The official roll cage theory, design, fabriction technique, and picture thread!!!
08-27-2007, 07:29 PM
#26
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Re: (Ekasey)
I have to add that stiffening a car doesn't always mean more tubing.
It often means just spreading the load at the points where the cage meets the body.
Also, to be fair, any material that is not contributing to the stiffness of the structure can and should be removed to offset weight issues.
All the area between the outer suspension points front to back should be very stiff, and most outside is simply there to hang sheetmetal on.
It often means just spreading the load at the points where the cage meets the body.
Also, to be fair, any material that is not contributing to the stiffness of the structure can and should be removed to offset weight issues.
All the area between the outer suspension points front to back should be very stiff, and most outside is simply there to hang sheetmetal on.
08-28-2007, 07:10 PM
#27
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Re: (Ekasey)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ekasey »</TD></TR><TR><TD CLASS="quote">Grand Am Cages are built simply and effectively. To completely stiffen the entire car to reduce suspension deflection etc. would turn a 2600lb racecar into a 3000lb pile of crap, with absolutely no performance returns that would outweigh the huge amount of weight added
</TD></TR></TABLE>
well obviously there is a point where you're going overboard. i tell you what, how about you just lay some knowledge on us and tell us how they do it in grand am.
unless you are on a team with a tube frame car or one of those corvettes that has converted to solid rear axle. if so you can take your heretic knowledge elsewhere.
</TD></TR></TABLE>
well obviously there is a point where you're going overboard. i tell you what, how about you just lay some knowledge on us and tell us how they do it in grand am.
unless you are on a team with a tube frame car or one of those corvettes that has converted to solid rear axle. if so you can take your heretic knowledge elsewhere.
08-28-2007, 07:18 PM
#28
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Re: (Mr.E.G.)
Originally Posted by Mr.E.G.
1. hitting your head on bare car frame metal is just as bad as hitting your head on roll cage metal. agree or disagree?
2. if someone took a piece of roll cage tubing and wrapped it in roll cage padding and swung it at your head like a baseball bat the padding woudnt be enough to protect you? agree or disagree?
3. car interior plastic is no better (and possibly worse) at softening the blow. therefore if you wrapped roll cage tuning in car interior plastic and smacked someone in the head, they are just as fucked as if they were struck with roll cage tubing wrapped in padding.
wellllllll, hitting your head on car metal is just as bad as hitting it on roll cage metal, and the plastic wont save you from the roll cage metal, then how in the hell is hitting car frame metal with plastic better? lol
Modified by Mr.E.G. at 6:41 PM 8/27/2007
2. if someone took a piece of roll cage tubing and wrapped it in roll cage padding and swung it at your head like a baseball bat the padding woudnt be enough to protect you? agree or disagree?
3. car interior plastic is no better (and possibly worse) at softening the blow. therefore if you wrapped roll cage tuning in car interior plastic and smacked someone in the head, they are just as fucked as if they were struck with roll cage tubing wrapped in padding.
wellllllll, hitting your head on car metal is just as bad as hitting it on roll cage metal, and the plastic wont save you from the roll cage metal, then how in the hell is hitting car frame metal with plastic better? lol
Modified by Mr.E.G. at 6:41 PM 8/27/2007
so
1)It depends. What is the radius of the part you are contacting? In general hitting anything hard (metal) with anything soft (you) can only end poorly for the soft thing.
The softer the radius (such as a flat part, the easier it will be on the soft thing because it will distribute the energy. I would rather walk into a steel door than into a steel cutting knife. 
2)Roll cage padding isn't really meant to protect you in an accident. If you get the SFI stuff you'll notice it's surprisingly stiff, but still just foam. It DOES do a little bit, but not alot to protect the occupant.
3) It's not the plastic that protects you, its the dead space behind it. When your head hits the plastic, it bends the plastic into the empty space behind it. The plastic will have a very gentle curvature to it as well to prevent from cutting you up. Extending the length of time the impact your head has with the metal/plastic frame of the car even by milliseconds can be the difference between debilitating harm and a more pleasant outcome. NHSTA and IIHS have quite a few documents on this sort of thing, unfortunatley they are a major pain in the *** to get your hands on. You'll also notice that the plastics they use are bendable. By bending around, the material absorbs more energy more progressivley than if it was brittle (like bakelite, which is hard, and just crumbles and snaps when it gets hit)
Hitting the bare frame of a car with your head is absolutley just as bad as hitting a roll cage tube of the same radius of curvature. given the choice I would always take a caged car if I was wearing a harness and a helmet, and I would always take a stock safety system street car on the street otherwise.
