Stephen

iTrader: (12)

I'm already a believer of round being stronger than square, but that's not REALLY my question...In a way.

The KBDDs are square tube, but does the double diamond design equal stronger? Overkill? Extra unneeded weight?

What would be the strongest, between the 3 designs? If KBDD are...Would they be even stronger when made of round tubing?

Stephen

iTrader: (12)

Here are the Kenny Brown Double Diamond (KBDD) ones, for those who don't know what they are.

George

Looking the KB design I'd say it will result in a stiffer chassis than my perimeter/tubular SFCs because the KBDD seems like it would do a better job of cross bracing the car. The perimeter SFCs don't do much to stiffen the floor whereas the KBs go right across it - that may or may not be a critical issue though.

Probably they could be lightened by using tubes but the weight isn't that big of a problem if the design improves lap times with better handling. That said though, lighter part for the same gain is usually better.

Where our cars really lose out is in the corners. They are big and heavy and just don't handle as well as smaller cars - but they are fast in straight line..lol

So, what I'm wondering is if the KB design might result in a frame that's too stiff causing it to lift a wheel mid corner which reduces grip and slows the car. If that happens then you'd have to make other changes and could just end up back where you started.

You don't get anything for nothing..lol

Guest

In regards to your questions:
1.The KBDDs are square tube, but does the double diamond design equal stronger? Overkill? Extra unneeded weight?

The thirdgen chassis to say the least is a wet pretzel. Adding rigidity to the only significant frame element tying the rear subframe to the front subframe is of course beneficial, but far from ideal. You'll notice some include a tie in to the front subframe from the rockers. If it was useless, probably would not be there. The actual tie ins on the front and rear frames (leaving the argument of what really constitutes a frame behind) is a joke. I have a picture somewhere I can post that someone took of the underside of a thirdgen (its linked here on thirdgen somewhere) but the main components tying in the front and rear subframes aside of the body sheetmetal is the side rockers. Take a look under your car how the front subframe has a 90 degree cantilevered member towards the rocker, and how its not really completely tied in. You'll see a similar idea in the back, even more poorly executed. Absolutely anything to improve on tying in these elements will make a significant improvement. I'm still getting cracks in my t-top chassis with SSM subframes, they are similar to the UMI in design without the front tie in. So things are still moving around too much... but at least I can put the tops back in without having to make the car completely level.

2. What would be the strongest, between the 3 designs?

For the chassis, as a whole, there's no question. The KB.

3. If KBDD are...Would they be even stronger when made of round tubing?

Vague question, at best. Without section sizes, indeterminable. But... and sorry for being rude... how about this... FORGET ABOUT IT. There's nothing more inane than trying to argue that round is better than square. If you're fabbing something up and you really think round is better then go make them round if it makes you feel better.

Stephen

iTrader: (12)

I don't road race or autox and I'm always on street tires. My tires would lose grip first, before I hit that level of chassis flex.

So I think they'll be good for a street car.
----------
A friend of mine wants to copy them, that was really my only real reason for questioning...Him making them out of round vs square tubing.

Guest

I would choose one over the other strictly based on ease of construction and ease of installation... or if you have something on hand already of appropriate size use that.

I have a REALLY long document I worked on some time ago and havent put it anywhere public yet about this subject and these cars, but... I could I guess. To answer a basic question about 2 connectors (and PLEASE this is not to choose one over the other, but rather just an objective analysis of the main sections themselves, both have inherent shortcomings and I cant accurately model in their entirety):
The rectangular connector is 11.5% stronger in axial loading, 37.2% stronger in pure bending on the strong side axis (this is how its oriented as installed), and 12.1% stronger in shear (vertically).

The round connector is 2.8% stronger in torsion.

So round isnt always stronger, in fact you would quite likely run into trouble claiming that and trying to back it up factually.

Stephen

iTrader: (12)

Interesting...Your #s sure sound like there is some homework behind them, to back them up.

Not to try to argue with you here....We can have a legitimate discussion...

But....Why are race cars, roll cages, monster trucks, sand rails....EVERYTHING performance vehicle...Build out of round tubing instead of square tubing?

If you take a square tube SFC & a round tube SFC, can it be argued that the square tube resists twisting forces better? I would put my $ on round tubing having more torsional stiffness.....Which is mainly what SFCs would be most prone to. Right?

Apeiron

Round tubing is easier to work with when your shape isn't planar. You don't have to worry about compound angles, just a rotation of the tube and a single angle.

