Roll bar change from 818R rendering to "pre-production" example

[Turboguy]

Hey guys-

I apologize if this has been addressed elsewhere and I missed it, but I'm curious about the change in the main roll hoop configuration between the initial "renderings" FFR released and the pre-production example that debuted at SEMA 2012. I find the double-bump hoop on the original rendering, and the way the rear bodywork envelops it, far sexier than the route taken with the pre-production example.


I'm just wondering what the reasons for the change were, and if there is a chance the initial version might return -- even if it's at an up-charge since it appears that it would be more complicated to manufacture. I can't see it as being safety/regulation related as they would have had all the sanctioning body rules through the first phases of design up to generation of the initial rendering.



FFR released rendering:
http://assets.mensjournal.com/img/essential/the-diy-thrill-machine/618_348_the-diy-thrill-machine.jpg


Pre-production car @ SEMA 2012:
http://www.factoryfive.com/wp-content/uploads/2012/10/1a_a.jpg

[Mechie3]

IIRC, the top hoop needs to be a single piece. Adding those small pieces makes them the top piece and not legal. Likely they just did that roll bar for fun for the rendering like car makers have crazy body work on concept cars and tone it done for production.

[Hayai]

^ Yep. I think the newer design with the single bar is going to be both stronger/safer and cheaper to manufacture. I'd rather drive the safer car. :)

[RM1SepEx]

racing sactioning bodies req. single continuous hoop for roll bars, the original rendering is not legal with any organization that I'm familiar with

[C.Plavan]

racing sactioning bodies req. single continuous hoop for roll bars, the original rendering is not legal with any organization that I'm familiar with

+1 Very unsafe- You roll, those welds would be easy to break do to "smashing" nature. If they could of done a one piece formation/bend- that would of been cool, but the rollbar is still way too low for helmet clearance.
Pre production does look better, but I would rather be alive :P

[longislandwrx]

From a cosmetic standpoint if you are not enamoured with the looks of the R bar, the S bar is lower, blending better with the body. For competition at the speeds this car is going to run, i'll opt for the full bar.

[Turboguy]

+1 Very unsafe- You roll, those welds would be easy to break do to "smashing" nature.

Well, I don't know about that - properly welded and normalized, a welded tube is just as strong as one made from a single piece of material.



If they could of done a one piece formation/bend- that would of been cool, but the rollbar is still way too low for helmet clearance.
Pre production does look better, but I would rather be alive

With a few minor cosmetic changes to the original design, I believe it could be done in 1 piece with CNC mandrel bending. I'm just not sure it would be cost effective.



An in-between position would be keeping the cage essentially as it is (with the flat top on the main hoop) but sloping the sides inward from the body line upwards. This would allow the rear bodywork to be more like that of the rendering, wrapping around the bottom of the cage.

[akjason]

The change from the initial rendering was indeed for safety regulations. This is from the NASA CCR, although most sanctioning bodies have similar regulations for the main roll hoop:

The main roll cage hoop should be as wide as the full width of the interior and must be as close to the roof as possible without violating CCR section #15.6.20 Inspection. One continuous length of roll bar tubing shall be used as the main hoop. The main hoop must consist of not more than four (4) bends maximum, totaling one hundred eighty (180) degrees +/- ten (10) degrees.Even if you make a "double bump" roll hoop with 4 or fewer bends (it can be done with 3), those bends will total more than 190 degrees, and will not pass inspection.

[Turboguy]

:( I wasn't aware of the 180 degree rule. That definitely nukes the idea of the sexier main roll hoop :(

[Rasmus]

From the SCCA's General Competition Rules (http://lmgtfy.com/?q=SCCA+General+Competition+Rules).


Roll cages may be of two (2) designs, low front hoop (top of steering
wheel) or high front hoop (top of windshield). Specific installations are
subject to approval by the Technical and Safety Inspectors at each event


The basic purpose of the roll cage is to protect the driver if the
car turns over, runs into an obstacle such as a guardrail or catch
fence, or is struck by another car. It shall be designed to withstand
compression forces from the weight of the car coming down on
the rollover structure and to take fore/aft and lateral loads resulting
from the car skidding along on its rollover structure.


One (1) continuous length of tubing shall be used for the main
hoop member with smooth continuous bends and no evidence
of crimping or wall failure. The radius of bends in the roll cage
hoop (measured at centerline of tubing) shall not be less than
three (3) times the diameter of the tubing. Whenever possible,
the roll cage hoop should start from the floor of the car, and, in
the case of tube frame construction, be attached to the chassis
tubes by means of gussets or sheet metal webs with support
tubes beneath the joints to distribute the loads. It is recom-
mended that gussets be used.

Regarding the following:


properly welded and normalized, a welded tube is just as strong as one made from a single piece of material.

You're correct in stating that a properly welded and normalized tube is just as strong as one made from a single piece of material but it still wouldn't be legal for SCCA rules as a main hoop. That's the way SCCA rules are. You could argue this point until you're blue in the face and you'd lose.

[Turboguy]

Regarding the following:

You're correct in stating that a properly welded and normalized tube is just as strong as one made from a single piece of material but it still wouldn't be legal for SCCA rules as a main hoop. That's the way SCCA rules are. You could argue this point until you're blue in the face and you'd lose.

:( :( :(