Originally posted by clairetoo
Easy enough if you have one of these
From time to time I have a look around at what is out there, picking up tips and ideas, and from time to time I look at what sorts and types of
chassis people are making.
So, just as the title says, why is it that so many chassis are built of round tube?
John
[Edited on 15/5/09 by mr henderson]
'Caus round tube is stronger for a given weight. Thus round tube chassis are stronger and lighter. The downside is that you need a notching machine for round tube joints while square tube joints are just mitred.
quote:
Originally posted by sucksqueezebangblow
'Caus round tube is stronger for a given weight. Thus round tube chassis are stronger and lighter.
Round tube can be run through a bending machine too, so less cutting and welding.
I used round tube because its lighter than square of the same size. It is also more torsionally rigid I believe but not quite as strong in tension.
quote:
Originally posted by mr henderson
quote:
Originally posted by sucksqueezebangblow
'Caus round tube is stronger for a given weight. Thus round tube chassis are stronger and lighter.
If it is stronger for a given weight then surely that's either stonger or lighter?
Round tube is stronger in torsion and square tube is stronger in bending.
In theory, the centreline of the chassis is in torsion, so here it is better to use round tube, the further you move from the centreline the more the
tubes become subject to bending. So there is a point at which it is best to switch.
Of course a proper spaceframe only has tubes in tension or compression, so none of that is relevant.
So what it really comes done down to: round looks better but square is easier to build with.
Cheers
Rob
'stronger'
tensile strength for same grade steel is CSA - therefore stronger = heavier.
strength in bending is 2nd moments of area - square profile uses CSA more efficiently
compression in slender members is also 2nd moments of area - square wins (if the diamater of round was same as square)
torsion is based around r^3, cirular section provides more efficient distribution of stress.
CSA = cross sectional area
IMO it depends entirely on how well used they are - a chassis using round should be desinged differently to a chassis using square.
Will
[Edited on 15/5/09 by dinosaurjuice]
Round tube is lighter, for any given strength so you can put more tubes in the chassis for less or the same weight.
The issue really answers itself. Where panels attach, square is used, while round can be used elsewhere. One may be theoretically better but it doesn't matter if it makes fabrication impossible.
Notching machine to cut joints what about using a hole saw(metal cutting type as use by sparkies) in the pillar drill way cheaper
quote:
Originally posted by austin man
Notching machine to cut joints what about using a hole saw(metal cutting type as use by sparkies) in the pillar drill way cheaper
quote:
Originally posted by mr henderson
quote:
Originally posted by austin man
Notching machine to cut joints what about using a hole saw(metal cutting type as use by sparkies) in the pillar drill way cheaper
Not so good if you need a 45degree angle though.
if you want T45 , you need to ring malcolm wilson up !
I have one of those!
Bought it from ebay US though and had it shipped over as a gift...
quote:
Originally posted by clairetoo
Easy enough if you have one of these
I think this is the one that I bought - he happily labelled it as a birthday gift for me...
TUBE NOTCHER FROM THE STATES
All the above.
Plus, round tube chassis look better!!
quote:
Originally posted by clairetoo
quote:
Originally posted by mr henderson
quote:
Originally posted by austin man
Notching machine to cut joints what about using a hole saw(metal cutting type as use by sparkies) in the pillar drill way cheaper
Not so good if you need a 45degree angle though.
Easy enough if you have one of these
I build round tube chassis for a living,the reason square is used is simply that it is less labour intensive,it is much easier and cheaper to manufacture.
I could answer this question with all my mechanical design knowledge, all the time sitting through those boring dynamics lectures absorbing all that
information, but it can be summed up simply....
....because it looks prettier 
quote:
Originally posted by fesycresy
I could answer this question with all my mechanical design knowledge, all the time sitting through those boring dynamics lectures absorbing all that information, but it can be summed up simply....
....because it looks prettier
Your missing the point
quote:
Originally posted by wozsher
Your missing the point
quote:
Originally posted by mr henderson
quote:
Originally posted by wozsher
Your missing the point
Who is missing the point, and what is the point?
Hi
Remember of course that the square tube dose allow the chassis to panelled correctly and act as a stressed member. IF done correctly. And that dose
add significant strength.
Cheers Matt
I have heard that the paneling adds strength - I would like to see some evidence that unstressed, flat 1.2mm ally adds anything to the dynamics of the chassis. If it was in a 3 dimensional shape, I could see their point.
Clever folk can still panel a round tube chassis..and it's a doddle to create the joins
I found it very difficult to weld round tubing... 
...that's 'round tubing' not 'around tubing' - or should it be 'around round tubing'?
I think I'm getting one of my headaches...
quote:
Originally posted by Mark Allanson
I have heard that the paneling adds strength - I would like to see some evidence that unstressed, flat 1.2mm ally adds anything to the dynamics of the chassis. If it was in a 3 dimensional shape, I could see their point.
quote:
Originally posted by Badger_McLetcher
quote:
Originally posted by Mark Allanson
I have heard that the paneling adds strength - I would like to see some evidence that unstressed, flat 1.2mm ally adds anything to the dynamics of the chassis. If it was in a 3 dimensional shape, I could see their point.
If attached correctly it can act as a shear panel, much like having a diagonal cross brace.
And using square tube would provide a much wider bonding surface for the aluminium
John