The thing is, there are so many variables at play here, it REALLY depends on the car, the thing the car hits, the speeds, the structure, the size and shape of the driver, and the saftey systems in the car. There are some crashes where a cage would make a street car safer, and there are some that would go the other way. IN GENERAL I would say it is not a very good idea to put a cage in a street car. you could always add side impact beams in your doors or something if you are worried about getting t-boned. The thing is, without alot of real world data, all we can do is argue about the mechanics of collisions and resultant injuries. Which is why I said (not trying to be a jerk) if you feel that caging your car is a valid approach based on the variables you have weighed and what your design goals are, just do it. The ermpical data I've seen says it's probably going to be a crapshoot with a favorabilaty towards not caging. A rollbar would probably be a plus in an open top car though.
Either way, I'm out to make more parts so i can fund my racing. Good luck Mr EG
08-28-2007, 07:54 PM
#29
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Re: (Niles)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Niles »</TD></TR><TR><TD CLASS="quote">
Hey Mr. EG. Props for keeping this thread going, lets hope everyone learns something new. I would have replied earlier, but having 2 jobs and trying to do investment projects etc on the side is kicking my *** right now.
so
1)It depends. What is the radius of the part you are contacting? In general hitting anything hard (metal) with anything soft (you) can only end poorly for the soft thing. The softer the radius (such as a flat part, the easier it will be on the soft thing because it will distribute the energy. I would rather walk into a steel door than into a steel cutting knife.
2)Roll cage padding isn't really meant to protect you in an accident. If you get the SFI stuff you'll notice it's surprisingly stiff, but still just foam. It DOES do a little bit, but not alot to protect the occupant.
3) It's not the plastic that protects you, its the dead space behind it. When your head hits the plastic, it bends the plastic into the empty space behind it. The plastic will have a very gentle curvature to it as well to prevent from cutting you up. Extending the length of time the impact your head has with the metal/plastic frame of the car even by milliseconds can be the difference between debilitating harm and a more pleasant outcome. NHSTA and IIHS have quite a few documents on this sort of thing, unfortunatley they are a major pain in the *** to get your hands on. You'll also notice that the plastics they use are bendable. By bending around, the material absorbs more energy more progressivley than if it was brittle (like bakelite, which is hard, and just crumbles and snaps when it gets hit)
Hitting the bare frame of a car with your head is absolutley just as bad as hitting a roll cage tube of the same radius of curvature. given the choice I would always take a caged car if I was wearing a harness and a helmet, and I would always take a stock safety system street car on the street otherwise.
The thing is, there are so many variables at play here, it REALLY depends on the car, the thing the car hits, the speeds, the structure, the size and shape of the driver, and the saftey systems in the car. There are some crashes where a cage would make a street car safer, and there are some that would go the other way. IN GENERAL I would say it is not a very good idea to put a cage in a street car. you could always add side impact beams in your doors or something if you are worried about getting t-boned. The thing is, without alot of real world data, all we can do is argue about the mechanics of collisions and resultant injuries. Which is why I said (not trying to be a jerk) if you feel that caging your car is a valid approach based on the variables you have weighed and what your design goals are, just do it. The ermpical data I've seen says it's probably going to be a crapshoot with a favorabilaty towards not caging. A rollbar would probably be a plus in an open top car though.
Either way, I'm out to make more parts so i can fund my racing. Good luck Mr EG</TD></TR></TABLE>
ahhhh, good info. i hadnt considered the issue of the radius of the tubing. that's a good point.
i have more to say but i need to get some work done as well. thanks for your input.
Hey Mr. EG. Props for keeping this thread going, lets hope everyone learns something new. I would have replied earlier, but having 2 jobs and trying to do investment projects etc on the side is kicking my *** right now.
so
1)It depends. What is the radius of the part you are contacting? In general hitting anything hard (metal) with anything soft (you) can only end poorly for the soft thing.
The softer the radius (such as a flat part, the easier it will be on the soft thing because it will distribute the energy. I would rather walk into a steel door than into a steel cutting knife. 2)Roll cage padding isn't really meant to protect you in an accident. If you get the SFI stuff you'll notice it's surprisingly stiff, but still just foam. It DOES do a little bit, but not alot to protect the occupant.
