Criticize my roll cage design

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BrazilianZ28Camaro
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Criticize my roll cage design

Post by BrazilianZ28Camaro » Mon Nov 02, 2015 2:08 pm

Hello Gents,

I tought would be a good idea to hear your opinions abou my roll cage & subframe design. I built it by myself with 1 3/4" mild steel tubbing to my '71 Z28 street strip machine.

My car also have subframe connectors made with 40mm square tubbing welded at the rear frames and to the floor reinforcements under the seats and is bolted to a plate on the H-member.This way you can remove the H-member when needed.

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The Roll Cage have ten attachment points, two under the dash, welded to a reinforced L plate with is welded to the floor pan and the side sheetmetal next to the A-pillar. The plates have four M8 allen bolts attached to a undercar 1 7/8" tube, welded to the H member:

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The main loop is welded to a 4mm thick L plate welded to the floor and B-pillar base. The diagonal bar behind the seats go through the floor and is directly welded on the subframe square bars:

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The next two bars are welded from the main loop to the 4mm thick plates welded on the top of the shock towers :

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The rear bars wich extend through the rear seat sheet metal are welded to 4mm plates welded directly above the framerails to hopefully stop any movement there while launching. The rear "X" is welded tho those bars and to the main loop:

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Be cool with me, this is the very first roll cage I built ..took me three hours to fabricate each bar and two full saturdays to weld everything...plus three full days to paint it...lots of work for sure :)

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Lets hear ya!
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: Criticize my roll cage design

Post by ProPower engines » Tue Nov 03, 2015 12:29 am

Having working in a chassis shop for many years there is several key things you missed.
The cross bar that goes behind the seat diagonally to the lower mounting point of the main hoop to just about below the drivers window opening as well as the cross bar just below the holes in the seat going from side to side to mount the belts to as well as a tie bar from that tube to the lower cross bar also missing just about the floor.
And the seat belts look like they come from the stock mounting points on the upper door post area also not recommended for a race car.Do you not use a 5 point racing harness??Not the old Y style belts but 5 separate belts which include an anti-submarine belt attached to the seat mounting in from of your seat in the crotch.
And the seat appears to be attached to the floor not suspended from the main cage structure.Bad things can happen in a crash. Seen that many times where the belt mounts come loose when the car folds up or tries to cut the driver in pieces like a knife when the seat goes one way and the cage goes a different way in a crash.

Now I get it that it is not NHRA approved design or materials but wondering what wall thickness tube you used?? .065 .095 or .120 wall for the main cage hoop above the driver??

Most sanctioning bodies such as NHRA say .120 wall but to get that you have to use .134 wall because of the mill tolerance if using ERW tube.
DOM tube while closer is not right on the money for size either. It can be had but you have to check lots of tube to get it.

My point is that the driver needs some further protection just to be safe on the track to prevent the sides of the cage from collapsing inward as well as the seat from moving independently from the cage if stressed in a side impact or roll over.

The job quality looks good to this point it just needs some more work to finish.
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Re: Criticize my roll cage design

Post by BrazilianZ28Camaro » Tue Nov 03, 2015 2:28 pm

ProPower engines wrote:Having working in a chassis shop for many years there is several key things you missed.
The cross bar that goes behind the seat diagonally to the lower mounting point of the main hoop to just about below the drivers window opening as well as the cross bar just below the holes in the seat going from side to side to mount the belts to as well as a tie bar from that tube to the lower cross bar also missing just about the floor.
And the seat belts look like they come from the stock mounting points on the upper door post area also not recommended for a race car.Do you not use a 5 point racing harness??Not the old Y style belts but 5 separate belts which include an anti-submarine belt attached to the seat mounting in from of your seat in the crotch.
And the seat appears to be attached to the floor not suspended from the main cage structure.Bad things can happen in a crash. Seen that many times where the belt mounts come loose when the car folds up or tries to cut the driver in pieces like a knife when the seat goes one way and the cage goes a different way in a crash.

Now I get it that it is not NHRA approved design or materials but wondering what wall thickness tube you used?? .065 .095 or .120 wall for the main cage hoop above the driver??

Most sanctioning bodies such as NHRA say .120 wall but to get that you have to use .134 wall because of the mill tolerance if using ERW tube.
DOM tube while closer is not right on the money for size either. It can be had but you have to check lots of tube to get it.

My point is that the driver needs some further protection just to be safe on the track to prevent the sides of the cage from collapsing inward as well as the seat from moving independently from the cage if stressed in a side impact or roll over.

The job quality looks good to this point it just needs some more work to finish.

This roll cage is in a low ten second ET, street-strip car. I mentioned it have ten points, but it really isn't like a NHRA certified ten point rollcage, certainly.

You see the main loop haven't the diagonal bar crossing side to side , because I need that space to carry the slicks to the strip.

I used .100" wall mild steel tubing. This is ok with our regulations.

Yes ,the seats are fixed on the floor and I have the stock four points seat belts on the car.

My main concern with this topic is to have opinions from experts about the rigity and eficiency of this design to actual power level (around 620-650 hp) because I'd hate to bend the car at launch.

First time I drove the car with this cage, I felt instantly the chassis more rigid, and the car accelerate straight than before, so I do know it makes a difference, but would like to hear from experts about its efficiency to tie the chassis.

So far the car is running well and straight, best sixty foot is 1.52s and may improve.

