A simple Lego Pneumatic Engine which runs with two pumps, unmodified switch and cylinder, even the hardest, with building instructions and available for sale.
Direct purchase of the instructions
Preview of the instructions at the end of the article.
Since the launch of the new service Buildamoc, I wanted to create an affordable and reliable small pneumatic engine, to compare with the more expensive Steam Machine. Therefore, I have chosen to use only one cylinder and one switch, in order to be able to run with only 2x Lego pumps and reduce the cost to the minimum. I wanted also to propose a design which can work with any switch or cylinder, even the hardest, in order to be sure it will works.
There were consequently two challenges : make the engine running with only one cylinder, and be able to work with any switch or cylinder regarding internal friction. Make run a single engine is a bit more complicated than a two cylinders engine, because the second cylinder can help the first when he needs, for instance on the dead point of the switch. To overcome this problem, the solution is easy : add a inertia wheel. As on my previous engine, I have chosen the big rack wheel with 1/5 ratio to create a big inertia wheel and help the engine to run smoothly.
The second problem regarding using any switch or cylinder is caused by the internal friction. It can be overcome by a large inertia wheel but as there is only one cylinder, the inertia must be enough to pass the deadpoint without bump but not too big if the cylinder has lot of friction. Therefore, the inertia wheel can’t be the only solution. The deadpoint of the switch must be reduce. As I do not want to modify the internal design of the switch to easy source the parts, I use a special mechanism to reduce the moment when the switch is on the deadpoint. It is based on a big crankshaft to have important displacement of the connecting rod, and a sliding connecting rod with two end stops. In this way the moment when the airflow is locked is limited to a small time, enabling a smooth running, even on low rpm.
Pictures and Video
Purchasing the creations
As for what I have explained, I think this creations is a good start to work with Lego pneumatic engine, to understand how it works, fell the limitation of the Lego and the solutions to overcome them, including the deadpoint of the switch, the inertia of the wheel, the gearing, but also its basic functioning with physical value like the airflow, pressure, speed and torque.
That is why I have added this creation to Buildamoc, in the version, “2x Pumps in handpump”. You can purchase either the whole creation on the website Buildamoc including the Lego genuine parts and building instructions in PDF, or just the building instructions on nico71.fr.
Want to buy this creation ? The Vertical Engine has been indexed to Buildamoc and is for sale. The whole package included the Lego genuine parts, and the Pro rendering PDF building instructions.
Please note that the color and the length of the hose can vary, you only need to respect where each hose is connected and have to cut it if they are delivered in one piece.
There are not so many instructions for non-modified pneumatic engine, that is why I wanted to create a high-quality building instructions for this pneumatic engine including three version depending of your collection of parts. The building instructions are 3x PDF of about 70 step by step pages computer rendering building instructions in a same way Lego do.
Here is the complete bill of material for the “2x Pump in handpump” version but you will also receive the inventory for each version :
You can buy the three PDF instructions + 3x Bill of material with the following button for 5€. You can also buy other building instructions and get an automated discount. You will get 15% off for 2 PDF, and 20% off for 3 PDF on the total), available for all the instructions for sale on nico71.fr.
After your payment, you will be redirected to a page for downloading your instructions, and will receive also the link to download by email. Please check the spam box and be patient to receive it. If you have trouble to download your copy of the PDF after payment or open the document, do not make a paypal dispute, please contact me using the contact form. The link to download the instructions expires within 24h. Contact me if you have lost your instructions. Note that you can print it, but not copy or distribute. Thank you for supporting my work 🙂