3) It's not the plastic that protects you, its the dead space behind it. When your head hits the plastic, it bends the plastic into the empty space behind it. The plastic will have a very gentle curvature to it as well to prevent from cutting you up. Extending the length of time the impact your head has with the metal/plastic frame of the car even by milliseconds can be the difference between debilitating harm and a more pleasant outcome. NHSTA and IIHS have quite a few documents on this sort of thing, unfortunatley they are a major pain in the *** to get your hands on. You'll also notice that the plastics they use are bendable. By bending around, the material absorbs more energy more progressivley than if it was brittle (like bakelite, which is hard, and just crumbles and snaps when it gets hit)
Hitting the bare frame of a car with your head is absolutley just as bad as hitting a roll cage tube of the same radius of curvature. given the choice I would always take a caged car if I was wearing a harness and a helmet, and I would always take a stock safety system street car on the street otherwise.
The thing is, there are so many variables at play here, it REALLY depends on the car, the thing the car hits, the speeds, the structure, the size and shape of the driver, and the saftey systems in the car. There are some crashes where a cage would make a street car safer, and there are some that would go the other way. IN GENERAL I would say it is not a very good idea to put a cage in a street car. you could always add side impact beams in your doors or something if you are worried about getting t-boned. The thing is, without alot of real world data, all we can do is argue about the mechanics of collisions and resultant injuries. Which is why I said (not trying to be a jerk) if you feel that caging your car is a valid approach based on the variables you have weighed and what your design goals are, just do it. The ermpical data I've seen says it's probably going to be a crapshoot with a favorabilaty towards not caging. A rollbar would probably be a plus in an open top car though.
Either way, I'm out to make more parts so i can fund my racing. Good luck Mr EG
</TD></TR></TABLE>ahhhh, good info. i hadnt considered the issue of the radius of the tubing. that's a good point.
i have more to say but i need to get some work done as well. thanks for your input.
08-28-2007, 11:33 PM
#30
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Re: (Mr.E.G.)
To be perfectly honest everyones cars are built different (unless they're copies of the fast cars ) which is fine. A lot of engineers, fabricators, etc. have different design theory's and ideas. Doesn't mean they're right and doesn't mean they're wrong either.
The fact of the matter is(this is not directed at anyone here necesarilly), if you don't know what you're doing take it to a professional. When I have a question or a thought even if I know i'm right I always double check with somebody smarter then me, especially when my life or somebody elses life could be on the line.
So basically follow this
Follow the rule book
If you're not racing at pro level, safety above and beyond anything else chassis stiffening a very minor concern.
use common sense
Keep bars away from driver
Remember you dont want a 100% solid structure, you need something too give to attenuate the crash impact.
and there's a few more but if you can't figure them out take it too a pro and get it built
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. »</TD></TR><TR><TD CLASS="quote">
well obviously there is a point where you're going overboard. i tell you what, how about you just lay some knowledge on us and tell us how they do it in grand am.
unless you are on a team with a tube frame car or one of those corvettes that has converted to solid rear axle. if so you can take your heretic knowledge elsewhere. </TD></TR></TABLE>
) which is fine. A lot of engineers, fabricators, etc. have different design theory's and ideas. Doesn't mean they're right and doesn't mean they're wrong either.The fact of the matter is(this is not directed at anyone here necesarilly), if you don't know what you're doing take it to a professional. When I have a question or a thought even if I know i'm right I always double check with somebody smarter then me, especially when my life or somebody elses life could be on the line.
So basically follow this
Follow the rule book
If you're not racing at pro level, safety above and beyond anything else chassis stiffening a very minor concern.
use common sense
Keep bars away from driver
Remember you dont want a 100% solid structure, you need something too give to attenuate the crash impact.
and there's a few more but if you can't figure them out take it too a pro and get it built
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr.E.G. »</TD></TR><TR><TD CLASS="quote">
well obviously there is a point where you're going overboard. i tell you what, how about you just lay some knowledge on us and tell us how they do it in grand am.
unless you are on a team with a tube frame car or one of those corvettes that has converted to solid rear axle. if so you can take your heretic knowledge elsewhere.
</TD></TR></TABLE>
08-30-2007, 07:30 AM
#33
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Re: (LumpyTheGrumpyCamshaft)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LumpyTheGrumpyCamshaft »</TD></TR><TR><TD CLASS="quote">what about roll cage materials, whats the different levels, pro's con's. What do they use material wise in jgtc/supergt cars.
</TD></TR></TABLE>
ahhh, good question. im curious as well.
i think its exceptionally interesting that you brought up super gt cars since they are part unibody and part tube frame. for those that may not be familiar, jgtc (which has now become super gt) cars are based on production car chassis. the entire cockpit area of the chassis has to be composed of the factory unibody chassis from the firewall to the rear bulkhead. fore and aft of the cockpit designers are free to modify the frame as they choose. in its current state super gt cars are some of the most advanced gt cars on the planet as they have virtually unlimited freedom in terms of suspension design and very flexible aerodynamic requirements.
current super gt cars employ inboard suspension.
i think this is a great type of car to discuss since the roll cage is most certainly integrated into teh frame and not just a safety device.
