oliwb
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| posted on 24/9/06 at 07:50 PM |
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Box Vs. Round
Anyone know how much of an advantage round section tube chassis have over traditional square section? I only ask as I'm thinking of building
one but does the extra expense and effort of usng tube actually yield some noticeably positive results or is it not worth the bother?? Cheers Oli.
If your not living life on the edge you're taking up too much room!
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smart51
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| posted on 24/9/06 at 08:03 PM |
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for the same weight, round is stiffer. There are two ways of doing this, same size but greater wall thickness, same wall thickness but bigger size.
Bigger diameter is better.
If 25mm x 1.5 square is more than strong enough then 25mm x 1.5 round is lighter. I'm told it is easier to weld than 25mm x 1 square.
round is easier to bend, if you have a tube bender. this will save you some welding.
round can be harder to fit panels / brackets to.
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oliwb
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| posted on 24/9/06 at 08:10 PM |
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Really I always thought that round tube was much harder to weld....hmmm I shall have to have a play with the welder me thinks. So really you can
either have the same weight but stiffer or same stiffness (oo-er) but lighter. So when all these companies go on about the tube being so much stiffer
and stronger and lighter etc etc they're bending the truth a bit! Are Mcscorely (don't know how to spell it!) 's plans considered
the ones to go for now days? I'd also like to use an Avon type rear end using a sierra or freelander diff and drive shafts on double wishbone
rear suspension. Does such a design exist at the moment? If not anyone fancy knocking me up one  ???? Any good sites on how to design/build
chassis that are worth a read? Cheers Oli.
If your not living life on the edge you're taking up too much room!
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smart51
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| posted on 24/9/06 at 08:21 PM |
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quote:
Originally posted by oliwb
I always thought that round tube was much harder to weld.
I'm told that thin wall is harder to weld well.
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mark chandler
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| posted on 24/9/06 at 08:45 PM |
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As above 1" round is lighter than 1" box although not as strong if you try and bend. It is however stronger in twist if tha makes
sense.
I went for a hybrid, box for the bottom of the frame as it makes fixing the floor easy, tube everywhere else.
Tube is harder to weld, only because your torch has to be in 360 different positions as you follow the seam, square is just 4.
Regards Mark
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Catpuss
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| posted on 24/9/06 at 08:52 PM |
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At the donnington show one trader went to great lengths to explain to be the big difference between round and square and that is that you can bend
round quite a bit which means less welds and more continuous lengths. This means a stronger chasis. Of course you could beef up the square section but
thats another matter.
For square section bending it can distort the walls. Look at square section steel on some cheapo chairs where the inside face on a bend dips in.
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leto
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| posted on 24/9/06 at 08:53 PM |
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A rough estimate. If you use Ř25x1,5 instead of 25x25x1,5 you will save about 10-15kg on a book frame. Depending on what equipment you have, it will
cost you a few hundred to maybe a thousand hours of build time. For a serious, competitive, lightweight build it's worth it, if you planing to
use a pinto and go to a track day now and then, no.
“I'm gonna ride around in style
I'm gonna drive everybody wild
'Cause I'll have the only one there is a round”. (J. Cash)
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Aboardman
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| posted on 24/9/06 at 09:35 PM |
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would the round tube not be a more pain to cut as it would cutting to a curve to match the adjoining piece.?
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JB
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| posted on 25/9/06 at 04:30 AM |
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Shaping Tubes
If you are buildinga simple square structure then square tube is easier to shape the ends.
However if you start playing with compound angles then round is easier to profie the ends.
All true space frames should have the tubes in compression and or tension so the twisting argument should not hold any weight, but in reality it
does.
I would go for a square base and round everywhere else.
John
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silex
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| posted on 25/9/06 at 07:03 AM |
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if you want to maintain the same bending strength as 25mm square tube, use 30mm dia round tube - you would still save some weight, just not quite as
much.
[Edited on 25/9/06 by silex]
Murphy's 2 laws
1. If it can go wrong it will
2. In case of emergency - refer to rule 1.
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caber
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| posted on 25/9/06 at 06:59 PM |
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Oli what are you up to? Are you after building another car?
Caber
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