Re: Leg Press Question

    Quote Originally Posted by kb0thn View Post
    Look at IGUS bushings. And linear motion "Thompson" shafting for the shiny shaft. McMaster-Carr has both.
    https://www.mcmaster.com/precision-s...tion-shafts-5/
    https://www.mcmaster.com/bushings/li...ng-type~plain/
    Those look great, but not in this guys budget.

  7. #7
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    Re: Leg Press Question

    You might take a look at pex tubing. It's cheap and durable.

  8. #8
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    Re: Leg Press Question

    They have cheaper alternatives : For 3/4" Shaft Dia.
    7/8" 1 1/4" 1 1/16" 1/16" 155 lbs. @ 60 rpm 50 lbs. @ 60 rpm White -200 to 180 Made of FDA Listed Materials 57785K226 $9.29

    Name:  57785k217c1-d03c-digital-master1569533450-p9@1x_637051283172597801.png
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    https://www.mcmaster.com/uhmw-polyethylene-bushings/

    Available in 3/16" to 1-1/2" shaft dia.

    Mcmaster isn't the cheapest, you could find on Amazon cheaper if you needed bulk. You could also make your own on a lathe. UHMW needs a nice sharp tool to get a nice cut.

    good luck
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  9. #9
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    Re: Leg Press Question

    Just for added info UHMW is also available in ROLLS of self adhesive strips in various widths and thicknesses.

    I have used them on barbell storage racks.

    :

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    Re: Leg Press Question

    Quote Originally Posted by Lis2323 View Post
    Just for added info UHMW is also available in ROLLS of self adhesive strips in various widths and thicknesses.

    I have used them on barbell storage racks.

    I will look into that. I use 1/4 thickness in 2 and 3" widths frequently.

  11. #11
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    Re: Leg Press Question

    Quote Originally Posted by albrightree View Post
    They have cheaper alternatives : For 3/4" Shaft Dia.
    7/8" 1 1/4" 1 1/16" 1/16" 155 lbs. @ 60 rpm 50 lbs. @ 60 rpm White -200 to 180 Made of FDA Listed Materials 57785K226 $9.29

    Name:  57785k217c1-d03c-digital-master1569533450-p9@1x_637051283172597801.png
Views: 358
Size:  11.3 KB

    https://www.mcmaster.com/uhmw-polyethylene-bushings/

    Available in 3/16" to 1-1/2" shaft dia.

    Mcmaster isn't the cheapest, you could find on Amazon cheaper if you needed bulk. You could also make your own on a lathe. UHMW needs a nice sharp tool to get a nice cut.

    good luck
    That might be perfect

  12. #12
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    Re: Leg Press Question

    Is that a common style bushing on press machines. I was wondering, how will those handle the compression from hitting that spring. The hammer effect might affect both ends? Seems like internal machining of the tubing might be necessary?

    Is bronze not an option.

  13. #13
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    Re: Leg Press Question

    Good point. Bronze is an option

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    Re: Leg Press Question

    Quote Originally Posted by Reebz View Post
    Good point. Bronze is an option
    surprisingly , Bronze is cheaper(at least in this size). These are common machine parts, and should last a fairly long time, even in compression.

    Name:  7815k31c2-d03c-digital-master1569619879-p9@halfx_637052131539706793.png
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    Multipurpose Flanged Sleeve Bearings

    These leaded bronze bearings are strong, wear resistant, and excellent at handling shock loads. They’re sometimes called 932 bronze bearings.


    For 3/4" Shaft Dia.
    7/8" 1/2" 1 1/8" 1/8" 1,500 lbs. @ 60 rpm 2,200 lbs. @ 60 rpm Required -350 to 450 7815K45 $3.60
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  15. #15
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    Re: Leg Press Question

    Stupid question, How do these stay in place?

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    Re: Leg Press Question

    Name:  IMG_2999.jpg
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    This is something at the gym similar to my idea

  17. #17
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    Re: Leg Press Question

    Here is a better angleName:  IMG_2998.jpg
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    Attached Images Attached Images  

  18. #18
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    Re: Leg Press Question

    That is what I meant by internal machining. Otherwise, I suspect the parts could vibrate out or be damaged by the hammering? I would suspect even bronze would break or deform due to normal use on the machine.

  19. #19
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    Re: Leg Press Question

    Tapwelder
    What would you suggest I do?

  20. #20
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    Re: Leg Press Question

    What they did, is the way I would do it. Machine a seat for the bearing and slot for a lock ring of some sort to hold the bearing. Doesn't appear they are using a straight tube. No need DOM, if dimension is sole reason for selection. Just machine the ends to fit the bearing appropriately.

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  22. #21
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    Re: Leg Press Question

    Design begins with the shaft size necessary to carry the load.

    then a bushing should be seleced for wear, and clearance . If your concern with damage to a flanged bushing select a straight bushing.

    Select a tubing whose od fits the bushing you have selected , keeping in mind that a larger wall thickness will have less distortion from welding (don't over weld).

    Select a "push lock" retainer that works in the ID of the tube , that retains the bushing, and allows clearance for the shaft.

    Most of the ID, and OD are standard sizes so you should be able to get away without having to do any machining of part to fit an internal fit, and retaining ring.

    Good Luck
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  23. #22
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    Re: Leg Press Question

    https://www.grainger.com/product/4YR...87MP9:20500731


    tbh i didnt fully read not sure if someone suggested it already. They come in diff sizes, they're not cheap though.

    As a gym rat myself, a lot of people have asked me to make gym equipment and honestly its rare I can make it for the same price or less than they can buy it for.

    I'd look for replacement smith machine or leg press parts, and build off them.
    Last edited by BrooklynBravest; 4 Weeks Ago at 07:28 AM.
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  24. #23
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    Re: Leg Press Question

    Thanks Guys. I have been out of town and unable to respond. I don't have access to a lath. At this point I think I'm going to try Wear-Resistant Cast Nylon Tubes https://www.mcmaster.com/84755K414.

    Zach I agree about gym equipment, I work toooooo cheap

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