The point of the discussion was whether the tubular sfcs would be BETTER not if they would be "adequate." As for the elderly person complaining about the supposed "youth" of the posters, perhaps he should contribute rather than simply flame? The figures posted by Eric were quite intriguing. We'll have to see how this all pans out...

 

Hey, If Steve says they're better, I'll take his word for it
I was planning on buying a pair this summer anyway, since his brand looked to be the best out there especially considering price. Upgrades are even better!

"Yep, including STBs, needed this machine for them as well, and I have dies to bend SFCs and STBs"

I'll probably snag one of those too if I can afford to at the time. Damn college budget.

 

As for contributing, I could not do any better than Steve himself. He laid everything on the table for everyone in his explanations. His commitment to produce a superior SFC in strength, quality, and reduced weight in a form preferred by the majority of his customers left no questions in my mind.

My apologies to almost everyone who took my “youth” remark as a flame. It was expressed jokingly considering the all the buildings, curved windows, castles, and cannonballs. But if you look at the initial post, this whole thread started as a flame of Steve’s business ethics and commitment to quality…..

cheap, inferior, effort to raise profit margin? Sounds like flame to me.

 

Not a flame at all, simply asking whether this rumor I heard was true. Did you bother to read the figures posted? Is knowledge of history somehow a revealation of youth? You didn't contribute a thing to this thread by saying that somehow all the posters were kids by making valid analogies... Beyond wording the initial remarks I made were the furthest thing from a flame, they were simply a request for information in a public forum, it was an expression of my disbelief that he'd change an already superior product to something that I've always read was inferior in terms of strength and resistance to flex and have already stated that we'll have to see if it makes much of a difference when he does finally release the finished product. It's too early to tell, as the rumor was just confirmed by Mr. Spohn himself, and we have not yet seen the finished product. I'm not trying to flame here at all. I do hope that the new SFCs will be as good if not better than the old ones, but I'm just pissed I didn't have the opportunity to get the old ones, and that he didn't put a notice of a design change on his website before going ahead and changing it...

 

Fair enough, we'll agree to disagree.

 

Amen!



:hail:

 

As far as SFC's go, shouldn't we be concerned with torsional strength??

 

I have my boxed spohn sfcs still sitting waiting to be installed. I trust steve and if he says either design is overkill, then what are we fighting over? Anyways, hey steve any chance we could get a sneak peak at the new tubular design?

 

quote:
--------------------------------------------------------------------------------
Originally posted by ANDYZ28
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
--------------------------------------------------------------------------------



This has nothing to do with the topic, but yes, there are structural parts of aircraft that are rectangular. In fact, the wing structure is mainly rectangular ribs, stringers and formers. I have worked on military aircraft (F-15C/E and F-117A) since 1984 in the Air Force.

I guess it does have something to do with the topic?

Mark

 

As an Engineer I would like to say that theoretical formulas are great...but the flaws don't necessarily lie with the design (tubular vs boxed), but rather what can be built effectively for the intended purpose. I trust that Steve knows what he's doing.

 

Like Steve said before, he's not building these things for tanks. So what's the big deal boxed vs tubular, bla bla bla. Are you guys debating which is better for installation on a 3rd gen or are debating which is better just for the sake of a good debate.

 

 

 

Hey Inwo, what the hell have you started here?!

 

This has nothing to do with the topic, but yes, there are structural parts of aircraft that are rectangular. In fact, the wing structure is mainly rectangular ribs, stringers and formers. I have worked on military aircraft (F-15C/E and F-117A) since 1984 in the Air Force.

I guess it does have something to do with the topic?

Mark

I was refering to small planes with welded tubular frames. For example a "Stearman".

 

I simply asked a question, I can't help if it turned into a Great Debate I'll still support Spohn as having the best LCAs Torque Ars etc, I'm simply questioning his design decision for the SFCs. That's all I started, apparantly it's a hot topic for debate? I'm very interested in seeing how it'll turn out, and whether this thread will be resurrected in a few months with one of you all saying "told you so"
Lets all hope for the best eh?

