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Magnetic Fridge Climber

A simple walking mechanism using magnets to climb a fridge.  


Completion date: 03/07/2023
Power: electric (BuWizz 2.0)
Remote control: BuWizz 2.0
Dimensions: length 47s / width 19s / height 9s
Weight: 0.42 kg
Suspension: none
Propulsion: 2 x PF L motor geared 8:1
Motors: 2 x PF L

We have recently acquired a fridge with flat metal front, and it got already scratched by kids, so I was free to experiment on it. Naturally, I was able if a LEGO vehicle could climb it using magnets. To the best of my knowledge the best LEGO magnets in terms of size VS pulling power are the old LEGO Train magnets, so I have adapted a chassis from my old walker MOC and started testing.

It turned out that with six magnets the vehicle was able to stick to the fridge but kept sliding down from it, with eight it could stay in place but would slide down when trying to move, so I went for sixteen and that made walking possible for as long as at least six legs remained in contact with the fridge – so only two legs could go up at a time. Essentially, for a vehicle weighing 420 grams 12 magnets were needed to keep it anchored, and of course the center of gravity was a huge factor too, which is why the vehicle was so flat. It was possible to add more magnets and perhaps try walking upside-down, but at certain point the magnets would be so strong that they would block the motors from moving the legs, and I felt that this point was already close.

Of course, it would be way easier to simply build e.g. a tank with magnets on tracks instead of a complex walking mechanism, but there is a purely economical issue – seeing as these magnets are quite expensive, I was trying to use as few as possible. With the walking mechanism requiring 12 magnets to stay on the fridge, I was able to make it move with 16 magnets total. With a tracked vehicle requiring 12 magnets to stay on the fridge, at least 28 magnets would be required in total, since tracks have two sides and some height, too, so let’s assume 2 x 12 + 4 magnets.

The vehicle was only able to go up and down with very little left/right inclination, it couldn’t turn around without falling off, and it would still sometimes fall off when walking straight. Still, I feltthis was an interesting experiment that demonstrated the strength of LEGO magnets.


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