I thank you for the explanations about design and do understand your points about safety.I'll think carefully about that =D>
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: Criticize my roll cage design

Post by ProPower engines » Tue Nov 03, 2015 3:42 pm

I get convenience is a priority but life is worth more.
But as far as the extra space needed for tires well its your ass in the seat so that said even a 10 sec car can kill you with the belt set up you have in there and lack of seat support is asking for life in a wheel chair. There is absolutely nothing to keep you from sliding out of the belts and under the dash in a crash.
At the very least you can fab up a bolt in system for the seat and belt support which is fine and I have built many over the years for street/strip cars.

Make up some tube collars that will allow you to slide in the supports before racing that way the belts have a chance to do their job and it can be removed for the drive home have been the safety inspector at the local track for about 25 years and I have seen and heard every excuse in the world why guys can't or don't want to be as safe as possible when it comes to seat belt mounting and usage.And it always comes down to the car is considered finished and painted and no one wants to do anymore after that.

Its all fun till you or some one else gets hurt. Thats how safety rules get improved but its always too late by that time.
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Re: Criticize my roll cage design

Post by BrazilianZ28Camaro » Tue Nov 03, 2015 5:36 pm

ProPower engines wrote:I get convenience is a priority but life is worth more.
But as far as the extra space needed for tires well its your ass in the seat so that said even a 10 sec car can kill you with the belt set up you have in there and lack of seat support is asking for life in a wheel chair. There is absolutely nothing to keep you from sliding out of the belts and under the dash in a crash.
At the very least you can fab up a bolt in system for the seat and belt support which is fine and I have built many over the years for street/strip cars.

Make up some tube collars that will allow you to slide in the supports before racing that way the belts have a chance to do their job and it can be removed for the drive home have been the safety inspector at the local track for about 25 years and I have seen and heard every excuse in the world why guys can't or don't want to be as safe as possible when it comes to seat belt mounting and usage.And it always comes down to the car is considered finished and painted and no one wants to do anymore after that.

Its all fun till you or some one else gets hurt. Thats how safety rules get improved but its always too late by that time.

Ok thanks for the suggestions I'll think how to fabricate the seats supports and will get five point seat belts soon.

Have you any comment regarding the cage anchor points I selected and their effectiveness to stiffen the body?
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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Re: Criticize my roll cage design

Post by ProPower engines » Tue Nov 03, 2015 8:19 pm

I appears that you just welded plates to the stiffer parts of the floor which is OK but we would add a wing off the sub frame and fit it through the floor carefully to mount the cage to. This would also allow the wing to be stitch welded to the floor boards for add'ed stiffness.
In your case it can be done later in the off season.

You can take a piece of 2 inch 120 wall about 4-5 inches long and weld 3/4" slugs of tube with 3/8" holes in them welded on the sides of the tube then cut the tube length wise in half ( 2 pieces ) to make a clamp that will fit your cage.
Its similar to the many styles of bolt on mounting brackets used in most class's of circle track and drag racing today up here.You may have to have a slight down angle on one side to make it easy to remove. Some test fitting is needed not not a big deal to do and will make you car safer by allowing you to mount the belts correctly. Seen a guy in the street class break an axle this past week end and back into the side wall at half track and his stock type bucket race seat bent backwards allowing him to be injured

Then fit a tube to the main hoop behind the driver and weld it to the clamp as this will allow the cross bar to be removed easily when needed and re-installed at the track.
This is similar to the way some door slammers are done to pass tech at the track yet still be street legal by not hindering the access to and from the car.

Padding on the bars in the drivers side will keep the bumps and bruises to a minimum as well. Get the padding the stock car guys use on the pipe insulation as it will deteriorate over a short time inc your weather :D
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Re: Criticize my roll cage design

Post by ZIGGY » Wed Nov 04, 2015 9:03 pm

Don't have anything to add to Pro's excellent cage advice but the bar padding is most important to
protect you from "bumps and bruises" that can break bones and scramble your brains. If you crash,
God forbid, your body and your safety belts stretch. You'd be astonished at how much is possible.
You don't want your head or your limbs bouncing off the steel bars. Particularly on bar areas near your
head, use dense SFI-rated padding. Anybody who has been around circle track racing for a while has
seen the results of ignoring safety concerns. Doubtless you won't have as much exposure but the risk
is there no matter how you choose to go fast. Believe it.

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Re: Criticize my roll cage design

Post by ProPower engines » Thu Nov 05, 2015 1:20 am

ZIGGY wrote:Don't have anything to add to Pro's excellent cage advice but the bar padding is most important to
protect you from "bumps and bruises" that can break bones and scramble your brains. If you crash,
God forbid, your body and your safety belts stretch. You'd be astonished at how much is possible.
You don't want your head or your limbs bouncing off the steel bars. Particularly on bar areas near your
head, use dense SFI-rated padding. Anybody who has been around circle track racing for a while has
seen the results of ignoring safety concerns. Doubtless you won't have as much exposure but the risk
is there no matter how you choose to go fast. Believe it.

SFI belts stretch 30% for their length. Stock automotive belts can be muck more depending on the width and thickness of belts.
Real Race Cars Don't Have Doors

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Re: Criticize my roll cage design

Post by melancia » Thu Nov 05, 2015 12:29 pm

Lindo! Parabéns!!!!

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Re: Criticize my roll cage design

Post by BrazilianZ28Camaro » Thu Nov 05, 2015 2:14 pm

melancia wrote:Lindo! Parabéns!!!!
Valeu!
'71 Z28 Pro-Street Camaro
Pump gas -T-ram - All motor SBC 427"
3308 lbs- leaf spring/Caltrac Car
29x10.5 Hoosiers
New best 1/8 mile ET
1.45 60' / 4.12 330' / 6.38@109mph :D

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