Roll Cage Construction.

[Duncan]

Any particular reason why you have done the side intrustion as the X rather then the )( bent two sections gusseted together. Looking at the UK and Aus tin tops and many of the current rally cars they tend to be going for the bent sections rather then the 3 pieces welded in X together

I'm pretty sure cams rules require a 1 peice diagonal instrusion bar unless you get it cad engineered

Brad don't worry about the door opening, john is built like a jockey anyway. plus it will make sure Pete never drives it.

[Roy]

So this isnt legal by CAMS without engineering?

http://farm1.static.flickr.com/74/19597400...cc2495e.jpg?v=0

Will be interesting to confirm that!?!?!!? I thought after the Simon Evans accident and leg injury less and less engineers were supporting the X type....lol which makes sense if they have to be paid to use the U sections type of intrusion????

[Risking]

X intrusions are prefered and have been for a very long time

U shaped bars are typically used when the rest of cage is to be engineered anyways and or made from molly.

Every cage builder is different, Peter at bonds does not like U shaped intrusions and will only do them upon request but others like mediteranian do them alot.

Ive seen U bars passed without engineering but ive also seen X bars knocked back.

There is two sets of requiremements to meet as well CAMS and FIA which do differ greatly.

Cams dont require intersections to be gusseted but the FIA do. When you read the regs it requires gussets but when you talk to someone who knows the requirements (again I speak with peter alot) they will tell you CAMS dont require them.

Same as the drop bars, FIA likes them to be a one peice bar without a joint at the intrusion bar, however in such a small car thats impossible due to the need to have a steering wheel......

So common sence prevails and they are made in two bits and will pass without an issue.

Any diagonal member is meant to be straight but is aloud to follow to contours of the vehicles internal shape. So it does or doesnt have to be straight.................?

Edited August 22, 2009 by Risking

[warps]

Any diagonal member is meant to be straight but is aloud to follow to contours of the vehicles internal shape. So it does or doesnt have to be straight.................?

"as straight as possible" I think would be the idea. The cage diagonal members (and in fact most members in a well built cage) are going to be loaded in compression. this gives the whole cage its strength, making it act as a rigid structure, rather than a bunch of pipes glued together. A well designed cage should not have to withstand bending forces in any members as there is very minimal strength this way. (I'm talking about the rigidity of the whole cage - not individual members). Now, a steel pipe is very strong in compression, but as soon as you put any eccentricity into it, ie a bend, it loses a massive amount of its buckling strength. Hence the straighter you can keep any compression members, the stronger they will be - lots stronger. There is a formula for calculating the loss in strength due to eccentricity (Euler column buckling strength - might find some info if you google it) but I'm to lazy to do manual calculations these days

Ideally, every member will be straight. In reality, we don't always have that luxury.

Just a little back ground for anyone not fully conversant with cage design and failure modes. Sorry if it's a little simplistic to those already experienced in cage design.

[Risking]

good explaination.

Was a rehitorical question on my behalf

[t01-100]

I find the straightness of bars is always an interesting one to debate with some scrutineers on cages that are constructed to the standard CAMS manual design model with mild steel. Some say, (thanks to a little ambiguity in the manual in a couple of para) that the top windscreen bar is in theory meant to be straight, as is the A-pillar bar with only one bend at the dash area... the a-pillar in one of my racers has no less than three bends (all thought only one major) to be fitted as tight as possible to the a-pillar (as one para in the manual suggests) and welded to the pillar instead of plated... and as you can see the windscreen bar has been positions as far forward as possible too with five bends. Although it could be argued that this isn't appropriate for the windscreen as it doesn't follow all that closely to the shell... anyway, all ticked off and registered now.

With my next race car, who knows what that will be! but I reckon I'll run a ladder style side intrusion like in my Evo, but with a Sainz bar... and maybe a little higher up than the Evo.

