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View Full Version : Newb question on cutting a 4130 cage and re-assembling it



broke33
09-06-2010, 01:58 PM
Im a newb here but I hope you guys can help me with my cage. I had a cage built for my 1991 F150 ext. cab truck out of 4130 by a well known racer in the Detroit area (Don Hardesty) a few years back. It is 4130 seamless, 1.625 diameter with 0.083 wall thickness. It is a complete over head hoop with 4 down legs and has a cross bar across the back 2 legs. He built it into the truck and I never got a chance to get the truck out of the garage before I decided to cut the cage out of. I now have a 1978 Bronco that I would like to put the cage in. It will not fit without me cutting it, positioning it inside and reassembling. My questions are as follows:

1) Where would be a good place to cut the cage (or is it ok to cut it)? I was thinking of cutting it in half at the middle of the hoop area on top then positioning it inside the bronco.

2) If that makes sense I was thinking about getting a piece of 4130 tube about 3 inches long that can slide over both pieces and pinning them together by drilling a hole and sliding a 1/2" hardened steel pin through both sides or I could get a piece of solid rod and slide inside the center of the pieces and do the same pinning operation.

3) I will be cutting the 2 mount plates off the front and will need to weld 2 flat plates to the feet for mounting. Is it ok to weld 4130 to a 1018 plate?

I do not have a tig but I have a Lincoln PM200 mig welder. I have researched this a little and if welding is required I was going to use the ER70s-2 wire for it.

I know Im asking alot here but before I start cutting, pinning and such I figured I would ask some experts.

The intended use for this cage is to protect the wife and kids when we go off roading, this will not be used for any competition racing or anything.

Thanks in advance for your advice.

tresi
09-06-2010, 04:44 PM
For splice a welded tube structure get a copy of AC43.13 , Acceptable methods and practices. While it covers most all forms of aircraft repair slip to the part that deals with repair of tube structures. There's alot of other usefull info in there too. I believe you can get it online at AircraftSpruce.com . Basically what you to is to fish mouth your sliding piece and weld it in place. Traditioally you mig a mild steel cage and TIG a 4130 cage

Booger Welder
09-06-2010, 05:15 PM
The answer is that you don't cut it out of one vehicle and weld it into the other.

I don't know anything about this guys work, but I have been in racing a long time.
The bars across the top is called the Halo bar and it's purpose is to protect your noggin.
If you put a pin through it - it no longer has it's original structure and anytime you change structure - you have to replace it with more structure. You can't cut any of those top pipes (Tubes - like they would say to me at Gortech) and retain the original structure.

My first thought is to pay the man to do the job again. A truck and a Bronco are the same physically, but the truck has no cab behind the driver and the Bronco does. So what you need is a full cage and not just a couple of loops over yours and your wife's head. You already mentioned something about having kids. Don't you want to protect their heads too.

The end result is that you never weld a roll bar directly to the frame. You first weld steel plates to the frame and then you weld the roll bars to the plates. You never attach the roll bars to the floor boards in the vehicle - you attach it to the frame. And - you never attach the front seat to the floor when you use a roll cage, you attach it to the cage.

Let's say that something happens and you get T boned. The body will move, but the roll cage will not - at least not at the same rate as the thin tin they put on these vehicles.
So what happens is that you are not protected and you get hurt. You actually want the seat to move with the cage and not with the body..

Your thoughts of just taking the cage out of one vehicle and putting it into another - had no forethought. All it did was fill a need - which was to put some type of cage on your vehicle as cheaply as possible.
If it was my family riding around in that vehicle, you would be darn sure that I would have a experienced welder putting the cage together and not you in the backyard with a cheap mig welder.

broke33
09-06-2010, 07:57 PM
The answer is that you don't cut it out of one vehicle and weld it into the other.

I don't know anything about this guys work, but I have been in racing a long time.
The bars across the top is called the Halo bar and it's purpose is to protect your noggin.
If you put a pin through it - it no longer has it's original structure and anytime you change structure - you have to replace it with more structure. You can't cut any of those top pipes (Tubes - like they would say to me at Gortech) and retain the original structure.

My first thought is to pay the man to do the job again. A truck and a Bronco are the same physically, but the truck has no cab behind the driver and the Bronco does. So what you need is a full cage and not just a couple of loops over yours and your wife's head. You already mentioned something about having kids. Don't you want to protect their heads too.

The end result is that you never weld a roll bar directly to the frame. You first weld steel plates to the frame and then you weld the roll bars to the plates. You never attach the roll bars to the floor boards in the vehicle - you attach it to the frame. And - you never attach the front seat to the floor when you use a roll cage, you attach it to the cage.

Let's say that something happens and you get T boned. The body will move, but the roll cage will not - at least not at the same rate as the thin tin they put on these vehicles.
So what happens is that you are not protected and you get hurt. You actually want the seat to move with the cage and not with the body..

Your thoughts of just taking the cage out of one vehicle and putting it into another - had no forethought. All it did was fill a need - which was to put some type of cage on your vehicle as cheaply as possible.
If it was my family riding around in that vehicle, you would be darn sure that I would have a experienced welder putting the cage together and not you in the backyard with a cheap mig welder.

