Bent Frame

[MadOgre]

ya ya the loc tite. I gotta remember that lol.

 

[DoubleDingo]

I get that you're trying to save some cash by doing it yourself, but would a frame shop really charge that much to correct it? I mean, you've made it as easy as possible for them. They wouldn't need to play with body lines or any thing, just make the 2 rails parallel again.

Without seeing it in person the frame doesn't look that bad. If I were you I would check to see how much a frame shop would charge to give it a tug or two to get it back in spec. It would be worth the money spent vs the hours of grinding rivets, line reaming the holes to make sure the bolts are in there with a tolerance fit and replacing with bolts. The rivets will hold the frame a whole lot better than any bolt can. If they have to do a bunch of repairs and welding and such it will cost a fortune, but to get thing back in spec without a body on it, it should be easy as @CSFJ said. Now if it looked as bad as the one I have on my parts truck, where they apparently tugged on the frame from every damn angle possible and obviously wrecked it too, I would just get a new one somewhere.

Replacing the rivets with bolts is doable, and I believe there is a write up for the procedure in the shop manual to do it, but I think even the manual states the rivets are better.

 

[highdesertrange]

I like the idea of installing new good cross members and recheck. oh yeah grade 8 bolts and nuts. highdesertranger

 

[MadOgre]

Well the rivets are grade 5 with less material then a bolt and nut. So it would stand to reason that bolts are stronger. Right? Well the rivets are installed hot and when cooled exert even more clamping force. Bolts are only as strong as the threads holding them and the nut together.

rivets completely fill the hole and so have greater shear capacity? A properly fit grade 8 bolt has just as much if not more shear capacity.

Im still at a toss up as to which one is better?

On top of that it is suggested that mixing rivets with bolts will cause uneven stress loading and actually cause the remaining rivets to fail.

So I suppose the longer the nut, the better the grade 8 bolt and nut becomes.

 

[MadOgre]

I like the idea of installing new good cross members and recheck. oh yeah grade 8 bolts and nuts. highdesertranger

That's the plan for now. Im so lazy though lol and I need a bottle jack so I can reinstall a non bent transmission cross member in between the rails lol so I can recheck for square before attempting any further repairs.

I also noticed that the rear springs are both swayed in the opposite direction which actually makes the axles only out of square about 1/4"

 

[firebane]

Well the rivets are grade 5 with less material then a bolt and nut. So it would stand to reason that bolts are stronger. Right? Well the rivets are installed hot and when cooled exert even more clamping force. Bolts are only as strong as the threads holding them and the nut together.

rivets completely fill the hole and so have greater shear capacity? A properly fit grade 8 bolt has just as much if not more shear capacity.

Im still at a toss up as to which one is better?

On top of that it is suggested that mixing rivets with bolts will cause uneven stress loading and actually cause the remaining rivets to fail.

So I suppose the longer the nut, the better the grade 8 bolt and nut becomes.

In theory and I would agree the rivets would be better when the truck was new. But being thes trucks on average are 30-40 years old and seem a lot of flex and wear and tear just how secure are those rivets now?

I would honestly say that as long as you use grade 8 bolts and torqued them to spec there shouldn't be any issues at all.

 

[MadOgre]

In theory and I would agree the rivets would be better when the truck was new. But being thes trucks on average are 30-40 years old and seem a lot of flex and wear and tear just how secure are those rivets now?

I would honestly say that as long as you use grade 8 bolts and torqued them to spec there shouldn't be any issues at all.

That's what I keep thinking ............... But then.............There's this little voice that keeps saying " are you sure about that? "

 

[chengny]

Rivets are used in situations where two plates - that will be subjected to shear forces - are fastened together. Like threaded fasteners, rivets (when properly installed) do a great job at providing the necessary clamping forces. Clamping force - as the name implies - is what keeps the surfaces of the two plates tightly up against each other. The expectation being that they will stay that way forever, no matter whether joined by rivets or threaded bolts.

