I am making a small robot with an Arduino and Technic LEGO powered by stepper motors. I am planning on moving small rocks throughout my machine. Does anyone have an idea of what kind of Technic LEGO parts I can buy to make a variable length conveyor belt? I have a lot of gears so it's the underlay that's my problem. Does some kind of elastic LEGO parts exist that I can use for this? Chain-like or rubber or hard plastic. IT Would be best if I could make it as long connected as I want.

Maximum size of the small rocks is about the same size as an 1x1 LEGO brick, so the conveyor does not need to have a width of more than 2 cm.

  • Rough dimensions would be useful here. How big are your "small rocks", for example?
    – Kramii
    Commented Apr 22, 2013 at 8:20
  • @Kramii Thanks for the comment, i've tried to clarify the size now
    – bogen
    Commented Apr 22, 2013 at 8:24
  • Or, you could use rubber bands.
    – J. Walker
    Commented Jun 11, 2013 at 0:18

4 Answers 4


You will need to decide between 3711 Technic Chain Link and 3873 Technic Chain Tread, or possibly use them together.

Each link of chain is about 1 cm long and 0.8 cm wide 3711 Chain Link and you can get them in packs of 108 (Chain Link Set Product Code: 2000645)

Chain Link Set Product Code: 2000645

The Chain Tread are wider, 3873 Chain Thread but seem to be available only in smaller packs, such as
Set # 9938-1: Conveyor Belt Links (Nominally 36 links)
Set # 1149-2: Bulldozer Chainlinks (nominally 52 links)

  • Thanks for the reply. Do you know what gears fit to those smallest chain links you posted?
    – bogen
    Commented Apr 22, 2013 at 11:27
  • To my knowledge, all LEGO gear teeth are the same size (regardless of the overall size of the piece) and they fit that chain.
    – Fortiter
    Commented Apr 22, 2013 at 11:33
  • 4
    You are correct that the teeth on all of the non-bevel gears will work, but the small 8 tooth gear doesn't work well on the ends due to the minimum radius of the chain.
    – jncraton
    Commented Apr 22, 2013 at 12:06

In this great GBC machine built akiyuki, you can see 2 types of conveyor belts. The first one is made of the small tread links (3873). The second and third ones are made with the large tread links (57518)

enter image description here

He provides many videos and pictures through his blog and YouTube channel.


Dropping stones onto your LEGO doesn't sound like a kind way to treat your expensive Technic parts; I imagine that small bits of stone and dirt will fall through a belt of Technic Chain Link 3711 Chain Link or Technic Chain Tread 3873 Chain Thread, what with them being a chain rather than a belt. This will then lead to other bits of your contraption becoming polluted with abrasive gunk.

Akiyuki also built a brick sorter with a simultaneously tedious and exhilarating video of a machine sorting arbitrary LEGO parts; Photos and an extended discussion in Japanese at レゴのレゴ選別マシン その1). The conveyor belt perplexed me as I didn't know what it was made of. I thought it might be some kind of fabric or custom-manufactured belt.

Searching the interwebs pulled up this video of an effective conveyor belt built by a small child, comments to which make it clear the belt is paper. It's actively driven by rubber tyres at one end, and idles at the other (I'd suggest using part:41531:5 41531 Technic Cylinder 4 x 4 with Pin Holes and Center Bar as a crowned pulley rather than tyres).

This is the same material that Akiyuki uses as you can see in this low-angle shot up into the tensioning mechanism of the paper conveyor belt in Akiyuki's brick sorter. low-angle shot up into the tensioning mechanism of a paper conveyor belt in a LEGO model

Sticky-tape, paper and a smooth LEGO surface underneath the paper to ensure solid support (you don't need to use tiles; try a SNOT technique instead). Presumably you could up the paper to something more robust in the face of having stones dropped on it. You might want to also line the sides of your conveyor to prevent the stones scratching the sides.


Another option is to use LOTS of 60483 Technic, Liftarm 1 x 2 Thick with Pin Hole and Axle Hole as shown in:


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