Freight charges for any length of 4130 over 8 feet are a joke. I understand business is business, but a 12 foot long 1.625″ diameter tube is considered something like 2 pallet positions. Roughly $250 to freight something that can be slid underneath a pallet is a bit much. Anyway…
So I’m somewhat lucky for the fact that I live roughly 2 hours north of S&W Racecars. So I loaded up and made the trip to get the previously mentioned longer than 8 feet pieces of 4130 tubing. Most of the tubes on the chassis are smaller pieces, but the main hoop required a length of a hair over 121″. S&W cut me two lengths and I drove down and picked them up. A closer, local to my area vendor wanted to butt rape me at triple the going price. No thanks. After years of business, with all due respect, honorably, please kiss my ass.
So here we are at the main hoop, the central structure of any roll cage build. I do all my design in BendTech Pro. It has never let me down and I will never draw full size pictures on the floor. Swallow your pride and transfer your brain into the 21st century. Old school does not cut it for me. I don’t like carburetors, why would I draw in chalk on my garage floor.
So the main hoop. Four bends and 121.145 inches of 1.625 x .083 4130 tubing. The process is quiet simple. I cut the tube to length on the bandsaw, transferred bend marks to it with a black sharpie, then Pedro and me fed it into the Model 3 and bent away. Now, theres a method to this, it can be done alone but is best done with a helper. I like to get the pipe into the bender at position 1 then on the other end clamp and zero a digital angle guage to the very tip. I’ll make the bend, reposition the tube, Pedro will call angles out to me, then when it’s all set I’ll lock in and bend again. Repeat for the last remaining bends.
We’ve always done it this way and it’s always worked. So long as I dont mismark the tube.
So there it is. Main hoop.
My goal was to get the hoop as tight to the roof as possible, while having it follow the 10° rearward rake of the door jamb at the “b” pillar. The angle was simple. A mirroring 10° miter at the base if each hoop leg did the job. Dimensionally I was successful in maintaining that tightness I want. I had to drill welds and cut material away from the inside top corners of the “b” pillar just to fit the hoop. It will all be replaced and grooved to fit, then get welded to the hoop during the final fitting of the body to the chassis. If calculations are correct this will add a little extra rigidity to the body/chassis structure.
Forward laterals were next. These extend from the forward facing top corners of the main hoop towards the upper windshield frame, mirror the “a” pillar angle, before shooting down the front door jamp and into the frame. They were bent in the same manner as the main hoop, however, they had a 20° twist added at the second bend to allow for the kick out of the body as it progresses down the sides of the windshield frame. After these are fitted and notched they are tacked to the hoop, then the assembly is tacked to points on the frame according to design specs.
Speaking of notching, we’ve got a handful of options to get that done. If you are really close on the length and have a little wiggle room to shift the free pipe around to it’s perfect spot you can use something like the Pipe Master. It comes in every tube size you would use on a roll cage/chassis and it works great. It’s a plastic frame sized to fit the tube and a bunch of stainless steel needles that take the shape of the mating line. Very handy. Trace the pattern onto the tube and hand grind. Great for getting contours from a multi tube intersection.
Next up is good old traditional angle finder. Brace the tubing across, under, over, or against your point of intersection, measure, mark, and cut out on the cope on a notcher. To do this I use two tools. First I use a small angle finder with a groove in it to rest on the base tube, lock its angle, and then measure angle with a larger degree marked guage. Basic and easy to do, but ads difficulty on unions with more than three tubes and steep angles. Notching is easily done with a tube notcher. I use a Baileigh TN-255.
The next method involves a paper wrapper. And I’ve done this two ways. First way involves the Internets and requires measuring as previously describe. There’s a website out there somewhere and you put in your measurements. It then spits out a printable wrapper you can manipulate on the tube to get your setting, mark tube, and grind out.
Lastly I use BendTech Pro. When chassis or cage building I spend a lot of time in BendTech making an exact model of what i want to build in real life. If design parameters can be followed to an accurate degree this is undoubtedly the best way to build. BendTech spits out angles and wrappers that make this very simple. You can also buy a tube marking/cutting machine called the Dragon that marks all your bends and copes all your tubing before you even bend it! I’m not there yet. Lately I’ve been into the paper wrappers and hand grinding the notches out, it seems to increase the level of accuracy for getting that mechanically tight fitment I always like to go for.
More in the next installment on overall chassis design with a few tips for keeping this thing structurally rigid and some insight on keeping the atoms of your materials stacked in the right direction. Pedro and me are also whipping up a video build series for all the losers who want to see this in the works and watch me act politically incorrect….don’t worry we don’t ever talk politics, terrible shit just has a way of exiting my mouth into the atmosphere. Oh, we switched from the Ramones to Manowar. It’s the only thing that seems to work anymore.
On a side note. I saw a truck with a “Locally Hated” sticker on the back screen. Put down the crack pipe and take the sticker off your truck and the dick out of your asshole. And what’s the deal with wheels and tires on modern pickups? They look like shit, that’s the deal. More tire, less wheel cock suckers. Good night.
Chassis builder, engine builder, cynic