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EF Ian

Cages - Experiences wanted

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1 hour ago, EF Ian said:

 

Cage.jpg

 

 

Very curious about what the smart people here think about this design.  I'm planning on going down a similar path, also with the main hoop also protruding into the wheel wells slightly.  I've got full length box frame rails that the hoop would brace down into as well.

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The things I would do if I had time, space and money. 

 

I think my ideal design would be: Start at the plane where my harness bar currently is, make a hoop that goes to the top and welds to the roof. Have the sides so it bolts to the factory holes or just go all out and gusset to the side, goes through the wheel well and welds to an out rigger that welds to the frame rail connector. The legs go back and hits the shock tower, then continues back and hits the floor with a cross brace, continues through the floor and comes out through the rear panel where it has a plate so I can do a sacrificial rear bumper/bash bar that has an integrated jacking point tucked under the car that meets up with the bars that went through the floor.

 

Speaking of I forgot I have an inner brace for the rear subframe where my fuel cell mounts, basically a 1x1 box structure that bolts to welded brackets on the sub frame to hold my fuel cell. I guess my rear is even more together than I thought.

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Posted (edited)

I've got some thoughts about that roll bar design:
1. Don't like the X up high. Too much weight, and you're reinforcing the strut towers with the top of the tube where it isn't very stiff. 

2. I would do the backstays to the top of the strut tower. Plate that whole trapezoidal area and weld the stays to the plate.

3. The bars in yellow are great if you are connecting to door bars on the other side of the main hoop. Without door bars I think it's just extra weight to carry around.

4. If you want an X, you can do it low, from the strut towers to the bottom of the hoop. I did this on mine. Would be MUCH easier to install if you cut out the storage cubbies. I didn't. 
5. I'd just go with a straight bar across the strut towers

EDIT--Also connect the top of the hoop to the map light area of the roof with a shear plate.

Edited by JMortensen

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for a street car these few pics should give you an idea of what I have on my two street cars and I feel that this is ideal for chases stiffness without the wasted space and issues bars for a street car.  I can jack the car up with a jack stand and have three wheels off the ground; it give me the stiffness of my crazy Primadonna Z car with a 9 point cage so for street use I think this is ideal.  If you worry about rolling the car you can add a basic hoop but no need to do the rest of the roll bar work for street as that just becomes a pain for anyone else you give a ride to, as they will not like the bars interfering with easy entry in the car, etc.  Believe me very few women want to ride in a car that is too caged.  This boxing of the frame rails goes from the front all the way to the rear sub frame and is boxed inside as well.  It follows the factory fake rails and give is true strength of a framed car or a Z with a cage without the bars in the way for a street car.  Unless you really want to compete for a track I think this is way better.

IMAG0258.JPG

rear floor to rear frame2.JPG

front wheel well frame.JPG

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Link to AU regs which show variations of designs using self explanatory sketches, a handy design reference  http://docs.cams.com.au/Manual/GeneralRequirements/2018 Edition/GQ11-Schedule J-2018-1.pdf  As Jon has mentioned this is the time to consider structural aims, from my observations this is often neglected. The priority, tag the cage to the body wherever possible which requires the builder to keep the bars close to the body which some of them don't like because it makes their job harder. In particular keep the A pillar bar snug, the common idea of having a big plate with lots of 'structural' flanged holes spaced away from the pillar gets me, other than looking fancy it's nonsense from a driver visibility and a structural point of view.

 

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On 30/03/2018 at 1:53 AM, JMortensen said:

I've got some thoughts about that roll bar design:
1. Don't like the X up high. Too much weight, and you're reinforcing the strut towers with the top of the tube where it isn't very stiff. 

2. I would do the backstays to the top of the strut tower. Plate that whole trapezoidal area and weld the stays to the plate.

3. The bars in yellow are great if you are connecting to door bars on the other side of the main hoop. Without door bars I think it's just extra weight to carry around.

4. If you want an X, you can do it low, from the strut towers to the bottom of the hoop. I did this on mine. Would be MUCH easier to install if you cut out the storage cubbies. I didn't. 
5. I'd just go with a straight bar across the strut towers

EDIT--Also connect the top of the hoop to the map light area of the roof with a shear plate.

Thanks for your thoughts.

 

I can say now that whatever cage goes into my car won't be perfect, it will be a compromise because I'm trying to have a car that car is good at many things, its mainly a street car and I want to  keep that classic feel to it and don't want to loose interior functionality. It also has to be capable on a circuit and on a drag strip.

 

 

1 - X up high - good point, I can do without an x and just use 1 diagonal bar to save weight. 

 

2 - I would like to do the backstays to the top of the tower, but doing so would mean loosing my seatbelts and I sure as heck don't want to be running harness anywhere other than on track. If you have any idea as to how I can re-engineer my seatbelts to somewhere else them let me know.

 

3 - Will do without these bars

 

4 - Again, I want to keep the interior nice looking and as original as possible so I don't really want to have bars running there.

 

5 - Not sure what you mean, the bar is straight across the towers, albeit slightly forward of where would be ideal, if this is what you mean I could always have it right across the middle and have this bar separate from the rest of the cage.

 

I will be connecting with a plate to map light area.

 

 

 

 

This is about as good a cage I get while keeping the seatbelts and keeping weight down, will it still have enough of an impact on stiffness to be worthwhile?

 

Cage%20redesign.jpg

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Posted (edited)

For the reasons I stated earlier, you're going to have to re-engineer your seat belts regardless since your main hoop is going where the lower seat belt pockets are, and I don't see how they can both possibly occupy the same space. My plan was to do what you show in the picture above there - mount the bars to the front of the strut tower where the strut bolts in - unless there's something I don't know, I can't imagine that would be much worse than having it on the top of the tower.

 

Interested to see what you do, since I'm facing the same problems.

Edited by rturbo 930

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I'm not sure, might be able work with it:

 

IMG_8400.jpg

 

 

 

What doesn't help is that I work away from home, so I can't actually physically check things, doing all my planning from my memory and photos.

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