PogueMoHone

Lets try this one:

If you look at the center hoop, around the B pillar, you will notice 2 tubular bars making an apparent X. They are not part of the same loop.

The bar (part of the apparent X) that runs from right to left (downwards) is welded to the center of the car and this is heavily triangulated and gusseted. In addition, but it can't be seen, it is also welded on the inside to the B pillar (or near it) below the window.

The other bar (of the apparent x) that runs left to right (upwards) is tied into the center hoop at the roof and then welded in at the rear of the car, which you can see from other photos.

I will try and take other photos with a digital camera, or find someone who is more adept to clarify.

If you mean "by the main hoop" the B pillar hoop, it is doesn't have the diagonal bar. See above explanation, it is tied to the B pillar and center of the car from below window level.

When I look at the engineering in this cage, it is pretty thorough and mind boggling.

RedlineMan

Hmmmm....

It is a Mini, eh? I wasn't quite sure from the 1st batch, but the 2nd confirms. Cool. I too would like to see more/better photos. Something taken more globally to show more of the cage at once, not so close up. It is a very interesting layout; one that piques my curiosity, and it is certainly finely crafted. I'm not sure that it meets the letter of some race rules I've seen, but that certainly does not mean it does not accomplish the intended function of those rules, perhaps far better than the "convention." While doing things in an uncoventional way can run you afoul of scrutineers and cause you a lot of work to get your ideas accepted, it is a lot more fun. Generic is boring!!

PogueMoHone

^ It is the Mini World challenge car -Factory built, and 1 of 2 in the US. More photos to follow, when I find the camera.

PogueMoHone

Without a fish eye it is hard to get more complete shots, hopefully you can piece together the following sequence.

Picture #3 is the lower center bar, and shows how it is welded to the floor of the car behind the driver's seat.

Peter Carroll/Toronto

So it's a show us your cage thread now. One observation is I don't see enough door bars here.

A couple of years ago we had a regional racer at mosport who was impaled by his cage when he got t-boned I think at the bottom of 2 or 4.

I know the rules do not require them. But, door bars are your friend.

Lots of shiny new cage pics here... http://www.driversmeeting.com/pcarroll/albums/10

Larry Herman

Nice looking work there Peter. Looks kind of like a belt AND suspenders. The Nascar bars will hold them off, giving the X brace less work to do. Some will probably carp that it is too heavy. Everything's a compromise.

RedlineMan

Thanks Pogue;

That is an interesting cage, and superbly crafted. I particularly like the treatment of the side hoops near the head tube. The double tubing and gusseting with sheetmetal REALLY increase the rollover protection in this most vulnerable area. Unfortunately, it also makes it much harder for tall folks to get in/out. I do indeed like the main hoop bracing to the center tunnel. Exceptionally good intrusion protection and support for the main hoop at the door bar node. I did my cage this way. I'm not wild about the pedestal mounting of the rear stays and door bar braces to the rear frame sill. Seems it would enter a lot of bending/levering force into the rail, instead of a more linear force. A quibble.

The only thing that really "does not work" at all is the long belt paths. The belt bar arrangement on yours is an FIA design that is specified in one of their manuals as acceptable. Unfortunately, it creates excessively long belt paths.

In any event, it is a fascinating piece, and is likely uber effective. Thanks for posting.

Peter Carroll/Toronto

Some weight is worth adding. The car weighs in at a tad under 2200lbs. For an E36 that's insanely light.

