Im looking into building my own k-member. Im not going after absolute light weight capabilities, just think it would be a fun project.

I see all the aftermarket k-members made in a tubular construction. What do guys think about square tubing? I would assume that its stronger, maybe not as light but it will hold its own. Also, its easier to cut pieces more exact when its square. Thickness can be determined later but what do you guys think about this?

Karl

Edit: I should add that it would be for a 95 camaro with and LS1

 

If I'm not mistaken round tubing is stronger. But if your welding skills are up to the task and you are good with geometry and math I don't see why it can't be done. Just be sure you confident in your welding and material selection for safety reasons

 

First off square tubing is absolutely stronger and slightly heavier. That being said, OP you need a jig to build this off of. Due to the time investment needed, I would say its not worth it when you can buy an already established company's k member for less then $500. I highly doubt you will ever break their round tube version, so WHY build one out of square tube? Unless your design is inferior. Heavier parts to compensate for design flaws is the opposite of modding IMO. I normally stand behind home projects, but this one seems to be more effort then its worth.

 

Ya i have been welding in my dads metal fab shop since i was 8. So hopefully this thing wont fall apart when im driving down the road haha

Well the square tubing would be lighter than the stock kmember but heavier than round tubing i believe. Also, i cant see the justice in buying a piece of metal for $500 when i have the full capabilities of making my own for $30 (not including powdercoating price). Maybe ill have to touch up on tube welding...

 

As an x-welder, trust me I get where you are coming from. Some are just more ambitious then others. I would recommend making lots of things skill permitting, K member just doesn't happen to be one for various reasons.

 

Well would you like to name those various reasons? I think that the geometry of a k member is pretty simple and easy to replicate on CAD. Not trying to argue with you, but this was the purpose of this thread to get as much info on what people thought of it.

 

I just think the easiest way to make it would be to make a jig based off the stocker. Then you need a finalized design of your own. Then there is material selection, double checking clearances including test fitting and tweaking with motor placement, and also powder coating. It just honestly wouldn't be worth the time involved just to make one single k member. Thats just my .02. Good luck though, post up some pics of the progress.

 

Whatever you do, do not use square tubing . There are many reasons people make them from round tubing . How many have you seen made from square tubing ? If the load was normal to one of the four sides of the tube it would do fine . A K member see loads from a lot of different directions . Think about where you've seen a square tube frame used and where you've seen a round tube frame . For the same weight per lineal foot round tubing is stronger and stiffer .

 

steel is steel, it all pretty much weighs the same, so saying a heavier piece of box is stronger than a lighter piece of round is like saying more steel is stronger than less. In general, in most directions round will be stronger for the same amount of steel, with the possible exception of trying to bend the box in a plane across the corners, of course, unless there is lot of structure there to prevent it from twisting, the box will twist and bend on a flat side.

 

Square is stronger by design. No other way about it.

 

If square is stronger than round why is round tubing used ? Round is more difficult to fit up . If round tubing of the same wall thickness as the square tubing it will most certainly be stronger . This is very basic engineering . Decisions like the one the OP is making must be made with sound info . Material type, sizes, and dimensions need to be evauluated in order to make the correct choice for your intended application . A K member fabricated from square tube could be made , why doesn't anyone make one if it's stronger ? Aircraft frames have been fabricated from 4130 round tubing for decades . Have you ever seen a roll cage made from square tubing ?

 

Dude, seriously. You aren't talking to someone in Pre-K. So if no one makes it, that makes it inferior. Give me a friggin break here. You just stated material type, size etc etc. Well EXACTLY. Round tube can be bent much easier. LOOK at an aftermarket k member, they must be engineered correctly to A. be strong enough, and B. be cheap enough to make to make a profit. Round tubing does this combination of things better. That absolutely does not make it stronger. And if your theory is so correct, why are square tube sub frame connectors stout as hell and round tubes ones are crap? Answer that

 

The reason square tube subframes are stronger was answered in my first post but you did not understand it . The square tube is stronger IF the load is normal to one of the four sides . A subframe connector does not see much of a load . If the load comes from any other or multiple directions the round tube is stronger . This is a simple fact . The square tube does not handle these stresses as well and will buckle from the load . I did not learn this from reading a suspension manufacturer's website about their product and why I should use it . Since you do not agree with me, atleast take a look from other sources or do the calculations yourself . If the only example you can provide is automotive subframe connectors I'd advise you open your eyes and see that these principles are applied in a lot of places .

 

OK, so you insist on being wrong.... fine we'll leave it at that.

As far as using it for a K-member... it will work and would be easier to build if you don't have a tube bender and want to use welded tubing anywhere where you need a bend. You'll need to use larger or more tube to get the same rigidity, but I would argue that in most cases you're going to overbuild things whether you're using square or round tubing, so I doubt that you'll end up with something significantly different in weight or strength (depending on your fab skills it may end up stronger if you can better design/build joints with square tube)

I would argue that a bigger debate is why you're building a tubular K-member and what are your needs design wise? IOW, if you're just going to use it at the dragstrip it doesn't need to be as strong as if you're rolling on the street or road racing, and making it as light as possible and meeting the strength/rigidity that you need for the app... Also, I would suggest that you'd want to end up with slightly different geometry for different applications.