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Cloud Warrior
I will not be using any standard to build this - it is an experimental home build so I will try and use as much commonsense as possible. I am not sure what CAA requires but I know they want a static load test which I will do with sandbags up to at least 4g's.
I am still considering the FE (finite element analysis which means doing a lot of modeling and calculations on the computer). I might do FEA for the pylon only but note that I am not a mechanical engineer, electronics are more in my line. Furthermore the software is prohibitively expensive for a hobby project (in the order of R100000 for Solidworks with FEM, I use Alibre for my drawings which is much cheaper but the FEM is still in the order of R10000 and I do not know of anybody using it) The pylon I know can hang 3 tons without deformation so I think that I am at least in the right ball park.
---- Warning: do not read if you are not interested in maths -----
I have done some thumb suck calculations on the pylon but these are done with a lot of assumptions (so no criticism please, I know that they are not accurate but if they are totally stupid you can say so):
If I assume that the pylon only hangs on the inner side of the rectangular tube ( this is very rough because some of the stretch might be transferred to the back or there might even be compression on the back in which case I have underestimated it)
The MAW without the wing hanging on the pylon is about 450-60kg = 390kg
using a 80x40x1.5mm rectangular tube the inner metal area is 1.5 x 40 mm = 60 mm2
The yield stress (stress before permanent deformation) of 304 is about 220 N/mm2
This gives a yield of 60x220 = 13200 N or about max of 1350 kg at 9.8kg/N. This gives about 1350kg/390kg = 3.5g before deformation. Not quite enough so I might have to use 80x40x2mm rectangular tubing which gives:
a 80x40x2mm rectangular tube the inner metal area is 2 x 40 mm = 80 mm2
This gives a yield of 80x220 = 17600 N or about 1800 kg. This gives about 1800kg/390kg = max g's of about 4.6g's
the max tensile strength of 304 is 515 N/mm2 which means the g's before the pylon breaks is about 10.7g (you should have passed out by then)
A cable under tension might also be added inside the pylon.
The max stress on the pylon is just above the brace (between the top and the bottom section). I will look at strengthening it there.
The hang point is easy, I know more or less where it is supposed to be and will design around that. The pylon I will make last when everything is fished and adjust the hang point position after I have done the weight and balance.
Fatigue is an issue, but to be honest, I do not have a clue how to take it into account. Any advice welcome. I plan to over design a bit to counter this and do early detection, e.g. pylon pressure leak detection. I will also minimize vibration where possible. The engine mount will be Chromoly and will be the same as the one used on oupG's trike. If resonant frequencies are a great risk I might consider measuring these when the trike is finished but I do not think that this is is a problem on a trike if everything is build relatively stiff.
Advice is always welcome Cloud warrior and if you know of a way that I can do the FE in an affordable way, please let me know. I have tried to find free ones but they are to complicated for me.