fatbillybob

Peter,

Wow! what a job. That's the kind of work we would all love to do. I question 2 things. 1) the steering shaft. Yours looks like a straight solid spear looking right at you which may or may not be a concern. OEM's do two things I have seen that I incorporate into my safety system designs (usually when moving a steering wheel to gain more interior space.) They will use a collapsible shaft. OE one are usually big and heavy but there are light purpose built ones that are like a rod that slides in a tube from stock car parts guys. A second thing OEM's do is to use helicopter U-joints and place the steering rod in offset shear allowing the straight section of rod to mostly remain intact but crush distance can be gained by folding on the helicopter joints. 2) is the concept of why we use an "X" vs. why we use a NASCAR bar and is using both getting us less than either single system? I do not think you can draw the conclusion that by having both systems you are any safer. My understanding of the intrusion resistence of the "X" is that impact puts the A/B pillar bars in tension. Conversely the NASCAR bar uses total mass and puts the A/B bars (and sill in proper design) in compression to spread load into the cage. So what happens if with the NASCAR bars you bend the A/B piller bars in compression and bend them out of shape then put them in tension from the "X" as the crash continues? My thinking is that the tension feature of the A/B pillar would be compromised and the whole cage will collapse. It would be interesting to see an FEA of your setup to see if my intuition is anywhere close to reality. The good thing about your current design is that your NASCAR bars look to rely on mass only and not directing forces into the A/B pillar because of their shape. Your bars are curvy vs. more angular like what John H described as a paper soup bowl turned over with the lip glued down on the table. Your NASCAR bars look to be an easy fold in until they hit the "X" once the mass of the NASCAR bar is overcome. Again the NASCAR bar looks to be unsupported at the sill further reducing effectiveness and effect on the rest of the cage. I think my biggest fear would be what negative effect your NASCAR bar could have on the "X" and how the "X" needs to work with the cage. Again it is about safety "system" and mixing a bunch of techniques may or maynot work well together. So on this one I have more questions than answers.

fatbillybob

On Pogue's cage the rear shock looking area why tie the 2 bars into a 3rd piece of open tube and weld that to the anchor plate? Is access needed down the open tube? If not then more strength could be gained if the 2 bars are just welded as a single node to the anchor plate and lighter too. I would think an open tube would just crush unless you at least supported it by capping the open top. I could crush that open top even if it was 120 wall with just a pair of vise grips. Nice cage overall. And my comment is picky because you have welded the 2 tubes very low on the open one and maybe no strength is lost there...I don't know. Oh..I agree with John H. on belt lengths...too long=belt stretch

Peter Carroll/Toronto

I suspect these tubes are to pick up a suspension mounting point. The open tube allows you to bolt something from below. Mine was done like the to pick up the differential mount points.

PogueMoHone

No, it a demonstration of a professionally designed cage, used in an International race series.

I assume, but have no certainty, that BMW knows what it is doing this area. Hopefully, some of the techniques and methods visible (impossible to describe) will inspire those inclined to design/construct their own cages. And everyone wil be safer as a result.


As always, take the best and leave the worst.

For me, that means added weight to "professional" engineering and I think that was a point, or implication, of the original thread.

RedlineMan

Hey;

Given the ample bracing and transmitting of forces into many areas and on different tangents away from the driver, I don't take any particular exception to Peter's door bars. I might have wanted to create a bit more outward protrusion in the X to create more geometric strength, and I feel the NASCAR portion is more of a "scattershield" or "5mph bumper" than anything. Still, it looks pretty safe to me, and certainly nicely built.

Glad you survived last year's "deflatus" coming home from Calabogie, Peter!

2BWise

Take a look at the cages designed for any of the Euro touring car series. Those cages have essentially one purpose, stiffen the chassis as much as possible. The cage in the Mini is very similar. Wherever they could use the safety structure of the cage for increased stiffening they did. The assumption being that the vehicle will need to be able to perform at a high level 100% of the time and only be safe for one crash. Production vehicles are inherently safe and should only need minor improvements for safety for racing, your basic six pt cage will do this, everything beyond that should be for improving performance. Like the Nascar bars as well as the door X. The door X will be stiffer than Nascar bars, but Nascar bars are ultimately safer. Its a race car and should be build to go as fast as possible within the rulebook. Why not take advantage of the cage to do so as well.

fatbillybob

All true but...whether we like it or not, or intend it or not, we change the engineered design in unknown ways because we don't have facilities or cubic dollars to crash test. So we do not know what we have done to "inherently safe". Sometimes we weld in aspects of our cage to chassis and change the way the OEM designer intended force distribution to occur in a crash. Such changes can alter the whole way the inherent given OEM safety system works. That's why I'm a big believer in designing cages with seats anchored to cages not chassis thus considering the car as expendable. I want that safety capsule to survive on its own merit with no help from the chassis because I don't know how I altered it from the OE design. Gaining chassis stiffness is a side benefit not first interest. Maybe I'm just too safe and should give up racing for golf.