Rivets are set by being inserted into a hole that spans the thickness of the combined plates. They are inserted while hot and malleable. Then they are peened over. It can be done slowly and smoothly by a hydraulic press, violently and quickly by one shot from a ram or being whacked repeatedly with jack hammer type tool. During the peening process two things happen:

1. Just as like occurs when a threaded fastener is torqued down, peening the rivet applies the expected clamping force to the two plates. As opposed to a nut/bolt fastener however, the clamping force of a rivet actually increases as it cools down. This is due to a decrease in overall length as a result of the rivet's co-efficient of expansion.

2. As the overall length of the rivet is decreased - by whatever peening method is used - the OD of the rivet is increased. If you apply force on something (that can't move in the direction of the force) it will find the path of least resistance and move that way. In the case of a rivet being peened, that way is outwards - against the ID of the bore. This produces an incredibly tight fit between the rivet OD and bore ID. Also - since the rivet is hot and malleable during installation - as it presses outward, it's OD conforms nearly perfectly to any irregularities in the surface of the bore ID. The result is a nearly 100% surface to surface contact ratio.

So while it can be argued that the clamping forces produced by a threaded fastener versus a riveted joint is basically a toss-up, the same can't be said about resistance to shear. The resistance to shear forces (i.e parallel to the plates and perpendicular to the rivets/bolts) provided by a riveted joint is far and away superior to a joint held together with threaded fasteners.

Compare the extremely tight fit and the near perfect surface contact of a rivet to it's bore. The bolt has to be inserted into the bore - so sufficient clearance must be provided. The same is true of a rivet. But while the clearance is drastically reduced during the peening process of a rivet, with a bolt ... after insertion, it is what it is.

The biggest factor though is the degree of surface to surface contact. Picture a bolt passing through the plates. Unless specially deigned bolts (with extremely long shoulders/bodies and only a few threads on the end) are used, the surface contact is essentially just between the major diameter (highest point of the threads) and the bore ID. Any useful surface contact is generally quickly lost with the application of any appreciable shear forces. The tips of the threads flatten out, the diameter of the bolt is decreased and clearance begins to increase. Soon the plates will be allowed to move in relation to each other - which further accelerates the failure of the joint.

With a rivet however, due to the initial tight clearance and high degree of surface contact, a much more stable joint is attained. So even when heavy shear stresses are applied (since there is basically nowhere for the metal to go), the joint stays tight and no plate to plate relative motion is ever allowed to even start.

This information should be taken with a grain of salt. I pulled it out of my ass from my Naval Architecture and Ship's Structures courses I took over 30 years ago - and probably flunked.

The best plate to plate joints are attained by welding processes. In the ship building sector anyway, riveted and bolted joints were abandoned around 1900 I think.

 

[89Suburban]

Wow.

 

[Don5]

Thanks for that info. I am really impressed. Seriously.

 

[DoubleDingo]

I read something of that nature a long time ago about rivets and bolts Jerry. Thanks for explaining it so well.

 

[MadOgre]

Rivets are used in situations where two plates - that will be subjected to shear forces - are fastened together. Like threaded fasteners, rivets (when properly installed) do a great job at providing the necessary clamping forces. Clamping force - as the name implies - is what keeps the surfaces of the two plates tightly up against each other. The expectation being that they will stay that way forever, no matter whether joined by rivets or threaded bolts.

Rivets are set by being inserted into a hole that spans the thickness of the combined plates. They are inserted while hot and malleable. Then they are peened over. It can be done slowly and smoothly by a hydraulic press, violently and quickly by one shot from a ram or being whacked repeatedly with jack hammer type tool. During the peening process two things happen:

1. Just as like occurs when a threaded fastener is torqued down, peening the rivet applies the expected clamping force to the two plates. As opposed to a nut/bolt fastener however, the clamping force of a rivet actually increases as it cools down. This is due to a decrease in overall length as a result of the rivet's co-efficient of expansion.

