Travis R

Ooo, you've got a lathe. Nice.

cagedruss

Here is a couple of more pics on the Pro 7. Promise to have it done tomorrow. List gets bigger everyday to finish it off.

There has to more people out there that has not posted pics of their race car cages, please share!

Dick Elliott

Your welding 1020 (mild steel-cold roll) to 4130 (chrome-moly)? I always though that was a big no no. How are you normalizeing the 4130 welds? DICK.

cagedruss

This is a 1020 cage (mild Steel).

ER70S-2 is highly recommended for welding 4130 chrome-moly tubing in many applications since you can't easily put an entire car into an autoclave to control the heat and cooling, you are better off to use the above material.

ER80S-D2 is recommended for welding 4130 chrome-moly tubing if a higher strength, less ductile weld is required. ER80S-D2 filler metals contain a high level of deoxidizers (Mn & Si) to control porosity when welding with Co2 as the shielding gas, and molybdenum for increased strength.


If your weld will be heat treated to obtain optimum strength, then use a filler metal which matches the chemistry of your tubing, which neither 70S-2 nor 80S-D2 wires do. Surprisingly, only 2.3% of Chrome and Mollybenduim alloy material is added to give this 4130 its superior strength.

Dick Elliott

ONE of the reasons to add a cage to any car, is to add rigidity to that car. That stated, why do SCCA cage builders do not make the cage symmetrical? Your own car has NASCAR bars on the drivers side and an X bar on the passanger side. Now everthing I learned in school tells me the car will flex differently when put through a right turn and then a left turn. Look at a NASCAR road race car and you will see both sides of the cage look pretty much the same except the "PETTY" bars. Looks like to me, you would want the door bars of both sides of the car to be the same, reguardless of their shape. Both Nascar or both X bars, but not one of each. If your building an IT car, you need as much rigidity as you can get IMHO. After all, without a frame, the car is just one big torsion bar to start with. Help it all you can please. DICK.

cagedruss

You are correct, but most cars do not have the same door bars on both sides. SCCA regulates door bars per class. I am not allowed to open the passenger side door to put in the NASCAR type bars. I am allowed on the driver's side.

The reason for the door bars is to protect the driver in a side impact. Cage is meant to protect driver first and foremost, not to gain advantage for chassis stiffness. I do believe it is actually a rule in this class. I am gaining chassis rigidity through the main hoop, which is also the foundation for the cage. With the rest of the cage installed he will notice a big difference in chassis stiffness.

I could have added a x on the driver's side along with the side protection, but I did not want to add the extra weight to the left side of the car. I would prefere to go through a side impact with these door bars over an "X" bar anytime.

I worked on the Driver's door aluminum panel today, spent to much time on it. My loss is Rick's gain.

Dick Elliott

There are MANY people out there who think that a SCCA NASCAR type door can hurt you more in a side impact than a X bar because its not really a NASCAR bar to start with. Its only tied to the cage at each end, and will fold inward if hit in a side impact. Very few PRO/TOURING road race cars have Nascar bars. Almost all have X bars on both sides. Hey I watch them on FOX SW all the time. But then they don't have SCCA rules do they. DICK.

cagedruss

If the door bars are 44" wide, and the x is flat and is 44" wide, it will bend through out the whole 44". The NASCAR bars are 44" at the mounting points and usually about 24" wide between the bends. Load is transfered throughout the flat to the bent bar at the attaching point. Much stronger, plus it is 4-10" further away from the driver's seat. May not be an actual 4 bar NASCAR bar with uprights every 8-10" and tied into the main frame rail, but it is better than nothing. If more people bitched to the Sanctioning bodies to allow more attaching points, things may actually change.

I have seen both in impacts and would argue that the people who say it is worse needs to investigate it further. All fast classes are now required, like GT and Touring. Most likely all IT car will be required to do so in a few years.

I really need to have somebody explain how a straightline _________ is better for side impact than a \______/.

cagedruss

Here are some examples from Rolex Sports cars built from around the world. As you see there are X's and NASCAR. X's sre for frontal impact and NASCAR for side impact!

These are in BMW's, Porches, and Corvettes.

Speed Raycer

The main reason most proponants of the X bar over the nascar bar site is that \_____/ can become _/-------\_ with enough force. There is enough material there to be bent inward as much as outward. With the X, there's no additional material to be bent before the impact pulls on the main hoop.