</TD></TR></TABLE>
ahhh, good question. im curious as well.
i think its exceptionally interesting that you brought up super gt cars since they are part unibody and part tube frame. for those that may not be familiar, jgtc (which has now become super gt) cars are based on production car chassis. the entire cockpit area of the chassis has to be composed of the factory unibody chassis from the firewall to the rear bulkhead. fore and aft of the cockpit designers are free to modify the frame as they choose. in its current state super gt cars are some of the most advanced gt cars on the planet as they have virtually unlimited freedom in terms of suspension design and very flexible aerodynamic requirements.
current super gt cars employ inboard suspension.
i think this is a great type of car to discuss since the roll cage is most certainly integrated into teh frame and not just a safety device.
08-30-2007, 07:34 AM
#34
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4130 is used over DOM steel simply to save weight, i.e. either use 1.75X0.120 DOM steel or 1.75X0.095 4130. Chromoly (4130) is stronger/stiffer per unit weight.
Casey hit it on the head again, the point of diminishing return is very real and easy to attain. It's a point of how many bars can you add to increase safety or rigidity before it soon becomes unsafe or the rigidity attained is so high that whatever class your car is in, will never need that kind of strength? Think of a Nascar tube frame racing in Solo2, and this is what I mean.
Long story short, build the car for the class, these rules set are designed by people who really know what their doing
Casey hit it on the head again, the point of diminishing return is very real and easy to attain. It's a point of how many bars can you add to increase safety or rigidity before it soon becomes unsafe or the rigidity attained is so high that whatever class your car is in, will never need that kind of strength? Think of a Nascar tube frame racing in Solo2, and this is what I mean.
Long story short, build the car for the class, these rules set are designed by people who really know what their doing
08-30-2007, 11:50 AM
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Not to step on anyone’s toes but, I think there is something people are missing here. Whether it is a weekend racer or street car (this is excluding purpose built race vehicles) without accompanying safety devices your cage simply becomes a death trap. As stated before any factory vehicle is designed to deform and absorb during impact to mitigate as much bodily harm as possible. When you stiffen the chassis with a roll cage you are essentially negating much of this absorption. This is not a problem when properly restrained with harness, helmet, and HANS device (or other neck restraint system) but otherwise you are just going to wind up with a broken neck. I see too often, at local meets, people with weekend racers that drive them daily with a full cage, Racaro seats, and Takata harnesses thinking that they are safer because of it. Their problem isn’t going to be there head hitting anything because they won’t have much of a neck to hold the damn thing up if it ever moves far enough to come into contact with it, except perhaps in the case of a rollover. I know this is a little off the point but with the discussion of safety and cages being brought up I thought I might chime in.
08-30-2007, 12:38 PM
#36
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Re:
impact absorbtion: ?
most cages , at least for typical unibody track cars (honda challenge, etc) , don't have any tubing from the rear shock towers to the rear of the car.
and in the front from the front of the car to the shock towers. and most don't have any tubing from the firewall to the front of the car (not to mention the extra weight penalty for tubing through the firewall)
isn't the main concern, keeping the driver compartment intact as much as possible?
a front or rear collision, the "stiffness" of the cage may not come into play much, as the vehicle is going to deform. i believe the "frame rails/unibody construction" is even designed to keep the driver compartment intact, as the front and the rear of the car will crumple.
a typical 6 point cage that ends at the rear shock towers, may not significantly increase stiffness in a rear end impact , nor a head on collision. unless the entry is so far that it crumples the entire rear of the car past the shock towers? the majority of the impact may be absorbed by the car crumpling, then the cage can help prevent excessive intrustion into the driver compartment.
In a side impact wouldn't you sacrifice energy absorption for driver containment???
if you are rear ended with enough force, where the chassis deforms quite a distance, that same impact may kill you if it was directed to the side of the car. just the fact that the object that is hitting you is going to deform and enter the compartment and cause injury due to actual contact with your body.
where as driver door bars (nascar bars, X bars) for instance, may in effect transfer the bulk of the crash energy into the cage and car structure, which your body may have to absorb somewhat. but is that better then your door or B pillar residing where your drivers seat used to be seconds before? to me that means you are going to definitely have some bodily injury just from cockpit intrustion?
and now it seems like alot of professionally built cars are employing energy absorbing foam at least in the drivers door. at least I found this looking up some info on cage construction for FIA, and in other countries, some of which do not employ the traditional 1 piece main hoop.
