I heard a most disturbing rumor going around that when Spohn starts making SFCs again instead of the high quality Boxed SFC design he's going with the cheap Tubular SFC design in an effort to raise profit margin... Is this true? Did I miss out on getting the GOOD sfcs? Hopefully someone bought an extra set and is selling them cause I know I sure don't want to waste my money on an inferior Tubular set....

 

Thats what I heard too.... I certainly hope that isn't true. Guess the only thing that made an F-body a BODY is no longer on the market

 

arent race cars made from tubular chassis??

 

Well, tubular is a good design so I don't see what the problem would be. I just hope he puts up pictures of the new SFCs on his site; installed pics and off the car.

 

Sure I got a set of Spohn's SFC's for sale, only $999.95. Guess I lucked out if it's true ordered mine like a week before he stoped. As a matter of fact I'm installing them tomorrow.

 

Cheap tubular?? High quality boxed? Whatever dude! Tubular is much better than boxed any day. Has a much higher strength and is usually lighter in weight. Besides, no matter what Spohn is making, i'm sure it will only be high quality. Tubular is the only type of suspension that I install on my car!! Hmmm...A Nascar chassis is made of what....I can't seem to remember! Maybe someone can refresh my memory on that one!

 

Wow, you must be a stud with your winston cup car in the parking lot next to all the minivans.


THE REST OF THE CAR IS TUBULAR


your thirdgen fbody isn't

 

Anyone heard when he plans on starting up production again? Also when's he going to start manufacturing STB's and steering brace's?

 

So you're saying that the added strength of boxed sfcs is inferior to the cheap Hotchkis style tubular sfcs? I'm confused, somehow Hotchkis that everyone passes over in favor of Spohn or Kenny Brown's are now superior equipment? I don't doubt that the SFCs will still be decent but I don't see how they could compare to the style hes been making with the thousands of satisfied customers. Tubular suspension is different from a tubular frame. Sure if I was putting a cage in my car I'd want the tubular sfcs to fit right along with them but really how many people have roll cages in their cars? I don't know, I guess we will have to hear from Spohn himself for the definitive answer and have a few people with the new SFC design installed before passing judgement...

 

I think that tubular SFC's or any type of tubular frame is less prone to flexing as compared to a square frame. I believe because tubular frames are like this that they are able to make them thinner which in turn means less weight and still get the same results as the heavier guage square frames. But to see any actual gains from running tubular frames you would have to be involved in some hardcore racing. Just having them installed on a daily driver won't do much for you. If Spohn is going with the tubular SFC's I can understand why, there cheaper and you get the same results, and having them lighter will probably save you a couple bucks on gas in the long run.

Mark

 

They will be tubular, BECAUSE THAT"S WHAT EVERYONE KEEPS BUSTING MY *** TO BUILD!!!!!!!!! This is what everyone has been telling me they want, I build what the customer wants! Everyone griped about how heavy the rectangular ones were!

Price wise there is no difference, I don't know who told you that. Rectangular and round tubing is pretty much the same exact price per foot. Round will give you the same strength (actually better) with less weight.

Don't compare my product to what's out there when you haven't even seen it yet! I'm not using wimpy 1.25" tubing like the other guys. These boys are 1.75" round with .120" wall, same wall as the boxed SFC. Of course they'll be lighter, especially if you get the .083" wall 4130 version

Steve

 

Hotchkis SFCs are boxed, not tubular.

Steve

 

Steve,

Curious what going to the tubular SFCs is going to do to the ease/dificulty of "stitching" the SFC to the underbody? When do you expect the new units to be available? And when do you expect the details to be on your web page?

Thanks, getting ready to get a set this spring.

 

Steve,

I will be waiting to order a set of tubular sfc's. I was going to build my own (square) if I could find time. I would rather support your efforts now that you're designing a tubular model.

Will they have any tabs attached for connecting to the rocker panels? I have looked at the units S&W makes and they seem pretty decent. I have faith yours will be superior.

My problem with tubular was that they were such small diameter tubes, 1.75" diameter sounds better.

 

Dude, PLEASE make a set for convertibles.....better yet, make them fit T-tops and convertibles.....

 

Im wondering why I've never seen a "tubular" building if its stronger

 

Curved glass windows are too expensive.

 

Steve,

Is the design of the dual cat SFC going to change? I don't care if it's tubular or rectangle, as long as it does what it's supposed to do.

Thanks,
Dylan/formul8

1989 Formula 350

 

That always sucks when you get yours just one week, and now find out of the switch.

Oh well.

I wish the STB would come alone, I guess I'll just use the Edlebrock.

 

Wow, You don't have a clue dude. I'd suggest not posting for a while. At least until you figure out what the heck you're talking about...

