Hot Bulb Pneumatic Tractor

A lego pneumatic tractor based on a hot bulb engine Lanz tractor. Features drive, single pneumatic engine, adjustable ignition point, steering and suspended seat.


Direct purchase of the instructions

Hot Bulb Pneumatic Tractor
10,00  -Excl. Tax
A LEGO Technic replica of a Hot Bulb Tractor, with a working pneumatic engine. Features drive (operated by the pneumatic engine with gearbox), manual adjustable ignition point and steering, and a suspended seat.

I wanted for a long time to build another tractor to improve the previous and use a single engine with inertia wheel as on my pneumatic machine. The result is here : a pneumatic single engine tractor with a special feature : adjustable ignition timing.

The model is basically composed of a frame which handles the engine, the transmission and the bodywork. The engine is a very simple pneumatic engine with one cylinder. This cylinder drives an axle that is connected to the inertia wheel axle by a gearing of 5:1. On the left side, there is the pneumatic valve that is controlled by a crank connected to the engine rotation through the adjustable ignition timing. On the other side, the axle of the inertia wheel protudes and drives a wheel and a 40-tooth gear which is connected to the fan on the top of the tractor.


The adjustable ignition timing is based on the differential principle. One side of the differential is connected to the engine rotation (input), the other side is connected to the valve rotation (output), the ring gear is locked by a worm gear on it. In nominal rotation, the input rotation crosses over the differential and the angular difference between the  input and the output is null. In set up configuration, the user moves the worm gear, which drives slowly the ring gear, consequently the input is move back and the angular difference between the input and the output is not null. This device makes exactly what an electronic ignition point system makes on a car. It enables to do two things :

  • Find easily the starting point of the engine
  • In motion, find easily the best functioning which makes the running as smooth as possible


The steering is operated by the steering wheel near the seat, it drives an axle which crosses over the frame on the center and operates the steering with a worm gear on a 8-tooth gear. Then, a lever in rubber operates the steering thanks to its resiliency which also enables to have a good turning radius. To finish concerning the steering, the front axle is also  equiped with a pendular suspension which is an improvement of my previous tractor.

The transmission is quite basic, the rotation of the engine is given to a rear axle thanks to many gearing. At the end of the transmission, I have placed a driving ring which a change over catch to make a basic clutch. Thanks to that, the engine can run and after switching the transmission move the tractor.

To finish, I have placed a suspended seat with a spring under it and the whole bonnet can be opened to see the engine running.


On this video, you can watch more presicely how the engine is built :

Building Instructions

As usual I have created instrutions using photo sequence, and Alex an afol (afol1969) has made a brilliant work with it, with creating the pro building instructions ! Therefore I can propose you two version of the PDF instructions, one freely available based on picture, and one other made by Alex, for sale with pro-looked like. The bill of material is available as jpg here or on rebrickable.



Want to check before if you can build the Lego Pneumatic Tractor ? The tractor has been indexed to, the website which matchs your parts with mocs !

You can buy the instructions with the following button for 10€. 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

See it on the shop :

Hot Bulb Pneumatic Tractor
10,00  -Excl. Tax
A LEGO Technic replica of a Hot Bulb Tractor, with a working pneumatic engine. Features drive (operated by the pneumatic engine with gearbox), manual adjustable ignition point and steering, and a suspended seat.

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 🙂

Here is some preview of the building instructions :

If you have not a compressor or correct handpump, you can download for free the 4 Hand Pump controller, which can runs the tractor.


You can modify your switch and cylinder to enhance the performance, even if the tractor works fine with non modified pneumatic parts as they are smooth enought.

Here is the free available building instructions, as a photo sequence :

Downloading the high definition PDF building instructions. Lego Pneumatic Tractor Nico71 – 10mo, PDF

(12) Comments

    i build it and it works i also removed the pump and other bits to it and it runs smooth some of the pices i got for den mark so get them from their

    Bonjour je suis fan de vos création.J’aurai deux question en rapore de ce magnifique tracteur:et on obliger d’avoir plusieurs pompe pour que le moteur marche?Un air-tank?
    merci de me répondre et merci de partager vos créations!

    I made ​​a pneumatic your engine.
    But it does not move…
    I think the switch to it but do you have crafted something to switch?

    I am curious, in the instruction’s bill of materials is a pneumatic pump. I don’t see that anywhere in the build?

    Also, why the long hose behind the tractor? Is it attached to anything?

    Thank you for your generosity in sharing your MOCs and build instructions.


    je me renseigne

    Et t-on obliger d’utiler 4 pompes lego ?
    avez vous un Air Tank lego?

    merci de me répondre

    thank nico for publishing this the time I spent on the net searching for pneumatic engines.

    sincerely, vince

    Je voulais me renseigner avant de monter ce Magnifique tracteur:

    Peux t-il fonctionner avec une pompe


Comments are closed.