also doesn't the race seat come into play. aren't the FIA rated seats meant to deform slightly and absorb some impact, as they are somewhat flexible? and possibly also the side mounts deforming some to absorb impact? ( is this why most FIA seats are typically side mount? because the bracket design will deform, yet still maintain connection to the floor and seat ?)
again i don't know how all these concerns play out on a partial tube, or full tube chasis car. but i think everyone here is more interested in Cage theory in a stock chassis car.
i plan on employing a 4 point roll bar and race seat in my autocross car, to stiffen the car up slightly. i don't see personally how it would be dangerous to drive this car on the street? my head will be nowhere near the Hoop.
though it will not be a daily driven car.
most cages , at least for typical unibody track cars (honda challenge, etc) , don't have any tubing from the rear shock towers to the rear of the car.
and in the front from the front of the car to the shock towers. and most don't have any tubing from the firewall to the front of the car (not to mention the extra weight penalty for tubing through the firewall)
isn't the main concern, keeping the driver compartment intact as much as possible?
a front or rear collision, the "stiffness" of the cage may not come into play much, as the vehicle is going to deform. i believe the "frame rails/unibody construction" is even designed to keep the driver compartment intact, as the front and the rear of the car will crumple.
a typical 6 point cage that ends at the rear shock towers, may not significantly increase stiffness in a rear end impact , nor a head on collision. unless the entry is so far that it crumples the entire rear of the car past the shock towers? the majority of the impact may be absorbed by the car crumpling, then the cage can help prevent excessive intrustion into the driver compartment.
In a side impact wouldn't you sacrifice energy absorption for driver containment???
if you are rear ended with enough force, where the chassis deforms quite a distance, that same impact may kill you if it was directed to the side of the car. just the fact that the object that is hitting you is going to deform and enter the compartment and cause injury due to actual contact with your body.
where as driver door bars (nascar bars, X bars) for instance, may in effect transfer the bulk of the crash energy into the cage and car structure, which your body may have to absorb somewhat. but is that better then your door or B pillar residing where your drivers seat used to be seconds before? to me that means you are going to definitely have some bodily injury just from cockpit intrustion?
and now it seems like alot of professionally built cars are employing energy absorbing foam at least in the drivers door. at least I found this looking up some info on cage construction for FIA, and in other countries, some of which do not employ the traditional 1 piece main hoop.
also doesn't the race seat come into play. aren't the FIA rated seats meant to deform slightly and absorb some impact, as they are somewhat flexible? and possibly also the side mounts deforming some to absorb impact? ( is this why most FIA seats are typically side mount? because the bracket design will deform, yet still maintain connection to the floor and seat ?)
again i don't know how all these concerns play out on a partial tube, or full tube chasis car. but i think everyone here is more interested in Cage theory in a stock chassis car.
i plan on employing a 4 point roll bar and race seat in my autocross car, to stiffen the car up slightly. i don't see personally how it would be dangerous to drive this car on the street? my head will be nowhere near the Hoop.
though it will not be a daily driven car.
08-30-2007, 12:42 PM
#37
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Re: AsS_PiRaTe
im a industrial pipe/plate welder
dont wanna weld a cage, just interested.
i recently saw a post of roll cage tubing welded directly to the car frame.
is that even safe?
...thought all tubing should be welded to plate/gussets before the sheet metal
also ,i thought fasteners were required even if the plate/gussets were welded.
dont wanna weld a cage, just interested.
i recently saw a post of roll cage tubing welded directly to the car frame.
is that even safe?
...thought all tubing should be welded to plate/gussets before the sheet metal
also ,i thought fasteners were required even if the plate/gussets were welded.
08-30-2007, 12:49 PM
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Re: AsS_PiRaTe (Quick 200k Mile Motor)
in a unibody car, you must weld in floorplates to weld the tubing too. it's size and thickness are usually determined by the sanctioning body the car will be raced in. they usually have a minimum sq inch size that the plate has to be.
for full frame cars, i believe the cage extends through the body structure and is welded directly to the frame rails.
for full frame cars, i believe the cage extends through the body structure and is welded directly to the frame rails.
08-30-2007, 02:11 PM
#41
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Re: (artifex)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by artifex »</TD></TR><TR><TD CLASS="quote">Is one allowed to mix cage materials (like mild steel and chromoly - assuming they can be welded together properly)?</TD></TR></TABLE>
I've asked this question before and never gotten an answer, so I'll make it specific. In HC, is it legal to use more than one type of metal for your cage (assuming the different types of tubing are in line with the specifications listed in the rule book)?