Guest

They arent. There are some specific components that are square, generally in the 'frame' area of the vehicle. One example is http://www.hendrickmotorsports.com/t...360.asp?bhcp=1
I had Mark Martin's short track cup car (think Bristol) up on a lift years ago (IIRC 1998) on my birthday, not to mention checking out the rest of it, and it was quite similar in construction.
I've noted that most of the heavy use of round tubing where they use something other than square is near the passenger compartment. Round tubing when it bends generally provides a much more pleasant surface to smash a body part on. It is also completely insensitive to direction of force or impact.

Round fares better in torsion depending on section size of course but more because of the distribution of force within the element itself. The force is in the direction of the shape of the tubing. But thats a moot point when you're talking about SFC's because contrary to common misguided thought, rocker SFC's are not subjected primarily to torsional forces. They're in the wrong spot of the chassis to be.

Stephen

iTrader: (12)

SFCs are connected at either end (let's ignore the seam welds along its length for this comparison).....

Grab both ends of a round steel pipe....Try to twist. It isn't going to.

Now try to twist a rectangular tube from both ends...It'll twist MUCH easier.

Keep in mind that SFCs are connected to the car at end end, same as if you were holding them in you hands. That is the torsional stiffness I was referring to.

The car is going to try to twist them, more than anything. Square twists, round doesn't.

I'll contend square is stronger in terms of bending....But bending isn't an issue for SFC. Twisting is. Right?

Apeiron

If your SFC was a single tube running down the middle of the car, and the car applied a twisting force at each end, then yes it would be under torsion. SFCs aren't made like that though, they run down the perimeter of the car. As the car tries to twist about a central axis, the perimeter bars are bending, not twisting.

Guest

The best way I can think of to describe what you're referring to with SFC's and torsion is this:

Imagine the body of the car as a bicycle wheel. Cut the car right across the middle, from the driver door, through the roof, passenger door, through the floor. The body will twist approximately around its center (good enough for this discussion) so you can imagine the roof, side glass, doors, and floor as the rim, and the axle is where the center of the torsional force is. Fix the axle to the hub so it cant spin anymore, and turn the wheel. There's your body in torsion. So in the middle where the axle is, there's a lot of torsion. ALONG the exterior of the car or along the rim, there's your torsion. Now take a spoke, snap it off the hub, and bend it 90 to the rim, outward from the rim. Turn the wheel. What force is in the spoke? Attaching a crude diagram to try and help anyone reading this to visualize what the heck I'm talking about.

George

So it would seem.

I can't remember if this car has SFCs or not.

Guest

Before you say it... oops too late.

Actually TRY this with similar sections, MEASURE the angular deflection, and get back to me. This is a fallacy. I have some 1.5 x 2 rectangular tubing that I guarantee you will not be able to twist whatsoever.

Nice picture above this. Imagine the only thing connecting that left front wheel to the car is the SFC. Do you think its in torsion, or is it a cantilever resisting bending?

UMI Performance

Post Deleted

soultron

iTrader: (2)

^
Well, that's one way to get involved. Heh.

91_5.7_TPI

iTrader: (2)

After reading this, I wish I had gotten square tubing instead of round. Especially if I got them on group purchase....

Stephen

iTrader: (12)

And now we see what UMI is made of....They resort to thread jacking to post an AD!

Well, you can be assured now, that UMI will NEVER get any $out of my pocket. Hell, I wouldn't run UMI now if they GAVE me stuff for free!

If they had good products, it would sell itself & they wouldn't have to resort to thread jacking to post an "ad".

UMI Performance

I am sorry you feel that way....

Although I posted an ad I offer a lot of advice as well.... I post steadily on sites like Ls1tech offering free advice and excellent customer service. I have began over the past few months of posting on here... NOT only to sell products but to display information and build relationships. I see no reason for you to bash me over a sale post and me recommending our product. If you think that is that bad I highly suggest you do not visit sites like ls1tech.com ... sponsors fight all day long on that site posting products. If you do a search on my name you will find many helpful posts....

Thank you,
Ryan

Here is a good example of me helping another member- https://www.thirdgen.org/forums/susp...poly-ends.html

George

So you've run your ad for your product and now you're running another ad to tell us all how great you are as a person.

You just don't get it do you.

I agree with Stephen.

Your conduct is obnoxious and your reasoning is laughable.

On account of this post I won't be buying anything from your company or sending anyone your way.