There is a great discussion on X vs Nascar bars on the sr20 Nissan board... I'll find the link if I can.

Russ, you are a wealth of info. This has become one of the better cage threads on the web.

jimeby

iTrader: (1)

I agree with you, Russ. We should be allowed to tie the door bars into the door sill/frame rail. I tied my door bars into the door sill for more crash protection. This changed my 8 pt cage to a 10 pt cage. I originally built the car for circle track where that wasn't an issue. (In fact, most upper class stock car rules require this.) When I got tired of replaceing body panels and struts every week I switched to SCCA & Conference racing. The extra attachment points could be an issue if pressed, but the inspectors approved the cage as built without comment.

cagedruss

All depends on which class you are running. ITE, Prod, and SP all allows it.

jgrewe

iTrader: (1)

Back when Super Touring was running here, a friend had a car that had been built in England for Honda's effort there. The car had and X in the drivers side and attached to it was a really cool, hi-tech carbon fiber over honeycomb crash absorbing 'pod'. Any body know if something like this is available still? Or do I have to fire up my autoclave and make my own?

1985_RX-7

Nothing too special, everything will be painted soon.

Dick Elliott

Now thats GREAT NASCAR door bars. Best I've seen in a long time. Whats on the other side of the car? Whats not good is the window net POP riveted to the upper bar. POP rivets require holes, and thats a no no even at our local dirt track. Show us some more pictures of the cage. DICK.

jimeby

iTrader: (1)

Hi Dick: Thanks for the complement. There are other pics of the cage on page 4 of this thread https://www.rx7club.com/showthread.p...ghlight=jimeby
I was sure someone would nail me on the POP rivets. But not for drilling holes in the door bar... I was expecting to hear that it wasn't sturdy enough to hold the net in a bad crash. There are varied opinions on this and I still may change my mount method.
Has anyone seen evidence of tubes failing from 3/16" holes as I have drilled?
Russ: Thanks for your input. I know the upper classes allow more attachment points. Unfortunately, this car is kind of a Frankenstein car. When building it, I did some things that make it questionable for PRO7 which is the best class for this car. Now, I run it in the local Radial Sedan class which is kind of a catch all class for cars like mine that don't really fit any class rules.

rynberg

For a car that sees street and track duty (no racing, just HPDEs), what do you experts think of the M2 rollbar with rear diagonal support:

http://www.m2performance.com , click on the rx7, click on the safety, base bar is shown in the top 3 pics, the bottom 2 pics show the rear support diagonal added in.

The bar is 1.75 x 0.12 chromoly.

Thanks for your opinions.

cagedruss

Looks to be a nice kit!

rynberg

Cool, I have an opportunity to pick up an M2 rollbar used at a very fair price....thanks for posting.

Travis R

I don't like how the shoulder harness attaches at all. But the bar itself looks fine.

rynberg

Could you explain why? There is also the option to use the shock tower brace part of the bar.

Travis R

It seems like the eye bolt is going to be the weak link in the system... and if it fails you are no longer restrained.
Hopefully they've done their homework and the bolt is strong enough. But there are a couple of ways they could have done it differently to make it really strong... either looping the strap around the tube entirely, or welding in a gusseted plate for the harness to bolt to.
It's just one of those "if" scenarios people like to play...
*if* you crash, it *might* fail, etc.
It looks like the shock tower version uses the same threaded eye bolt... so not any better IMO.
For what you're doing it will probably "work".
No math was harmed in the formation of this opinion.

rynberg

Yes, I will not be racing the car, just HPDEs. Would you advise trying to wear the stock seatbelt in addition to the 5-point harness while on the track?

cagedruss

The eye bolt is probably fine if it is the cad plated forged bolt that comes with the harness kits. Bolt has a very high shear rate. Multiply your upper body mass by 10 plus 500lbs to be safe, bolt probably has a 5000lb plus on it shear. Figure out the leverage on the bolt by the strap brackets. Plus the load that it is supporting has give to it under compression which softens the force, compared to a suspension point or chassis part.

We wrap the strap around the whole bar and secure from side to side to keep it from moving.

I really would not worry about it much, your brain can't handle the force it would require to shear that bolt any way, most likely, but who really knows for sure?.

Speed Raycer

This thread's been in hybernation too long!!! Here's a 10 sec. Miata cage I just finished.





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