I've asked this question before and never gotten an answer, so I'll make it specific. In HC, is it legal to use more than one type of metal for your cage (assuming the different types of tubing are in line with the specifications listed in the rule book)?
08-30-2007, 02:51 PM
#42
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Re: (artifex)
dont think there is any advantage to using Chromoly in NASA.
according to the CCR, they Spec the same dimension tubing for both Chromoly and for Mild steel
<U>NASA spec for 2201-3000 pound car.</U>
1.5" od x 0.12" wall Chromoly / DOM mild steel
or
1.75" od x 0.95" wall Chromoly / DOM mild steel
typically the benefit of chromoly is that for a similar chasis weight you could use a thinner wall chromoly tube.
i believe SCCA, the same car could use 1.5 x .12" DOM , or 1.5" .095" chromoly.
the .095" chromoly tubing would be lighter then 1.5" x .12" DOM.
however the chromoly isn't really any lighter then the DOM mild steel in the same size.
i.e.
1.75" x .095" DOM shown as 1.679 lbs per foot
1.75" x .095" 4130 chromoly shown as 1.679 lbs per foot.
(source Onlinemetals.com)
If you could run the 1.5" x .095" chromoly in place of the 1.5" x .12" mild steel, you'd save about 0.15 lbs per foot .
according to the CCR, they Spec the same dimension tubing for both Chromoly and for Mild steel
<U>NASA spec for 2201-3000 pound car.</U>
1.5" od x 0.12" wall Chromoly / DOM mild steel
or
1.75" od x 0.95" wall Chromoly / DOM mild steel
typically the benefit of chromoly is that for a similar chasis weight you could use a thinner wall chromoly tube.
i believe SCCA, the same car could use 1.5 x .12" DOM , or 1.5" .095" chromoly.
the .095" chromoly tubing would be lighter then 1.5" x .12" DOM.
however the chromoly isn't really any lighter then the DOM mild steel in the same size.
i.e.
1.75" x .095" DOM shown as 1.679 lbs per foot
1.75" x .095" 4130 chromoly shown as 1.679 lbs per foot.
(source Onlinemetals.com)
If you could run the 1.5" x .095" chromoly in place of the 1.5" x .12" mild steel, you'd save about 0.15 lbs per foot .
08-30-2007, 03:19 PM
#43
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Re: (hybridmoments)
Must've been SCCA I was remembering. I was thinking it would improve the weight distribution in an FWD car to use mild steel in the back and chromoly in the front, at least a little bit.
thanks
thanks
08-30-2007, 03:51 PM
#44
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We need to clarify the discussion. lets limit it to race cars. Street cars with cages are too much of a compromise to be a real race car.
That said, rules say you have to have a cage. Might aswell make the most of it since you have to carry the extra weight. Use the cage to stiffen the body. If you aren't in the 12-16K lbs/deg for torsional stiffness you aren't even in the right ball park.
Chassis stiffness is of vital importance. A properly built cage will stiffen the chassis and provide the necessary levels of protection for the driver.
Most weekend warriors are better off copying the big boys. They have the engineering expertise and dollars to do the research. Although the little guys can do well with balsa wood models.
Check out these links for good papers on chassis building.
http://www.eng.clemson.edu/~lo...1.pdf
http://www.ces.clemson.edu/~lo...3.pdf
http://www.ces.clemson.edu/~lo...4.pdf
That said, rules say you have to have a cage. Might aswell make the most of it since you have to carry the extra weight. Use the cage to stiffen the body. If you aren't in the 12-16K lbs/deg for torsional stiffness you aren't even in the right ball park.
Chassis stiffness is of vital importance. A properly built cage will stiffen the chassis and provide the necessary levels of protection for the driver.
Most weekend warriors are better off copying the big boys. They have the engineering expertise and dollars to do the research. Although the little guys can do well with balsa wood models.
Check out these links for good papers on chassis building.
http://www.eng.clemson.edu/~lo...1.pdf
http://www.ces.clemson.edu/~lo...3.pdf
http://www.ces.clemson.edu/~lo...4.pdf
08-31-2007, 03:12 AM
#45
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Re: (Mr.E.G.)
I would much rather hit my head on the stock chassis than a piece of roll cage tubing. You can dent a piece of sheet metal (even one that's been folded to stiffen it) with a good kick or your head (not that I'd want to). But try to put a dent into a piece of tubing without a good sized hammer.
Also, your argument about space isn't quite there. If your head is 6" away from metal stock, that's exponentially better than being 2" away from a piece of roll cage.
The trucks that we take to rigs scare the hell out of me. They're Land Cruisers which have a 6 point cage installed with the halo circling the rear seats and the front down bars are basically at the B-pillar.
