Thinking of a full cage for my car???

[norvalwilhelm]

I have been thinking more and more about installing a cage, not a roll bar but a full cage.
I want the rigidity that it provides plus I am starting to play harder and harder and want the protection.
I have built a number of cages in the past and the car really feels different afterwards. I particularly notice it pulling into driveways. The car feels really solid.
IN the past I have only built them of 1 5/8th stainless for good looks and my pipe bender can do a good job on that size but they weight too much for my vet.
I am looking into chrome moly but the down side is the price and far worse HOW to weld??
Tig is the only solution that I know because you have to use 4340 wire as filler. Also tig is more controlled going around each joint.
A rear roll bar is simple because the frame is exposed in the wheel well and you can plate the frame on top and weld the bar to it.
I do want a full bar over the top of the windshield and comming down the window posts in front. I also want a bar through the floor connecting as far into the engine compartment as possible.
I also want side bars. They will have to be swing out, I am not going to crawl over any bar. The mustang has more room and the wife would not be impressed with climbing over a side bar regardless of how safe it is.
Bending chrome moly might also be a problem and until I can get a sample piece I don't know how good a job I could do.

I just wieghed a piece of stainless that I have been using in cages and it weighs 14 ounces to the foot. That is nearly 1 pound for every foot of tubing. The lengths add up fast so chrome moly is the only answer.

I would also like to glass all bars into the floor for water/weather/sound proofing and wonder if the body flexes enought to break the joints.
When the car is blocked up for working on the underside you also have to make sure the car is sitting level so any twisting of the frame is eliminted and at the same time the bar holds whatever twist you have already put in the frame.
Might be a good time to pretwist the frame so the passengers rear is lower and the drivers front is higher.
Our cars tend to have a problem across these corners.
What do you guys think?????

 

[Fuelie]

Hi Norval,

I think with the calibre of car that you have built, that a full cage is an excellent idea. Just as you mentioned, these cars are very flexible in their original form and benefit greatly from some increase in structural rigidity. Having had a blown BB street car in my past I can relate to the amount of torque that you are putting through the car. Do the full cage!

As for the material, I agree that the chrome moly is the answer. The fact that it needs to be TIG welded is not a drawback as I feel that all cages should be done with TIG. Although during the past years I have built my share of mild steel bars / supports and cages with mild steel tubing.

I have not bent any CM tubing, but was under the impression that it should not be any more difficult to bend than your stainless. Let me know how your test peice comes out.

As for glassing the floor at the pass through points for the cage, I would look at some sort of rubber seal instead. The cars may be too flexible for a "solid seal" at the tube pass through.

These are just some thoughts.

BTW do you own a TIG welder? I am presently in the market for one and will probably purchase in the next few weeks. I would value your opinions on a machine for hobby car use.

Love your car!

Brian

 

[Ken]

For the floor area around my bar we first glassed it in so that the gap was not as wide, then we filled that area with silcone sealer. That provides the flexibility I needed for mine.

 

[SG4206]

I suggest getting a NHRA and SCCA rule book for guidance. I always hear " I'll never enter a real sanctioned event" , well the next thing you know your car isn't legal for anything and you really wanted to try the car out just once on a real race track. And , the re-sale value is much better if it's able to be certified.
Just a thought---

I cut alum. templates to pop rivet around the bars to cover the gaps between the bar and fiberglass. The outside edges can be round or square shaped.

 

[norvalwilhelm]

Fuelie I do have tig facilities in the shop but the unit is years old and made is sweden. It is a good unit, works great but no available anymore. I do stainless exhausts with it and stainless roll cages.
As for moly I am being talked out of it. We build a Indy car chassie each year from chrome moly and while being light it is tough for weld properly and it doesn't stand up as well as mild steel.
Listening to very knowledgable people talking and I am loosing my desire for it. I might end up with mild steel just because they say it is better in a street driven car and over the years will stand up better.
Our cars do flex and I have a 6 point cage in the mustang and you can feel the rigidity. Pulling in a driveway you can feel the car flex but the mustang just feels so much better.
I can always but a extra tooth or two in the blower pulley to make up the weight difference. LOL

 

[norvalwilhelm]

I suggest getting a NHRA and SCCA rule book for guidance. I always hear " I'll never enter a real sanctioned event" , well the next thing you know your car isn't legal for anything and you really wanted to try the car out just once on a real race track. And , the re-sale value is much better if it's able to be certified.
Just a thought---

I cut alum. templates to pop rivet around the bars to cover the gaps between the bar and fiberglass. The outside edges can be round or square shaped.

That is a good idea. A chassie shop near me would have all the information I need to be legal. A friend builds tube frames, cages and tubing for a living and he would certainly give me all the help I want. He just never has done a corvette.
I like working with fiberglass and want to try glassing first to totally seal off the area. I hate noise, wish my blower would stop whinning, I want quiet mufflers but will not sacrafice performance to gain these things. I will insulate everything very well