Clem

 

Haha

riiiiiiiiiiiight

how long you been working on buildings bud?

 

Uh, why are you guys busting on Steve? Tubular isn't "cheaper" than boxed. I'd actually prefer a set of tubular SFC's. My Spohn boxed ones are still in the bubble wrap in my garage waiting to go on, so maybe I'll switch.

I think you guys who are bagging on tubular SFC's need to go check out the Global West site.

 

Buildings aren't made of tubular anything, they're made of I-Beam for all main load-bearing supports. I'm AWS certified in ANSI D1.1 structural code, which is welding together "buildings". I can bore you all day long on that stuff! So you want I-Beam SFCs, they'd only weigh around 100# per side

Seriously, and I'm not trying to be a smart *** here. If you wanna study up on chassis construction, strengths, etc. buy the book Jerry Bickel sells, it's the best book out there on chassis construction.

The large O.D. 1.75" tubing lays very nice to the floor pan to get the same quality welds. It lays even better, since there's another 1/4" of material to the rocker panel, compared to the 1.5" high rectangular.

The single cat version will fit ANY single cat, including the SLP, so there will no longer be a "SLP version". The dual cat version will also still be available. Y-pipe clearance will be better, shouldn't have to do any y-pipe tweaking with these.

Yes, there will now soon be a convertible version as well. The convertible was impossible to do with rectangular because of the bends that are necessary. The Alston's are tubular, they fit the convertible, unfortunately for you drop top guys it seems they aren't making them, or not many, these days. We'll be taking care of that.

I would have went this route long ago, the majority of email I get about SFCs is to build them tubular. I had to buy a 25 ton hydraulic tubing bender, digital read out and all, it's a nice machine that will allow me to build quality tubular products. Yep, including STBs, needed this machine for them as well, and I have dies to bend SFCs and STBs.

Just a little more time to tweak the designs and the SFCs will be back on the website. Then we'll move on to STBs and convertible SFCs.

Bottom line here, if I didn't think this was superior to what I already had, I wouldn't have done it. I guess you just gotta trust me on it

Steve

 

Anyways, back to the point befor this goes off into some flame war


Personally, unless someone can offer some proof otherwise. I'd tend to believe that a "circle" would be one of the weaker configurations as far as shapes go. A triangle being the strongest If i remember.. The box shape at the same given thickness as a tubular one I feel would offer more structural integrity.

Example: When was the last time you saw a perfectly circular piston rod? The Beam shape is to maximize strength while saving weight and space.

My $.02

 

Like steve said about I-beams

 

Well, we'll try this again. With my signature this time. You'll see I haven't worked on buildings. I'm not professing any particularity toward round or square either. I just have little tolerance for people who talk when they don't know better.

You're comparing apples and oranges (it's a saying...trust me). I could give you design proof about the superiority of one design over another, but I won't bother because you wouldn't pay any attention. You've already proven that much.

Clem

I don' t follow the whims of "sys admin" in the realm of chassis design and construction

[edit] D'oh. so the sig isn't working. Anyway. I've got a few years experience as an SCCA TransAm Series Crew Chief. Might mean something. Then again...maybe not .

 

I think i've proved quite the opposite

In fact consider this a request for proof

lets see if you come through with it.


By the way, my current job is just that. I've done plenty of other things and I too like steve am AWS certified, nowhere near to the extent he is, but i've spent my endless hours in welding booths, constructing trailors, and whatever I could find something to attack with a mig.

Now lets see your design proof.

 

Rectangle/boxed tubing has sharp corners where the metal is stressed to make the sharp bend.

On a circular tubing, there are no sharp corners (duh), therefore the stress load is distributed much more evenly.

 

With metal fatigue and strees taken into consideration, yes the boxed tubes have been "bent" and they'll be easier bent the second time.

However, the sides offer latteral support that a circle doesn't have any of, as well as a horizontal support, the only time the corners will be weaker is when stress is diagonal from corner to corner.

Unlike Mistar meanie up here im not professing to be any sort of g0d

Im looking for the truths, even inside of his insults should there be truth in there....

 

Round tube subframes yield stronger torsional resistance then square, per given weight. As stated there are no stressors.

Anyway, let's not turn this into an engineering debate. The bottom line is either type/size tubing is overkill for the application. It doesn't matter if you weld in a 1.5x2.5 SFC, or a 1.75 tubular SFC, either one is gonna lock the chassis together and do the job we want it to do. We're not building Abram's tanks! The actual goal is to have a piece that will adequately tie the frame together, and not weigh any more then necessary.

Steve

 

I like debates


Anywho, I agree that a tube would offer better tortional resistance, ie drill bits. I just see the force exerted under the car not being that kind of stress, more of a up down on opposite side kind of tweaking..