 

most of an aircraft consists of 'J', 'T', 'L', and 'I' cross sectioned structure. This is true for most of the structure such as the stringers & stiffeners (J, T, L), spars (I), ribs, etc. But they use these shapes because they allow a flat side to be fastened to the skin and the perpindicular surface to give some stiffness.

Tubular is fine. More importantly is how and where they connect to the car.

 

A few years back I had an associate who ran an Alston chassis in his drag car. I remember that Alston had some great videos on installing wheel tubs, back-halving a car, etc. (wish I knew where I could get them now1) Also had some good tips on chassis design as it applied to guys like us so I started searching. What I found was Chris Alston’s Chassisworks and the following are excerpts from what he has to say about some things we’ve been talking about and then some. While it applies, in this context, to straight-line racing there are obviously some underlying fundamentals.

BOX vs ROUND RAILS
Anyone who decides to step into a full chassis must next choose between a box frame or a round frame. Fact: There is no advantage to a box-rail car! A lot of people are under the mistaken impression that a box-rail car is stronger; in fact, the strength of any car comes mostly from its roll cage. While a box-rail frame is physically larger, it’s also made out of thinner material. And it adds about 30 pounds to the car — a considerable amount of weight, considering that a round-tube chassis costs about $100 less. (Whoa guys, he's talking about a FULL frame here)

A-ARMS vs STRUTS
As for performance, the reality is that the strut is not an infinitely better suspension than the A-arm. In some cases, an A-arm might actually work better, because it has a bit more front-end travel than a strut. If you have a nose-heavy car (which most cars built economically tend to be), or a high-horsepower car with a marginal tire, more front-end travel is an advantage.

The modified MacPherson strut is the latest technology. For anybody who’s building a serious car, it’s the preferred choice. An internally adjustable strut must be taken off the car for adjustment of its valving; an externally adjustable strut can be
readjusted without removing it from the car. The latter is a very sophisticated piece. In the hands of a person who wants to spend some energy working on it, that’s an advantage — not because of the strut, but because the shock absorber is adjusted externally, and has more control and more variables. A well-equipped strut car is going to be a few hundredths faster than a well-equipped A-arm car.

MILD STEEL vs 4130
Some people believe that 4130 chromemoly cars are stronger than mild-steel cars. Not necessarily! While 4130 tubing is a stronger material, because it’s made out of an alloy steel, the rules let us use thinner material (.083- and .065-inch wall). Thus, a stronger material that has a thinner wall is about as strong as a thicker-wall mild steel.

The 4130 chassis is going to be 20- to 25-percent lighter because it’s made out of thinner material; there’s simply less steel in the car.

The only real disadvantage is that a 4130 car must be TIG-welded. That means every single accessory, bracket and tab has to be TIG-welded. For the first-time, build-it-yourself type of guy, this is not the way to go; he shouldn’t even consider it. Chromemoly is for a higher-skilled, more capable fabricator. Mild steel, on the other hand, is extremely forgiving.

I also hear people say that 4130 is more likely to crack. Wrong again! This tubing was originally developed for the aircraft industry to make airframe parts, and nothing is stressed worse than airframe parts. If this stuff didn’t have excellent fatigue life, it wouldn’t be in airplanes. I have never seen a worn-out 4130 “door” car that was assembled correctly. Nor have I seen a worn-out mild-steel car that was assembled correctly. So, durability isn’t really a consideration.

If you want to see all of the Tech Tips go to http://www.cachassisworks.com/techtips.htm.

Also, in addition to Steves SFCs, here is another one that I haven’t seen on the boards.
http://www.swracecars.com/f-body.html

 

BTY.. Just thought I'd throw in the strut thing since we all have 'em.

 

I had a set of the edelbrock Tubular subframe connectors on my fourthgen and they were made out of approximately 1.75" round tube and trust me that car didn't move a bit after the sfc's were put on the car.

I am shure the parts that steve makes will be more than up to the tasks you guys will be putting them up to. I think this thing has gotten way out of hand. Were can you find a subframeconnector that is a cheep as steves and at a quality as high I am shure he won't skimp on the quality this guy makes a living off of us on this board and you think he is willing to risk that?????I don't

 

Steve, are you going to make a stb for carbed cars?

