Technical Conduit for mock roll cage?

So I'm going to be putting a full cage in my 29 Tudor. Its not for racing but more for the **** happens moments in life. The cage will be made out of 1 5/8 mild steel tubing, but the cost of it makes me not want too worry about messing up with it. I was thinking the other day about using 1/2 in electrical conduit as a template to build off of. Its cheap and easy to work with and bend. It can be tac welded together, and could really give a good idea for what works and what doesn't. I'd rather s**** conduit then tubing if the design falls short or needs to be tweaked, not to mention the cost factor. Any thoughts on that, or any one attempt the same thing before. Thanks

 

As long as it's just for mock up, it sounds like a good ideal to me... and if you've got a friend in the IBEW they could more than likely help you get the bends right the first time...

 

we use 1 1/2 PVc tubing as you can heat bend it with a heat gun and a wood mandrel cut and mounted on a sheet of plywood to the 7 1/2 inch radius my bender uses its a lot closer to the actual size and you find more problems in mock up .
you can reuse the straight sections by using couplers sanded out so it slip fits

 

Stimpy, that's another good idea. How do you get your cross sections and spreaders bars to stay in place while working your way around the car?

 

a drop of crazy glue or the small area of the pipe cement and hold it with duct tape for a few minutes , to undo the crazy glue use acetone or nailpolish remover ( when done with the remover give it to the wife if she paints her nails ) the acetone stays around for also removing sharpie marker marks ( only stuff that will do it) or when I need to make a special fuel mix ... one thing get the hole saw tubing end cutter ( pipe notcher ) as your going to need it when you make the roll bar and use a 1 1/2" hole saw while cutting the mock up as it will give you practice on cutting the ends and make them perfect so the welds are cleaner and smaller .

also do not forget to make floor plates ( per NHRA/ SFI ) or figure a way to hook it to the frame of the vehicle , recently we had a Poser kid in a honda roll his car playing "the fast and stupid" on the interstate ramps by my house and the cage turned into a s***ch maker and made the extracation lots longer as it folded him up when it punched thru the floor as there was no spread plates on the ends it punched clean circles where it went thru the sheet metal .

as for the bending die I had a friend who is a woodworker ( and loves challenges ) make me my shoe with the pipe radius cut into it so the pipe stayed round when it hot bent it . he made it out of laminated plywood squares and machined it from a aluminum master used for Electrical conduit ( thats the shoe/dies the budget ch***is benders use ) the ears or sides of the shoe should be atleast 3/4 thickness of the plastic pipe dia to help keep its shape . packing it with sand makes it a mess . we bent a kit of 8 90*s ( IIRC the straight length was 21-23") and then used the couplers to joint them to the main pipes oh and use Schedule 40 , 80 is a pain in the rump ! .

parts of these I built this way wound up under my house as part of the bathroom drain .. bent a beautiful 45* pipe too bad you have to crawl in dirt and spiderwebs to see it

 

one thing I do reccomend is you might want to go to 1 7/8 on the main bar as the 1 5/8 we use in safety are only in a cage use where you have a minimum of 8 points and a halo , a roll bar should be 1 7/8 down legs and all make sure its A- 513 tubing spec too . ( it will have it printed on it ) HRew is ok for this , DOM is better but $$$ , seen several HREW roll cages take a beating and not split like everyone says it will .

 

The PVC sounds good. But if you are still thinking about EMT, that is what I used to mock mine up with. Worked fine.

 

I have a 1 3/4" pro tools bender and I use a standard 3/4" emt conduit bender for mock up at times. It fits the center line of my radius perfectly. I just make sure I have 3/4" all around it and I know the big stuff will fit.

Also my .02 cents. Put a cage in there and you will modify your driving style and risk taking. It's natural. I've built a ton of off broader cages and I hear it all the time, most admit to it after a while. With that said my 35 is getting a cage. I also only use .120 wall DOM. I agree with stumpy HREW will take a beating but bend that and then DOM with a manual bender and you will see and feel the difference.

 

The harbor freight tube notchers work pretty well. I use a tube coping calculator I found on a bicycle building web site. The program is free to use and prints templates to trace on the tube. I use the plasma and cut it then final shape it with the grinder. It's pretty amazing and free.

 

Thanks every one. For the cage I'm thinking about making a subframe that bolts to the frame, that has three hoops, all tied together. Body mounted to the cage, floors and so on. In other words building it like a unibody that bolts to the frame.

 

I've been thinking about a cage in my '30. Post some photos as you go, if you don't mind.

 

The conduit method works well. Cheap, too! Although the cage in the '57 came from S&W, there was still a little fitting to do. That was my excuse to buy a drill press.

 

I can't begin to remember every roll bar and cage I've installed, most were mild steel DOM, 1 5/8 for cages, 1 3/4 for bars. YES, attach it to the frame and box the frame as well. Before you box it, use that hole saw to go through the top of the rail and burn it in on both top and bottom sides. For every weird custom bar I did I just used brake line for patterns. That tube notcher is ok, requires a good quality hole saw to be effective, but my favorite tool for notching is a vertical band saw. Think about this, the tube is already round isn't it? A straight cut at the proper angle and voila, a perfect notch. Exponentially faster than the notcher too. I also had some paper notch patterns for common angles and slipped em over the tubes, run a sharpie around the pattern, saw it off, a lillte grind with the 5" and done. Time was $$$$ back then but the nice thing about the saw cut was the minor bevel left over for a beautiful confident weld. Speaking of the weld, and for attaching points, give a light sand or grind at every joint. On tubes I used an 80 grit disc, on plates a 50 grit to remove mill scale or to prep frame locations. Clean metal is literally GOD when it comes to bar/cage work and welding. Enjoy the job as it can be fun and rewarding, but don't take any chances or short cuts. And oh yeah, PICS OR IT DIDN'T HAPPEN!

