front bulkhead

[de fox]

hi all, new here

Is there any reference on what the front bulkhead should be made from? Tube? Cutoff plate? Square tubing? Round tubing?

[RobLav]

Recommend read the SCCA GCR for the rules.

[glenn cooper]

Here's a link to the General Competition Rules
http://www.scca.com/clubracing/content.cfm?cid=44472

Regards, GC

[de fox]

thank you.
i am familiar with the 2012 GCR. I am deep in it at the moment actually
My background if from FSAE cars. i noticed that in the F1000 there are no rules for a side impact structure and nothing about the front bulkhead and its supports. Am I free to do as I will or am I missing something?

Also, if I have your attention…. The rules states that the main hoop bracers should face foreword. Why not backwards as well?

is this the place to ask these questions?

Thank's

[R. Pare]

Braces: You can run them both directions if you wish, but the minimum is forward - unless you go the Alternative Structures route.

Front bulkhead: At the minimum, you need at least one tubular crossbar to satisfy the definition of a bulkhead - the rest of the structure can be a machined alu plate (or a casting) if you wish. There are no other requirement, other than pedal placement, that have to be satisfied.

[de fox]

Braces: You can run them both directions if you wish, but the minimum is forward - unless you go the Alternative Structures route.

Front bulkhead: At the minimum, you need at least one tubular crossbar to satisfy the definition of a bulkhead - the rest of the structure can be a machined alu plate (or a casting) if you wish. There are no other requirement, other than pedal placement, that have to be satisfied.

thank's
i ment backwards insted
Out of curiosity, why are the main hoop braces ok to be forward but not backwards?
You mention the cross tubing as a definition of a bulkhead, where can I find that definition?

Cheers

[R. Pare]

There is no real definition for the structural requirements outside of what is given in the Glossary. In practice, to meet that Glossary requirement, the frame needs a minimum of one tube across the front to define the bulkhead, otherwise there is no part of the frame the delineates that point. you could also possibly define that point with just side verticals, but that has never been put to the test.

[de fox]

coming from the FSAE world, i am trying to understand the main hoop forward bracing....

and here is another one :

"The lower mainframe
tubes shall be a minimum of 25cm apart (inside dimension) from
the front bulkhead to the rear roll hoop"

does this refer to the lower side tubes of the driver cell? what i want to ask... if my lower suspension pickup points are closer then 25 cm and lower then the driver's legs, can i have a frame member running parallel under the driver legs that are closer then 25cm to accommodate the pickup points?

[R. Pare]

Good question. I think that it would depend on just what sort of layout you came up with. the reason for the rules was to put a limit on just how much you could shrink the width of the footbox area - at the time (1984-5) footboxes were shrinking to unacceptable widths (from the safety standpoint), and that dimension came from the DB1.

If the more centralized tubes did not encroach on the width space for the drivers feet, it would probably be deemed acceptable, even if it doesn't meet the exact letter of the written rule

[de fox]

hi....

I am having some trouble understanding the front braces issue. What is the rationalization for forward bracing and not rearward?
I am looking at a lot of F1000 pictures and I am having a hard time spotting cars with forward bracing. Am I missing some thing or all of those cars goes alternative?


Noam

[kea]

Twin diagonal rear bracing would do the same as the front, as far as keeping the roll hoop from folding over, forward bracing was probably chosen in the rules, to force any structure (guard rail?) to go up, over driver.
Or something like that.

[S Lathrop]

I can add a little to what Keith posted.

The rules were written in the late 70's after a crash at Mid Ohio that took the life of B J Swanson. He died in a F5000 car that split the guard rails and went under the top one. The roll bar structure was intact but BJ was on the wrong side of the structure.

The very first formula car homologated for SCCA racing built to the new roll cage rules was the 1978 Citation-Zink Z14 FSV. The rules were not mandatory at that time. They became mandatory in 1984-85

The rules are for roll cages. The rules imply a protective cage for the driver. That means the entire driver, toes to head. And the rules give minimum material requirements for the cage.

One change in the rules was to brace the roll bar (main hoop) forward, to the dash hoop if possible. This requirement came about because there were several instances where the engine was separated from the chassis in severe crashes. Bracing the roll bar to the rear of the chassis was useless in such a case. In a few crashes the roll bars went with the engines.

In the Citation frames, I maintain at least the minimum structure for roll bar braces from the top of the dash hoop to bottom of the front bulkhead. At the rear, the Citation roll bar structure is totally behing the driver, but the cockpit opening and one critical brace in the side of the cockpit (beside the drivers pelvis) are the equivalent material or greater in strength for roll bar braces.

