ABOUT ME

I live in a camper van with a couple of West Highland Terriers for company.
My passion is photography but it is a work in progress.
I am always willing to share what knowledge I have and can be contacted through the comments on this post or e-mail ADRIAN
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Wednesday, 5 August 2020

I DON'T BELIEVE IT.

"I Don't Believe  It." Was the catch phrase of Victor Meldrew years and years ago. Can you remember those times when television was worth watching? 
I have been impersonating Victor for six hours with added expletives. It's my own fault as I don't like paying for software and am too thick to understand the error messages that can and do crop up in free stuff.
 I never got as far as doing a stress analysis on the Tensegrity table as the designer sacked me. I have never used FEM stuff so thought I would give it a whirl........... I wished I hadn't. Now I'm glad I did as it works. It was my version of FreeCAD that was at fault. I nipped down to the Co-Op for a bottle of wine about fiveish to help my tea go down and on the way back thought I'll try uninstalling the little bugger and downloading a current version. I did try to reload the software but FreeCAD won't let you install over a loaded version. Blender does but these wiz kids will go to endless lengths to make life difficult for geriatric hopefuls like me. Half an hour later FreeCAD works like a dream. I wish I was better at this malarkey, I looked for advice online and got more and more confused as I can't understand half what script writers advocate. My fault not theirs as although they cuckooed in the first place they did put matters right. I am happier in Blender as I have had more practise and recognise when it's them and when it's me being thick.

Here is twenty minutes modelling and FEMing.


 This is just a square steel section. It's anchored on it's right face and load is being applied to the pad on the left. This is a fifty millimetre square section with the corners knocked off and a force of 50 Newtons applied to the pad as a static load...That's about 5kg...Bit less.


What Ho! It's working. As one would expect 5kg on a two inch square piece of steel doesn't do anything very much but when I up the factor it gets brilliant.


Maybe not brilliant but at least the little tinker moves.

I'll try and think of other things to do with FEM. I'll happen make a video. Bet you can't wait.
It is quite easy to stress test models once one has the job to rights. The computer does all the heavy maths automatically. When I think back to my days at Sheffield Poly and what they let us use slide rules for and what they wouldn't. Bloody sadists they were. FEM is real magic you split ones model into a triangular mesh or little bits. The little bits have to be triangular for FEM. With calculus it is possible to work out the force on two points of a triangle if you know the force on the third...Cunning buggers are mathematicians. If you are interested then this WIKI ARTICLE explains most of it. I have to admit I haven't tried to understand anything but the basics and then only because FreeCAD was being a twat.
I find it wonderful that this sort of computing power is available on a Knackered Laptop.
Before I go here is a message for all.
Have fun.


Have fun. 


4 comments:

  1. Fascinating. Can the program show different reactions depending on the material. Say between cast iron, steel, plastic?

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    1. Yes John. FreeCAD has a long list of materials from steel and other metals through to plastics and glass. If you know the material specifications you can enter them. It appears to do fluid flow and thermal analysis as well. I can see a few hours or weeks of entertainment with this.

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  2. I have absolutely no idea what you're talking about, but I am so glad you're happy with it! Now I'm off to have fun. (Twice). 8-)

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    Replies
    1. Marcheline, few folk have. I usually have a vague idea but by no means always.

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