Meet Maker Don Smith of the Lego Crane

Engineering & Building the Lego Crane
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I am a 57 year old mechanical engineer who has been tinkering with Legos since the late 60’s or early 70’s.  I have always enjoyed the Technics series which allowed my creations to be automated.  Working in the construction industry, heavy equipment has always been of interest to me. 

I have built and disassembled many things over the years, such as tractors, bulldozers, trucks, and several different cranes.  Cranes have always been my favorite.  The other items just allowed me to experiment and collect a large quantity of Lego parts.  A few years ago Lego released the Power Functions series that included new motors and infrared remote controls.  I was re-invigorated! Now I could create things that could move on their own! 

My first model was a crane that would move and lift small loads.  I then built a truck that could move, steer, and dump by remote control.  Each took me about a year to engineer and construct.  During this time I was able to estimate the strength of various Lego parts and their capabilities. 

The idea of a huge remote controlled crane came to mind.  I disassembled all of my previous creations and started engineering my crane, using the Lampson LTL-2300, the largest mobile crane on the planet, as a model.  This was around June of 2011.  I quickly realized that even though I had accumulated a vast quantity of Lego parts, it wasn’t going to be enough.  I spent a lot of time on websites tracking down and purchasing the required parts.  In late September of 2012 I actually started to construct the crane.  The main deck assembly was first, including the winching assemblies, counterweight, and gantry.  I completed it in early December of 2012.  During this time I engineered the main and jib boom structures and acquired the parts for them.  By February of 2013 I had them built.  Finally came the track assemblies.  These were the most difficult.  Not only did they need to function, but they needed to do so under loaded conditions.  Lego motors have very limited torque capacity, so fitting the gear reduction transmissions into each corner of the tracks was very daunting, allowing the motors to generate enough power to move the crane.  In April of 2013 the crane was finished and ready for testing.  A few minor modifications were made over the next couple of months.  The most drastic of these changes were the main pivot pins and the “headache balls”.  Lego does not make axles strong enough to lift over 15 pounds or so.  I had to substitute metal stud bolts.  I machined the “headache balls” from steel to generate enough weight to keep the lifting lines from fouling and to make them look “cool”.  I even added lights!  The pennant cables were made of 1/16″ stainless steel cable.  The lifting line is 100 pound test braided fishing line.  All-in-all, there are 18 parts of over 90,000 that are not Lego.  There is not a drop of glue in it!  The crane has a lifting capacity of 20 pounds from the main line and 5 pounds from the jib line with 12.5 pounds of #4 shotgun shot as counterweight.  Without counterweight the crane weighs 26.4 pounds.  Most real cranes can lift 40 to 45 percent of their total weight.  This crane has lifted 51.4 percent of it’s total weight. 

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I have performed demonstrations at the Lampson Crane facility in Denver, the Home Depot in Loveland, and several for friends and private parties.  All who have seen it function have been impressed.  It has been a lot of fun to engineer and construct, let alone showing it off.

-Don Smith

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