If you'd just left it at the ad I'd have forgotten about it but the content of your second response and attempts to justify yourself say a lot about you - none of it good.

UMI Performance

Wow tough crowd... I am sorry I tried to promote business in your thread, I didn't think it would turn into this. I will delete my post now

All I was stating was as a sponsor of this site I also give valuable information and not just post sales... and many who have dealt with me will justify that.

The difference is this site is free to you.. no charge but us as a sponsor, we pay to be here. Sponsors are one of the main things keep this site alive... please remember that...

I will delete my post, I never asked for a arguement or to be bashed because I was sharing a group purchase... I thought being on this site as a paying sponsor for 2 years now I would get a little more respect.

Again I apologize,
Ryan

Doug Phillips

Nope, just Upper control arms, Koni SA shocks, Strano springs, 35 mm front bar, T2R diff. 1 week old brand new 275/40/16 A6 Hoosiers on 16x10 rims.

This is from the 2007 Canadian National Autoslalom in Toronto. The car was running great but unfortuately I still lost 1st place by 62 thou of a second over two days combined times. I also blistered one of the tires after only 13 runs.

Car is sold and the two sets of 16x10 rims are for sale. One set is only 12 lbs/rim!

Stephen

iTrader: (12)

UMI....

If you want to post RELEVANT information...Feel free. There is a difference between posting pros & cons of tubular vs square, like why your company chose square over tubular. And why the passenger side SFC is 2 pieces welded vs 1 bent bar.....FEEL FREE.

Just don't come on here ADVERTISING in a thread. Ads are displayed on the right. You might as well thread-jacked. Not very well liked.

As for advertisers fighting on LS1tech-whatever...All I can say is there is a difference in the maturity of the 3rd gen crowd & the 4th gen crowd....Also one reason I own a 3rd gen.....

//<86TA>\\

iTrader: (14)

i didnt see UMI first post, so i cant comment other than to say that I have a lot of UMI's parts and they are all, by far, some of the best made pieces ive seen being provided by any suspension manufacturer who makes parts for the 3rd gens. I also like the material selection used to build some of there parts a lot better than another sponsors choice. As well as a couple other suttle differences, that IMHO, put them a step above of the rest.

and as far as maturity, jumping down someones throat, calling their stuff garbage, just because they are trying to make a living and put their name out there, on a board that they sponsor and support, is a bit immature.

anyway,

I Like square/rectangular because its easier to weld, but i also like round because it looks cleaner for some reason, maybe have to use oval tubing or something,

As for the strength between round and square, strength is relative, and in this application is there really enough force applied to the SFC to cause either material to twist enough to notice or cause a failure. I dont see any of these designs being drastically stronger or weaker based on what they are made of. The KBDD will probably offer a little more support since they tie into the trans subframe, and if they were made from round, they would probably not be a whole lot stronger if any, but they could be a little lighter.

There are also the Alston SFC, they ties the rear subframe piece just inboard of the LCA mount, to the trans subframe. They seem to work very well, though you do loose a little ground clearance, though even with a lowered car i have never hit them on anything.

-Phil

Stephen

iTrader: (12)

Then you should read up, before posting anything on the subject.

I didn't bash UMI products..I didn't jump down his throat. I just pointed out, that it is very business-like to thread-jack with an ad.

Explain your product...If it is good, it'll sell itself. Bad products are the ones that need to be "shoved" down the customers throat.

//<86TA>\\

iTrader: (14)

its deleted, i cant read it .

seems rather rash to me.

Stephen

iTrader: (12)

I was only stating MY opinion & what I would do....It wasn't anything about them

Was I bashing myself? Oh...Ok...I can deal with that.

UMI Performance

Thanks for the positive words Phil.. I appreciate it.

As for the post, I was simply posting we had ours on sale.. that was the entire post. I should have gone into more detail like I did in this thread, usually I do- https://www.thirdgen.org/forums/susp...?highlight=umi

Stephen, you are correct, a product should sell itself... that is a good point. And in all honesty ours do... actually to the point at times we can't keep them in stock and I would say a good percentage of members on this board are using them.. they were our first 3rd gen only item and we have sold hundreds of sets and have very positive feedback. I guess that's why I posted our sale price... people usually can't wait until we put them on sale... I was trying to help as well as promote products.

If we can end this and let this go back to the original question that would be great.

