Boxing frame vs. Roll Cage (67-72 C-10)

[Ethereal]

I'm thinking about boxing my frame, but I also am planning to install a roll cage. Given the effort to box my frame, I'm wondering if it will be beneficial in an auto-x setting with the cage installed? In addition, is it typical to fully box the length of the frame rails or just partially box?

[cornfedbill]

If you are going to install a full cage, it can provide more stiffness than boxing the frame. If it were me, I would go with cage over boxing the rails.

[dontlifttoshift]

So your roll cage would be attached to the top of a piece of C channel?

Just autox? Skip the cage, box the frame, go have fun.

[Mean 69]

A cage in any car or truck will provide significantly greater rigidity that any ladder style frame alone. Nature loves three dimensions for creating rigid bodies, and a reasonably well though out cage is not that hard to pull off - you do want to have the main structure of the cage to be directly welded to the frame of the truck, not just the body as the bushings between the two defeat the intent. Way better approach than boxing the frame.

[raustinss]

DONT WELD THE CAGE TO THE C CHANNEL FRAME , IF you put a cage in you must box the area that the cage attaches to ,to achieve max benefits . If the truck is going to be an off road race only then yes id also say just cage it . If the truck is used for more then just autocross id say box the frame and have fun

[dontlifttoshift]

A cage in any car or truck will provide significantly greater rigidity that any ladder style frame alone. Nature loves three dimensions for creating rigid bodies, and a reasonably well though out cage is not that hard to pull off - you do want to have the main structure of the cage to be directly welded to the frame of the truck, not just the body as the bushings between the two defeat the intent. Way better approach than boxing the frame.

I agree in general but in a truck? Setting aside that we don't know what the OP thinks a cage is, even a basic 6 point that actually ties into something useful on the frame is a pita. If it's a street/autox truck and no more, the juice isn't worth the squeeze when it comes to caging the truck.

[Mean 69]

Sorry, I was thinking purely in race car/good engineering practices. I am in the process of dealing with a similar car (65 El Camino, but for drag race well below 10's), but the logic stands that a cage, appropriately done, will outdo a ladder frame any day. Now, would I pull the body off of the truck solely to do a boxed frame, with the only intention of running a few laps in autocross? No. I wouldn't cage it either. I'd just throw some reasonable suspension at it and call it good. The suspension will make the biggest difference, even if it won't reach full potential due to flexy chassis. If I wanted to extract some decent times out of it, and therefore wasn't opposed to pulling the body off, then I'd cage it. Period. And no, not onto a non-reinforced are that is not boxed. But that is stupid easy once you have access to the frame itself, the boxing in this case only adds cost, and weight.

[Ethereal]

Thanks for the input. To be clear, I'm going to cage it for safety because it's also going to be a driver and I know that these old cars are many times less safe than what's on the road now. My real question is that given the fact that I will install a rollcage is boxing necessary and it sounds like the answer is that boxing will only be needed where the cage attaches to the frame.

[raustinss]

if its a driver then maybe box the frame and do a 4 point cage ...no door bars to fight over ..simple as a pimple

[Ethereal]

I'm going to auto-x it as well as daily drive it, but the door bars are imo an important safety feature for side impacts since the doors don't have bard like factory doors do nowadays. But maybe I can think about how to add bars internal to the doors?

[Mean 69]

Roll cages, like so many other items in this hobby, will garner so many opinions - the majority of which are not expert based. You note the added safety feature of a door bar, the door bars of most drag race and street cages will offer you pretty close to nothing in terms of added safety in a "real" side impact. If you look at a rally car, or a stock car, both of which have a real danger of serious side impact, you will see that they are serious in nature, and not just a few straight bars connecting the front of the cage with the rear. For autocross, it's not needed, I have seen few courses that have real side impact dangers, and the speeds are low - relative terms, which is the whole reason autocross exists, a "safe" place to run your car way harder than on the streets - but it ain't a race track.

AFAIK, door bars started in the early 70's, I know my 70 Camaro had them, whereas my 69 didn't have as much of a side structure, although the doors on the 70 were LONG. I'd probably not bother for what you are looking to do.

Really, not to offend anyone on the forum, but roll cages are serious business, really serious and there is a science behind them, for cars that need them. I had a roll "bar" in a previous 69 Camaro, which I felt pretty good about, until approaching turn 1 at Willow Springs big track at "probably" 150 mph (probably because I didn't have speedo that would register, and second because going those speeds approaching said turn would scare the **** out of me, so I wouldn't look anyway) when I saw three cars off in the dirt, then realized that a prior Ferrari that went through broke an oil line and greased the track, I slowed way done and still got sideways. The dudes that went off in the following driver's meetings were white as ghosts, scared ****less. I agree with them.

