Last month Josh David posted a cool LEGO model of a lawn mower endlessly cutting grass. As soon as I saw it I wanted to build my own version with my Sisyphus figure pushing the lawnmower. I guess you could think of it as a ‘modern day Sisyphus’. I explain how it all works in the video, and you can find building instructions below.
The figure uses the same walking mechanism as in my original Sisyphus model, called a Hoeckens linkage, though I modified the geometry a bit to give it a more upright stance and shorter stride. The ‘grass’ consists of two conveyor belts, one in front of the lawnmower with tall grass and one behind with cut grass. This is essentially the same as in Josh’s original model. The lawnmower is held down by gravity so that the conveyor belts turn the freely spinning wheels. It is loosely mounted on a LEGO brick to keep it in the correct position.
I added some simple decorations on the base to represent what is happening on top of the model, with uncut grass on the left, the lawnmower blade in the middle, and cut grass on the right.
Update 11/18/2017: Thanks to the efforts of Kevin Williams, building instructions are now available for this model! He analysed my ‘building of‘ video to recreate the model digitally and generate step by step building instructions. I know how large a task this is for a model this size, so a huge thank you to Kevin for doing it.
For those ambitious enough to try building their own, there are a few things to note.
As I mentioned in the showcase video above, the connection of the plates to the tracks isn’t as solid as a standard LEGO stud connection. If the plates catch anywhere on the frame as they are traveling, they might fall off. This is why I designed the base of the model open underneath the belts, so that you can just lift the model to retrieve the detached ‘grass’. One thing you can do to minimize this issue, is that as you finish building the frame, gently pull the sides apart to ensure they aren’t binding tightly against the conveyor belts.
There is also very little clearance in a few places where the grass travels through the frame and also between the uncut grass and the front of the lawnmower. You will want to ensure the carrot tops are pushed in as far as possible and the plates are as snugly attached to the tracks as possible. The orientation of the carrot tops on the outside rows will also affect how smoothly they enter the lawn mower.
As with any LEGO Technic model, it helps to check that things are running smoothly as you are building it, and that none of the moving components are connected too tightly together to hinder their motion.
If any of the instructions are unclear, watching my ‘building of‘ video might also give you some insight into how parts of the model are constructed.
A huge thanks to Josh for posting his original model that inspired this!
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