don't think this is good engineering wise , any better ideas ?

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On the first Python front end I slit a pair of round tubes down the middle and welded them to drop out extenders.



Whilst it worked and umpteen years latter is is still being ridden it created a couple of problems , due to being
slit down the middle the tubing on the inside interfered with both the brake disk and the cassette.



So I though being smart [ ok bare with me ] as this tubing is rectangular I can slit it neatly on one of the vertical walls and this will give me the same 4 welds per tube but not the interference ?

On reflection are the welds on the inside a waste of time as all the loads are being taken on the narrow piece of tubing on the inside face at the end of the slot ?

Maybe it would be better just to lay the tubing on and do welds in the V's where it meets the long sides ?

Or ...

Paul
 
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TBH I think it is hard to "tear" metal and what you have will most likely be absolutely fine.
If you really want to add some unobtrusive strength to it add a flat 2mm plate to each inside face of the rectumangular tubes that goes past those vertical slits.

:)
 
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No it's not about the strength - I hope !



I am questioning why weld on these 3 sides [ red lines ] when all the forces are being taken on the blue line ? I think

Paul
 
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I don't think there's anything fundamentally wrong with what you have. Just fully weld as as you were going to do. Fully welded will ensure the entire box takes the loading.
 
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I am questioning why weld on these 3 sides [ red lines ] when all the forces are being taken on the blue line ? I think
Exactly! If you weld all the red bits to the plates the bit that wants to tear free is the blue-bit.
Its unlikely to, but as I said put an additional plate right through and a little bit beyond and it can never tear.
 
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Should be ok. Improvements could be, project the upright plates through the cutout slots, better than having them flush. You may be doing this already. 5mm fillet then.
If you want belt and braces you could put an external plate on the bottom to prevent any possible cracking, at the bottom of the blue lines.
Fore-thought, the plates could have been triangular with a longer bottom line that raked the plate (green line). This stops having a common vertical weak point where stresses could act on.
Ignore the pink lines, they are just fanciful.
 
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Dale rider

Thanks food for though ....

It is a poor picture just grabbed from the bunch I took for a different reason.
The rectangular legs will actually be higher so the centre of them is level with the centre of the axle.
Then when welded all the way around to the 4mm , the 4mm will be trimmed and tidied leaving a small border

Paul
 
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