[sav man]

why choose ladder over the cross? triangles are stronger than squares. I know the yanks love the ladder for oval, but wrc cars run a cross. But a wrc car is designed to run into trees (force spread out over tree size 30-40cm?) and a nascar is designed to be run into by other cars (force spread over 1.5-2m?).

at what point can you get your caged approved? can it just be painted/unpainted in a rolling shell?

[t01-100]

A triangle is strong on the surface, but consider the force being applied to it... in a side impact for which the intrusion bars are designed, unless the point where the triangle creates a cross has been gusseted (which isn't the case with most, or my RX7), or reinforced in the centre with a vertical bar to the floor (eg V8SC or WRC) the weakest point will always be the join in the centre, which is what Troy is talking about.

With the ladder bar you not only have two horizontal bars, but also reinforcement of those two bars every 300-350mm with a vertical bar in the case of my Evo. In the event of a big side impact the ladder bar will hold up better than a simple cross as there is there is more material to bend at the weakest point... not that I have or ever want to find out!!

You can rego the cage as soon has the builder has filled out the CAMS carbon sheet form. In the case of the RX7, it’s still not back together, but there were questions over the changing cage regs when it was about to be built, so I got a logbook for the car issued without the cage, then rego'd the cage and had it noted in the logbook... the car is still in a million bits though! In principal the car is meant to be competition ready when the logbook is issued.

[t01-100]

this simple diagram might explain what i'm trying to say better... consider the brown lines to be the outside edges of a tree!

both methods work, both can be improved and any side instrusion is still allowing for the crash that might never happen. in each of my cars I have ramped up the bar work with every project... maybe i'm just becoming a lady as I getting older! bottom line is racing a car with a cage has to be smart than a bike!

[badhairdave]

You're smacking it in it's weakest plain anyway. Provided the welds don't tear off in either situation they are about equal as they both mount at 4 points. So i'd say ladder bar potentially better as you have 2 full width bits of tube as opposed to 1 with the other bar chopped in half and welded up so one less weak point.

Potato/Potaato, as long as it meets the regs for the category either is better than nothing.

[t01-100]

I always thought this was cool because it looks crazy! Maximum Motorsport (Herridge) built it I understand... not 100% sure though.

This is about as good as it gets without going totally nuts.

[Roy]

Yeh that Rex has been for sale in WA for a while. Was asking good money but appears to be a good car

[RAZOR32]

I always thought this was cool because it looks crazy! Maximum Motorsport (Herridge) built it I understand... not 100% sure though.

This is about as good as it gets without going totally nuts.

The only thing with the blue WRX is it’s got no x bars in the roof?, still not sure if I’m going to get them put in mine or not, what would you do Stu? Az starts mine in the next week or so just worried about head room in my R32, but with new seats mounted as low as possible should be ok just, will post up progress pics in coming weeks and I’ve chosen X bars for the side intrusion because that’s what Az wonted to do

[DJRIFT]

i dont even want to get into the debate in this thread as its a never ending circle as its up to every ones own perception of the CAMS manual.

i think so long as you are happy to get in it if you have designed or built it yourself than that is the main thing. if you have gotten a workshop to build it for you because you cant/ havent got the time ect than you just hope that they know what they are doing. its just like getting an engine built. on will say do it this way while another will say do it that way. if you cant do it yourself than have faith in the builder.

Having faith in the builder will come from how many cages they have built / any accidents that have had.

In SAV MANs case the builder has built many cages in all sorts of cars and started out building them for rallys so Trees was the main concern. I questioned him at the time about why things are done what way and he answered with all the right reasons.

i Know that a cage was built by a new Hobart bloke a while back in a supra and the front leg collapsed as it rolled down a hill and crushed the blokes finger on the steering wheel. its bad enough having a crash but watching the cage crumble around you as you are crashing isnt a good sight.

