Chopped Cab

[Hipster]

Our previous race car hit the wall at MSR Houston and destroyed the front suspension. Afterwards I went to cut the cage out of the car, and the main hoop was welded on a plinth at the B-pillar. BMW welded together 7 sheets of steel at that point. It was strong-like-bull. I couldn't cut it apart. I used a sawzall, a half dozen deathwheels, a plasma cutter, and a torch. I just couldn't get through enough layers to get the underlying layers. I ended up cutting the cage tubing and we built taller plinths in the new car. If the factory A-pillar in our trucks is made from several sheets of steel folded over and welded to the roof in layers, I'd definitely want to duplicate that in the chop.

Maybe slice the pillar right at the top, cut back the layers a little bit, then weld in new layering, spread onto the roof?

There was more then likely some HSS in there. Hss will with chew the teeth off a sawzall blade and destoy cut-off wheels. It can be tough stuff to work with. 9 times out of 10 you replace the piece in it's entirety as opposed to sectioning and welding it pependicular to it's longitudinal.

For that Bmw there might or might not be a an OEM repair procedure for the structural part of the windshield post. In certain situations certain types of damage the Oem deems the vehicle as "structurally totalled" An example of the is Benz. Benz doesn't sell a replacement floor pan for any of their vehicles.(At least not when I worked for Benz) The Oem repair procedure is to total the car if the cabin floor pan that sits under the occupants has been compromised. The technicians need to be educated and aware of this when you have an insurance adjuster telling you to straighten the floor. In many cases today it's deemed once something is bent it's done it's job and needs to be replaced.

On the flip side, you don't want to use sectioning methods or repair procedures using sleeves or fishplates that strengthen certain parts such unibody frame rails. You end up in a situation where instead of something collapsing at a controlled rate as engineered it intrudes into the passenger compartment.

I don't want to be the guy that gets sued because a car I fixed doing bs repairs collapses faster then the airbags deploy. Airbag timing is a big thing. Caged cars, 50's rods manufactured from mild steel, etc is a different game.

Edit, Bmw's are pretty stout vehicles structurally. I've been to their facility in S.C for training classes. Along with the factory, they have top notch body repair program and a race track where purchasers of a new Bmw can have their cars delivered to and have an opportunity to be trained by professional level drivers. Kind of comical to comical to see a 7 series 4 door screeching tires and spinning out through the grass. It was a pretty cool experience.

 

[Erik the Awful]

I just used the BMW as an example of how strong it can be when you layer the steel together and weld it like that. I don't know that any of it was HSS, it was just layered so well that I couldn't cut it apart. When our car clipped the tire wall at 70 mph, the car stopped instantly. The left front suspension folded in, but none of the main structures distorted. It was built freaky strong. We didn't reuse any of the original chassis - we cut the cage out and put it in a new chassis.

I was just thinking that layers & fishplate would be stronger than simply plonking the roof down and seam welding what's left. Is it as strong as what was originally engineered? Probably not, but that's not going to stop somebody from doing a chop, and if I were in the mood to chop a top, it wouldn't stop me. Liability? If you're buying a truck that has had the top chopped, you know it's been modified, and you know it's likely not as strong as factory. Let the buyer beware. As far as the engineers building it to an ultimate strength, it depends on the engineers and how talented and motivated they are. There are a few parts on our trucks that could have been engineered better by a drunk monkey.

 

[CATman]

It would be cool look to chop the top of an obs truck. I had put a targa top on my mini truck back in the day. My friends either had t-tops of convertible top. They had some kits back in the day for these mini trucks.
On my truck, I had to shim under the body to get the doors and top to align back up. I knew if I ever crashed the truck or flipped it, the roof was no protection. I am no body expert but, I think most factory convertibles are strengthened in the lower body section and frame. Trucks have strength on the rear of the cab and a- pillars. (I could be wrong).
If you did chop the top, be aware that you shouldn't rely on the roof to protect you in a roll over or even a head on crash. It is the cost of customizing trucks, or cars. Unless you reinforce the cab after. Even that can have failures. Once you cut and weld metal back together, the metal changes.
It still looks bad ass when the chopped tops are done right. Plan it out and have someone with experience to do the work. It probably won't be cheap.