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Lego PF throttle for pneumatic engine
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Here is a post of a recent invention; an electric throttle to control the air supplied to my inline 3 pneumatic Lego engine. As can be seen in the photos below, the linear actuator controls the Lego switch, which gauges the amount of air available to the engine, much like a throttle to a combustible engine gauges the amount of fuel that is available to that engine.
About this creation






The Lego switches are actually quite difficult to switch. Much force is needed. Therefore, I did a couple of things to facilitate movement of the switch. One, I geared down to 1:2.8 (as can be seen in the photo above), increasing the amount of torque on the lever but also slowing the speed of the actuator. This did two things; (1) as mentioned, increased torque and (2) slowed the speed of the actuator. The latter was beneficial because I also wanted the available air to the engine very precise, so slowing the actuator speed was desirable. As can be seen in the video at the end of the post, this made minute changes in engine speed possible. I also lengthened the switch axle, which works much like using a larger wrench when trying to screw on a bolt; it increases torque.



Below is a pic of the whole getup.....

This gadget is large and fairly unwieldy, and including it into any MOC may seem difficult. However; it is totally possible. Couple of things….. One, I created this only for illustrative purposes. Making this same gadget in a smaller, more compact form is easy. First, I used a large linear actuator because original Lego switches are very hard and rigid. These can be modified and indeed often are to create better Lego pneumatic engines (interested readers can simply google “modifying Lego switches” and they will get a litany of responses). I have used all of mine, and therefore do not have any, so I needed to use an unmodified switch which necessitated the large actuator for this invention in order to push the lever. Modifying a switch, and therefore making it possible to use the small actuator to control the throttle would reduce the size immensely. Doing so would also rid the need for gear reduction, decreasing the size further. The motor could also be mounted sideways and connected at a 90 degree angle with the beveled gears, increasing the width but increasing compactness. Overall, this contraction could easily be modified to fit into a MOC. I have not attempted to do so for two reasons (1) modifying switches is hard, and every time I try it I go through several switches before I get it right, therefore it is expensive, (2) really, there is not much of a need because in order to make this throttle useful, the air supply would have to be on board, and not provided externally. This obviously, would require a very large MOC. You can see how large my air tanks are in the pics, and even this tank only provides about 60 seconds of power. Although building such a huge project has been done before http://www.youtube.com/watch?v=_ObE4_nMCjE.



The draw to a contraption like this is obvious…. There are some really cool cars driven by pneumatic Lego engines out there, my favorite being http://lpepower.com/. However, all these cars are driven manually, that is, the speed is controlled manually by either manually controlling the Lego switch or manually controlling the air compressor. Why do something manually when you can control it electronically with gizmos???!!!

The air tank is my own creation. Pics below. Cut out the nozzle of any bike tube (I used a tube from a racing road bike) to get the intake valve. Not Lego  Although Lego does have its own tanks, I would need a bazillion to make them purposeful for a Lego pneumatic engine.





Last, a video. Yes, this gives a little sneak peak of a project I have been working on (What???!! A pneumatically driven Unimog!!) but not quite finished (darn steering and weight issues!)





Comments

 I like it 
  May 25, 2015
This is pretty cool. I have not experimented with pneumatic engines, but this makes me want to.
 I like it 
  December 30, 2014
Excellent bit of LEGO engineering and documentation on both throttle and air tank! Especially like your use of the bicycle valve as an air tank fitting. BTW, if you find a way to make a small LA work, I recently found a very simple but very robust LA-to-lever coupler allowing just the right degrees of freedom -- the "Technic Rotation Joint Ball Loop with Pin with Friction" (BrickLink #41680; cheap but sometimes hard to find). Pin goes into LA shaft connector; free end of lever goes through the loop. I find that looping the free end of a 3L straight #2 angle connector provides both a little more leverage and a stop to keep the loop from sliding down the lever toward the fulcrum.
  September 2, 2014
Hullo good sir! I just wanted to say you have added quite a few builds to the group The Fellowship of the Brick. One of our rules is that you only add LOTR based Mocs and some of your added creations are cars, ships, ect. Please do not add anymore non LOTR Mocs to the group please. Thank you
 I like it 
  July 28, 2014
Very nice!
 I like it 
  July 28, 2014
What you did is a typical example of a theoretically simple thing which is very hard to do it corretly and reliably in the practice. Especially from Lego. Lot of engineering, great work!
  July 27, 2014
Extremely cool!
 I like it 
  July 27, 2014
like it great concept
 
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LEGO models my own creation MOCpages toys shop Lego PF throttle for pneumatic engineTechnic


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