Boxing frame to prevent frame flex

[wildcat455]

I am thinking about doing this to my 1972 F-250 4wd highboy. The main reason is for added strength and rigidity. I know these trucks have pretty stout frames from the factory, but being 40 years old, and kinda rusty in some locations lead me to believe that this is the way to go.

Has anyone else here done it?

I've got some ideas of my own, but I'd be interested in hearing from anyone who has done this and how they tackled it.

Thanks.

[averagef250]

Much of the forward frame area is boxed in.

What many people do to box in a frame sure strikes me as putting a ton of stress into the frame from welding and not really making the thing that much stronger for the way they go about doing it.

A better way to go about box a frame, provided it's straight like these frames are, is start with two frames, cut the rails away from everything else and weld the rights and lefts together to form two identical tubes.

[cleane1]

this is just an idea on our old jeeps we used to take all the hardware spring hangers and such off and run a 1/4 thick strap from front to back on the top and botom rails. It added lots of stringth but still allowed twist to keep all the weels on the ground. I fulley boxed a frame once and it was so stife it runed the rig for eneything but pavement.
I do own a 68 F250 4x4 thats bean in the famely since 1972 and just did a resto on and i saw no damage to frame I have seen pitc of frames from midwest that were rusted through from salt on roads. Just my 2 cents worth hope it helps

[BobbyFord]

Boxing the entire frame will result in stress cracks. The frame on these trucks is designed to flex. I would not recommend boxing the frame.

[GIJoe4500]

What is the purpose of this truck? Light wheeling? Daily driving? Hardcore wheeling rig?

Coming from the hardcore 4x4 world full of people with dedicated trailered wheeling rigs, I say get some 1/8" steel, and box away! Frame flex is a BAD thing. Know though, that in doing it, your rig may feel more rigid (a good thing), and your suspension will do what it is meant to do, instead of the frame. Then, you can build your suspension to be top notch and awesome to make up for the loss in flex.

[Kurt Combs]

Your frame was designed to flex and if it needed to be boxed Ford would have boxed it at the factory. If you need to make repairs to rusted parts, then cut them out and do a 100% weld without excessive weld buildup. This is why I recommend this. Back in the day (1969) I worked at a Navy shipyard. My wonderful job was to grind welds on the pressure hull of nuclear submarines and this is how my job was explained to me. Keep in mind I was grind down a weld that went clear through inch and a half, or more, think steel. This wasn't mild steel, I don't remember the type if was, but it had to be heated when welded to prevent cracks. We had to grind the weld down to a specific height above the hull and we could only grind a little bit into the hull to remove undercut. It is better to blend undercut than to leave the abrupt, sharp hole it creates in the base metal. Now here is why we had these very specific requirements. The hull of a submarine shrinks when it goes underwater at great depths and then expands again as it surfaces. This constant contraction and expansion causes cracks if there is a point of greater rigidity or weakness. If the weld was left thicker than allowed it would cause cracks along side the weld and if we ground off too much at the edge of the weld it would also crack at that weak point. Notice, I did not mention the weld cracking, a good weld doesn't fail, the metal around it does. Now onto your frame, if you box it you will be taking all the force that would have caused it to flex and move it to the weakest point where it starts to flex, probably at spring mounts or the end of your extra reinforcing material. This is why I cringe when I hear people recommend extra reinforcement in the middle of a frame, it creates a place for a crack to begin next to the most ridged point. You want it to flex the way it was designed, or consult an engineer or someone who has a vast amount of experience with this process. Just my two cents worth.

[averagef250]

Your frame was designed to flex and if it needed to be boxed Ford would have boxed it at the factory. If you need to make repairs to rusted parts, then cut them out and do a 100% weld without excessive weld buildup. This is why I recommend this. Back in the day (1969) I worked at a Navy shipyard. My wonderful job was to grind welds on the pressure hull of nuclear submarines and this is how my job was explained to me. Keep in mind I was grind down a weld that went clear through inch and a half, or more, think steel. This wasn't mild steel, I don't remember the type if was, but it had to be heated when welded to prevent cracks. We had to grind the weld down to a specific height above the hull and we could only grind a little bit into the hull to remove undercut. It is better to blend undercut than to leave the abrupt, sharp hole it creates in the base metal. Now here is why we had these very specific requirements. The hull of a submarine shrinks when it goes underwater at great depths and then expands again as it surfaces. This constant contraction and expansion causes cracks if there is a point of greater rigidity or weakness. If the weld was left thicker than allowed it would cause cracks along side the weld and if we ground off too much at the edge of the weld it would also crack at that weak point. Notice, I did not mention the weld cracking, a good weld doesn't fail, the metal around it does. Now onto your frame, if you box it you will be taking all the force that would have caused it to flex and move it to the weakest point where it starts to flex, probably at spring mounts or the end of your extra reinforcing material. This is why I cringe when I hear people recommend extra reinforcement in the middle of a frame, it creates a place for a crack to begin next to the most ridged point. You want it to flex the way it was designed, or consult an engineer or someone who has a vast amount of experience with this process. Just my two cents worth.

Exactly! You can box a frame, but rarely does anyone who have a clue what the hell they're doing when they do it.