 

I'm currently building a O/T project that some would say is a street racer but since it is a unit body it will need at least an eight point cage. I searched the Internet and found a lot of companies that build kits with prices ranging from $299 to $800 depending on the size of tubing and type of steel. I called the tech people at Alston Ch***is and they have a form and you fill in the measurements and they make up the kit to weld in. Their kits conform to NHRA requirements as far as floor plates, gussets etc. Strangely the rules say the welded joints don't have to be 100% welded.

 

I have used electrical conduit to mock up lots of things to made of tubing before the actual build. it does take some ciphering after the fact but it is not a bad idea at all.

 

Some times those "kits" fit loose within the confines of the body and really become tight for the driver in a small car. They do this so that the welder can get around all the joints with the mig gun. Something to consider if one is spending more than a couple minutes driving the car.

 

I retired from the union and bent miles on conduit of all sizes and types.....The normal bend radius for 1/2 inch EMT is about 4-1/4 inches. this can vary depending on the bender and the user.
What is the bend radius on non electrical tubing benders for 1-1/2 or 1-3/4 DOM?

 

Personally I think your making way to big of a Job out of it. They are not that tough to do! Common sense. That should be your number one tool. Just think about it before you start. You said "if the design falls short" . How can that happen? N.H.R.A. has designs already layed out for every body profile there is. Start with there profile and eliminate what you don't like and just build it.
I understand first time reluctance but there are guide lines for what your trying to do and every tube ch***is gets a little adjustment as it goes. Practice on some s**** to make nice joints and get to it. Once your done no matter how nice it turns out your going to sell the car off because roll cages in street cars (especially a Model A) are user un friendly and your going hate the finished product.
If your worried about getting Creamed in your A Bone just remove the wood from the A and B pillers and replace it with heavy wall sq, tube and move on. You can hide all that behind the upholstery.
The Wizzard

 

Most shops that bend 1 5/8 or 1 3/4 will have either 6" or 7" clr dies. The tighter the radius the better as that puts the bend in the corners of the car a little better so that any longitudinals are easier to place. If you want it to be NHRA legal (in mild steel) you will need to use .134 wall tubing. The spec calls for .118 but the nominal wall of .120 (apart from DOM which costs about as much as moly) is around .114 so go with the .134.

Roo

 

Here is another little known N.H.R.A. fact. If you have a cage or bar in a car and want to make a p*** at any vintage day race it Must meet current spec's. It don't matter if your running a 14 second car that clearly does not require a cage or bar at all. You will not even be allowed to make a test p*** if it don't p*** inspection. That means tube dia. for each section and wall thickness. Roo is correct about heavier wall and they sonic bends on the outside of each bend right where the stretch happens and gets thinner.
The Wizzard

 

My .02 is that if you're going to cage it, do it to NHRA rules. Even if you NEVER plan to take it to the drags. Even if you're not doing a full cage such that it won't need to be redone later if you or a future owner wants to add on to it. They are very specific about measurements around the driver, tubing diameter and wall thickness. Never grind on the welds. Instant fail. See page 16: http://www.nhra.com/UserFiles/file/General_Regulations.pdf

 

I race bikes not cars in LSR....I've been told that a cage built to NHRA rules won't p*** SCTA, ECTA etc LSR rules... Any truth to this?

 

I have gone thru about 40 ch***ie certs between my cars and customer cars and have never seen or heard of a ch***ie tech do that.. The specs are written with that in mind because there is no getting around the stretch

 

Yes. I'm not sure about LSR but SCCA and NASCAR won't p*** a NHRA cage. Always build to the rules of each type of racing use. When rule books contradict each other on multi purpose builds be sure to discuss it with inspectors from all sanctioning bodies.

IMHO, cages in street cars are a serious hazard. There's no helmet to protect your head from it on the street. A low impact fender bender can be life altering or fatal if your head hits the tubing.

 

I use cardboard, it seems simpler and fool proof to me. make a pattern that fits the car good, lay it on the ground and bend the tubing to match then tack it in place and move on to the next piece....

 

S&W race cars in PA. sells nice kits for almost anything. I put one in my Daughter's Falcon.

 

You could also download a program called bend tech that takes almost all the guesswork out of the process for any bend intensive project. With a few critical measurements and some very basic computer skills you can build a 3d model of your cage, from which the program will calculate your start of bend measurements, play a video of the bend sequence, print templates for tube copes and even calculate spring back for common tube benders.

 

Hey Butch, what year Falcon and how well did it fit?

 

I fully intended on putting a cage in my coupe. I had the main hoop tacked in, and had the front two legs tacked in. Through that process, I banged my head on the roof rail bars 3 different times! That light contact hurt! The cage came out. I was afraid I might knock some sense into me. Gene

 

Good info...So if I have an original 4 point cage its a no go at nostalgia events? How about if I replace the bars with correct size and thickness?