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Gravel Spray

And by standard X I mean the current vouge two long tubes bent and touching in the middle, then wrapped with a gusset like this pic....then again, neither of us are structural engineers so it's all opinion.

The trouble with this style with the two bent Vees is there are no tubes in tension and there is hardly any contact area between the upper and lower Vee. You are relying totally on the the gusset with that design and the example you show has a laughably small gusset. Not even FIA legal, really. If you take a big whack against a tree and the gusset fails those two bent Vees can swing in pretty far. An intersected X at least has one bar in tension and can prevent more intrusion than the bent Vees. I agree that an intersected X that only has gussets on the acute angles is still only the diameter of one tube at the intersection but that's why I like to use a connector from there to the sill bar (like on the BMW, see below) or a long taco gusset on the underside of the X and even on top. Also, in the example shown with the bent Vees the gusset is so small it's really no better than an intersected X. Any design with a bent Vee should have a big taco gusset made with material the same thickness as the roll bar material, IMO. But like Pete says, when your number is up, its up. Any design can fail in the right (wrong?) circumstances.

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Doivi Clarkinen
... but that's why I like to use a connector from there to the sill bar (like on the BMW, see below)...

I'm a bit curious about something with that connector.
FIA 253-8 does not show member like that as optional members to the cage design so - from what I understand - adding those elements would mean that the cage would no-longer be FIA 253-8 compliant. yes... no... ???

As Gene has said, sometimes common sense would tell you that adding that connector is not a bad thing.

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Morison

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Doivi Clarkinen
... but that's why I like to use a connector from there to the sill bar (like on the BMW, see below)...

I'm a bit curious about something with that connector.
FIA 253-8 does not show member like that as optional members to the cage design so - from what I understand - adding those elements would mean that the cage would no-longer be FIA 253-8 compliant. yes... no... ???

I'm not sure how that works. FIA and most others show a minimum cage spec. SCCA used to show a max spec in the IT classes...stupid. I don't see Dave's connector adding a bunch of strength and I think a plate gusset on the inside of that joint would be a good thing. However the cage is very sweet and logging that kind of work is a real pleasure.

Everyone should have a straight sill bar (imo) and then the door bars above that. The 2 solid bars that Petre has shown seem the best. I don't think the hinging Dave refers to is that big of a concern when welded and gusseted. I guess it is a damned if ya do, damned if ya don't thing however. As Dave so wisely mentioned when the jig is up..... a stump could easily drive right thru the side window.

Sprongl got pinned in his seat by the X bars going over his legs I believe. Having a straight sill bar and a bit lower door bars may prevent that. In my mind I see the door bars moving in and pushing the seat bolster (ideally the seat would be mounted to the cage and move with it I think). Too many of these X bars start at the belt line and the X is way too high plus the car is a bitch to get in and out of.

....or it could be said (imagined) that a relatively hard side hit via stump in the vicinity of that little connector could focus the entire load upward onto the single tube section on the X resulting in..?

Like I said, people debate cage design to no end, "imagining" all manner of senarios that could result in a failure of some type...and usually the point is moot because at that point the impact itself is going to result in death...regardless of cage deformation.

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heymagic

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Morison

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Doivi Clarkinen
... but that's why I like to use a connector from there to the sill bar (like on the BMW, see below)...

I'm a bit curious about something with that connector.
FIA 253-8 does not show member like that as optional members to the cage design so - from what I understand - adding those elements would mean that the cage would no-longer be FIA 253-8 compliant. yes... no... ???

I'm not sure how that works. FIA and most others show a minimum cage spec. SCCA used to show a max spec in the IT classes...stupid. I don't see Dave's connector adding a bunch of strength and I think a plate gusset on the inside of that joint would be a good thing. However the cage is very sweet and logging that kind of work is a real pleasure.

Everyone should have a straight sill bar (imo) and then the door bars above that. The 2 solid bars that Petre has shown seem the best. I don't think the hinging Dave refers to is that big of a concern when welded and gusseted. I guess it is a damned if ya do, damned if ya don't thing however. As Dave so wisely mentioned when the jig is up..... a stump could easily drive right thru the side window.

Sprongl got pinned in his seat by the X bars going over his legs I believe. Having a straight sill bar and a bit lower door bars may prevent that. In my mind I see the door bars moving in and pushing the seat bolster (ideally the seat would be mounted to the cage and move with it I think). Too many of these X bars start at the belt line and the X is way too high plus the car is a bitch to get in and out of.

damned if you do, damned if you don't...

The last rally I drove in was 08 doo wops, last stage of day 1 we had a full-on highspeed 80mph off into the trees...broad side>codriver side of course, man it got dark. I kept it pinned and the steering wheel pointed in the direction I last saw the road going, don't know if it was a log buried in there, a dirt burm or the devil himself unready to accept me, but we were launched to the other side of the road, and when I say launched I mean the bottom of the car was 6' off of the ground and we were still going 80mph. We landed in the ditch on the left side of the road still hauling, mowing down 100's of saplings, through the saplings I saw the bottom of a 10" diameter log about 3 feet off ground the heading straight for my face. At the last second the ditch ended at a road junction and we again were launched out but this time we landed dead center in the road. I lifted looked at Mikey who was smiling and said HOLY FUCK, Mike looked at the temp gauge and said "were still have X to go, coolant good, floor it man". This incident is why my Sunday moring times were REALLY slow...Mike thought that 4-5 econd moment was badass.