 

I already have Spohn's boxed SFC's and I love them but I have a few question's about the 4130 SFC's, will they have to be welded in any special way? I'm no welder but I can usually stick things together pretty good with a MIG, but I've heard that 4130-4140 type metal needs to be preheated before welding. If that's true it will be a lot harder for the avg. muffler-frame shop to weld them in since I dought that they would have the correct wire on hand. And does the 4130 steel weld good to the 1018 type used on car frames? But as far as being boxed or tubular the only drawback I see for the tubular is it won't make a good jacking point like the boxed one's do because the jack would tend to want to slide on them.

 

Carbed STB yes, my beater jig car is carbed, so that's covered.

The tubular SFCs will be available mild steel OR 4130, just to clarify. The 4130 won't be $155, the tubing costs 7 times more then mild steel, and it's more (alot) labor to build them as it must all be TIG welded. So, that answers your question 4130 may NOT be MIG welded, it MUST be TIG welded. Now, the rear and front mounting plates will be mild steel on either set up. So, if you just want to MIG weld the front and rear mounts to the sub frames, you could install them with MIG. But if you want to weld the actual main tube to the rocker panel lip, that would have to be done with a TIG on the 4130 version.

Steve

 

steve, do you have any date that you expect these to be finished? i need sfc's bad and i want these. i can probably hold off til the beginning of april.
thanks

 

Ok, I have a few real questions, not flames.

Will we be able to jack the car off of these tubular SFC's? That is number 1 on my list of reasons to get SFC's.

On the subject of the STB, i was almost set on the Edelbrock, but now I'll wait. I have a TBI car and I need a brace that will clear all of the factory AC and emissions equipment since I'll be keeping that stuff(most people don't). I would even like to keep the factory single snorel air cleaner if possible. Will the version you make clear this stuff? Will it be triangular?

I think that's all of my concerns, thanks.

 

falkin a!

'moly sfc's. looks like procrastinating on ordering sub frames actually paid off. might as well start bending mine up cause im ordering them as soon as you put em up. you got a ruff estimate on the price of the moly's? oh yeah, nice work on the T56 torque arm you sent me a month or so ago. i wasnt really expecting much performance wise, but setting that pinion angle really makes one hell of a difference.

 

Steve,
Do you have the title or ISBN of the chassis design book you mentioned by Jerry Bickel? I searched Amazon, but didn't come up with anything. Thanks!

Andris
Z28tt - 89 IROC T56 DFI Twin Turbo
http://www.skulte.com/turbo.html
Rollcage Fabrication in progress

 

Just as a side note... Torsional stresses are a "twisting" motion and the "bending" motion is Flexural stress. There's also Longitudinal Compression and Tension. As, SFC's are subject to all of these forces... And the fact that a round tube does all of these better (per weight) Round tube is the way to go. Set me down for a pair. I'm running LT headers, dual cat or single? What will better suite my application?

 

WOOHOO!!

 

Ok, Let's get serious. I used to watch Mr. Wizard when I was a kid and I remember him demonstrating that a tubular bar is better then a boxed bar. So Steve is doing good.
He's coming out with Convertible SFCs TOO!
If they are worth the price over the IRS (Alston) version I'd get them. The alston is still out so in my opinion Steve really has to beat the price and strength
IRS-18292W Terminator Weld-on Subframe Connectors 82-92 Camaro/Firebird $159.99
IRS Terminator Series Subframe Connectors are manufactured of large 1.625" x 1.20" wall steel tubing with .135" thick mounting boxes that completly box in the front and rear subframes on 3 sides
You've got a tough act to follow steve, but I think that you'll be able to do it for us convertible guys.

 

Any idea when they are gonna be ready steve? I want to get em under my car before i go to the track again but doesnt sound like its gonna happen. I seem to be having somewhat of traction problem and im hoping they will help out a bit. I just ordered your relocation brackets by the way.

 

Bravo Steve:

Put me on the list. I'll buy a set for my ragtop the day they become available.

Larry

 

According to an email I recieved from Spohn a few days ago, they will be ready in about 2-3 weeks and the price will stay the same.

