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I am designing a tractor implement for harvesting root crops. Similar to this one here, but stronger construction with cutting discs in front of it to prevent weed jam. These images will help you understand my question. The whole implement is 1400mm wide and the pipe at angle is 200mm long relative to x axis.

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https://ibb.co/FmvS3RM

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https://ibb.co/wBsQXgT

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https://ibb.co/SmV7LqZ

The main frame has 2 square pipes welded together at 45 degree angle at each side. The pipes are 120x120mm(4 3/4"x4 3/4") with wall thickness 8mm(0.315"). I was sceptical about using butt joint so I put a 15mm(5/8") steel plate between pipes. Now the pipes are welded with a fillet weld (at 90°, 45° and 135°). I'd like to hear some expert or practitioner opinion on how structurally stable welding pipes in such arrangement is with respect to flat pipe without any welds. The forces will act on the sides, that are just 20cm(8") from the three point hitch arms so the leverage is pretty small.

Thanks!

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  • $\begingroup$ It comes down to you knowing what forces will be applied to the structure and working out if the implement has sufficient strength in the right places. If it does not it WILL fail. If you don't have all the information of the forces then you can test the implement in the ground - if it survives then it is strong enough - until, of course, it hits a big enough stone. $\endgroup$
    – Solar Mike
    Sep 26 at 12:03
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You are complicating the matter and weaken your design by replacing the square pipe with a flat bent plate.

I don't get the reason you can't get the weld done if the weld angles conforming to the limits set in the figure below:

enter image description here

Note there are other ways to built-up the weld around this joint. Also, an angle smaller than $60^o$ is permitted; however, in such a case, the weld is considered to be a partial joint penetration groove weld.

AWS D1.1 Specification Section 2.11 Skewed T-Joints indicates:

"2.11.3.1 Z Loss Reduction. The acute side of prequalified skewed T-joints with dihedral angles less than 60° and greater than 30° may be used as shown in Figure 3.11, Detail D. The method of sizing the weld, effective throat “E” or leg “W” shall be specified on the drawing or specification. The “Z” loss dimension specified in Table 2.2 shall apply."

This article will help you in designing a welded T-joint. http://www.jflf.org/v/vspfiles/assets/pdf/design_file102.pdf#:~:text=not%20present%20%20%20%20%20%20,0.541%200.576%20%20%2014%20more%20rows%20

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