Monocoque Roll Hoop Rules

[rjwoods77]

Hey all,

Just wondering about the rules and equivalency of doing a monocoque. The rules say that the main roll hoop(has to be steel)and the front roll hoop(has to be metal) have to be made out of steel, and be a continuous structure from the lower side impact rail top the other side impact rail. Or that is how I am interpreting them so far. I have seen a couple teams that have had front roll hoops that arent continued all the way to the lower part of the car. Anyone care to eleborate. Also the main roll hoop supports(made of steel), is there any requirement as to where these have to extend to. I dont really see anything in the rules that says how far down they have to attach to the cage/tub on the lower portion of the car.

[rjwoods77]

Hey all,

Just wondering about the rules and equivalency of doing a monocoque. The rules say that the main roll hoop(has to be steel)and the front roll hoop(has to be metal) have to be made out of steel, and be a continuous structure from the lower side impact rail top the other side impact rail. Or that is how I am interpreting them so far. I have seen a couple teams that have had front roll hoops that arent continued all the way to the lower part of the car. Anyone care to eleborate. Also the main roll hoop supports(made of steel), is there any requirement as to where these have to extend to. I dont really see anything in the rules that says how far down they have to attach to the cage/tub on the lower portion of the car.

[JPS]

is the front hoop mandatory no matter what?
i thought it could be replaced. i havent seen a monocoque FSAE up close but arent you able to use an equivalent bulkhead? sorry for not answering the question but i also have some questions on this subject.

[TG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by F2003-JP:
is the front hoop mandatory no matter what?
i thought it could be replaced. i havent seen a monocoque FSAE up close but arent you able to use an equivalent bulkhead? sorry for not answering the question but i also have some questions on this subject. </div></BLOCKQUOTE>

Yes, they all have to have front roll hoops.

Getting back to the original question. The main roll hoop has to be made out of a continuous steel tube with equivalent Buckling
Modulus EI to the baseline material.

The front roll hoop can be of steel or aluminum (just has to be designed in as as-welded condition unless can be shown otherwise). Part C of rule 3.3.4.3 states:
"The Front Hoop must extend from the lowest Frame Member on one side of the Frame, up, over and down to the lowest Frame Member on the other side of the Frame. With proper gusseting and/or triangulation, it is permissible to fabricate the Front Hoop from more than one piece of tubing."
Therefore, they don't have to be continuous adn can be made of aluminum or steel.

I'm not too sure about the monocoque rules so I'll leave that up to someone else to explain.

I do have a related question:
If a car is using a stressed engine and the roll hoop is above it, where must the roll hoop extend down to? Could it simply be the top of the engine, because that is probably the lowest chassis member.

[Colin]

There is nothing in the rules that states the main roll hoop bracing must extend to the lowest point of the chassis, so attaching them to the top engine mount is permitted as long as all the included angles are within the rules, however (and this was mentioned to us last year at tech) it is a good idea to weld in a bar between your two top engine mount points, so that the roll hoop bracing is still effective if those top engine bolts become loose.

[TG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Colin:
There is nothing in the rules that states the main roll hoop bracing must extend to the lowest point of the chassis, so attaching them to the top engine mount is permitted as long as all the included angles are within the rules, however (and this was mentioned to us last year at tech) it is a good idea to weld in a bar between your two top engine mount points, so that the roll hoop bracing is still effective if those top engine bolts become loose. </div></BLOCKQUOTE>

I wasn't asking about the bracing, I was asking about the roll hoop itself. Sorry about and confusion you had.

[Alber]

sorry people but i have another question:
you said that one can build the front hoop either by steel or aluminum, if you can use aluminum then maybe one can use magnesium?
im asking couse im part of a first time team from israel and we wanna build the frame from Mg so if we could use Mg for it ill be a blast.
Eldad
ben-gurion Uni in the negev

[TG]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Alber:
sorry people but i have another question:
you said that one can build the front hoop either by steel or aluminum, if you can use aluminum then maybe one can use magnesium?
im asking couse im part of a first time team from israel and we wanna build the frame from Mg so if we could use Mg for it ill be a blast.
Eldad
ben-gurion Uni in the negev </div></BLOCKQUOTE>

Can't use magnesium. Must be aluminum or steel. I'm not sure if there are aluminum alloys that are compatable to weld to magnesium other than with friction welding (which you can weld a lot of dissimilar materials to one another). I'd look around to see if there was a high magnesium content aluminum alloy that would be compatable to weld to magnesium.

[Chris Clarke]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I do have a related question:
If a car is using a stressed engine and the roll hoop is above it, where must the roll hoop extend down to? Could it simply be the top of the engine, because that is probably the lowest chassis member. </div></BLOCKQUOTE>


See rule 3.3.4.2.C

It says basically what you posted before for the front roll hoop. That it has to extend from the lowest frame member on one side to the lowest frame member on the other side.

Also, 3.3.4.1.C states that it must be incorporated in the "Primary Structure" (side impact, roll hoops, supports, etc)

Rule 3.3.8.1.B talks about the side impact, and says that the lower side impact tube must connect the lower end of the front and main roll hoops.

So the main roll hoop has to extend down to the lowest side impact tube, regardless if you use a stressed engine or not.

[Chris Clarke]

I dont know if you meant in a monocoque structure or not, but if you did mean in a monocoque, it clearly states in rule 3.3.4.2.F that it has to go down to the bottom of the frame.