Building the roll cage

The first step to building the roll cage is reading the rules for the class. CMC requires

1.750 x .120 Seamless Alloy (4130), Seamless mild steel (CDS Mechanical) or DOM (Drawn over Mandrel). This is the requirement for cars over 3000 pounds with out driver. The next step is buying the steel. I bought the steel from a local supplier, Hagerty Steel in East Peoria Il. The price is fluid based on current steel prices. I bought three twenty foot sticks for $110 each and bought two more at $106 each. The sticks being twenty feet long does require a trailer to pick it up, Too long to shove in the back of the Suburban.

Tim Bennett and I built the cage in Tim's CMC car two years ago and we were very happy with the results. Tim put together a program on his computer to figure out the lengths and bends of the tubing. We used a manual tubing bender for this project. It is slow but it is just the right speed for a novice. I am afraid if we used a hydraulic bender it we would bend the tubing too much. Whatever the case this bender works great for us.



Front Plinth



We had the benefit of learning from the mistakes and or improvements from Tim's car so we had a pretty clear direction of how we wanted to do things on this build. For example, on Tim's car I had a heck of a time welding the tube 360° because it was difficult to reach the top due to the roof panel. Rules require all welds be 360° around the tube. This was done but very difficult. On this build to make this easier we made 1 inch tall pedestals for the main hoop and 3 inch tall pedestals for the front down tubes. With these pedestals we are able to weld 360° then lift the main hoop up, slide the pedestals in place and then weld in the pedestals. This adds a little weight to the cage but it is a safer cage in my opinion because the upper welds are of high quality.



Front plinth placement







The main hoop and the front down tubes are the hardest to bend. they have got to be right. The main hoop went pretty smooth and fits very well. Once this was done and the location of the hoop was established we could begin trimming the front down tubes. At this point nothing is tacked into place. We held the main hoop in place with a large welding magnet to the roof. this can be seen in some of the photos. We then trimmed the lower part of the front down tub to set the height then we were able to easily set the for and aft of the front down tubes by trimming the end. Once trimmed we put the end in the tubing notcher and the bar was done. Rinse and repeat for the other side and this porting of the cage is done. We have not welded anything at this point. Next steps are the cross bar in the main hoop and size and fit the rear down tubes to the main hoop. Then the upper and lower cross bars between the front down tubes.



Magnet to hold main hoop





Rear
plinth

 in place

I have finished the Front section of the cage. I was able to tack the bars in place then was able to remove the entire front section to weld 360° around the tubes. With it out I masked the areas that need future welding and then painted the whole sub assembly. This is nice to get a smooth even finish around the entire bar.

The rear section / main hoop i have done the same thing. I was able to remove it and sub assemble and then paint. I still need to do the rear down tubes. When that is complete both sections will be fitted in the car and I will only have the welds that unite the front and rear sections to do in the car. I will then bend the side impact bars or more commonly known as the NASCAR bars for the drivers and passenger sides. I am not going to install these bars until after I have wired the car. They are too difficult to climb over when you are wiring a car. that is the plan anyway, we will see if it works.

As you can see here the front and rear sections are held together with my welding magnets.

More cage pictures. I am progressing nicely.

                Rear bars set in place. Trial fit not welded.

                                                 Front hoop reinforcment.

                                                                     Rear bar mount plate.

                                                Plinths welded in place.

Front hoop to rear hoop reinforcment.



The tear down

The tear down.

This is a very simple and self explanatory step. The pictures tell a thousand words. I dropped the engine and transmission out the bottom of the car and it was very easy to do. All in all it took me about two hours to get the engine and trans on the floor. The tricky parts where getting the fuel lines unhooked and finding all the wires that are hooked to the various sensors on the engine. The Fuel lines need a special tool to remove. As stated earlier the interior was completely trashed and was either thrown in the garbage or put in the scrap metal pile. I called a local transmission shop to see if they wanted the automatic trans for a core. they told me it was not worth anything so I scrapped it and the engine which had a rod thrown out the pan. I am saving some pieces to modify and or use later. I am not sure if I can reuse the radiator but I am keeping the fan assembly to use a t a later date. I am very careful not to throw out anything unless I am absolutely sure I am not going to need it. The whole process took about two weeks to get it completely torn down to the tub and ready for the roll cage.

The Start and ground rules

I am starting this blog as a way to document my 4th gen CMC build and also give friends a way to check the progress of the car as I work on it over the winter. As I write this I am a few steps behind in documenting the progress so I hope to soon catch up.

A Few comments before I get started. 1) I am no english major...There may be gramatical errors mis-spellings etc. I dont care!  I am just trying to document the build and am not going to get caught up in grammar and such. 2) I did not put this blog together to solicit comments from the internet know it alls. If you have some questions on how I did something or need help because you are building a CMC car feel free to ask and I will try to answer your questions. 

This is the car. A 1998 firebird that has a blown up 6 cyl engine. I paid $800 for it and It is truely a piece of crap. Perfect for a racecar. The interior is trashed, the engine is blown up but the body is solid and it does not have T-tops. I much prefer a non-Top car for my race car. I dont want to deal with fabricating a cover. Rumor has it that non-t-top cars are lighter. I dont know if this is true or not.

   The build plan is simple. I am going to use the LS1 engine with a t56 trans and use the original disk brake rear end. I am going to use Wilwood brakes in the front with a two piece rotor design. At this time I am not going to run a fuel cell. All of these sub catagories I will document in the future.