Thanks for the info. This is not a race application but a family offroad vehicle. As for the rear seat and the kids I have a seperate roll bar that mounts right behind the rear seat for their protection.

I never said anything about welding the cage to the frame. The cage has 8"x8" square plates welded to the bottom of each foot and then these plates were welded to the floor of the cab. Then there were supports welded to the frame that met underneather the floor of the cab where the footing plates were welded and the 2 plates wrre bolted together with 9/16" hardened steel bolts. Is this not structurally strong enough? You say that cutting the hoop would require that the replacement of the section should be stronger than what was there originally. If I place a thicker wall sleeve over the cut and overlap each side of this cut 3 or 4 inches would this not be strong enough? I could weld it or have another expert weld it for me if thats the support it requires.

What Im gathering from your response is it is better to not put anything in the cab unless it is a full cage front to rear? I was thinking that having something would be better than nothing but I guess Im wrong? I would probably never have the vehicle in a situation where it could roll but accidents happen and it would never be at a high speed.

I spent $1000 for this cage and would like to try and use it but if it cant be done Ill use it as a close hanger on the back porch.

Rojodiablo
09-06-2010, 08:53 PM
Just figure the fewest places you'll need to cut it, and try to keep the cuts in straight sections. Sleeve them on the inside, and weld them back together when reinstalled. To make sleeves, get some 1.75" tube, cut it in 6" pieces. Slit cut it with a slot that when pinched down will fit the ID of the cage. Weld the seam up, it doesn't need to be a 100% weld on that. Slide it in, leave enough for a root weld to get everything together, and go to town.

Crawford
09-06-2010, 08:59 PM
if it were me doing it, i'd buy a pre-fab for the new truck and not dick with shoe horning that one in and out of two different vehicles.

broke33
09-07-2010, 07:21 PM
Ill probably just follow the recommendations here and ditch the cage but I thought I post pics of the concept here:

http://picasaweb.google.com/103600498454584221125/DropBox?authkey=Gv1sRgCPH-8Pu1rKOWTA&pli=1&gsessionid=vMVgxdPdcU1yg3x6lVtDEA#

I would still like to get an opinion of using the rear roll bar for behind the rear seat and having a seperate halo for the front compartment. The reason for this is I have a tonneau cover I will use in the winter time that will make the Bronco look more like a truck and reduce the area that the heater has to heat. I would then just remove the rear rollbar for this, but have the front cage welded in permanently. Does this make sense?

ZTFab
09-07-2010, 07:28 PM
That cage you had built is lacking in many ways for any sort of protection.

There is absolutely zero triangulation in it and about half as many tubes as there should be. It will fold at any sign of a roll over, possibly causing more injury than without it.

It would be better to start over and design a cage system that will work for your purposes and still keep your family safe.

broke33
09-07-2010, 08:20 PM
That cage you had built is lacking in many ways for any sort of protection.

There is absolutely zero triangulation in it and about half as many tubes as there should be. It will fold at any sign of a roll over, possibly causing more injury than without it.

It would be better to start over and design a cage system that will work for your purposes and still keep your family safe.

What are the thoughts of a cage like this for the Bronco:

http://www.swracecars.com/store/10-Point-Roll-Cage-OSCARItem_113=11-3560-DOM.aspx

Broccoli1
09-07-2010, 09:41 PM
What are the thoughts of a cage like this for the Bronco:

http://www.swracecars.com/store/10-Point-Roll-Cage-OSCARItem_113=11-3560-DOM.aspx

That only protects the Driver and Passenger- no rear seat protection.

Booger Welder
09-07-2010, 10:12 PM
The roll cage - behind the back seat does absolutely nothing for the occupants in the back seat.

What you need is a full cage.

What I implied about not cutting the original cage and not putting anything in or on the cage to make any one part of the cage stronger then the other parts - the design of the cage should be such that when the vehicle rolls over, it keeps the occupants inside of the cage and does not have any place in the cage where someone can fall out or any one place where the cage is weaker then the rest - where the cage can bend and fail and trap someone to hurt someone to the point of where they might be injured.

So what everyone else here is telling you - if they are telling you to get a new cage - that is the best advice I heard so far. If you aren't going to use your old cage, sell the truck and get your money out of it. There is always a bunch of old Ford Fans that will pay anything you ask - if it is what they are looking for.

I have a idiot neighbor who has a new Dodge truck, yet drives around in a 1978 F-150 because that is his vehicle of choice. I have another neighbor who has a 78 F-150 and refuses to sell it, and he has had it since 1979.... I have a Uncle who owned a 1975 F-100 and sold it for $3600 and it didn't even run right. I wouldn't have given them $500 for it. But someone came along and it was the truck he wanted and had to have and paid them what ever they asked for it.

makoman1860
09-08-2010, 08:57 AM
Question I have,
Why waste the money on 4130 for a non competition roll cage for a tank? Would the extra 20 lbs from using mild steel really matter?

broke33
09-09-2010, 05:42 PM
Question I have,
Why waste the money on 4130 for a non competition roll cage for a tank? Would the extra 20 lbs from using mild steel really matter?

Thanks for the advice guys. Ill move forward with a new cage.

Regarding your question above the cage was originally designed into a mud truck that was going to be used for competition. The S & W racecar cage I referenced above is a DOM cage.