Another roll cage question

[Motorcitydak]

I am in the planning stage of a roll cage for my car. Rite now I have small rope going around the car to help me plan out the tube placement. I had originally thought that I would cut holes in the floor next to the rockers to allow the bottom of the A and B pillar bars to drop down a little. This would allow me to weld the tops of the joints. Then I could build stands to weld to the rockers and then the tubes to that.

When I got to laying it all out, it looks like a better idea would be to place the tubes rite onto the rockers. The problem now is that I want the bars to be really high up and out of the way making it impossible to weld the tops of the joints unless Id cut holes in the roof (not doin that).

Now, Im thinking about going about it another way. What about if I cut the tubes short, say maybe 4 inches. That would allow it to be far enough away from the roof to get at the joints. I can then sleeve the bottom of the tubes with another piece of tube. Maybe 6 inches long, it would fit on the outside of the tube and be in place loose during assembly. After the joints are done up, Id just push the cage up and weld those telescoping ends in position with a plug weld or two on the sides along with one bead on the top to secure it to the cage and then to the rocker.

Has this been done before? or is there another way of doing it that Im not thinking of?

[67zo6Camaro]

Lots of different ways to get a fully welded gage in a car. However, some ways are not allowed by racing groups. Depending on your answer about what the car is going to be used for, street only vs. some track days, may indicate your direction. B pillard hoop, halo and front A pillard down bars are typically one piece bends. There are some tricks to getting these in the car fully welded and up tight against the interior roof. So whats the car going to be used for?

Brett
Fab53.com

[Motorcitydak]

Good points. The car will be mostly a street car that I can take to open track days and autoX stuff. The ultimate goal however is open road racing stuff if I can ever find some on my side of the country (Silver State Classic type stuff). I do not have any decent regular racing going on around me that I am aware of so I do not have a specific bracket or class that I have to follow the rules for. Im going more with an overall safety/chassis stiffening approach. The cage will be welded to the A pillar and will capture the B pillars seat belt bolt on the roof.

Another point you made about the bars being one piece. Just to clarify because I think I understand what you said. Are the A pillar bars supposed to run up from the floor, make a few bends to follow the A pillar then another at the roof to continue back to the B pillar hoop? Then a single piece going between the 2 A pillar bars? Or the Halo you said. Going forward from the B pillar hoop to meet up with the A pillar bar at the roof line, carry across the top edge of the windshield making another bend at the other A pillar corner to go back to the B pillar

If I make the B pillar hoop then weld a halo to it, those weld would be easy since I can just tip the cage forward since there is no A pillar yet. That would make the A pillar welds the hard ones to get to, as well as the ones for the bars running rearwards to form the C pillars

[67 ls1 vert]

Your idea about the telescopic tubes has been done lots of times. It allows you to make the necessary welds and height adjustments to get the top up tight.

[67zo6Camaro]

Your last statement is the typical way I would do it. Bend and fit the B pillard with 1/8 mounting plates already welded to the floor. Stand the B pillard support up and strap into place with tie downs, then bend and fit halo that goes from B pillard hoop to the front of the top of the windshield. After fitting, then tack in place before tilting down. You can also use a support at windshield and tie downs to the top of the B pillard hoop here. Tilt down if needed to weld halo to B pillard hoop. Support both into position and fit as necessary, then weld the B pillard hoop to the floor plates already welded to the car. The best way to get the A pillard in is to remove the windsheild. You'll need to test your tig welding skills hear by using a gas filter on your tip, leave that electrode out +-1" or so, turn up the argon and get that weld up top. Not easy, but do..able. This typical set-up fits most race group requirements. Just remember, all down tubes to the floors or sills must have 1/8 backing plate. Lots of options and styles for cross bars and additional supports. Try to use 1 5/8 .083 4130 chromoly tubing if you can. It welds up much cleaner when using a tig and has a strength and weight advantage.

Brett
Fab53.com

[Motorcitydak]

Your idea about the telescopic tubes has been done lots of times. It allows you to make the necessary welds and height adjustments to get the top up tight.

Ok, good to know. I just did not want to use some new renegade idea that would end up failing or weakening my cage. Good to know that its a tired and true idea.

My car does not have a windshield rite now so that is a plus. Its just a shell rite now so I do not have an interior to worry about either

I was planning to use 1.75 0.095 DOM but I could use the 1 5/8 chromo tubing since I have not bought the tube or die for my bender yet but all I have is a MIG to stick everything together

[67zo6Camaro]

Yes the mig....that will limit your clearance, and typically if you are using a mig then stick with the dom.

Brett
fab53.com

[Motorcitydak]

Ok, ill stay with the DOM then. You think 1.75 0.095 is a good size? I landed on that size after reading an SCCA rulebook iirc. I want the car to be at or below 3000#. Im pretty sure it said 1.75 0.095 for anything >3000#. I think it also stated I could use a smaller (1 5/8 maybe) with a slightly thicker wall

[67zo6Camaro]

Yes that's about the typical size in dom. But as you have already done, keep in mind the safety rules for the group you are wishing for. Most groups have similar roll bar sizing, but they have limitations on style. Im not sure of the Silver State rules. So, if this is your ultimate goal, then try to build the cage to their specs. If I remember... Silver State has high speeds, and most likely their cage requirements will exceed others.

