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PostPosted: February 17, 2010, 12:40 am 
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Gonzo and Vincent, you may want to consider doing what I've done prior to building my cage - instead of just asking the questions on an internet forum (as good our forum gets! :lol: ), just email your local tech director in the racing body that you're planning on racing with and ask THEM the questions.
Not only that you'll get an answer from the person that you'll be dealing with at the end, you'll also have a trace of emails to show it.

I emailed simple diagrams for approval too.

Moti

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PostPosted: February 17, 2010, 12:59 am 
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Yo, Moti-
Very good idea. And I would do just as you suggest... Except that the National Scrutineer that will inspect my cage/car is my buddy JK. I've talked with him several times about the design of the cage and the chassis, and I've already changed a few things to suit the rules per his instructions. Before I finalize anything, I'm probably gonna have him ride up and look it over. I guess in a way, that is what you suggested, just a bit more personal and low tech! :D

Horizon, in reference to your comment about the rear of the car and the rear down-bars of the cage: In my cage, the rear down-bars go to the bottom rails of the frame, where they attach to an X-braced section of the rear frame. The bodywork and such will hang off some kind of light aluminum framework, which I'll add later. Anything important (like the battery) that goes in the back will go inside the cage. See pic... Hope it helps!

Oh, and Moti- One of the pictures you see taped to the wall of the shop behind my frame for inspiration is from your build log!

Edit-
The two side bars between front and rear hoops are what I was calling "door bars" in that earlier post. There will be another pair of bars from front to rear near the upper corners of both bars, over the driver and "passenger" compartment. (No passenger seat, just the compartment.)


Attachments:
Frame n Cage Feb 15 10.jpg
Frame n Cage Feb 15 10.jpg [ 69.71 KiB | Viewed 8993 times ]

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PostPosted: January 31, 2014, 1:19 am 
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This seems to be the best place to ask this question...

Does anyone know of a reason for SCCA, and likely other sanctioning bodies, requiring that the continuous roll cage hoop(s) be lateral/transverse, rather than running fore & aft on each side of the car.

From the SCCA GCR - "The main hoop (behind the driver) must be the full width of the cockpit for all cars."
This leads to a roll cage design that looks something like this:
Attachment:
FPSevenLateralRollHoop.jpg
FPSevenLateralRollHoop.jpg [ 68.37 KiB | Viewed 8117 times ]


For larger cars this can work just fine, but for smaller cars, like a locost or similar car, this design requirement of having lateral continuous hoops tends to lead to more bends in tubes in order to keep the fore & aft "above the window" bars far enough from the occupant('s) heads. In the picture above you can see the inward bends in those above-window bars just before they meet the main roll hoop in the cage. Those bends are necessary to keep the fore & aft above-window bars far enough from helmeted heads.

For a small car I see only structural, safety, and appearance advantages to a design that has two fore & aft continuous side hoops (A-pillar, then "above-window", then "rear brace" all in one tube, with one on each side of the car, with straight cross members "above-windshield", and behind&above-driver, and at-dash, and for-shoulder-harnesses, with two near vertical straight bars to form the sides of what would formerly be the main hoop, like this one:
Attachment:
SprintCarForeAftRollHoops.JPG
SprintCarForeAftRollHoops.JPG [ 341.65 KiB | Viewed 8117 times ]


This design keeps all the tubes easily away from the occupant's head, without adding extra bends or raising the overall height. I am thinking of going on a letter writing campaign to SCCA first, to request that having the continuous hoops run fore and aft, on each side of the occupants, rather than transverse behind and in front of the occupants. If adding a cage within a closed production car body, the continuous hoops being fore-aft on each side of the car likely makes it easier to tuck all the cage tubes close to the body and further from the driver's head, so the design advantages of a change may apply more broadly than to just small cars.

Continuous transverse hoops seem to me to be a tradition-driven requirement, rather than a structural or safety driven requirement..?

Am I missing something here?

If a visual of this cage design applied to a locost type of frame would help, I can model in in Solidworks when I can get some time.

