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Home of the Spodplane
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Date: 4-5-2022
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Number of Hours: 3.00
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Manual Reference: 23-01
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Brief Description: Engine mount tube cutting
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F&%king imperial system of measurement!!!
After much agonising about my mild steel forms cut up 4130 for the engine mount. First thing i note is bending the lower cross tube without heat is not going to happen, so heat it red hot before making the bend, starting a nice fire in my bending form. Hope it doesn't take too many to get the required tubes.
Continue notching and hot-glueing the completed tubes to my jig then stand back and compare with the full size drawing. Then I notice the second thing... The first welder I had dealt with, (who subsequently declined to weld anything), had recommended making it all out of one size tube, so I had 'upsized' all the tube to 5/8"OD. Now that I have actually cut out the tubing, I note that the 5/8"OD tubing looks smaller on the full size drawing than the 'smaller" 3/4"OD. It takes me a terrific time to figure out what was going on, then realise that if it was all to be one size tube it should be 3/4"OD, which is actually larger. I should have stuck to the more familiar decimal inches that is actually marked on the reeking tubes. One excuse may be that the former welder was going to supply and notch the tubes, so I hadn't really thought about it previously.
I wander back to Bunnings Aerospace and grab some 3/4"OD mild steel tubing, and start again with the paper jigs and the mild steel forms, and whack an order in for some 3/4"OD 4130. To use the tubing I have already, decide to go with the plans mixed tubing sizes.
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Don't do this. It should be a 3/4" tube...
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Having got the mild steel form to fit I wrap it in paper and transfer the shape to the 4130 tube
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Make gross cuts with a cutting wheel, and fine tune with the 80g flapper wheel.
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