Ryan

Stephen

iTrader: (12)

Yes..And feel free to discuss square vs tubular...

samiam91RS

wow should i bring my weapon in here to the fight? lol anyways, i think the best thing to do is try a set of round...and try a set of square. i have round lca's (i know theyre not SFC's) but they are dam good imo. i think ill try both considering the fact that i dont have a set yet. first ill go with square then try round and see formyself whats all the differ.

87 formy

Maybe you should put the round on first and then the square, it'll save you from swapping your SFCs out an extra time

Guest

1.5"x1.5" x .187 thick square tube Vs 1.5"x .187" round tube?

Round tube is lighter and wins in torsion strength.



To the guy with the car pictured with the front wheel off the ground- You said you blistered a tire. Thats becasue you ran too high of pressure on a new uncycled tire and your suspension was not st correctly obviously be the picture where you were diagonally x-loading the rears and lifting the fronts. I can see why your rears blistered in 13 runs. That is way bad ANY time a car lifts a tire (unless its dragracing with just straight line preformace). Your shock and spring package needs work, you are rolling over on the rears on exit and are too tight off. I am sure you then correct it by stabbing the throttle to steer it off and loosen it- thus blistering the hell out of the rears.

Note- any time you run a brand new tire you should always run it out on lower pressure (aprox 4-5lbs lower) on a sticker tire then shock treat the rubber with wet towels to condition it. Next purge the tire and refill up to normal operating pressures and you will greatly reduce any chance of ever blistering a tire again.

Dean

Guest

Using both 1.75" OD tubing .120 wall thickness, in round and square, the square tubing is about 45% less stressed and the deflection (which is what you should be concerned with) is ~30% less with the square tubing than the round in the quasi-truss arrangement of the KBDD SFC's. So given the same space to fit a frame element into, the square is better in this particular case.

Additionally, if you were to use the same area of steel (which is to say use the same amount or weight of steel) in both round and square, you'd end up with a 1.4" OD square tubing (not available) and it would be ~15% more deflection than the round. Using 1.5" OD square would likely be near identical in deflection, but of course the square would consume less physical space in a place where space may be at a premium. Then of course too there's rectangular. Placed 'correctly' vs the load, it'd be a lot stronger than the square, and weaker if placed 'incorrectly' vs the load.

Thats kind of why I keep saying round is not necessarily better, it all depends on what you're doing and how you're loading things.

I'm using a 3D structural modeling program with a single deflection at one joint, basically a single wheel movement.

Stephen

iTrader: (12)

I just finished measuring...

The KBDDs are 1" x 1" x .120" wall tubing...
.180" thick & .120 wall thick mounting plates

Guest

Kinda... puny. lol.

The most stress, of course, is in the piece that runs the length of the rocker. Its about 30-35% more stressed than the others in a worst case scenario. So you'd want that piece that much larger if possible.

UMI Performance

Hello Everyone,

Here are some reasons why manufactures choose there material and sizes we use. This reasons do not pertain as much to strength but more towards fitment and fabricating conditions.

Round tubing is easier to work with when it comes to bending, there are more bending options available and it allows for tighter radius's. Square and rectangualr tubing can be bent but the options are limited when compared to round tubing.

We choose rectangular tubing for a better fit... we used 1.500" x 2.000" tubing with a 0.125" wall. The 1.500" tubing is designed to fit into the seam of the car with ease... the 2.000" then offers the width and strength we were looking for in the item. For mounting plates we use nothing less then 3/16" thick steel. From the findings on the KB sizes it shows were manufactures can cut cost very easily but using smaller tubing and thinner steel for there mounting plates.

Hope that helps,
Ryan

noroxus

iTrader: (1)

When it comes to SFCs torsion is not the leading force. It's a bending force.

You are bending a rectangle, not a straight line.

RED_DRAGON_85

there are numbers to back up any claim, but what it all comes down to is what you want and what you feel is the best way to spend your money

because they dont make mandrel benders for square tubing as far as i know

Guest

When square tube twists, it can bend. It needs to be ladder bar construction.

//<86TA>\\

iTrader: (14)

im quite sure they do

joeblue83

iTrader: (8)

Not to hijack the thread but I have been looking for a good set of SFC. I am going to have a 3.5 mufflex, and with the cheapo SFC I have right now, which are below the exhaust and cut out. I am looking for a set the would fit (weld on) without denting the exhaust or other major modifications. I have been looking at the spohn and the umi one. They are both the same price. Just need a little advice
thanks