:rockon:

 

Hey all I want to know when they tubulars sfc's will be ready...Thanks Kevin

 

My question ^^^^^^ is answerd now..Kevin

 

Sweet now i wonder how backordered they will be

 

Tubular steel shouldwork jsut as well for SFC's. You guys are forgetting that SFCs mostly are under horizontal stress, so basically its trying to compress the SFC lengthwise, not bend it downward. This would essentially make it jsut as stron as a boxed SFC.

 

Well I can attest to the forces your subframe connectors see. I purchased the Spohn dual catalyst subframe connectors. After putting the screw to them for approximately six months the narrowed down piece that clears the cats has flexed inward a couple degrees.

Dave Freeman
Mechanical Engineer

 

ummm, when the front of the car is up in the air and the lower part is not(you know on jack stands) the car almost "folds" that puts a vert stress on SFC....or am i missing something.

 

Would this carbed version clear the old style air conditioning with the a/c compressor on the driver's side, or will I still be out of luck? Will it be triangular?


Nothig to do with this topic really, but this got me wondering if an aircraft or a submarine is stressed worse. Anyone know?

 

Wow... this thread is still alive?

I'd think the submarine is stressed more due to the EXTREME pressure per inch pushed on it from all sides when it's diving deep, but the round shape of the sub is to give it a more aerodynamic shape, not for strength per se, could be wrong though.

 

For those of you using the "It's Steve, so I trust him" arguement, drop the BS and use a better arguement. You know, I know, and everyone else here knows that anyone that makes a product and profits off it is going to support their product regardless of what they REALLY think about. Do you honestly think Steve is going to sit here and say "nah, the tubulars won't be as strong and it's cheaper for me to make so I'll make more profit too"??? I don't think so. That would be stupid on his part because then no one would want to buy his SFCs. That's like saying "hey, it's GM so if they make a FWD Camaro and say it's better than RWD I'm going to trust them." It's all about the $$$$.

With all that said and done... I too will be amongst the people buying the new Spohn SFCs this summer.

 

Well now that I am not at work I can elaborate on my former comment. After using my 91 GTA for autocrossing and drag racing I have seen subframe deformation. After studying it closely it looks as if the deformation was caused from compression loading. In that case both tubular or rectangular material should be sufficient as long as the cross sectional area is large enough (1.75" should suffice) and the cross sectional area does not vary too much (the start of the failure on my SFCs). Another thing to look at is the load path. Look at the subframe as if you are going to stand it on end and then load extreme amounts of weight on the top of it. Are there any areas that may cause it to prematurely buckle.
Here is my 2 cents on tubular and rectangular as far as chassis loading is concerned. Take a large tube and pretend that it is your F-body. Draw a line down the side of the tube and draw another one directly across from it on the other side of the tube. Now twist the tube. The lines you drew are bent one up abd one down those line represent the subframe connectors. They see mostly bending loads (drivetrain torque) and compression loads (from weight transfer). This is the worst loading condition material can experience. In a bending load you want an I-beam it is out and out the strongest structure to combate bending. Pick up a text book. If you think about it a rectangular tube is an I-beam with the center material moved to the out side edges and if you look at the calcuations for an I-beam and rectangular tubeing subjected to a bending load they are very similar.
With that said don't go assuming that rectangular is the end all answer because you must take into account the compression loading and truthfully I think this is how my subframe connectors were comprimised. The tubular material will resist compression loading better because it is less prone to stress riserscaused from material imperfections. So see you may take a hit in bendind loads but you make up for it during compression loading. So each set of SFCs have there strengths and weaknesses.
I think of it this way a SFC is more than what you had there before and as long as it is built logically out of good material and is anchored to legitamite loading point on your chassis it is going to be better than what you started out with.
For those of you welding these things to you floor panel and rocker arms if your car sees extreme use you may want to think that over, both are made of much thinner sheet metal than you SFCs and when you are putting the screw to your vehicle be asured the chassis is deviating from its intended place. The best chassis's have movement under extreme conditions. Since the SFCs are more robust you cn bet they will flex at a leser rate than the rest of the metal you have welded it to and something will have to give. Sorry for the long post, but I feel that this is the kind of info we should kick around on this board for it will help to better everyones knowledge and hopefully their vehicle also.