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Modern Applications of Hot Rivets 3

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flash3780

flash3780

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Dec 11, 2009
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Just a curiosity, really, but I was wondering if anyone knows of any modern applications for hot-driven rivets. I was trying to think of someplace where they're commonly used (or used at all) in modern designs... and I couldn't. They used to be used all of the time in ships and bridges, but these days those sorts of things are just welded or bolted (as far as I know, anyways).

I know that rivets offer the benefit of arresting cracks which would propagate right through a weld. They also don't back out like bolts can, but I don't know if the cost of installation is worth the added benefits.

Thoughts?
 
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Hot rivets are used frequently in ornamental ironwork.

I think that an induction heater would be a very efficient method of heating rivets for a production process.

They are probably annoying to remove...
 
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I last put some in 10 years ago, renovating an old WW 2 Cover on an artillery range finding station.
At that time the rivets were fairly easy to find 1/2" dia mild steel, I had to make my own rivet sets. In this case the "Forge" was a rosebud tip on a welding torch. The hammer a #7 slow hitting rivet gun, undersized , but all I had at the time. The other guys in the shop were amazed that this " Old fart" ( I was 59 at the time) could do something that they had only read about in books, and the younger guys in the shop had never even heard of it.
B.E

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor
 
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Now, remember, the rivets don't "arrest" the cracks that propagate through a welded joint. (The numerous holes inherent inside a riveted joint, and the localized pattern of stress from each rivet as it clamps the two/three/four pieces of steel together, actually tends to make cracks more likely.)

But a riveted joint joins two or three separate pieces of steel together, and a traditional crack generally doesn't propagate across the edges of the first plate to the next plate. Also, the very slight movement of one piece of steel to the next reduces the tendency to crack under heat stress or load changes: one overloaded rivet in a group of 8 or 9 releases its load to the lesser loaded nearby rivets. A welded joint can't "give" as easily, and can induce stress as it cools down and pulls the formerly separate plates
 
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Hot and cold rivets are still used in some truck frames and rail cars. Most now are cold set with the availability of hydraulic presses replacing the bell crank mechanical setters.
The last time I saw large rivets being hand set was at a Nashville Bridge Plant in Alabama near my home around 1970. It always amazed me that the riveters never missed catching a hot rivet thrown from the forge up to 75" away.
 
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unclesyd said:
Hot and cold rivets are still used in some truck frames and rail cars.
Click to expand...
Interesting. I wonder what the advantages are over welding or bolting in that application. What would cause one to select a hot rivet rather than a cold rivet, I wonder. I assume larger rivets require hot riveting, especially when installed on-site.
 
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A hot rivet is inserted into the hole "hot" - then is quickly hammered over to clamp the metal plates. Then, as the rivet cools, it shortens, and the applied force between the ends of the rivet increase.

More difficult to apply, less safe for unskilled and inexperienced installers, but it gives a tighter joint.
 
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Second the use in ornamental iron work and restorations. Also the shrinkage force is very high. Having made my own tongs, the rivet between the two halves tends to pull up so tight you can't move them. After riveting you heat the whole working end red hot in the forge and work them open and closed rapidly while quenching them in the slack tub. Nice thing about being a 'smith, when they get loose you just heat them up, tighten with a hammer and work them in the slack tub again. (And yes, it is called a slack tub.)
 
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boo1 said:
Steel ladle hooks laminated, riveted and welded designed to AIST Standard No. 7
Click to expand...
Neat. I wonder why they choose rivets. Maybe they're easier to repair than welded construction for those big hooks...
 
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boo1,

Wow, nice link!


flash3780,

I think this is an excellent example of why hot riveting is used instead of bolting-- it is not meant to be a connection that is ever disassembled, so conventional threaded fasteners are not needed. Based on the rivet diameter and length, high strength twist-off type bolts or lockbolts are probably not widely available. The laminated design/construction makes welding a problem.
 
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Ok, I see now. These things are built up from a stack of cut-out plates. Riveting definitely makes sense, otherwise you'd have to either get a massive forging or make a ton of welds around the perimeter. I agree, great link.

I assume that they use hot rivets rather than cold rivets because they make a tighter joint and fill the holes better when you mash them. You also get better ductility in a hot forging process, so I'm sure that the fracture toughness of a hot-driven rivet is higher.

Neat.
 
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Real sorry I missed this thread, being pretty passionate about the subject. Rivets are indeed still used in industry. The railroads use more than a million per year from just one supplier I know of. Airplanes, etc. The example of auto and truck shock towers still being riveted is telling.

I have two hydraulic presses (50 and 60 ton) in the shop that will drive up to 1" rivets (hot). I've used a friends 100 ton to drive 1 1/2" (because I could~)


Check out ballardforge.com, youtube under hydraulic riveting or my good friend Vern in Michigan at historicbridgerestoration.com for more details. I highly recommend Vern's workshops and lectures from luminary professionals who take the arcane into the scientific realm.

Personally, I try to use them whenever I would reach for the welder- as in this staircase
 
 http://files.engineering.com/getfile.aspx?folder=54d0bfe4-25b5-4fef-a230-6ff4aecf7dbf&file=Picture_018.jpg
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One other application for hot rivets is boiler tanks. I assume most are welded these days, but boiler tanks used hot rivets. The residual tension is necessary to seal the joint.
 
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