Front impact attenuation device clarification

[SSpiffytoo]

Since this rule has now passed and I'm looking at how to build one, I need two clarifications;

1. Is the 40 cm forward of the pedals to the front or rear face of a composite structure as set forth in C?
2. The minimum 5-ounce laminates, is that 5-ounce mat or 5-ounce cloth? This is significant because mat is measured by the weight per square foot and cloth by the weight per square yard.

Stan?

[Steve Maxwell]

In constructing a device like this NO ONE would ever use mat. I would guess, and would be safe in doing so, that this is a 5oz./yd2 minimum. The woven fabrics are WAY stronger than the CSM's. Strength is crucial and critical to a device of this nature.

Steve Maxwell

CCE composites Llc.

[Stan Clayton]

Steve is correct on both counts...use 5-oz cloth, and that CSM has no place in a race car. That said, thank you for asking the question! I will submit a clarification to specify cloth.

BTW, this spec was taken from the '98-'01 VD Continental nose, which has performed very well in practice. It is also a very affordable way to make or modify a nose, and the one most easily done by virtually any racer at home.

Stan

[Steve Maxwell]

That last point is quite true Stan however I would like to say that if someone does take on this project at home that several steps must be taken to ensure proper performance of the attenuator. It really should (must) be fabricated using good epoxy resin and "really should" be vacuum bagged. The vacuum bag soaks up excess resin and excess resin will embrittle the finished part. Embrittlement will essentially reduce the effectiveness of the attenuator by a significant percentage. This is not body work. This is, for all intents and purposes, a structural part. Meaning no polyester resin; no chopped strand mat; and use of a vacuum bag and woven fabrics preferably (believe it or not) fiber glass and Kevlar. Carbon will work well but just slightly too brittle for this application IN MY OPINION!!!!!! I don't care if someone disagrees with me. I make my living doing this s**t. everyone loves carbon fiber but in many applications it just isn't the best performing material. This is one of them. IN MY OPINION....

Thanks

good luck

SEM

[Stan Clayton]

I agree, Steve. OTOH, the inner laminates of the "crash tested" nose I saw photos of did not appear to have been vacuum bagged. Any readers have one of these?

Anyone not confident of their glassing skills and/or knowledge would do well to send their car's nose to a reputable composites shop to have the work done. Owners of FE cars should contact Enterprises for guidance.

Stan

[SSpiffytoo]

Steve is correct on both counts...use 5-oz cloth, and that CSM has no place in a race car. That said, thank you for asking the question! I will submit a clarification to specify cloth.

Stan

I am planning on using cloth, but just wanted to be sure that this is clear in the rules. Same with the distance, mine will be far enough forward to pass on either measurement, but for some with skinny noses it may make a difference on being able to get the required area.

[rickb99]

Is there a link to this new rule on the web? Guess my first question without seeing the rule is, does this have to be glass or will Keith Averills aluminum crush box work in terms of design for an FC?

With regard to home built units; I note with some concern the article in Racecar Engineering (June addition) about a 'design study' by 4 teams at Cranfield University. The teams were sponsored by Mygale, Ray, Van Diemen and Spirit with the goal of addressing an 'effective' nose box for FF's in Europe. The designs were then reviewed by the likes of Adrian Reynard, Brian O'Rourke from Williams and other engineers from the various company's.

Although some elegant concepts were presented (polymetric foam, etc), the only one that all agreed was a good design was considered 'old technology'. Built by the Ray backed team, it used aluminum honeycomb.

So, before doing anything for our '89 Reynard and jumping perhaps to a conclusion that Averill Racing's aluminum crush box on our 1990 Reynard meets the requirement, I'd sure like to read the rule and understand the goal.

[Stan Clayton]

The new rule is published in the Oct Fastrack, which you can download from a link at bottom right on the SCCA home page. Stan

[Tom Valet]

Stan,

Is it the intent of the BOD that only cars homolgated after 1/1/86 are required to have the front impact attenuation device? If yes, then the language the BoD used in the prefatory sentence is wrong. The rule as passed and published in Fastrack reads:

"All formula cars homologated with SCCA as of 1/1/86 must have a front impact attenuation device..."