The RFR which is a tube frame, has been tested to the F3 crash test standards. The frame deflected more than was allowable for F3 tubs but it recovered to its original dimensions, something that an F3 chassis is not required to do or is likely to do. Basically the tube frame is more elastic than a F3 tub but has a yield point that is beyond the test standards. In short the tube frame can take repeated blows without failing something that is not necessarily true for F3 tubs.

Over the decades, the tube frame designs have evolved to a point where they provide a very high level of safety even though the technology is considered obsolete by many.

[de fox]

thank you for your very interesting and in lighting answer

i am also trying to understand the rules for the stress bearing panels Prohibition in the F1000 frame rules. what is the rationalization behind that?

[S Lathrop]

thank you for your very interesting and in lighting answer

i am also trying to understand the rules for the stress bearing panels Prohibition in the F1000 frame rules. what is the rationalization behind that?

When the rules were written, aluminum monocoque construction was the standard for higher level formula cars. Dating back to the late 60's, the rules made a distinction between tube frames and other types of chassis construction. The distinction is common to both UK and USA rules makers.

The stressed bearing panels are desirable for the floor pan for safety. There was a very nasty accident involving an F3 chassis where the carbon tub had an aluminum belly pan riveted and bonded to the bottom. In the accident the belly pan was pealed back and the driver sustained serious injuries.

Stressed bearing panels were allowed for bulkheads because that was common practice from the beginning in tube frame construction. Look at the 50's vintage formula cars prior to monocoque construction.

The rules writers wanted F1000 to be tube frame construction, the same as FF and FC. With the new rules, the rules for all three classes are very similar.

[de fox]

so the Prohibition of panels doesn't have anything to do with safety issues? its all about an old distinction of a tube frame vs a monocoque as it once was?

because i can think of a few places i would incorporate a sheet metal structure in the tube frame not as to increase stiffness but as a simple way to construct and manufacturer pickup points for example....

if i were to build an FS car, could i do that?

[S Lathrop]

so the Prohibition of panels doesn't have anything to do with safety issues? its all about an old distinction of a tube frame vs a monocoque as it once was?

because i can think of a few places i would incorporate a sheet metal structure in the tube frame not as to increase stiffness but as a simple way to construct and manufacturer pickup points for example....

if i were to build an FS car, could i do that?

I would build to the FB/FC/FF rules. That way you have a lot of options for racing. An FS is very limited in where you can race. Keep the FS parts in the form of the power plant or transmission.

Sheet metal suspension pickups would not violate the stressed panel rules as long as your structure made engineering sense as a suspension bracket. The Lola FFs used a lot of brackets that were also used as parts of the monocoque chassis used for other classes.

[de fox]

an innocent question :

on the cover of the SCCA GCR there is a picture of a formula car. where is it's front bracing of the main hoop?

sorry if i come as a petty person.....

[S Lathrop]

an innocent question :

on the cover of the SCCA GCR there is a picture of a formula car. where is it's front bracing of the main hoop?

sorry if i come as a petty person.....

The tube just below the camera is the brace. It angles outward as it goes forward. The main hoop is behind the brace in the picturen and is hidden by the brace.

[Jnovak]

an innocent question :

on the cover of the SCCA GCR there is a picture of a formula car. where is it's front bracing of the main hoop?

sorry if i come as a petty person.....

I can understand your confusion. The picture on the cover is of a Van Dieman. This roll bar configuration fits within the alternative design specs as follows and is specifically covered by section 10 (red text):

[FONT=Univers-Italic][FONT=Univers-Italic][FONT=Univers-Italic]10. Single seat cars may compete with an approved MSA (Motor[/FONT][/FONT][/FONT]
[FONT=Univers-Italic][FONT=Univers-Italic][FONT=Univers-Italic]Sports Association UK) National Single Seater Roll Structure[/FONT][/FONT][/FONT]

[FONT=Univers-Italic][FONT=Univers-Italic][FONT=Univers-Italic]Certificate. All related engineering drawings and documents[/FONT][/FONT][/FONT]
[FONT=Univers-Italic][FONT=Univers-Italic][FONT=Univers-Italic]shall be submitted to SCCA Technical Services with the homologation [/FONT][FONT=Univers-Italic]request.[/FONT][/FONT][/FONT]

[FONT=Univers][FONT=Univers]F. Exceptions for Formula Cars and Sports Racing cars[/FONT][/FONT]