2. As the overall length of the rivet is decreased - by whatever peening method is used - the OD of the rivet is increased. If you apply force on something (that can't move in the direction of the force) it will find the path of least resistance and move that way. In the case of a rivet being peened, that way is outwards - against the ID of the bore. This produces an incredibly tight fit between the rivet OD and bore ID. Also - since the rivet is hot and malleable during installation - as it presses outward, it's OD conforms nearly perfectly to any irregularities in the surface of the bore ID. The result is a nearly 100% surface to surface contact ratio.

So while it can be argued that the clamping forces produced by a threaded fastener versus a riveted joint is basically a toss-up, the same can't be said about resistance to shear. The resistance to shear forces (i.e parallel to the plates and perpendicular to the rivets/bolts) provided by a riveted joint is far and away superior to a joint held together with threaded fasteners.

Compare the extremely tight fit and the near perfect surface contact of a rivet to it's bore. The bolt has to be inserted into the bore - so sufficient clearance must be provided. The same is true of a rivet. But while the clearance is drastically reduced during the peening process of a rivet, with a bolt ... after insertion, it is what it is.

The biggest factor though is the degree of surface to surface contact. Picture a bolt passing through the plates. Unless specially deigned bolts (with extremely long shoulders/bodies and only a few threads on the end) are used, the surface contact is essentially just between the major diameter (highest point of the threads) and the bore ID. Any useful surface contact is generally quickly lost with the application of any appreciable shear forces. The tips of the threads flatten out, the diameter of the bolt is decreased and clearance begins to increase. Soon the plates will be allowed to move in relation to each other - which further accelerates the failure of the joint.

With a rivet however, due to the initial tight clearance and high degree of surface contact, a much more stable joint is attained. So even when heavy shear stresses are applied (since there is basically nowhere for the metal to go), the joint stays tight and no plate to plate relative motion is ever allowed to even start.

This information should be taken with a grain of salt. I pulled it out of my ass from my Naval Architecture and Ship's Structures courses I took over 30 years ago - and probably flunked.

The best plate to plate joints are attained by welding processes. In the ship building sector anyway, riveted and bolted joints were abandoned around 1900 I think.

Yep bang on Jerry


The only proper way to use a bolt in this kind of application though is to ream the bolt hole with a step reamer. That will give you a pretty tight fit.


So you have to enlarge the 3/8ish hole to a precise 7/16 hole and then you must use bolts with a shoulder of roughly about 1/4 inch so that the shoulder fits snugly through both plates being clamped. Then if the shoulder protrudes past the two plates you must use a washer or spacer to ensure that sufficient threads are available to ensure proper clamping with the nut.


This way you are not relying on thread OD to fit the hole but rather the shoulder


I have done this before and if done correctly you must use a hammer to tap the bolt through and into the hole as it is that tight of a fit

 

[MadOgre]

UPDATE

So I replaced the bent cross member with an older style flat TH400/208 cross member. And now Im with in 1/8" of square. Pretty damn awesome!

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[CSFJ]

nice!

 

[chengny]

You might be able to spring that last bit of distortion back into alignment.

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Release the cross-member where it is bolted to the twisted rail.

If the web is twisted inward at the top:

Locate the point on the rail where the distortion is most pronounced.

Then, using a 36" pipe wrench (with the jaws tightly clamped to the rail on the upper flange - and the handle pointing up), try pulling outward with a bouncing motion.

Do this in a few other places on either side of the original spot.

Check the plane of the web for plumb.

You might find that the web is now perpendicular to the horizontal plane of the cross member.

Obviously, if the rail is twisted so that the web is canted outwards at the top, the procedure is the same. But, in that case, the torque is applied to the bottom flange. Also, you might need to use a shorter pipe wrench (and more Norwegian steam).