As written this would include all cars homologated PRIOR to 1/1/86, ie if your car was homologated with SCCA as of 1/1/86 then you must have the attentuation device. It would have been easier to just say "homologated after 1/1/86."

Am I reading it wrong?

Thanks

Tom

[Stan Clayton]

I don't know that you are reading it wrong, Tom, but the verbiage appears to have been lifted from D.6. on page 199. Nonetheless, we can clarify it to specify cars homologated "on or after" January 1st, 1986. Stan

[S Lathrop]

Stan;

I gather that the original intent of the wording to exempt the DB1 and all cars that were first homologated prior to Jan 1, 1986 still stands. For any car there are 2 relavelent dates: 1. date the design was homologated and 2. the date the car was manufactured. For this rule, the date homologated is the only date that really is improtant.

On first reading of the rule, I wrongly thought that any car built after 1/1/1986 had to have a nose box.


In my experience, 2 layers of 5 oz kevlar or carbon only gives .020 material thickness when properly laid up. I would question whether .020 aluminum or composite nose boxes would be adiquate.

One of the design considerations not addressed in the nose box rule is the placement of the master cylinders. The English rules require that the master cylinders be located behind the front bulkhead. In a crash the master cylinders have a tendency to destroy the integrity of the front bulkhead, which in turn causes the collapse of the forward portion of the frame.

For me the biggest problem in nose box design has been to have the box not fail at the attachment point to the front bulkhead. I had a driver very seriously injured in the Toyota Atlantic series when the nose cone failed at the attachment to the front bulkhead and then the front bulkhead of the tub failed. In this particular case the nose cone was an after market part not designed by the car manufacturer. Front wings can really increase the loadings of the nose box attachments. A nose box, ideally, should fail progressively from the point of impact.

[R. Pare]

If anyone wants the Cranfield University Group C Study Project that was published last March, I can send it to you in a zip file - I somehow lost the direct link to it.

This particular study was done to design a "spec" box for the British FFs that would pass some specific test criteria (uniform crush rate and a push-off test), and is quite good.

[Brian]

The idea of an additional bulkhead in front of the existing front bulkhead is one that has really caught my attention. It seems an easy way to add a fair bit of front crash protection fairly easily. An RF85 (what I have at the moment) has a reasonably robust perimeter frame around it's bulkhead, supported substantially by all the rocker mounts and framing up to the shock mounts. Can you suggest what additional structure might be added, material specs, etc, that would create a functional bulkhead ahead of the master cylinders?

I'm thinking of 3/4" or 1" square steel tubing, .050", tig welded with a rectangular section out front of the MC's, carried back to the existing frame with triangulated longitudinal members. It has to fit inside the nose, obviously, and you might also plate it with bonded and riveted aluminium, or even spot welded steel sheet.

Would a simple structure like this add significantly to the safety of the car? If so, it seems a good way to spend a Saturday in the shop, wouldn't take long to fabricate.

Thanks, Brian

[R. Pare]

Anything that you can do to keep the MCs from being hit will help - it only takes an impact at something like 2.5 g's to reach the yield point of many 'typical' front bulkhead crossmember arrangements, which then will severely compromise just how much the remainder of the frame can take before collapse. The down side of any structure that sticks out that far is that the nose will then need to be extended by the same amount in many cases so as to keep the decell rate to what you'd really like to see - an FF with an impact speed of 27 mph, if it is desired to decellerate at a constant 25 g's, needs something like 11.8 inches of useable crush space ahead of the frame.

This sort of double bulkhead is mandatory in most Pro formula car series, and I believe that the British club will adopt that criteria also, if they have not done so already.

A second thing to consider is the integrity of the attachment of the belly pan to the bottom of the frame - the more force the bonded area can stand before peeling away, the longer the frame lower rails will hold up, and the less penetration there will be into the driver leg area.