Recent door bars

To pull the main hoop bar forward would also require collapsing it, and with a X in the main hoop that is going to be tough. There is a lot more at play than just terminating loads in straight lines, with a mid stay.

I think the mid stay is a good idea though.

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ronerickson
Josh, any tips for half-lateral to front strut bars on the MKII? Haven't seen any close up photos, but the more I look at it, the more it seems like they could be a huge pain to weld.

Removing the rain tray makes it a bit easier but still a pain

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Josh Wimpey

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ronerickson
Josh, any tips for half-lateral to front strut bars on the MKII? Haven't seen any close up photos, but the more I look at it, the more it seems like they could be a huge pain to weld.

Removing the rain tray makes it a bit easier but still a pain

Roger that. Already removed it. Finally found photos of your setup on the diesel car. That's going to be hard to weld around!

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starion887

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phlat65
As far as interior color, I like white. Makes seeing stuff in the car much nicer, especially at night. Also white shows cracks and damage much easier.

And white is cooler; less of a radiant heat source when the floor panels get heated from the exhaust or engine. I painted one car flat black on the inside to reduce night glare, but man, did it ever radiate heat off of the floor boards over the exhaust....

Taking both those things(light and heat) into consideration. I still don't effing know hahaha. I suppose whatever color I pick Ill bitch about anyhow for one reason or another.... Thanks for the insight.

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phlat65
To pull the main hoop bar forward would also require collapsing it, and with a X in the main hoop that is going to be tough. There is a lot more at play than just terminating loads in straight lines, with a mid stay.

I think the mid stay is a good idea though.

The thinking above about the X is a good thought but there are 2 factors not considered above that allows the bending of the vertical partion of the main hoop that is not prevented by the X:
1) The main source of 'extra material' for this bending is the outward bend that exists in practically all main hoop vertical sections that is put there to have the main hoop tight to the B-Pillar. That by itself provides enough extra length of the main hoop vertical to be pulled forward to allow for many inches of inward bending on the side bar. This main hoop vertical section bending becomes partly torsional which helps a bit but not much.
2) Now let's build a cage with a perfectly straight vertical section of the main hoop between the upper and lower attach points of the X: there would have to be some EXTREMELY high tension exerted by the X brace on the main hoop veritcal section to limit bending of the main hoop vertical section. For no bending of the main hoop vertical section, the tension would actually have to be INFINITE, which we all know ain't reality. What will really happen with this theoretical cage is that the main hoop veritcal section will start to bend (which it HAS to do BEFORE the upper and lower X-brace points try to resist), and the upper and lower X brace points will move towards each other under the load which allows more bending. But this is a minor factor compared to that listed in 1) above.

So the main hoop X-brace is not enough of a factor to do much except under extreme bending situations; the side bar bending is far beyond what is acceptable by the time the X-brace comes into play. (Assuming all else holds together...)

EDIT to add: Now one brace that does do you some good is the diagonal brace between the half lateral and the main hoop vertical section by your helmet. It is not as good as moving the side bar out but it is the kind of aid that slows the process and helps the 'side bar in tension' theory work a bit better.



Edited 1 time(s). Last edit at 12/03/2013 08:31AM by starion887.

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Josh Wimpey

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starion887
If you don't mind my commenting on this (again), understand that a straight bar is only as good as the weld strength at the ends, the tube tensile strength, and the points to which it is anchored. The idea that the straight side bar will be held straight in tension is a fallacy; the half lateral with the A-pillar brace will stay fairly steady but the main hoop's vertical section will just simply bend forward under the tension (if a weld does not break). You have around 40" to 45" typically of free vertical tube in the main hoop vertical, and the tension will simply pull this forward. It only takes 1" to 1.5" of bending there to allow the side bar to move in 6" at the center.

What do you think of adding a mid-rear stay (And forward mid-stay to strut tower) like in this diagram?