First, they're made from square tubing. Second, they're wrapped in round foam. Your head sits basically against it while driving, and the foam is compressed around the tightly radiused corners of the tubing. The only thing that makes me feel ok is that they're speed limited to 60 km/h when we're off paved roads.
Also, your argument about space isn't quite there. If your head is 6" away from metal stock, that's exponentially better than being 2" away from a piece of roll cage.
The trucks that we take to rigs scare the hell out of me. They're Land Cruisers which have a 6 point cage installed with the halo circling the rear seats and the front down bars are basically at the B-pillar.
First, they're made from square tubing. Second, they're wrapped in round foam. Your head sits basically against it while driving, and the foam is compressed around the tightly radiused corners of the tubing. The only thing that makes me feel ok is that they're speed limited to 60 km/h when we're off paved roads.
08-31-2007, 07:13 AM
#46
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Re: (artifex)
According to NASA NO, it is not legal to mix different tubing types.
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by artifex »</TD></TR><TR><TD CLASS="quote">
I've asked this question before and never gotten an answer, so I'll make it specific. In HC, is it legal to use more than one type of metal for your cage (assuming the different types of tubing are in line with the specifications listed in the rule book)?</TD></TR></TABLE>
Here's the thing about chromoly; Chromoly maybe stiffer blah blah etc. blah blah blah. Stiffer is not better, a cage needs to be able to deform to disperse energy. Most of the people here are smart enough to realize that but for all the rice boys out there with their chromoy roll hoops and other mad tight nonsense, they need to realize that Chromoly maybe stiffer/stronger. However it is no way shape or form safer. The other problem that you run into with 4130 chromoly tube is that when welded it needs to post weld heat treated. If it's not post weld heat treared you will have embrittlement around the haz area in the weld, and In a serious impact the tube may fail at that point.
Best example I can give is a friend of mine at the Baja 100 last year. He was in a trophy truck, crusing through a dry lake bed at maybe 100 mph, maybe a lot less, hit a abandoned car, the whole front end of the tube fram chromoly truck sheared off right in the HAZ area, allbeit and extreme example, it's an example none the less.
Refer too the above. As far as Super Gt cars or their american equivalent ALMS GT1, I beleive it varies per racecar designer and constructor
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LumpyTheGrumpyCamshaft »</TD></TR><TR><TD CLASS="quote">what about roll cage materials, whats the different levels, pro's con's. What do they use material wise in jgtc/supergt cars.
</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by artifex »</TD></TR><TR><TD CLASS="quote">
I've asked this question before and never gotten an answer, so I'll make it specific. In HC, is it legal to use more than one type of metal for your cage (assuming the different types of tubing are in line with the specifications listed in the rule book)?</TD></TR></TABLE>
Here's the thing about chromoly; Chromoly maybe stiffer blah blah etc. blah blah blah. Stiffer is not better, a cage needs to be able to deform to disperse energy. Most of the people here are smart enough to realize that but for all the rice boys out there with their chromoy roll hoops and other mad tight nonsense, they need to realize that Chromoly maybe stiffer/stronger. However it is no way shape or form safer. The other problem that you run into with 4130 chromoly tube is that when welded it needs to post weld heat treated. If it's not post weld heat treared you will have embrittlement around the haz area in the weld, and In a serious impact the tube may fail at that point.
Best example I can give is a friend of mine at the Baja 100 last year. He was in a trophy truck, crusing through a dry lake bed at maybe 100 mph, maybe a lot less, hit a abandoned car, the whole front end of the tube fram chromoly truck sheared off right in the HAZ area, allbeit and extreme example, it's an example none the less.
Refer too the above. As far as Super Gt cars or their american equivalent ALMS GT1, I beleive it varies per racecar designer and constructor
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by LumpyTheGrumpyCamshaft »</TD></TR><TR><TD CLASS="quote">what about roll cage materials, whats the different levels, pro's con's. What do they use material wise in jgtc/supergt cars.
</TD></TR></TABLE>
08-31-2007, 12:47 PM
#47
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Re: (Ekasey)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Ekasey »</TD></TR><TR><TD CLASS="quote">However it is no way shape or form safer. The other problem that you run into with 4130 chromoly tube is that when welded it needs to post weld heat treated. If it's not post weld heat treared you will have embrittlement around the haz area in the weld, and In a serious impact the tube may fail at that point.
