Q: Roll Cage designs & Photos

#1

I’m nearing the final stages of my build :woohoo: and the cage is next on my list. I’m working out the details of my design. I know the rules dictate most of what can and can not be done. However, there are a number of things I’ve seen in other cages that I’m considering. But before I commit to anything, I thought I might seek some other opinions and draw from your experience.

I’d really appreciate any insight, photos, sketches, warnings, tips, tricks, things to avoid doing and/or afterthoughts that you’d be willing to share.

Thanks
Scott

#2

Are you building your own cage? Send a sketch of what you have in mind and we can look it over for you. If you do plan to build your own cage, the hardest part comes in planning the order of which tubes get done and welded up. If you don’t plan things in the right order, you end up not being able to put complete welds around all the bars and mounting plates. I have tons of notes from my build so feel free to pick my brain.

#3

search here for other threads on roll cages. There was a good one with pictures not too long ago.
cheers,
bruce

#4

Scott,

Did you see the article in GRM about cages in the last several months? I thought it was informative. Are you having Chris Schimmel build it? In addition to building an 8-pt. cage with door bars, I also elected to put a bar across the sunroof opening (within the halo) after seeing how flimsy the roof is with the sunroof panel just tack-welded in place.

Good luck,
Sasha

#5

traqrat wrote:

As much as I’d like to be able to build it myself… I’m going to have this project done by someone who has some experience with building cages.

this is kind of what I’m thinking about doing…

#6

not sure who I’m going to go with. I want to figure out what I want :unsure: before I talk to anyone.

I did see the article in GRM and thought it was helpful. I just want to be sure it built to Spec E30 rules

#7

What you pictured is good cage design. The only thing I would change would be to eliminate the lower green bar in the main hoop and the olive colored bar that runs down the middle of the halo bar.

#8

I agree with both Sasha and Damion:

I would get rid of the lowest cross bar on the main hoop.

However, I agree with Sasha about having the extra support up top and having the center halo bar.

JP

#9

I have also read that putting a strut from that lower cross-door bar up to the point of the X adds to the intrusion strength - may only be applicable if the X is pyramidal outwards. I don’t know if those taco wraps on the X provides similar strengthening or not.

I think I would put the rear diagonal the other way - maximize the support around your head.
For the mid-halo bar I would start about 18" away from the top left of the main hoop and go diagonally over to the front right of the halo.

cheers,
bruce

#10

The design looks solid. Get rid of the center halo bar like others have said. I would replace it with a bar that goes diagonally. Depending on your size and seating position, you’ll have to figure out which diagonal to use as it can rob you of headroom. The lower green bar joining the two legs of the main hoop may not be practical given that the transmission tunnel can get in the way. I also would recommend not having those two little bends in the bar that goes across the dash. If fitted correctly, those bends shouldn’t be necessary to gain clearance for your instrument cluster (which is why I assume you designed it that way). Also, consider running a bar from the door-X down to the horizontal bar below it.

#11

Thanks guys. Your feed back is very helpful.

I’ve made a few tweaks based on your comments and further research. What do think? [file name=cage3c.jpg size=102541]http://spece30.com/media/kunena/attachments/legacy/files/cage3c.jpg[/file]

#12

looks good. I’d be curious to hear what a professional cage builder has to say about it.

I think you should paint it all those colors too!

cheers,
bruce

#13

leggwork wrote:

[quote]looks good. I’d be curious to hear what a professional cage builder has to say about it.

I think you should paint it all those colors too!

cheers,
bruce[/quote]

There’se no need to paint it… it’ll be built out of Tinker Toys :laugh:

#14

Scott, the only change i would make in that design is change the direction of the diagonal in the halo bar. You have a lot of bars coming together in the spot closest to your head. I believe the cage will be super stiff on that side and not as stiff on the other. If you change the halo diagonal to the other side you will balance that out, it will be triangulated with your rear diagonal plus you’ll give yourself more head room.

Damion

#15

deleted because I couldn’t edit to attach an image

#16

there is a discussion going on over on the CR SIG list about footwell intrusion protection. Somebody was advocating triangulating the forward footwell points in three dimensions similar to how I’ve annotated Lance’s cage pic (front two green bars are new). Don’t know if this would interfere with your clutch foot or not yet.
I don’t see anything in the NASA CCR that would prevent this. BMW CR rules need to be updated to allow it (likely).
cheers,
bruce

#17

Yep, I basically built my cage with the additions leggwork put in. I didn’t put those two new ones up front in because there’s just no way to get that in there and be practical.

#18

leggwork wrote:

[quote]there is a discussion going on over on the CR SIG list about footwell intrusion protection. Somebody was advocating triangulating the forward footwell points in three dimensions similar to how I’ve annotated Lance’s cage pic (front two green bars are new). Don’t know if this would interfere with your clutch foot or not yet.
I don’t see anything in the NASA CCR that would prevent this. BMW CR rules need to be updated to allow it (likely).
cheers,
bruce [/quote]

I don’t see how those additional bars are going to help with foot protection. The intrusion that it seems we are trying to prevent is that of the trans tunnel moving over on the driver right foot towards the gas pedal.

The bars in that picture will do nothing to prevent that. To help with that intrusion you’d need to have a plate on the trans tunnel and then triangulate that back up to the cross member in some way. I just don’t see any useful additional foot protection there.

We are working the design of Simon’s cage right now as the car is going to Mark McMahon’s place on Tuesday. I’m gonna try to have it drawn up but basically it will be very similar to the cage I did in my JS car years ago…a few improvements but otherwise nearly the same. It will have a full X in the main hoop and the cage will be symmetrical from side to side. We will implement the use of clamshell guessets in several areas for added strength.

The biggest thing I keep going back and forth on right now is where to mount the rear down tubes. I’d prefer to attach to the floor in the trunk where the spring perches are at (since that’s where the load comes in) but this makes it difficult to trianulate back at the angel I want. The other option I see is to the strut towers but this is not very good because we are not running coilovers in the rear. Still thinking on this one.

I also do not see any real benefit of a roof diagonal, we’re not generating enough cornering forces I don’t think. It simply ends up being weight up high.

#19

thanks for the great feedback Jack.

I saw this pic the other day and wonder what folks think? (it’s not a BMW)

#20

leggwork wrote:

[quote]thanks for the great feedback Jack.

I saw this pic the other day and wonder what folks think? (it’s not a BMW)

[/quote]

Alternate/modern cage designs such as this certainly can be better than the standard designs that we are all using. However, at this point unless one is very seriously a structural expert it’s very difficult to visually understand the load paths and how best to account for them. With the standard cages that most people use it’s pretty easy to visually determine what is good and what is not…at least for me. I’m not a structural expert but I am a structural engineer with a lot of experience in areas like this.

And of course without doing a PROPER FEA on any cage design it’s guesswork. Now those with experience, knowledge, and eningeeing skills will generally be much better at the "guessing." ; )

Finally, due to the suspension and tires of our cars I think the added benefit of a modern design cage such as the one above are minimally incremental over a well designed/implemented standard cage. Heck, an entirely separate discussion could be had on implementation alone!