Hey Josh,

It'll certainly help in a moderate side impact, but it still depends purely on tension on the side bar to prevent too much inward bending. IMO, not as good as extra space to start with. Eventually, the side bar will stretch and start to yield. And the welds sure have to be good and the joints gusseted, even at the main hoop, IMO. I would prefer to use this with the double-U side bars as the typical X joints will see increased tension forces.

Everyone needs to grasp that depending on tension in the side bars in any form is limited. For any straight member between 2 support points, for the straight member to remain straight under a side force, the tension force in the straight member has to be infinite.....(really!)......which we all know is not going to happen. The straight member always deflects to start the loading process, and either bends (yields) and stretches or the support points move, or both.

I remember posting photos of a cage we were working on, & we bent the door bars outward towards the door. I remember being crucified for the outward bend, something about there being more leverage to brake the weld with the doors bars being bent outwards. this still doesn't make much sense to me.


hard to tell from this photo of the bend. The bars were straight just fish mouthed to bow out towards the door.


I also remember people having a problem with the roof spreader bar having two bends in it, saying that it would be stronger if it was straight, regardless of the gusset. But I also see on here people preaching the importance of having the cage as tight to the pillars to not obstruct the view.

what gives?

Your roof is the style that seems popular on west coast thanks to Jackson Rally and Dirty Impreza.
I do a straight but kinked bar across between the two.

The first BMW pic has the bars bowed outwards also. I've heard negative and good about that style.

People like to debate what is better, what is safer, etc. to infinity. Take the intersecting vs. dual V style door X. The intersecting was almost exclusively the only style of X you would see until the Lovell/Freeman accident at Oregon Trail where apparently had the massive internal injuries not killed them, the intersection at the X broke and severed the femoral artery (so I have heard) and from that point on people started saying, "the X should be two bent bars so they can't break and impale your leg." Really what they should have been saying though is, "we need gussets."
Both styles have their benefits and disadvantages. Some people way smarter than me have said that the dual V can be stronger but should have a larger and thicker gusset to prevent them from seperating.

Regardless, your cage is fine Sean.

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Grant Hughes

I like the design of the door bars on Adams car, the only thing i would change is running the upper tube on the "front" end of the cage flat to the front lateral bar. its halfway down this link;
http://www.rallyanarchy.com/phorum/read.php?5,70921,page=1

So what about these then?

Design number 1 is a thought I had after seeing that silver cage a couple posts up. The bottom bar is only slightly bent, what if you used a sill bar and a v?

I personally have style 3 in the neverending story, I mean rally car.

I feel designs 2 and 3 are probably the "best" followed closely by 4, and then 1 last.

Wouldn't the angles of the triangle created in the door bars matter? Or when its pushed sideways, vs trying to "compress" the triangle, the angles no longer matter?

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Welcome to the cult of JVL drink the koolaid or be banned.

Designs 3 & 4 are only legal RA designs...

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Grant Hughes

I think 1,2,3 and 4 are RA legal? Isnt Nasa the one that requires a sill bar?

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Unless they changed it recently, I believe that's correct. NASA requires the sill bar, RA doesnt.

I would rather have a sill bar though, than no bar.

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Welcome to the cult of JVL drink the koolaid or be banned.

Rally America has "required" a sill bar since 2006.

As of today, Rally America rules allow the old style 2006 cage ("X" in main hoop, sill bar, one additional door bar, A-pillar bar), a holomologated cage or an FIA cookbook cage from either DOM or CDS.

FWIW, the FIA cookbook cage does not require a sill bar, and only requires a single door bar for cars built after 2006. I've had arguments with RA scrutineers about this as my car was built with an X-bar in the door, but no sill bar. But when you show them the actual rules, they don't want to read them as they know what's best. I had to have Hurst call the scrutineer to straighten him out and now my logbook has a letter in it from Hurst saying my cage is legal.

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Jason McDaniel



Edited 1 time(s). Last edit at 12/08/2013 12:21PM by modernbeat.

I think its silly.