The point is, if we hit a tree right side in the off, Mikey would be dead regardless of cage design, no doubt. If that ditch didn't end where it did, I'd be dead, the driver side A-pillar missed that log by inches. Our number wasn't up that day, but it could have been a real bad day, no safety cage or device would have helped. You boys keep that in mind this weekend when doing battle, have at it but keep in mind Monday morning too!


OK, I'm real green on the solid axle stuff, 3 llink, 4 link, watts link, panhard rod..... I see that RX car has a watts, most rally cars have a panhard rod, why? Travel requirements for each disapline??



Edited 2 time(s). Last edit at 04/27/2011 11:40AM by Gravel Spray.

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Gravel Spray
I'm real green on the solid axle stuff, 3 llink, 4 link, watts link, panhard rod..... I see that RX car has a watts, most rally cars have a panhard rod, why? Travel requirements for each disapline??

Panhard bar is the fuse. Hit something sideways and the longish bar bends. With a watts it's not that uncommon for the diff cover to get torn off.

Plus with a low roll center and a long travel suspension, the arms at the watt's pivot can hang pretty low.

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heymagic
Everyone should have a straight sill bar (imo) and then the door bars above that. The 2 solid bars that Petre has shown seem the best. I don't think the hinging Dave refers to is that big of a concern when welded and gusseted. I guess it is a damned if ya do, damned if ya don't thing however. As Dave so wisely mentioned when the jig is up..... a stump could easily drive right thru the side window.

Sprongl got pinned in his seat by the X bars going over his legs I believe. Having a straight sill bar and a bit lower door bars may prevent that. In my mind I see the door bars moving in and pushing the seat bolster (ideally the seat would be mounted to the cage and move with it I think). Too many of these X bars start at the belt line and the X is way too high plus the car is a bitch to get in and out of.

I remember being surprised they had no sill bar. The car really folded up at the rocker panel.

1 sill bar would'nt have done much at all, Nascar door bars might have minimized the intrusion but also would have not custioned the impact as much.

hmmm its going to look like a baja truck when it get off the ground,
I like the beam set up long and simple 4 link

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Morison

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Doivi Clarkinen
... but that's why I like to use a connector from there to the sill bar (like on the BMW, see below)...

I'm a bit curious about something with that connector.
FIA 253-8 does not show member like that as optional members to the cage design so - from what I understand - adding those elements would mean that the cage would no-longer be FIA 253-8 compliant. yes... no... ???

No. You are not allowed to add anything to an FIA homologated cage. For example, a Safety Devices or Custom Cages homologated cage kit. However, when building your own cage to FIA appendix J, article 253 you are allowed some latitude and can add additional members. It's confusing, I know, but FIA homologated cage rules are different and apply to manufacturers that sell ready made kits and have done all the testing and gotten the approvals from FIA.

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heymagic

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Morison

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Doivi Clarkinen
... but that's why I like to use a connector from there to the sill bar (like on the BMW, see below)...

I'm a bit curious about something with that connector.
FIA 253-8 does not show member like that as optional members to the cage design so - from what I understand - adding those elements would mean that the cage would no-longer be FIA 253-8 compliant. yes... no... ???

I'm not sure how that works. FIA and most others show a minimum cage spec. SCCA used to show a max spec in the IT classes...stupid. I don't see Dave's connector adding a bunch of strength and I think a plate gusset on the inside of that joint would be a good thing. However the cage is very sweet and logging that kind of work is a real pleasure.

I add the vertical in the middle to connect the X to the sill bar figuring it would add a little strength to the X and tie it all together. Maybe a couple more verticals would be even better, I dunno. Also, on a shallow X like that it's a bit of pain to do a taco gusset under there.

But yeah, looking at that photo of Sprongl's car, there are some hits that it just doesn't matter what kind of door bar you have, nothing's gonna stop that tree.

OMG can we get over the doorbars already.

How about the fact that looks like a 1031 axle out of a volvo 240 ! And with a set up that looks strangely like a Sooper Bitchin' type 4 link, although with some fancy pants watts-it-called panhard-a-majiggy and nancy-boy adjustable blade sway bar (which is for sissies).


Also, that looks to be the venerable "redblock" inline 4 engine, again found first in the volvo 240, in this case topped by the 16v head (found on volvo 740 GLE's, if you happen to be wondering your local pick and pull); the same one the good Mr. Nocoast has seen fit to slinp onto his motor!


Dammit I wish I was on my way to Oly right now. You assholes better have a good time.

How about this for a question... any inherent reason why 4-link plus whatever vs. 3-link plus whatever? "Whatever" in the previous sentence meaning Watts, Panhard, etc. I mean, I have the old Escort prep book in PDF so I know how they have the rear ends setup, but being an injur-neer and coming from a roadrace background, 3-links seem to make a bit more sense. Maybe it's just me.

Makes sense the watts link has inherent issues for long travel.

I think it was on SS that Mike Hurst(old NASCAR guy) explained the 3 link as being the most ideal for a rally car, in his opinion.

That RX car runs in Europe and from what I understand their tracks are smoother, no jumps so the watts and it's adjustability makes sense.