If the car is going to haul ass and you value life, do it right. Autocross doesn't typically class as hauling ass.

Your mileage may vary.
Mark

[Ethereal]

I'm more worried about getting t-boned driving around town than injury as a result of auto-x... I intend to daily drive this truck but can't justify doing that without adding some safety measures.

[raustinss]

Try to find a set if 72 doors .....they may have a internal door bar from the factory. My 70 chevelle does

[Skip Fix]

Also remember roll bars and cages are meant to be used in a race car WITH a helmet. Street driving and an accident your head can impact it and cause significant injury if not using a helmet.

[RobNoLimit]

My $.02. In the OP you say 'planning' a cage, so I see this is already part of the build plan. Boxing is the question. At a minimum, you need to box an 8" section, (+4" and -4" from center) at each cage landing point. If this is "in cab" only, that will be around the OE cab mount stands. If you are planning down bars in the back, you can go out below the window/bed top and back, provided you have a crossbar for belt mounts spanning the rear hoop, and the door bars can tie in to this intersection (near the door latch area). Going out front it will be easier to make a bolt through (firewall) assembly and land it on the frame just in front of the IFS. At this point, there are some real decisions to make. Rubber or Solid Cab mounts? If you use rubber or urethane, the cage needs to be somewhat divorced from the cab. - Big grommets. Or, you can make solid bushings for the cab, and the cage can be integral. Either way, chassis flex will be a big issue as time goes on. Any flexing starts to rattle, crack, ...... So, I would consider boxing the entire frame if you are going to cage, and for more than just chassis rigidity. Boxing the entire frame will add appx 70 lbs. That's weight down low, so I'd call it 'good' weight. Put a few holes in the boxing plates for access. I put battery cables, wiring, air lines and fuel lines inside the rails. Each item goes into a full length of 5/8" heater hose and then into the chassis, totally protected. Last, the added weight helps soak up the NVH (Natural Vehicle Harmonics) this is the reason a Bridgeport is quieter than a Jet mill. I recommend 8 stands under the chassis, ft bumper, ft cab, rear cab, and rear bumper on each side, and make sure that the chassis is level side/side and front/rear during the entire process. Hope that is helpful.

[Ethereal]

Thanks for the insight Rob, very thorough! I had second thoughts about the cage due to the mention of safety concerns, but I think that the benefits will outweigh the risks and I'll likely go forward with it. I am more concerned with front an side impacts vs rollover...

I think I get what you're saying re: attachment points, but to be clear why can't the cage be mounted to the cab itself via plates? I thought I'd seen this done in the past but didn't care enough to get a close look at the time.

[raustinss]

The cage is only as strong as the attachment points . Bolting it to the floor is almost pointless. In order to achieve the cages max benefits it must have a solid mounting system

[Mean 69]

Robnolimit, nice overall post on the cage approach.

One small correction, in the automotive world "NVH" stands for Noise, Vibration and Harshness. Harmonics are no doubt a huge issue in machines such as milling units, and mass, lots if it, helps a bunch. In the cutting edge end of performance automotive applications, mass is the mortal enemy. NVH is dealt with from the OEM's by lots of damping, such as rubber bushings, sound deadening mats, etc. Part of the reason that today's cars are so freaking heavy.

Cheers,
Mark

[Ethereal]

The cage is only as strong as the attachment points . Bolting it to the floor is almost pointless. In order to achieve the cages max benefits it must have a solid mounting system

I've seen cages with the hoop mounted to the floor, and then some bars angled inward toward the frame to provide the solid attachment points. I've also seen hoops with outriggers coming off the sides of the frame, so I guess it's a matter of preference.

[Marcus SC&C]

Just like the question of weather to go steak vs. ribs or 9mm vs. 45 the best answer is do BOTH. ;) Robnolimit makes some really excellent points! If this is going to be a street truck and not just a racer then consider welding the cage to the frame but isolating it from the body. That will help minimize NVH issues within the cabin. For best chassis stiffness you`ll want to come out of the back of the cab and tie into the rear frame rails near your rearmost suspension loads. Inside the cab be sure to keep the tubes far away from your noggin, on the street you will not be wearing a helmet and roll cage padding is inadequate to prevent cranial injuries on it`s own.