They said it couldn't be done.



They tried to say it was "Unnecessary"


or "Why would you bother?"


These are actual quotes from structural engineers and the topic in question is the validity of modern riveted connections in structural steel. One need look no further than the 100 year old trestle down the street for proof that the method worked then and could again. I've seen riveted bridges half rusted away and the trains STILL ran over them! Strong enough?! are you kidding?! For me, it's all about 'the look'. The look of how things were built to last. From ship's hulls to bridges to skyscrapers, riveted connections made a good deal of the 20th century possible.

Video of hydraulic driven 3/4" rivets at Ballard Forge



Image of driven heads.

For the better part of ten years I've been working on bringing the art of driving large structural hot rivets to fruition. Seeing as much of the knowledge, equipment and skills had been lost over time, I found out the hard way what a riveting apprentice probably learned in two days on the job. Many of the tools and accessories used in the process were built from scratch to recreate pieces I found unavailable.

Courtesy of Machinery's Handbook 1953

History

Rivets for structural steel were typically driven two ways: by hydraulic pressure or pneumatically with a percussive hammer. The former, known as 'Shop riveting' was done with large C-frame presses, the latter, 'field riveting' used pneumatic hammers that typically delivered approximately 1000 strokes per minute. Both cases used matching dies to create heads as shown in the above table. Rivets were held on the back side or 'bucked' up by a pneumatic 'holder on' or manually with a dolly held by a workman.

Riveting technology grew with industry and by the 1920's hydraulic and pneumatic machinery was developed to handle the largest tasks. Why isn't the method still used? The theory I like the best says that rivet gangs were experienced labor and knew it. Many jobs were held hostage by recalcitrant workers that felt they could get a better shake down the street, or cross-country for that matter. Project managers soon learned that anyone could stick a bolt in a hole while saving money in the process. In the meantime steel chemistry was rapidly improving and in 1951 the first high strength bolting specification was issued. These combination of events, both economic and technological spelled the demise of the rivet gang.

Technique



Of the two riveting methods described above, the hydraulic method is the most foolproof. The rivet dies are held in the press in perfect alignment that delivers a square application of force, virtually assuring a concentric head. The total length of rivet needed to form perfect heads can be found also in tables in Machinery's Handbook. A test beam is used as a training tool for using the pnuematic hammer.

Testing

You can tell alot about a rivet by it's tone; I can tell you that a riveted structure rings like a bell when all rivets are in and tight. You won't get the same sensation from bolted connections. Having the rivet completely upset into the hole is what was known as 'steam tight' back in the day and is what undoubtedly makes for a more resonant structure.
In the old days an inspector would follow behind the rivet gang and tap each rivet with a small hammer. A thud or rattle indicated a loose rivet. Modern bolting inspections, by comparison can require constant visual inspection, torque and tension calibrations , etc. Rivet's aren't without their problems, however. If you fail to 'get the heads up' while hot, you have to remove the rivet by drilling, flame-cutting or chiselsing out- a major headache. Making sure the process is capable of repeatability is the hallmark of good technique because you DON'T want to do it over!


1 5/8" diameter Pyramid heads




5/8 to 1" panhead rivets for a historic bridge restoration


A couple of movies on pneumatic and hydraulic riveting!




Faux rivets or real? Here's some new button, steeple and pyramid head rivets that are decorative as well as functional. Ballard Forge can produce rivets in compliance with ASTM A502, ASTM-A31 and even in wrought iron.

Some riveted stair stringers for a Ballard condo


Riveted cafe table

Circa Restaurant and Bar, Manhattan Beach, CA


Riveted bar brackets for a Dallas Cowboys fan


Steampunk riveted spaceship

Coffee Bar on Bainbridge Island, Washington

Some uber-cool schedule 80 hollow rivets


Steve was recently asked to provide his expertise for the History Channel's Titanic at 100- Mystery Solved pictured here with Parks Stevenson and Brian Flynn at the University of Washington's material science lab discussing the wrought iron rivet samples.


Wrought Iron- Good enough for tension rods for a late 1800's, early 1900's bridge. Good enough for Titanic.


Rehabilitating a historic bridge, building or structure? Let Steve and his crew from Seattle Bridge help realize your goal to save, reuse, repurpose and if necessary, replicate your original structure.




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