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Modern Applications of Hot Rivets
3

Modern Applications of Hot Rivets

Modern Applications of Hot Rivets

(OP)
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?

RE: Modern Applications of Hot Rivets

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...

RE: Modern Applications of Hot Rivets

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

RE: Modern Applications of Hot Rivets

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

RE: Modern Applications of Hot Rivets

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.   

RE: Modern Applications of Hot Rivets

(OP)

Quote (unclesyd):

Hot and cold rivets are still used in some truck frames and rail cars.
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.

RE: Modern Applications of Hot Rivets

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.

RE: Modern Applications of Hot Rivets

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.)

RE: Modern Applications of Hot Rivets

(OP)

Quote (boo1):

Steel ladle hooks laminated, riveted and welded designed to AIST Standard No. 7
Neat. I wonder why they choose rivets. Maybe they're easier to repair than welded construction for those big hooks...

RE: Modern Applications of Hot Rivets

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.

RE: Modern Applications of Hot Rivets

(OP)
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.

RE: Modern Applications of Hot Rivets

Rivets—ASTM A31, Grade A,
Ultimate = 45,000 psi min., Yield = 23,000 psi min.

RE: Modern Applications of Hot Rivets

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

RE: Modern Applications of Hot Rivets

Sorry, didn't see that in the intial post- not that I'm aware of

RE: Modern Applications of Hot Rivets

cold rivets

RE: Modern Applications of Hot Rivets

(OP)
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.

RE: Modern Applications of Hot Rivets

And to keep it sealed across temperature variation, no?

RE: Modern Applications of Hot Rivets

(OP)

Quote (btrueblood):

And to keep it sealed across temperature variation, no?
I think that separation due to thermal growth was dealt with by matching CTEs; I believe that the rivets and the tanks were generally both made of similar steels. Can't swear to it, though.

RE: Modern Applications of Hot Rivets

Either the same coefficent of expansion, or rivets had slightly less.  Riveted boilers that were leaky when cold would tighten up and stop leaking when hot, even with the increaded pressure.  Have not heard of a riveter boiler or pressure vessel made in the US/Canada in the last 30 years.  I believe ASME work went to all-welded in the 1950's.  However, I know of a railroad bridge that was all-riveted that was fabbed in the mid-1990's.

RE: Modern Applications of Hot Rivets

For bridge work, hot rivets from the past are now replaced with nuts and bolts on many DOT jobs.

RE: Modern Applications of Hot Rivets

Per the original post.
A modern application of hot rivets, is the use of hot rivets on chain shackles  by the coastguard on navigation aids i.e. channel marker bouys. I guess they don't want them coming loose.
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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