QSPSB2

Guys i have a question regarding why so many of you home builders go with the square tubing rather than the round tubing...You do know that round tubing is stiffer per unit weight and has fewer stress concentrations than the square tubing..correct??

I'm not poking at your choice of tubing you have chose to use at all.. don't get me wrong... But from my stand point i would never invest my free time in building a square tube chassis.. for one they don't look realistic.. Do you guy's NOT think it's easier to multi-tube junctions in round tubing as compared to square? To be honest... i find it difficult to do in 3 dimensions using square tubing..

I'm thinking you that are building the tube chassis from square tubing are mainly choosing the square tubing over round is because the brackets and such are easier to locate on the flat surface,,

Let's not get all balled over this guys.. i just wanted to speak my mind on it..and here your impute on it..

Later
Stoney

Dirty_Vinylpusher

Yeah........ I've been looking a bit at the 1/4 scale dragster builds over at QSL and they're all doing the round tubing.
In the back of my mind I've always known that round is stronger and better than square.
Most big things like cranes, scaffolding and giant roof structures etc is all made of round tubing.
Not to mention motorbike frames, dune buggies, and pretty much anything else that's got a welded tube frame....

Knowing all this I've stuck to square so far though.
Why?


Well, personally I'm still pretty new to working with metal and aluminium.
I guess there's some sort of illusion that square is easier to work with than round when it comes to marking and cutting?
Also, like you say, it seems easier to attach things like brackets etc to a square/flat piece than a round one.
I dunno.

Welding a square piece to another square piece at a 90 degree angle (or any ange for that matter) seems easier than doing it with round, as it has to be concave to fit snugly.




Ok I'm all out of excuses.
I'll go get some round tubing for my next build.

Giorgos_cupra

DVP pretty much covered it for me too...I only have to add that i don't have a tube bender and i personally find it easier to work around with it on rc s.Back in the days,when i was making go kart frames i was using tube

da mad maori

yes round tubing is alot stronger but ONLY if its bent, cut, joined correctly...which requires alot of skill, more tooling and and takes longer

every join has to be notch (fish mouth cut as some call it) like this

http://image.stockcarracing.com/f/te...+fishmouth.jpg

and when you are joining at a tight angle its even more difficult to cut.....

cutting and welding round tube at a small angle doesnt look good lol so its common practice to bend it to shape

you have to have GOOD pipe benders.. in most cases with these builds they have to be small benders....
you cant crease or collapse the round tube... any sign of it and the structural integrity is decreased ALOT....

and yes attaching brackets is easier...

its alot of work to make the round tubing joins and bends strong.....
if you dont do it correctly , it will be ALOT weaker than square tube joins

Dirty_Vinylpusher

See?
Too complicated.


Think I'll stick to square for now.

Bob-Stormer

Your right, but does it really apply? As long as the vehicle is structurally sound, it could be made out of cardboard and still be considered "engineered correctly". And as most of us aren't having major frame issues, I'd say we are way ahead of the curve.

Depends on who you hang with. the frame on every production vehicle ever made is rectangular in it's design. When you see back half kits on drag cras it's square tube. They have their place in the grand design scheme. I think it's more important to simply make something. If it breaks, build it again. It's the only way to learn. We could just as well be having a discussion on the best way to connect metal. "bolt's rule", no, brazing rules. No, TIG is best. Nah, for the buck and for speed, can't beat MIG. It's like the tubing... it's usually what you have. I don't know how many of us are making conscious design criteria based on round or square. Compared to "yep, this piece in my hand is PERFECT!..." ...lol...

You may want to look around. We ain't building NASCAR or F1 vehicles. Mines only going 8mph...

Round tubing requires (as a rule) more tools, technique and time. It's simply more difficult, to square, set, hold, everything. Why would you make something more difficult if you are happy with a particular method? I'd say we should have a thread that says, "Hey buddy, enough with the tube...get that frame nocked out, square tubing FTW!!!! It's just easier to do, easier to weld, grind, square up, hold down, and easier to find and purchase. The hottest axles for the fulls zie fab guys going offroad trail riding is telescopic square tube, not round. Look it up at Pirate4x4. It's empowering to know you can make an axle yourself. They did it on xtreme 4x4 as well.

And technically, I see more flat pan chassis cars than tube around here. And for good reason. I'd say the majority here are just home hobbiests with minimal tools, managing to pull of things that are actually very good! Seeing as how we are not racing these, no competitions, and no rules. I'd say we're having a pretty good time. No need to mandate anything particular. OTHER... than get out there and have some fun in the garage. To many people get stuffed up about the technical end when they really need to be cutting and welding metal and getting on with the project (where the real fun is)!!!!

troppo

I agree with a lot of whats been posted already and disagree with some of though i`m not going to join in on so war here.
I`ve used square or rectangular tubing mainly because of easy of availability (scrap bun at work lol) tubinh in this scale is easy enough to work with a little work and ingenuity in your jigs.
For me its mainly cost and availability that makes me keep using square or rectangular tube, and will be doing so again with the T i`m building now

Dirty_Vinylpusher

Bob, you should know that Stoney here is one of the most precise and pedantic (In a good way) homebuilders on this forum.
While a lot of us, as you said, knock about in the shed and build something that moves, hopefully in a straight line, others take things to the next level and CNC, lathe and machine everything to within half a millimetre.
They know the properties of different materials and grades of aluminium and things I couldn't even begin to consider caring about.

I find all this fascinating and take it onboard and store it somewhere in the back of my head.


And then I crack a beer and go to the shed and bust open an old powerdrill to see if there are any useful gears inside it.
(And most likely snip the powercord off and put it in a box just in case)

troppo

On a safety not, try to unplug it first

Bob-Stormer

Maybe I took it wrong. I guess I took it as a dig on the less experienced guys, rather than actual curiosity or as helpful information. I'm all about helping the guys that are new to fab work. I feel they get intimidated by some of what they see. I'm kind of from the school that you need to build the first one to build the second one. And if that first one is out of a fence post, and that's all you had, don't worry about it, and enjoy the build.

Dirty_Vinylpusher

Yep that's how I do it too.
Only problem is that halfway through the second one I get carried away with new ideas and then that becomes the rolling prototype for the third one and so on.

So nothing ever really gets finished......


Maybe one day.