Grandma Day 11: Roll Cage Part 2, Getting Funny

Tying the roll cage to the frame takes place at several points on the chassis, and we left off with Mike Ryan cutting the floor board so that he could weld the front down tubes to the chassis. With the Chassis Engineering main hoop in the car, we already showed you how we welded the hoop through the floor into the outer perimeter frame. Remember, every point where the cage is tied into the chassis makes the entire car stiffer. Welding the tubing to the frame is no joke and Mike used a couple of clever tricks to ensure a complete safe welds in those areas.


Mike cut a hole in the floorboards large enough to allow welding the front down tubes all the way around the tube.

Cutting the floorboard for the down tubes required a pretty good size opening so that the tube to chassis weld could be done from inside the car for the outside half, and from the bottom of the car on the inside half of the tubing.


Mike welds the down tube to the chassis from below for the part of the tube that faces towards the inside of the car.

After the front down tubes from the halo to the chassis had been welded into place, Mike tack welded the sheet metal cover over the hole that had been cut for the tube to run through the floorboard. Being ever mindful of aesthetics, Mike formed the sheet metal to mate with the existing bends in the floorboard.


Sheet metal cover completes the job. Mike fabricated the metal plate to mate with the existing floorboard bends.

Once the down tubes had been welded into the chassis and to the Halo, Mike added a couple of short tubes from the main hoop cross bar to the rear end upper control arm mount cradle. This brace will support the upper control arm mounting points from flexing under the torsional load during launching. Also, it is another place where the cage is tied into the chassis providing even further support from chassis flex.


The short tube from the main hoop to the upper mount cradle. This is the exact area that intersects where the upper control arms connect.

Welders are often under-appreciated so we wanted to take a moment to applaud their ability to get into areas where a regular Joe couldn’t or wouldn’t go. Welders also have this unique ability to weld with either the right or left hand depending on how tight the area is that they need to get to. So here’s to you Mr. Under-appreciated ambidextrous metal melter.


Cheers to the Fabricator that will get in any spot, in any position, right or left handed to ensure that a good weld is made.

After he had finished the bracing bars, Mike took on the task of adding the cromoly tubing that make up the funny car cage. These bars are custom fitted to the driver and the seat that will be mounted into the car. Each bar in this section is hand bent and fish-mouthed to fit precisely to the cage. Mike approached this task with patience. Trying to take too much metal off of a bar, or over bending a bar would mean starting all over.

The purpose of the funny car cage is to protect the driver in the event of a severe accident and structural failure of the outer layer of roll-cage protection – the doors bars (which in our case are X-bars). They also support the door bars with 2 additional triangulated bars on the driver side.


An outer hoop is installed first.

Once the framework for the funny car cage is made and tack welded, the painfully slow and precise work of fabricating individual support bars begins. Even moving forward cautiously, we managed to make a couple of mistakes and had to fabricate a couple of new bars for that perfect fit.


The funny car cage was hand fabricated to a custom fit.

Before we close out today’s blog, we felt it was necessary to pass along another one of Mike’s tricks of the trade. When welding tubing, the air inside the tube gets hot and expands. As the welder completes the weld at a seam, the structure starts getting air tight and there is no where for the expanding hot air to escape. This can cause what welders call “a blow out”. To prevent that situation from happening, our fabricator drills a small vent hole in the tubing so that the air can escape. This hole can be filled in later.


Vent hole in the tubing prevents “a blow out”.

With our day in the garage over, our fabricator made it through the day with out experiencing any “blow outs”, but he did contort himself in ways that would have made a circus clown proud. All in the name of getting the perfect weld. I bet he’s going to be sore tomorrow.

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