Square Tube for Bike Frame

admin

A lot of bikes I see use a round tube, why? Any advantages to that over square? If using square tube, what is the minimum thickness to use for a person ranging from 150-250 lbs?
Reply:Originally Posted by just_some_dudeA lot of bikes I see use a round tube, why? Any advantages to that over square? If using square tube, what is the minimum thickness to use for a person ranging from 150-250 lbs?
Reply:If you check out oldminibikes.com, you will see there are a couple of guys there who build with square tubing.  It is a little harder, because if it twists at all, it changes the dimensions of where tubes intersect, whereas with round tubing it does not matter.  It actually looks cool if you turn it on edge, so it is diamond shaped.Check out my channel https://www.youtube.com/channel/UCkz...bZg8AYNXGqBjZQ"Both oligarch and tyrant mistrust the people, and therefore deprive them of arms." - Aristotle
Reply:many recumbents are made out of square, steel and aluminum.   If you are using mild steel it might be difficult to get square tube under 1/16 in.
Reply:I had an 86 GSX-R750 that had a square tube frameNickESAB CaddyTig 2200iPowermax 45MM140 (Sold)
Reply:A frame made from round tubing will be stronger than one made from square tubing if they are the same weight.Dynasty 300DXSmith He/Ar gas mixerMM350PHobart Handler 120Smith LW7, MW5, AW1A
Reply:Meant bicycle frame, not motorcycle frame.
Reply:You building somthing like this.
Reply:Not necessarily. Just like the look of square tube. Wasn't sure what size I would use with square tube.
Reply:Back in the 80's their was a guy who make motorcycle frames fron sq. tubeingin western ky. - i met him once - he also did crome plateing - frames looked good but never saw one in action - just my 2¢The main thing is not to panic or get excited Bobcat 250, X-Treme 12VS,  MM211Meltabo, Milwaukee,Porter Cable,Dewalt,MakitaVictor O/A, Ingersoll-RandEvolution Rage2, 40 amp PlasmaLincoln 225 AC/DC
Reply:Round tube is equally stiff and strong in all directions.  Square tube excels when loaded against the flat faces (not in the diamond direction).  Round tube is better for torsion as well."USMCPOP" First-born son: KIA  Iraq 1/26/05Syncrowave 250 w/ Coolmate 3Dialarc 250, Idealarc 250SP-175 +Firepower TIG 160S (gave the TA 161 STL to the son)Lincwelder AC180C (1952)Victor & Smith O/A torchesMiller spot welder
Reply:Square tube will resist a moment of inertia bend better than a round tube. But, a round tube will have a positive effect of being equally resistant to bending from any direction. (Reinforcing Oldendums' post) Now, with this said, the benefit of a round tube over a square tube is that when bent, if the bend is a sharp impact type of bend, and not a gradual forced bend...... the square tube is likely to kink which will guarantee a loss of overall strength, and a loss of further bend resistance. Not to mention, it is nearly impossible to put back to straight.A round tube frame can be bent back into place with minimal distortion, and retain a nearly equal original strength, so long as the material was slowly pressed back into position rahter than pounded/ rapidly forced.Need some info from the OP; what are you looking to build a frame for?To make a correction to 4sfed's post, tube DIAMETER means everything, and wall thickness and weight are secondary to the tube diameter. EXAMPLE: Get yourself a piece of 2" OD tube, with a wall thickness of .045. Now, get a 1" tube with a wall thickness of .120. They will weigh nearly the same; very close weight per ft. Take a wild guess which tube is easier to bend if you get a 6ft section and try to lever it or otherwise bend it......??????You will make a paperclip out of the 1", while the 2" will be laughing at you. But at a cost; the 2" tube is very thin walled, so it requires much better prep and weldment than the 1", because the wall thickness will not allow nearly so much cushion. And, the 2" tube will possibly crack around the HAZ, whereas the 1" would bend somewhere before the weld or HAZ were compromized.Different strengths for different jobs.Could not comment on a tube size until we know the application, intended use, and size of bike/ power, etc. Also, if weight savings is a requirement, then we are talking alloys and not just mild steels.And then, after so much work...... you have it in your hand, and you look over to your side...... and the runner has run off. Leaving you holding the prize, wondering when the runner will return.
Reply:Originally Posted by Rojodiablo To make a correction to 4sfed's post, tube DIAMETER means everything, and wall thickness and weight are secondary to the tube diameter
Reply:Originally Posted by 4sfedOops, it appears I left off part of my statement.  I should have said "for tubes with the same maximum dimension."
Reply:Originally Posted by Stick-manThe only bike I know of that used other than round, was the PK Ripper, which used aluminum rectangle tubing. That's if you were referring to pedal bikes. Sorry I can't help answer your questions.
Reply:Originally Posted by weldermikeOne of my buds when we were younger was a sick freestyle ramp rider, he was sposored by them. Brings back memories bud, have'nt heard that name in years. His name is Walter Baus. We rode together for years!
Reply:Originally Posted by Stick-manHey weldermike, here are a couple threads that will spark a few memories!http://weldingweb.com/vbb/showthread.php...hlight=redlinehttp://weldingweb.com/vbb/showthread.php...hlight=redline
Reply:Look up "Hawk BMX frame". They were popular in the 90's. They had square tubes.Ian TannerKawasaki KX450 and many other fine tools
Reply:Specialized makes some mountain bikes with square style tubing. But it's already been pretty well explained that round is superior for bicycle construction for most purposes. If you want to see odd shaped tubing, look up some of the old Y frame mountain bikes or just even search for mountain bike frames.
Reply:Hmm... So help me out with this, because I wouldn't know where to start when calculating this...What square tube should I use if I am going to put about 200 lbs of pressure on it just in body weight.
Reply:Originally Posted by just_some_dudeHmm... So help me out with this, because I wouldn't know where to start when calculating this...What square tube should I use if I am going to put about 200 lbs of pressure on it just in body weight.