Anyways I agree, I'm done "debating".

Keep the migs glow'n steve

 

I guess we'll have to see how they turn out. I don't know, if the tubular sfc isn't integrated into a rollcage then I don't see how it'll offer the same stability the old style offered... I can't imagine them being as easy to weld on or anything, since they probably won't be tied into the frame as easily as the boxed ones. Too early to judge the new design since we haven't seen it yet.
First time I ever heard a rumor that turned out right. Hopefully I won't have to say "Wish I had bought them in the fall when I had the chance!"

 

Was no rumor, I told everyone asking for them that we were switching over, wasn't anything top secret. Don't worry, you'll like them, it's a sweet set-up if I do say so myself

Steve

 

I was going to order the current ones, but I'm gonna wait until the new design is ready.

Any ETA, Steve? I need the dual cat model.

:rockon:

 

Hey Steve, Have you ever thought of making a boxed swaybar [] vs a round one O. You might have another gold rush on your hands if you did.

Hope to order your sfc's this summer too.

 

I will also be happy to wait for the tubular ones.

 

I would also like to know the ETA for them. If I were to place my order now could you accept it and put me on a waiting list? My income tax is burning a hole in my pocket so I need to order them ASAP.

Also about the Tubular Vs. boxed I will just go with Steve on this one If people praised his boxed versions. and hes confident that they are better. than they must the the Sh*t

 

Formul8 hit the nail one the head. Tubular is better because of the lack of stress risers (The same reasons rods are shotpeaned and racers debur their whole block), yes they might flex a little, so little it would be measurable only in thousanths, but they wuld not weaken or be as likely to crack as squre tubing and have a higher fatigue strength.

 

I have always assumed that the torsional resistance (stiffness factor) would be most important when designing sfc's since we are trying to eliminate the twisting of the chassis. This is my assumption, Steve probably knows for sure.

Round sections (solid or tubular) are best for torsional loading because the shear stresses are uniform around the circumference of the section. The second best for torsion resistance is a closed square or rectangular section.

I did some rough calcualtions using formulas for thin sections and the results surprised me. I used Steve's specified sizes for comparison.

Round tubular= 1.75" O.D. x 0.125" wall thickness.
Rectangular= 2.5" x 1.5" x 0.125" wall thickness.

Torsional Resistance R= 0.526 in^4, round tube
Torsional Resistance R= 0.879 in^4, rectangular

Moment of Inertia I= 0.263 in^3, round tube
Moment of Inertia I= 0.911 in^3, rectangular

Section Modulus S= 0.300 in^2, round tube
Section Modulus S= 0.729 in^2, rectangular

The moment of inertia I is normally the rigidity factor (bending resistance) and the section modulus can be a simple strength factor.

Surprising to me, the round section is inferior in this comparison however, since its area is 68% of the rectangular sections area, the round sfc will weigh 68% of the rectangular sfc for a given length. If Steve's current models weigh 37 lbs. then the round version with the dimensions above should weigh 25 lbs.

Like Steve says, they are both overkill and probably the best quality available.

 

So in other words the tubular will indeed be inferior? Lets hope that the overkill doesn't turn out to be overkill only for stock motors...

 

*grins like an idiot*

 

LOL!

 

The superiority/inferiority of one design over another depends on many factors, including wall thickness, material type, and dimensions. This has been a long thread, so I may have forgotten some of the details by now. If so, I apologize for it. Anyways, I believe that the actual directions of the stresses on the subframe connectors would play the largest part in determining which shape is better (torsional vs. axial vs. longitudinal). Actually, nevermind. There's no point in worrying about any of this really because I'm sure Spohn himself has put more time into calculating it than anybody, so I trust him. The only thing I would ask is for a picture of an installed set after one is done. I'm interested to see how they will attach along the rocker panel.

MikeS

 

Well, medieval engineers switched from square towers on castle to round towers...

 

That comment was more or less directed at frame structure, as in Tubular structural beams as apposed to I-beam or square beams and what have you

 

That was because they wanted the added protection of round towers vs round cannonballs. In the end it didn't really help much, but that's the reason they had round towers.

 

Attention Posters... your youth is starting to show.

 

Well, as I am sure some of know. I am no stranger to controversy.

So let me ask a few questions; Has anyone seen an airplane frame work made of rectangular tubing? I havn't! Has anyone seen any Top Fuel cars with "rect" tubing?

The install photos of the new Spohn SFC's will be stunning. I can assure you of that.

Thanx,ANDYZ28

 

Is square tubing aerodynamical?

 

This is stupid. Honestly it doesn't matter. All the matters is if the new ones are better then the old SFC's. So lets not argue about things that don’t matter. Steve has been doing this for a long time I am sure he is making the right decision.