Frame Stucture Question...

I know that rounded things can be stronger in some cases but does it apply to this one? Which is stronger between a squared-off frame and a rounded frame that can fit inside the suared one (ie. it can be made from the squared one)? I guess this is assuming that they’re both hollow, and yes I realise that if they’re hollow the rounded one can’t be made from the squared one but let’s just say it could be. Any comments?

Andrew Carter



Here is a link to a post that i started a while back that might help.

I hope “new blood” also responds.

The above thread link has a link in it that is out of date. If you want to see the diagram for my optional crown designs, go to this link:

The oval tubing I ended up using, though not by choice was aero oval tubing for my frame. I wouldn’t recommend for trials.

The frame builder ended up punching a hole all the way through the crown. and welding it. Oval tubing was used in the blades, crown and the seat tube was round.

Good luck!

To be honest - both sections will have simmilar properties as the oval is fairly simmilar to the square in section.

The oval will be slightly lighter and better looking to boot.
the only other thing in Uni design is stiffness - this all depends on what wall thickness and overall dimentions you wish to use.
I have been faced with the same sort of decision and have gone for the oval on my trials frame.

I think for me it would be about half the cost, but significantly heavier with the rectangular tubing, but that’s just becuase of the thickesses we can get…

Re: Frame Stucture Question…

It depends. Since you are saying they are hollow, it’d depend on how thick the walls are on each of them. If each had the same thickness, then the rectangle one could take more stress, but it’d also weigh more. With an oval cross section, you can create a frame that is lighter and has the same strength, or you can create a frame that is stronger and the same weight.

Thanks a lot everyone.

Are you saying that they’ll both be the same strength but the rectangular one will take more stress? If so, what’s the difference between strength and ability to take stress?


Strength is hard to quantify (it’s not really an engineering term), as it’ll have different properties, but for the purposes of what I wrote, strength equals the ability for it to take stress before failure.