Friday, September 16, 2011

Hoover Dam Stories: The Jumbo Rig

My father worked his entire life in the trucking industry and I eventually did, too, working twelve years in companies that specialized in land, ocean container and air freight.  So I have been around trucks most of my life and frankly, I like trucks.  Stick with me on this one.     

Before the actual construction of the Hoover Dam could begin, the Colorado river had to be diverted around the site. This required the drilling of four tunnels, each 56 foot in diameter and approximately 3/4 of a mile long through solid rock.  Using pneumatic drills, a few dozen holes were drilled into the wall and stuffed with dynamite (a lot of dynamite. It's estimated that it took a ton of dynamite for every fourteen foot of tunnel).  After the blast, all of the rock and debris had to be shoveled out and taken upstream and the process started over.  In the beginning, it took countless men, drilling, dynamiting and shoveling to make an inch of progress.  

The old, slow way. And that's a big drill.



Using ladders to drill the holes at the highest points wasn't the greatest idea. The pneumatic drills that were used were big and bulky and weighed about forty pounds.  The vibration that was generated from one of those monsters alone was enough to knock a man off a ladder.

So how do you drill thirty holes at different heights, pack them with dynamite and move all of the valuable equipment and workers to a safe distance before a blast?  This was a question that the engineers working on the project struggled with.

Then in steps the Jumbo Rig. 

To build a Jumbo: You start with something as sweet as this 1920 Mack 

 The Jumbo Rig, or Jumbo Truck was the brainchild of Bernard "Woody" Williams.  Why not create a scaffolding system on wheels?  Why not.  Taking one of the 1916 International flatbeds that he'd seen around the site, Williams had planks of timber mounted on the truck's bed that would accommodate up to thirty drillers standing at three levels to drill simultaneously.  At first this was slow, too, as the vibration caused by all of those drills being used at once required that the wooden struts be hammered back together after every round of drilling. But the idea was sound, and steel jumbos soon followed.  These jumbos had two platforms for drillers to stand on, the third level of men working from the ground.  It also had horizontal bars at the three levels, where the pneumatic drills hung by swivels.  The process then became: Back the truck up to the solid rock wall, drill the holes, pack them with dynamite, tie them together and then pull the entire truck a safe distance away while the blowman detonated.  Then clear away the debris and do it again.  

And you turn it into this.



Eventually, there were eight Jumbo rigs used in the construction of the tunnels.  Did they save time? Of course, in fact, the tunnel crews finished a year ahead of schedule. 

14 comments:

Loree Huebner said...

Great post.

So interesting on how the construction of the tunnels progressed. Such an interesting part of our history. I love the in-depth details. Thanks for sharing.

Michael A Tate said...

I love little tidbits of information like that, and I can't imagine using a ladder to do that. Wow!

Erica Lucke Dean said...

I love big antique trucks. I love when they have the antique truck shows so I can go see the old beasts that my grandfather used to drive on his farm in upstate NY. It's funny how you forget what actually goes into things such as the Hoover Dam...as if it was always there.

Thanks for the history lesson!

Anonymous said...

Pretty cool, Kellinator. The truck and scaffolding ... first thought that came to mind was an opera house (looking at it from the audience). These guys were clever ... and brave.

Kellianne Sweeney said...

Very interesting. I do adore history. I can just imagine how excited they were when they got the idea to put the first one together. Human ingenuity continues to build on itself.

Amberr Meadows said...

I love antique photos and learning cool history about everyone else. I wish I had one of those old trucks, fully refurbished, and painted a shining candy-apple red. Then I'd tear through the roads, burning gas, and daring anyone to defy me. I'm curious as to how far I might get...I digress. Great history lesson!

P.S. Thanks for adding me to your blog roll. I'd love to see a funny travel story posted from you on mine at some point. No pressure, but it would rock! ox

regectedriter said...

You are just so awesome...another amazing read. Whenveer I read your blog, I feel comforted and informed...I love how much research you put in and share, and all the history. It was such a good read. Thanks for writing it.

Kelly Stone Gamble said...

Thank you for the comments. I know trucks is not the most interesting subject to most, but I just love the idea of the Jumbo. I'm glad you all enjoyed it.

theworldsetfree said...

Hi Kelly, I really liked this post. It is exactly the sort of history people don't normally think to ask about, but love to hear! Plus the pictures add that extra element to the story. I can just imagine the miners drilling away, the whole scaffolding shaking...incredible. (Katherine: Kath_ON).

Deanus said...

Great post Kelly! You're own personal connection to the subject and the images too really brought out the story. The evolution of technology and engineering has been so rapid, and this is a great example of one of those turning points.

Kelly Stone Gamble said...

In researching for my novel, I have just fallen in love with the stories, not only of the people but the innovations and techniques used for building the dam. I am thrilled that others are enjoying these stories. Thank you so much.

Beth Ann Garland said...

Pretty cool. Love the truck.

Safireblade said...

My Dad will love this post. You are being printed and mailed to him. Just so you know.

Anonymous said...

Thank you for showing my grand father's Jumbo, it is exciting to see my grandfather's idea being shown again. You might be interested that Woody also devised a "tunnel mucker" that modified a bulldozer by allowing the blasted rock/gravel to be scooped up and then dumped into a dump truck directly behind, lifting up and over, without having to turn in the tight confines of the tunnel. Anyhow, thanks for the trip down memory lane, grandson, Woody Williams.