Dean


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PostPosted: January 31, 2014, 6:13 pm 
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Actually I have always thought the roll-cage rules are a little silly with a lot of the sports-car sanctioning bodies.
I have actually seen rules that prohibit a "Nascar" style roll cage. Again I have seen the continuous hoop rules and what you are proposing would kinda-sorta fall into that style for some of the sanctioning bodies. I don't have a real answer for you but the obvious answer is usually because its always been that way.

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PostPosted: February 6, 2014, 11:35 am 
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Quote:
Continuous transverse hoops seem to me to be a tradition-driven requirement, rather than a structural or safety driven requirement..?


Do you have a pointer to the specs for a car like #22 above?

You probably have to show that your way is as strong/stiff as the continuous hoop including the diagonal and cross bar…

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PostPosted: February 6, 2014, 4:52 pm 
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horizenjob wrote:
Quote:
Continuous transverse hoops seem to me to be a tradition-driven requirement, rather than a structural or safety driven requirement..?


Do you have a pointer to the specs for a car like #22 above?

You probably have to show that your way is as strong/stiff as the continuous hoop including the diagonal and cross bar…



I believe that's a Silver Crown car. I found rules at http://www.usacracing.com/assets/files/ ... Silver.pdf . You will find the roll cage rules to be very sparse, with dia. 1.5 4130 required for the main hoops and 1.375 4130 for other members & 4" helmet clearance... I suppose tech inspections take care of design and construction approval.

Yes, I think analysis results sent with the initial proposal would be the only way to approach a rule change request.

Dean


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PostPosted: February 6, 2014, 6:03 pm 
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I would expect preliminary design limitations and guidelines would also have to be included as part of the analysis and proposal. A single cage design analyzed for a single vehicle would not be anywhere close to proving equivalency of strength for the general design, let alone overall safety. How many of what different loading conditions would be used for the analysis? What criteria would be used to determine equivalency? How many bends would be allowed? Where would they be allowed to be located? How far from the bend is allowable for the critical intersecting structural tubes and braces? I would think that each of these design elements will have to be known how they effect the overall integrity of the structure. The analysis would have to look at how as many different interpretations of the intended rule wording as possible might be implemented, and ensure that all of them would still pass the analysis.

I observed the hoops jumped through and time/effort/cost committed by the group of individuals (not the sanctioning body) trying to get 600cc motorcycle engines allowed into the SCCA F500 rule set, just to demonstrate competitive equivalency...I can only imagine that a fundamental rethinking of the very foundation of their, and the vast majority of other motorsport sanctioning bodies across the globe, proven effective safety requirements would require somewhere between exponentially more and orders of magnitude more of everything.

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PostPosted: February 8, 2014, 3:54 pm 
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Driven5,
Good point regarding the F600 efforts. I've been reading most of the material available on the internet regarding their efforts. After being part of the 1995 Oregon State U. FSAE effort, I do have some interest in what they're doing... It sounds like it's been a frustrating roller coaster for them. The CVT is the negative for F500 in my opinion. A 600cc bike drive train is a great way to create a class that is still lower cost like F500 while being more fun for everyone (watching or driving) in my opinion. Whether a separate class or integrated with equivalency established, I'd like to see F600 cars as a national class... I better get back on track here.

I'm more optimistic regarding what I would like to propose to SCCA regarding acceptable cage construction. What I'm proposing is a structural/engineering change for the most part, rather than a change that would possibly devalue all the former cars in a given class. Yes, safety is involved and since people are in the picture of a change proposal, politics could come into play. The first thing to ensure is that the proposed change has the same or better strength in the plane of the former transverse main hoop. The rest of the proposed structure that I would propose is essentially the same. The cage I would propose will be much more similar to a typical SCCA cage than it will be to the sprint car cage pictured above.

I may not succeed with the proposal I am planning, but of course the only way to find out is to write the best proposal I can manage to put together, then see how things go.

Thanks for the comments. Pointing out all the potential issues is what I asked for.

Dean


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