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  1. #1
    Join Date
    Jun 2021
    Location
    worldwideweb
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    27

    Question undercutter / bed lifter - how thick and which steel to use?

    Hello everyone!


    I am planning to build an undercutter/bed lifter tractor attachment. The goal is to slide a slanted board 10-12inch (25-30cm) deep into the ground and lift the soil just enough, so that you don't need to use a shovel to dig out root crops such as garlic or carrots. This is how it looks in action:https://www.youtube.com/watch?v=xAZrUAG3PcE . And a lighter version: https://www.youtube.com/watch?v=OrFVcQOJlB0

    These are my dimensions:
    https://ibb.co/QYWYbfN(top link arm isn't drawn)
    https://ibb.co/q1zYDPw

    I am unable to asses how thick should the sidewalls and the bottom lifting board be and which steel is best suited for such applications. Can you help me out? Does anyone have an undercutter on the farm and would be willing to measure how thick the steel is? The one in the video looks 3/4" to 1", not sure what type though.


    So my choice is between regular steel and hardened steel. I believe regular steel is marked as S355 or S235, the number 355 and 235 corresponding to the yield strength in MPa of the steel. Yield strength is determined under axial stretching of the specimen and corresponds to the maximal Force per area under which elastic deformation occurs. Hardened steel has yield strength 3-5 times higher than the regular steel. For example AR400 or Hardox 450 steels have yield strength 1187MPa and 1250MPa respectively(https://www.steelwarehouse.com/ar400/ and https://www.ssab.com/Products/Brands...cts/Hardox-450)


    Is yield strength directly proportional to how much the steel would resist bending in transverse direction too (as opposed to axial streching)? Because it is nuts to think that 1/4" AR400 would resist more to bending than 3/4" S355 structural steel. Am I reading this numbers correctly?

    Thank you for taking your time and answering this question!

  2. #2
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    1,322

    Default

    This one: https://www.tilmor.com/en-us/products/260/undercutters says it uses 1/2" x 4" cutting edge. The sides look a bit thicker though - maybe 3/4".

    No idea about what steel to use. If I only had mild steel available, I'd probably hard face the cutting edge and the faces of the sides with a welder.

  3. #3
    Join Date
    Jan 2004
    Location
    Mackay North Qld
    Posts
    6,446

    Default

    First up
    Hi Potato

    welcome to the MetalWork Forums
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    Again, welcome to our forums.

    Not all ground engagement tools need hardfacing.
    Factors you might consider are : It looks sandy loam

    Draw bar Horsepoer of the tractor
    The abrasiveness of the soil.
    The frequency of use or amount of acres/hectares worked.
    Hobby farm or commercial will dictate what you can spend on it ,I guess.

    Note the steel grade used in the American sample was 1060 grade -Not sure what that converts to for European steel classication.
    Note! it is not haedfaced. It looks similar to your design- why re invent the wheel if you may not need to. Is the tractor power comparable. Maybe all the decisions are not hard to make after all.
    Your dimensions seem heavy and I would consider holding off hardfacing until you give the unit a small test run.

    Measure thickness and weight from new and compare both after a fixed amount of work.That will tell you if the plate is wearing excessively for a short run. Do a small amount and multiply it out to give a expected wear rate for a total hectare-age for your growing season.

    At that point you may or may not wish to hardface dependent on you calcs.

    Certainly use low hydrogen electrodes or wire to weld it.
    Hardfacing is expensive and toxic as well. It may work out cheaper to run with the 1060.

    Again welcome to our forums

    Grahame
    Moderator

  4. #4
    Join Date
    Jun 2010
    Location
    Canberra
    Posts
    1,322

    Default

    Quote Originally Posted by Grahame Collins View Post
    Hardfacing is expensive and toxic as well. It may work out cheaper to run with the 1060.
    I meant using a hardfacing welding rod, like WIA Abrasocord.

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