[GIJoe4500]

You guys are totally over thinking this. 1st off, this isn't a submarine. 2nd, I'm not going to go into the reasons why welds are ground down on a submarine (I'm a professional weld inspector, by trade, particularly for naval vessels), but there is more reason behind it than to "prevent cracking".

Also, going into whether or not ford should have boxed the frames, blah blah blah. Can't really compare that. If ford didn't think the frames needed to be boxed in...why are they boxed in on the newer trucks? Also, people use their trucks for a LOT more than originally intended by the manufacturer. Do you think ford intended people to put 42" tires on their vehicles, and go climbing up the side of some mountain somewhere? Probably not, but people still do it. Thing like boxing your frame actually do help to increase the rigidity of your frame, and PREVENT cracking the frame in keep locations do to excess force applied by spring mounts, radius arm mounts, lateral forces from the steering box, etc.

Since i'm sure 99.9% of the people that build custom bumpers for their trucks aren't structural engineers specializing in vehicular safety, no one should ever build their own bumper either. You may get in a wreck and die because of it... by y'alls logic. If Ford wanted a 557 stroker motor, they would have built them factory, better leave your stock engines alone. C6's shouldn't have manual valve bodies, axles shouldn't have added trusses, and lift/lowering kits are the devil!

[Kurt Combs]

GIJoe, Please check the attitude when you log in. Members here are general supportive of each other and disagree in a friendly manner. BTW, I have passed the AWS inspector exam, been a certified welder, and have a teaching credential in the CCC for welding (and two other subjects), blah, blah, blah..... BUT the point we are trying to make is he may not need to box the frame and if it is done wrong there may be other problems down the line. Of course, I am not an engineer so I could be wrong. That is why I suggested talking to someone with experience in this subject.

[GIJoe4500]

I didn't mean that to come off with attitude. I apologize for that. I have grown use to seeing blanket statements on other forums that are so generalized that it doesn't fit every application. My original post clearly asked the purpose of the truck he is building, and before there was ever a response, every other post in the thread said, basically, "dont do it, it is bad!!!!" That, in my humble opinion, is the wrong approach to take with something like this. Until we know the final purpose/endgame for the truck he is building, no one can really say one way or the other which is actually best for his truck, to be honest.

[Kurt Combs]

GiJoe, I agree with your statement that we need to know what he is doing with the truck. If he is using it mostly on the road would give a different response than if he was just four wheeling with it. So Wildcat455 what do you do with you truck?

[BobbyFord]

You guys are totally over thinking this. 1st off, this isn't a submarine. 2nd, I'm not going to go into the reasons why welds are ground down on a submarine (I'm a professional weld inspector, by trade, particularly for naval vessels), but there is more reason behind it than to "prevent cracking".

Also, going into whether or not ford should have boxed the frames, blah blah blah. Can't really compare that. If ford didn't think the frames needed to be boxed in...why are they boxed in on the newer trucks? Also, people use their trucks for a LOT more than originally intended by the manufacturer. Do you think ford intended people to put 42" tires on their vehicles, and go climbing up the side of some mountain somewhere? Probably not, but people still do it. Thing like boxing your frame actually do help to increase the rigidity of your frame, and PREVENT cracking the frame in keep locations do to excess force applied by spring mounts, radius arm mounts, lateral forces from the steering box, etc.

Since i'm sure 99.9% of the people that build custom bumpers for their trucks aren't structural engineers specializing in vehicular safety, no one should ever build their own bumper either. You may get in a wreck and die because of it... by y'alls logic. If Ford wanted a 557 stroker motor, they would have built them factory, better leave your stock engines alone. C6's shouldn't have manual valve bodies, axles shouldn't have added trusses, and lift/lowering kits are the devil!

In order to do frame boxing correctly everything should be boxed, including the crossmembers, which should be welded through the frame (like the new trucks are). By simply boxing the side rails you're going to create more bad than good (which is what I think the original poster was referring to). Also, if not done correctly by a knowledgeable fabricator, stress can be welded into the frame, by overheating specific areas and by not allowing sufficient cooling in a given area of the frame. I was told this by a guy I know that builds his own custom frames.

[1970 Hi-Boy]

I am thinking about doing this to my 1972 F-250 4wd highboy. The main reason is for added strength and rigidity. I know these trucks have pretty stout frames from the factory, but being 40 years old, and kinda rusty in some locations lead me to believe that this is the way to go.

Has anyone else here done it?

I've got some ideas of my own, but I'd be interested in hearing from anyone who has done this and how they tackled it.

Thanks.

Seeing a little bit of surface rust isn't necessarily a bad thing, if you can take a chipping hammer and drive it right through the frame then you can start to worry. If you were to box the frame it will increase the rate of oxidation of the frame as dirt and moisture find their way in, but not out. Something for you to seriously consider, besides all of the other things mentioned here that, quite frankly, I have to concur with. I believe what they are trying to relay is, the rigidity you seek, will not be the rigidity you get, she'll be stiff as a brick, and quite useless as a 4x4 (unless installing a super duper independent suspension like on a racing truck, that you failed to mention). On the bright side, your truck may only need some minor repairs, that will save you time, money, head/heart ache and help keep your Ford running for a long time. Good luck with your truck.

[Kraig]

BobbyFord,
Do you have more pics of that frame and suspension?

[BobbyFord]

BobbyFord,
Do you have more pics of that frame and suspension?

No I don't. It's a "from scratch" frame that my buddy is building.