RAZOR32. here is a diagonal roof bar in a 2 door gtst. i am just as tall as you and i have mounted my seat super low. my head fits in the triangle formed by the main hoop, front leg and the roof bar. if i did it again i would just put a straight bar between the seats between the hoop and the front window bar. Drawing 253-9D in the cams manual. or Drawing 253-9C in the cams manual. there is no way in hell i would drive a car with a bar directly above my head like the Drawings 253-9A and B

ive put it in as its just that bit more safety.

also with a r32 cage try to get the front legs out to the side of the body as far as possible as my as the front leg is the only annoying part with my helmet on. by front leg i mean where it joins to the hoop.

also no one considers putting bars in the floor to help with side impacts

that gives you an idea but is not realy what i mean. i mean a pice of roll cage material between the seal panel and the g box tunnel. ive seen plenty of floor pans crumple with side impact.

[Risking]

how far away from the A pillir is your front leg???

From that photo the bend is in the wrong position and the leg starts to drop far to early not letting it sit close enough to the pillar??

Typically I put the downwards bend right up against the roof and have the leg travel down about 15mm from the a pillar. Im guessing yours is alot more than that??

[sav man]

damo's cage is a bond kit, and the front legs weren't long enough

[DJRIFT]

how far away from the A pillir is your front leg???

From that photo the bend is in the wrong position and the leg starts to drop far to early not letting it sit close enough to the pillar??

Typically I put the downwards bend right up against the roof and have the leg travel down about 15mm from the a pillar. Im guessing yours is alot more than that??

i really dont need to justify my cage but any how.

yep the front legs were to short so thats where they ended up. only bad point about the cage. but once in the drivers seat you can clearly see that it actual lines up perfectly with the A pillar to not block the view out the window. it is then also tagged off to the A pillar with plates like numerous cages are.

[klusio]

i dont even want to get into the debate in this thread as its a never ending circle as its up to every ones own perception of the CAMS manual.

i think so long as you are happy to get in it if you have designed or built it yourself than that is the main thing. if you have gotten a workshop to build it for you because you cant/ havent got the time ect than you just hope that they know what they are doing. its just like getting an engine built. on will say do it this way while another will say do it that way. if you cant do it yourself than have faith in the builder.

Having faith in the builder will come from how many cages they have built / any accidents that have had.

In SAV MANs case the builder has built many cages in all sorts of cars and started out building them for rallys so Trees was the main concern. I questioned him at the time about why things are done what way and he answered with all the right reasons.

i Know that a cage was built by a new Hobart bloke a while back in a supra and the front leg collapsed as it rolled down a hill and crushed the blokes finger on the steering wheel. its bad enough having a crash but watching the cage crumble around you as you are crashing isnt a good sight.

RAZOR32. here is a diagonal roof bar in a 2 door gtst. i am just as tall as you and i have mounted my seat super low. my head fits in the triangle formed by the main hoop, front leg and the roof bar. if i did it again i would just put a straight bar between the seats between the hoop and the front window bar. Drawing 253-9D in the cams manual. or Drawing 253-9C in the cams manual. there is no way in hell i would drive a car with a bar directly above my head like the Drawings 253-9A and B

ive put it in as its just that bit more safety.

also with a r32 cage try to get the front legs out to the side of the body as far as possible as my as the front leg is the only annoying part with my helmet on. by front leg i mean where it joins to the hoop.

also no one considers putting bars in the floor to help with side impacts

that gives you an idea but is not realy what i mean. i mean a pice of roll cage material between the seal panel and the g box tunnel. ive seen plenty of floor pans crumple with side impact.

Sorry daimo but you are incorrect.

Azcustom (aaron and myself) built the cage yes

New? dont think so, new to you maybe?

photos tell more thruth than your post unfortunately...

bloke had a sore head (no helmet on sighting lap)

his fingers are fine and I dont think that you class this as collapsed... considering the impact.

And it was a full bolt in cage.

hope these clear up any doubts about our workman ship.

Edited August 30, 2009 by klusio

[klusio]

some more photos I found during the construction

rear half was one piece bolt in item.

[klusio]

just for the topics sake here is my cage