A simple Lego Pneumatic Engine which runs with two pumps, unmodified switch and cylinder, even the hardest, with building instructions and available for sale.
How to build ?
You only need the parts and the instructions. You can purchase the PDF instructions on this shop which contains the partlist at the end, and you can check on Rebrickable (2x pumps in handpump) or in the instructions preview below.
Vertical Pneumatic Engine
The instructions are delivered in three different versions :
- No pump (you need your own source of air : compressor of bike pump / 2-3 bars)
- 2x Lego pumps
- 2x Lego pumps in handpump (better grip)
If you do not have the parts, you can purchase the complete kit from retailers :
- Using Genuine LEGO Parts : This model is available at Buildamoc, in a complete package including LEGO Genuine Parts and PDF instructions (2x pumps in Hand Pump)
- Using non-Genuine LEGO Parts : This model is available on LesDiy Store in a complete package, including parts (alternative bricks from China) and PDF Instructions. (2x pumps)
Design Process
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
How to build ?
You only need the parts and the instructions. You can purchase the PDF instructions on this shop which contains the partlist at the end, and you can check on Rebrickable (2x pumps in handpump) or in the instructions preview below.
The instructions are delivered in three different versions :
- No pump (you need your own source of air : compressor of bike pump / 2-3 bars)
- 2x Lego pumps
- 2x Lego pumps in handpump (better grip)
If you do not have the parts, you can purchase the complete kit from retailers :
- Using Genuine LEGO Parts : This model is available at Buildamoc, in a complete package including LEGO Genuine Parts and PDF instructions (2x pumps in Hand Pump)
- Using non-Genuine LEGO Parts : This model is available on LesDiy Store in a complete package, including parts (alternative bricks from China) and PDF Instructions. (2x pumps)
