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The roll cage in my car is almost finished. The fabricator wanted to know if I wanted a bar directly under the dash. If I do this then I lose the defrost vent. However, someone (I don’t recall who) told me that the regs were shortly going to change so as to require removal of the heater core, which would make this a moot point.
Any ideas/advice would be greatly appreciated!
Andy
Yes you do want this bar for side to side rigidity.
You do not need to loose any heat/defrost function. Sorry, I do not know the specifics of how the bar should be configured. I dd not see mine going in.
Don
you should still be able to retain the vents. however, i pulled the heater core altogether in my car. it’s yet another failure point imo. I’m going to devise some other means of directing hot air to the windshield.
I still have my center defrost vent with a bar going across under the dash. There is a flat piece of metal that comes ot just under the windshield, my bar sits on top of that. The only vent of mine that I was able to keep was the center defrost vent. All of the others I had to cut out. You will also need to trim a lot of the center vent ducting out to get the dash to fit. It is quite a bit more work to get it to fit. In my opinion it is worth it to be able to keep the defrost function.
My cage guy was able to put a bar that runs along the firewall and still kept my defrost. You don’t even know it’s there and you’re able to keep defrost. It’s a tight fit, but looks great and I assume it works well.
My center bar is almost like shifter11’s. Before installing the dash, I made an aluminum “scoop” that deflects the air towards the glass. I works.
With that said, I’m thinking about pulling my heater core and some how using the warn/hot air from the transmission tunnel (Bimmerworld 3" fan and some hose?).
Thanks for all the advice guys. That helps a lot. I’ll send a picture of shifter11’s setup to my fabricator.
Andy
kishg wrote:
I don’t diagree that the heater core is a potential failure point, but I will again cast my vote for “good defrost” capability.
Also, the addition of a non-factory blower would technically be illegal, but a weenie protest (except in a rain race if it really worked well and you could see better than me 
).
Removal of the heater core is permitted (new for 2009) but I haven’t heard about any change to make it required. I would strongly oppose that requirement.
The straighter you can make that cross bar the better. And yes, it is required if you want structural integrity, IMHO.
PS - Sometimes cage builders mount that cross bar down low (i.e. under the steering column). Avoid that location if you like your shins.
Ok, y’all…engineering quiz: What do you call a bent tube? Answer: A spring. Never install a bent tube where a straight tube can be used. Go just under the steering column and if your shins get there, that will be the least of your worries. CB
cwbaader wrote:
Fixed it for you. Let me add my opinion:
Always install a bent tube if using a straight tube requires a location that has potentially worse consequences than using that bent tube.
I am trying to come up with a situation where a perfectly straight tube over the steering column would be preferable to the slightly bent one below it. Say, an impact where one side of the car is against a solid, immovable object and is impacted directly parallel to the cross bar? In that situation, you want maximum rigidity.
In a normal ohsh!tI’minthemiddleofthetrack spin, the car that t-bones you transfers most of its energy to your car. Some is absorbed by the deforming sheet metal, a small amount is transferred to the “spring,” but most is converted to kinetic energy that hurtles you further along the direction of travel. The “spring” may add marginally to that kinetic energy.
But in a wicked rollover, you will never hit your knees or shins on that “spring.”
IMHO, YMMV, I’m not an engineer, all due respect, etc.
removal of the heater core will not be “required” in the rules updates
bruce
greensha wrote:
[quote]The roll cage in my car is almost finished. The fabricator wanted to know if I wanted a bar directly under the dash. If I do this then I lose the defrost vent. However, someone (I don’t recall who) told me that the regs were shortly going to change so as to require removal of the heater core, which would make this a moot point.
Any ideas/advice would be greatly appreciated!
Andy[/quote]
I agree with CB…this is one place where you want to have a straight bar, mine is over the column, thru the radio hole in the dash, it makes it tough to change the cluster, but with the dash loose it is not a real problem. A straight tube transfers the energy across the car to the other front bar. There is no way any part of my body can contact the dash bar. I did use an airbag column that has an extra u joint or 2 so my column is dropped 3/8th of an inch…maybe that is not legal, not sure.
Will try to upload a photo or 2.
I would not like a bar under the column, I am 6’3" and that wouldn’t work for me…
Al
Take a look at the Spec Miata “MiataCage.com” cage. The firewall mounted dash bar is ideal, awkward, but ideal. It’s location is tough and reinforced by the location. The issue however is that is a PITA place and often expensive place to mount it.
These guys are well known for being on something like the 4th iteration of this cage. Saving big guys lives in teeny tiny car for years and years now.
[quote=“FARTBREF” post=43228]I agree with CB…this is one place where you want to have a straight bar, mine is over the column, thru the radio hole in the dash, it makes it tough to change the cluster, but with the dash loose it is not a real problem. A straight tube transfers the energy across the car to the other front bar. There is no way any part of my body can contact the dash bar. I did use an airbag column that has an extra u joint or 2 so my column is dropped 3/8th of an inch…maybe that is not legal, not sure.
Will try to upload a photo or 2.
I would not like a bar under the column, I am 6’3" and that wouldn’t work for me…
Al[/quote]
Sorry to bring this thread back from the dead…
I am about to make my A-pillar bars, and need to decide where to put the dash bar.
I am definitely keeping defrost and would really really like to have a straight bar from one a pillar to the other. I was planning on doing what is quoted above ^… I dont see how people are fitting their dashes with stock vents with the bar bent around the bottom of the dash/firewall… definitely not enough room unless you do some cutting/hammering. Any pictures/ideas/postcageregrets would be appreciated.
My favorite (probably not legal, but let me know if it is!)
http://www.google.com/imgres?start=97&um=1&hl=en&safe=off&biw=1280&bih=873&tbm=isch&tbnid=I8C3E8IZPZpqUM:&imgrefurl=http://www.performanceforums.com/forums/showthread.php%3F67256724-318iS-Fasts-failing-to-load&docid=G4BU6CkvvJ7b2M&imgurl=http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1366.snc4/163867_473971742099_675317099_6240367_3566699_n.jpg&w=720&h=540&ei=GCJlT7DWCofy0gG-iKSrCA&zoom=1
I had a knee bar in the car I killed in Dec. A shin hit that bar pretty hard so that was not ideal. The new car has a bar high against the firewall, perhaps too high to stop engine intrusion into the passenger cell. I think the best solution would be something in between the two extremes. The ideal bar, IMO, would go over the steering column, be well forward towards the firewall, but would not be too high.
You can get the bar in and leave the heater core, but you need to make some new ducting. There is a great photo somewhere on this site on how someone did the ducts. Be carefule to fit the gauge cluster at the same time, it is easy not to leave enough room for them.
Here’s how I did mine. My bar runs directly on top of the two defroster vents. I used aluminum dryer ducting and routed it towards the openings in the dash. A little ghetto? You betcha. As effective as stock? Certainly not. Functional? Absolutely.
You have to bend it around a bit to get everything to fit underneath the dash.
