This idea came forth form a question from my oldest son (9). He has his LEGO with his brother (5) and I have mine. Up until now we have kept it as separate stashes. My collection consists of many Technic parts including many PF pieces and the entire RC motor set from the 8366 racer set.
My son loves the motors so came up with the idea of building a hovercraft.
So the result is a ;arge hovercraft made out of Lego and plastic bag, which rises up in several seconds to a height of 6 centimeters. The second fan, rear mounted and the steering mechanism make it fairly agile. It goes approximatey 3 km/h on a slick floor and can easily take a rough terrain.
Oh someone pinch me please! Yeah I'm back again. Well, now you know what kind of goal we set. The plan is there, now to make it work, if possible.
As I recalled the builds made by pixel on Brickshelf LINK and LINK, I figured this should be possible, but than on a grander scale. If real hovercrafts are able to lift many many tons, than the RC-set with the powerful high speed 5292 motors should be able to lift the battery box as well.
Our first build consists of two rotors – one in front and one in the rear – to provide lift via a propeller. We used different configurations: technic panels (4 blades), 4-wide plates (6) and 2-wide plates (10, using the new tracks on a track sprocket wheel) but they don’t give enough lift.
Google provided some backup. There appears to be a difference in setup depending on if you want high flow or high pressure. Surely, in this case the flow isn’t important, but the pressure is. Using a propeller, the buildup of pressure is too low and the ‘holes’ through which air(pressure) can escape are too big. That raises the question: how is this done with real hovercrafts?
The answer to this question is: using centrifugal fans. There are many types based on the wings attached in the wheel, but a backward facing type seems to be the most appropriate as was used by the large British hovercrafts as well (for instance SR.N4). The power of centrifugal in Lego was already proven by a builder with a YouTube movie using rotating gears to lift water fifteen centimeters purely by generating pressure LINK. So that’s what my son and I tried.
We built two types untill now and only tested it in a testing setup. Firstly with eight large fans and pretty small air intake in the middle. A single 5292 motor can handle this, but not with ease. The RPM slowly grows untill a pretty strong air flow is there. But is this enough?
The second looks more like a real Hovercraft fan, again with eight fans, but smaller ones and a larger air intake. Professional centrifuges are even thinner. I hope this gives enough power to lift a LEGO device. Alas we will have to rebuild the hovercraft itself due to other dimensions. For now, just something to share. Stay tuned.