Best example I can give is a friend of mine at the Baja 100 last year. He was in a trophy truck, crusing through a dry lake bed at maybe 100 mph, maybe a lot less, hit a abandoned car, the whole front end of the tube fram chromoly truck sheared off right in the HAZ area, allbeit and extreme example, it's an example none the less.</TD></TR></TABLE>
Ekasey
This is exactly what I was going over with a "redneck" welder today
when we talked about chromoly tubing. He had know idea what post heating was. I told him.. he'll need to post heat it with a torch and basically, delay the cooling.
I usually give it some heat up to 1200deg (using a one of those tempsticks). Oh, and also preheat to at least 300deg before welding.
Chromoly becomes very brittle in the HAZ just as you mentioned.
Best example I can give is a friend of mine at the Baja 100 last year. He was in a trophy truck, crusing through a dry lake bed at maybe 100 mph, maybe a lot less, hit a abandoned car, the whole front end of the tube fram chromoly truck sheared off right in the HAZ area, allbeit and extreme example, it's an example none the less.</TD></TR></TABLE>
EkaseyThis is exactly what I was going over with a "redneck" welder today
when we talked about chromoly tubing. He had know idea what post heating was. I told him.. he'll need to post heat it with a torch and basically, delay the cooling.
I usually give it some heat up to 1200deg (using a one of those tempsticks). Oh, and also preheat to at least 300deg before welding.
Chromoly becomes very brittle in the HAZ just as you mentioned.
08-31-2007, 01:13 PM
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Chromoly won't become brittle if you weld it with the right rod but it will anneal the weld joints. If you use a ER70-S2 or ER80S-2 you won't have to heat treat and it will be pretty close to the strength of the parent material.
08-31-2007, 09:14 PM
#49
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Thread Starter
Re: (Kookz)
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Kookz »</TD></TR><TR><TD CLASS="quote">I would much rather hit my head on the stock chassis than a piece of roll cage tubing. You can dent a piece of sheet metal (even one that's been folded to stiffen it) with a good kick or your head (not that I'd want to). But try to put a dent into a piece of tubing without a good sized hammer.
Also, your argument about space isn't quite there. If your head is 6" away from metal stock, that's exponentially better than being 2" away from a piece of roll cage.
The trucks that we take to rigs scare the hell out of me. They're Land Cruisers which have a 6 point cage installed with the halo circling the rear seats and the front down bars are basically at the B-pillar.
First, they're made from square tubing. Second, they're wrapped in round foam. Your head sits basically against it while driving, and the foam is compressed around the tightly radiused corners of the tubing. The only thing that makes me feel ok is that they're speed limited to 60 km/h when we're off paved roads.</TD></TR></TABLE>
you completely misunderstood the distance comment i made. please reread my comments, and if it still doesnt make sense then i'll rewrite it. im not being sarcastic. sorry if that sounds harsh due to reading it in print.
Also, your argument about space isn't quite there. If your head is 6" away from metal stock, that's exponentially better than being 2" away from a piece of roll cage.
The trucks that we take to rigs scare the hell out of me. They're Land Cruisers which have a 6 point cage installed with the halo circling the rear seats and the front down bars are basically at the B-pillar.
First, they're made from square tubing. Second, they're wrapped in round foam. Your head sits basically against it while driving, and the foam is compressed around the tightly radiused corners of the tubing. The only thing that makes me feel ok is that they're speed limited to 60 km/h when we're off paved roads.</TD></TR></TABLE>
you completely misunderstood the distance comment i made. please reread my comments, and if it still doesnt make sense then i'll rewrite it. im not being sarcastic. sorry if that sounds harsh due to reading it in print.
09-01-2007, 01:47 AM
#50
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Re: (turboteener)
Sorry but this is incorrect. It's a known fact that this happens regardless of the rod.
To be 100% honesty i'm way too damn tired, and lazy to dig up the engineering data on it but here's the long story short. Helicopter frames are thin wall chromoly tube, TIG welded, and then post weld heat treated, due to the embrittlement produced during the welding process
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turboteener »</TD></TR><TR><TD CLASS="quote">Chromoly won't become brittle if you weld it with the right rod but it will anneal the weld joints. If you use a ER70-S2 or ER80S-2 you won't have to heat treat and it will be pretty close to the strength of the parent material.</TD></TR></TABLE>
To be 100% honesty i'm way too damn tired, and lazy
to dig up the engineering data on it but here's the long story short. Helicopter frames are thin wall chromoly tube, TIG welded, and then post weld heat treated, due to the embrittlement produced during the welding process<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by turboteener »</TD></TR><TR><TD CLASS="quote">Chromoly won't become brittle if you weld it with the right rod but it will anneal the weld joints. If you use a ER70-S2 or ER80S-2 you won't have to heat treat and it will be pretty close to the strength of the parent material.</TD></TR></TABLE>