[FONT=Univers][FONT=Univers]Any roll hoop design which does not comply with the specifications[/FONT]
[FONT=Univers]in 9.4.5, will only be considered if it is accompanied by engineering[/FONT]
[FONT=Univers]specifications signed by a registered engineer. No alternate[/FONT]
[FONT=Univers]roll hoop will be considered unless it contains a main hoop having[/FONT]

[FONT=Univers]a minimum tubing size of 1.375” x .080” wall thickness. The roll[/FONT]
[FONT=Univers]bar must be capable of withstanding the following stress loading[/FONT]
[FONT=Univers]applied simultaneously to the top of the roll bar: 1.5 (X) laterally,[/FONT]

[FONT=Univers]5.5 (X) longitudinally in both the fore and aft directions, and 7.5 (X)[/FONT]
[FONT=Univers]vertically, where (X) = the minimum weight of the car.[/FONT]

[FONT=Univers]Cars can have alternative roll bar designs as long as the meet the criteria in section F.[/FONT]

[FONT=Univers]Thanks .... Jay Novak[/FONT]

[/FONT]

[de fox]

The tube just below the camera is the brace. It angles outward as it goes forward. The main hoop is behind the brace in the picturen and is hidden by the brace.

so the hoop itself is behind and tilting forward and the brace is actually another hoop with a 30 deg angel between them?

[S Lathrop]

so the hoop itself is behind and tilting forward and the brace is actually another hoop with a 30 deg angel between them?

Jay's post is correct. But most cars are as you describe, the hoop is to the rear and the braces go forward. In my car, there are 2 hoops of equal size joined at the top. The new versions of my cars are built under the alternative structures. The 94 version of the car was given an exemption on the 30 degree included angle between the brace and the hoop because the mounting point for the brace was wide enough to fit 1" braces that attached 6" below the top and would have the required 30 degree angle.

[R. Pare]

The 30 degree or greater angle is mandatory only on hoops that do not go through the alternative structures route.

[de fox]

Thank you all for all the info!

going back to the original topic

On the subject of what can be in front of the front bulkhead and how does the impact structure relate to that.

it's not clear to me by the GCR how does the impact structure should be mounted to the front bulkhead and what can be attached to the bulkhead on the impact side - steering rack, hydraulic reservoirs, ARB mounting point, ect.

Once again, coming from an FSAE car where nothing is allowed to be in front of the front bulkhead except the impact structure, this is an unknown territory for me.

It's obvious on all F1, F3….cars that all these components are in the crash area – in front of the bulkhead. Are there any rules on those issues?

thank you

Noam

[S Lathrop]

Thank you all for all the info!

going back to the original topic

On the subject of what can be in front of the front bulkhead and how does the impact structure relate to that.

It's obvious on all F1, F3….cars that all these components are in the crash area – in front of the bulkhead. Are there any rules on those issues?

thank you

Noam

Traditionally, the front bulkhead was the bulkhead in front of the drivers feet and was the location for the master cylinders, etc. The problem is that the things mounted on the front bulkhead will most likely compromise the front bulkhead in a crash. In particular, the master cylinders tend to collapse the cross members of the front bulkhead to which they are attached. There are lots of examples of this type of failure with very sever consequences for the drivers.

The rules do not prohibit you from extending the frame forward to an additional bulkhead. English FFs are required to do this.

In the case of the Citation, we have a crush structure that mounts to the front bulkhead and in effect extends the frame forward about 15 inches. The front the structure has a flat bulkhead well over 36 sq. in in size. The nose cone and front wings attach to the front of the crush structure and offer additional protection to the crush structure. This is how the Ralt 40-41 FA's were built. This arrangement minimizes the chance that an impact against the front wing will compromise the front crush structure.

The rules for crush structures do allow you to use composite forward of the front/pedal bulkhead. How you attach the front crush structure is a real design problem. 4 little tabs welded to 18 or 16 gauge tubing probably won't do much good. The crush structure needs to with stand a side impact almost equal to a frontal impact. My guess is that the structure should support double the car's entire weight at a 45 degree angle.

I have a collection of track tested aluminum front crush boxes I have built over the years. I started using crush boxes after the 1984 rules rewrite. Since that time I have had no serious damage to the front bulkheads of my cars. In many cases, one or more of the master cylinders have survived. In one case the impact was so severe that the entire engine bay and the shoulder harness mount had to be replaced but the front bulkhead and the driver were un damaged.