Welcome to the LEGO Engine home page.

Site of the first air-powered reciprocating LEGO engine.
(AFAIK)

Introduction

    I've had a lot of fun over the years building many projects out of LEGO blocks.  I can remember the first lego set my brother and I received in the late 70's which was nothing more than a bunch of square blocks with a few 2x2x2 wheels included.  Over time, we branched out into Master Builder sets (our first being the Go-Kart with the #9 sticker on the front which incidentally, I still have this original #9 sticker - new and never used), and Technic although I still prefer the "Master Builder" label.  Anytime we've ran across lego sets at garage sales and 2nd-hand stores, we've been quick to snatch them up with the result being tons of  miscellaneous legos from all over the timeline - many we don't have a clue as to what sets they are from and how they were originally supposed to be used.

    Prior to our LEGO engine revolution, we've made various projects that we are extremely proud of - sadly, we don't have pictures of any of them.  Projects we've completed to date are:

1)  Very nice model of the space shuttle using every last white lego block in our small set.
2)  2wd pickup that was geared down enough to haul a 2 liter bottle of pop across a linoleum floor.
3)  A pneumatic lift which hoisted a watermelon and 2 liter bottle of pop approx. 1 to 2 inches off of the floor.
4)  Centrifugal clutch with a 6" diameter - calculated to run over 2,100 rpm and reach a speed of approx. 53 m.p.h.
5)  Machine Gun & Pistol with approx. 10' range.
6)  Crash test dummy cars - built to purposefully explode on impact.  (Kids - don't try this at home!)

    But one creation that has eluded us for a long time is the LEGO engine.  Besides not knowing whether such a feat was possible or not, we always somehow ended up with projects that needed parts we didn't have, or the prototypes just didn't run.  Many projects were torn apart and eventually, we shelved our legos as we grew older but the lure to build the LEGO engine always ran strong inside of us.  In 1993/94, the urge to build with LEGO hit again due to newfound inspiration thanks to the 'net.  I then set out one evening in January of 1994, to build a LEGO engine and with a few new Technic sets and 4 hours of my time, I built the first running LEGO engine.  I was elated to say the least and to date, a total of 4 lego engines have been built - 1 by me and 3 by my 2 brothers.

Objective

      When I set out to make the LEGO engine, I had to know what limitations to work around.  It was obvious that if I was to mimic the reciprocating engine, my cylinder would have to be square (as well as the piston) due to the nature of LEGO itself.  We considered using the penumatic cylinders but gave up this idea primarily because we felt it was considered "cheating" to use a ready-made cylinder.  What you are actually creating then is a valve-switching mechanism which just happens to mimic an engine and not a true, pure lego engine.  The valve we did have worked awfully hard and we didn't want to tear into our only valve only to ruin it..  Also, this engine was going to have to be 2-cycle in nature and run off of compressed air.  Burning fuel or using steam was obviously out of the question.  Being familiar with 2- cycle and 4-cycle engines from a young age, I tried to envision the engine itself made out of LEGO but with all the LEGO limitations factored in.  In the end, I just started putting pieces together and building the engine as I went along.  Fortunately for me, it worked when I was done.

Operating Principle

     The nature of the LEGO engine is 2-cycle.  This means that as air enters the cylinder, the piston is forced downward and once it comes back to the top of the cylinder, it gets another blast of air and goes down again.  Controlling the flow of air is accomplished by valves that are timed to let air in and out of the cylinder.  These valves are operated by cams that are located on the crankshaft itself.  In 3 of our 4 LEGO engines, the valves are external and are opened and closed as previously mentioned.  The 4th engine however is a special case (the valve is operated within the cylinder by the piston.)

    To help one to understand how such an engine does work, here is the explanation of the cycles of the LEGO engine.

1)  Intake valve opens and lets air enter the cylinder (piston is at TDC.)
2)  Air flows into the cylinder under pressure and forces the piston down.
3)  When piston hits BDC, the intake snaps shut and the exhaust valve pops open.
4)  The flywheel helps the crankshaft to keep spinning and brings the piston back to the top of the cylinder.
5)  Piston is back at TDC and exhaust valve closes.
6)  Go back to step #1.

(TDC = Top Dead Center        BDC = Bottom Dead Center)

    Any anomolies in the timing and the engine won't run.  For example, if the intake and exhaust valves are open at the same time while the piston is at TDC, the air, taking the path of least resistance, flows right on out the exhaust port and the piston doesn't move.  If the exhaust valve doesn't open when the piston tries to come up, it can't exhaust the air and the engine will stall.  It's the fine balance of the valve operation in relation to the piston that makes the LEGO engine run - couple this with the limiations imposed by LEGO pieces and you have a real challenge on your hands.  You just can't slip that gear or pulley on the axle anymore - you have to position it on the axle just so or the engine won't run.  While building the LEGO engine, you've got to always keep in mind, "The valves must dance to the tune played by the piston."

Photos with Descriptions

    You can click on the following links to see pictures of the 4 different engines with descriptions and explanations of how these babies run!  Please keep in mind that all of these engines DO ACTUALLY RUN off of compressed air - they are not _just_ models.  Below, items 1 thru 4, are listed in the order of their creation.  The rest are other submissions (these are great!)