Switchless Pneumatic Engine

5,00  -Excl. Tax

A simple LEGO Technic Pneumatic Switchless Engine with one cylinder, custom valves, no set up and building instructions.


Video Presentation


How it works

This engine is built around a single double acting pneumatic cylinder, with air distribution using custom valves. These custom valves are composed of 2-hose loops by cylinder chambers (one for intake, one for exhaust), which are operated by pushers on sliding mechanism, connected to a rod mechanism, enabling to pinch the hose to restrict the air flow. It drives also a inertia wheel with a 5:1 gear ratio to provide momentum to the engine.

It is based on a modified version of the one I did 3 year ago and extensively a simpler version of my Switchless Machine, with less parts, fixed ignition offset and modified actuation to use the widespread 11l / 88mm hose instead of rare 11.25l/90mm that I used before.


How to build ?

You only need the parts and the instructions. You can purchase the PDF instructions on this shop and build it with your own LEGO parts. The instructions contain the partlist at the end, but you can check individually on Rebrickable.

Please note that you need to have you own source or air (2 bar with constant flow). You can use :

  • 4x pump LEGO like this one
  • Use a LEGO compressor according to the specs
  • Use a electrical compressor like automotive compressor, industrial or electrical pump, you will need to put the air in the LEGO hose with . You can use a ball needle.
  • Use a hand pump with ball needle.


The hose for the timing assembly have to be carefully chosen (4x 88-92mm lenght). They have to be soft enough to have an easy pinching and strong enough to handle the pressure. For instance, the last hoses in the 42100 are glossy and hard to pinch, the very old pneumatic hoses from 90’s is too soft and do not handle well the pressure.

The ideal hoses are those which come from the sets from some year like the 8436, or the 8455, you can use also the hose from the 8110, 42043 or 42157 if they are not the glossy version. The white hoses I use in the video are  from Blokbricks which are very similar to the LEGO one and can be purchased at meter.

You can use other hoses but you will need to increase the pressure if the hoses are too hard to pinch (like the glossy one) and reduce if it is too soft (like the very old hose). Regarding the dimensions, with the new design, I have tested 88mm, 90mm and 92mm successfully. 

I have not seen any wear on the hose, even if they tend to keep the shape of the loop some time after dismantling, they recover their original shape without any leak or damage after some time. But I think it can be damage if they rest for a long time on sun-display with no pressure. So if you display this creation, remove the two gray pegs, to remove the two yellow liftarm and so the grey fork assembly on the loop.


About this product

Instructions preview

Additional information

Model Size

19cm (L) x 13cm (W) x 16cm (H)




All, Machine



Building Difficulty


Piece Count


Purchased File

PDF Instructions (About 49 pages / 36 mo)