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Help! Making landing gear

Discussion in 'Giant / Scale RC General Discussions' started by acerc, Apr 12, 2018.

   
  1. That is a neat bit of handy.....
     
  2. Here is a pic of the same style gear, the arrow denotes the bend I am talking about, that is the only bend that will be that tight. I believe the rest would be ok. I know I said 5/8" but the wire may be a tad smaller, won't know for sure until I get closer to needing it.
     

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  3. This is a very doable tool, thanks.
     
    Snoopy1 likes this.
  4. Alky6

    Alky6 150cc

    If that gets brazed to the axle support that goes vertical including the washer, I wouldn’t worry about it cracking a little bit. And further with the struts included, you should be fine with mild steel cold rolled, IMHO.
     
    49dimes and acerc like this.
  5. What do you consider mild steel?
    By the way this will be a 40lbs'ish airframe.
     
  6. Alky6

    Alky6 150cc

    When steel is rolled through dies, it is done either hot or cold. Hot is cheap and usually has a dark crusty finish and os inconsistent in its sizing.. Cold rolled is the same process but the steel is formed cold. Takes a heck of a lot more pressure and work to form the steel into the determined shape. Cold rolled has a nice finish on the exterior of the surface and is typically much more workable and machinable and has consistent sizing along its length. ASTM A 108 -1018 is a very common mild steel (low carbon). It is also available in small sizes 1/4”, 5/16, etc.
    An example of a supplier:
    https://www.fastenal.com/products/details/47704
     
    pawnshopmike and 49dimes like this.
  7. Alky6

    Alky6 150cc

    To give you a rough order of magnatude on the capacity of a 5/16” A108-1018 rod in straight compression (one rod by itself), assuming no buckling, you would be good for about 1,000 pounds (Using allowable stress). Your design in the photo has three separate legs - call it good for 1,700 pounds. On a 40 pound plane an assuming a single tire hard hit that is a 43 g load. That would bend the axle long before the strut failed.

    You may wish to consider using piano wire for the piece that makes up the axle. The big concern you would have (if you were an aircraft full scale) is repeated loading and fatigue failure. With steel, as long as you remain under 50% of the yield stress, the member would have infinite life. But again, to give you a sense of maganatude - we are talking hundreds of thousands to millions of cycles. With your landing gear, I doubt you would ever see that. ;)

    A108 1018 has a yield stress of about 56ksi. Compare that to piano wire or spring steel and the yield stress is over 200ksi. (1 Ksi = 1,000 psi). It is designed to handle more cycles.The yield stress is equal to the point at which you bend the material and it takes a permanent set (it is bent at that point).
     
    Last edited: Apr 14, 2018
    pawnshopmike and 49dimes like this.
  8. Snoopy1

    Snoopy1 640cc Uber Pimp

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    Trying to understand the picture of the landing gear. Could you take a picture from the front. Just look at how the gear will carry the load or impact. Looks like three legs going to either wheel. Would like to see how the centre leg is supported and how it is connect to the plane. But just for reference you mentioned that you are trying to wrap or bend the wire around the axel. If I understand you correctly and I understand the gear setup then I would use piano wire but at the location of the axel just heat it up to a very dull red in the dark and wrap it around the axel. At that location the strength of piano wire is not required and the loss of some strength due it a little stress relief will not in way comprise the strength of the gear. But please understand that a can not see exactly how the gear is put together. Just trying to help.
     
    Alky6, acerc and 49dimes like this.
  9. 49dimes

    49dimes Damn I'm hungry

    acerc and pawnshopmike like this.
  10. This confirms what I was thinking or hoping. Thank you.
    I am not quite sure as to the rest of the gears design until I get that portion of the airframe framed. But like posted earlier the rest of the bends will be minor in comparison.
     
    Snoopy1 likes this.
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