That's my 3 cents. And good luck. It's a lot of fun building your own car.

Brett
fab53.com

[Motorcitydak]

I just read over the Silver State Classic Rules and Regs to see what they had to say about roll cage design among other things. I think Ill have to use 1.75 0.120 just to be on the safe side since my car may not be under 3000#. Id hate to finish it and realize that its too heavy for the thinner wall tubing. One thing I thought was interesting is what they have to say about the halo/A pillar thing

Page 17, Section XI 2G
http://www.sscc.us/docs/2010%20RULES%20rev%201-19-10.pdf

The forward hoops extend from the main hoop (in a forward direction) to the floor by following the roof and the "A" pillar of the car. There must be a bar connecting the two (2) forward hoops at the top of the windshield mounted as close to the roof as possible.

NASA says the same thing, page 59-64
http://www.nasaproracing.com/rules/ccr.pdf

[DynoDon]

Keep in mind that SCCA calls for the Main hoop (the one at the B Pillar) to be one continuous piece of tubing - no joints in this tube. And I denied log books to cars that came for inspection that had joints in them.

[Jim Nilsen]

If you go with 2" tubing on the main hoop it will make it easier to weld the other tubes around the roof. It also makes the car pass many more inspections for weight classes and it doesn'r really take up any more room or cost more.

[MrQuick]

I am in the planning stage of a roll cage for my car. Rite now I have small rope going around the car to help me plan out the tube placement. I had originally thought that I would cut holes in the floor next to the rockers to allow the bottom of the A and B pillar bars to drop down a little. This would allow me to weld the tops of the joints. Then I could build stands to weld to the rockers and then the tubes to that.

When I got to laying it all out, it looks like a better idea would be to place the tubes rite onto the rockers. The problem now is that I want the bars to be really high up and out of the way making it impossible to weld the tops of the joints unless Id cut holes in the roof (not doin that).

Now, Im thinking about going about it another way. What about if I cut the tubes short, say maybe 4 inches. That would allow it to be far enough away from the roof to get at the joints. I can then sleeve the bottom of the tubes with another piece of tube. Maybe 6 inches long, it would fit on the outside of the tube and be in place loose during assembly. After the joints are done up, Id just push the cage up and weld those telescoping ends in position with a plug weld or two on the sides along with one bead on the top to secure it to the cage and then to the rocker.

Has this been done before? or is there another way of doing it that Im not thinking of?

I think you should stick with your original plan. Hole and 3/16" cage box plan. You can still utilize the rocker just build into or off of it.
I also agree on the 2" main hoop.
Vince

[Motorcitydak]

The biggest problem I have with using a 2 inch main hoop is that it will cost me another $300+ for the die to bend it. I am trying to do this as smart and safely as possible, i just do not see what another 1/8 in diameter that one tube would do to justify buying that die as well (being on budget sucks)

[Motorcitydak]

Mr Quick, is that your car? I like what you did with the box attached to the rocker but i also noted in the rules that they only allow 4 bends in the main hoop. That one obviously has at least 6 with that one at the very bottom

Edit: Sorry, I looked at that pic again and saw that you have a shot of the bottom of the A pillar

[MrQuick]

yeah that was just an example.....what bender do you have?


vince

[Motorcitydak]

The one I have is based off a jd2 model 3. I think he bought one, then decided to make a few. It still uses jd2 m3 dies tho. The reason I bought it from him is because he build an arm for it to use a $80 air/hydro cylinder from harbor freight
http://www.harborfreight.com/8-ton-long-ram-air-hydraulic-jack-94562.html

If i wanted a hydro bender from jd2, it would have been a lot more $. Not so much for the manual bender, but then I would have had to drill bolts into the cement floor of the garage to mount it. Here is the link to the bender
http://pirate4x4.com/forum/showthread.php?t=797566&highlight=bender

[Motorcitydak]

Sorry, double post and I cannot delete it for some reason

[Jim Nilsen]

The biggest problem I have with using a 2 inch main hoop is that it will cost me another $300+ for the die to bend it. I am trying to do this as smart and safely as possible, i just do not see what another 1/8 in diameter that one tube would do to justify buying that die as well (being on budget sucks)

I know you want to do it all yourself but you could just have the main hoop bent for you and do the rest yourself. Don't put an expensive tool block in front of you, I've done that before and then found it easier to just go with the path of least resistance.

You can go with 1 7/8 if all you can bend is that. Mine is 1 5/8 .120 wall tubing to be lighter by 3 lb. and I wish I had gone bigger just to make the install easier. Rules are rules but most of the time where I go they don't even check that far.

[Motorcitydak]

I agree with you on doing this the easiest way, I just cannot see that another 1/8 in tube diameter will help me. I know it will be stronger and larger making it slightly easier to fit and weld the other tubes in, just cannot justify it.