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Step 3: The Thrust Engine

The thrust engine was a little bit harder than the lift. It has a larger fan, a pulley reduction and a large fan duct. I started off with the fan. It was hand made with a welder and some steel. This is not a good idea, the fan has to be perfectly balanced and the pitch of the blades has to match the power of the engine. I you are going to build a hovercraft do not build you own fan. I was lucky that my fan did not fly apart and kill me. Do not do what I did here and get a good fan to use.

So once you have a fan you need to build a duct. I used more lauan plywood to cut out the shape and screwed in a bunch of 1x2s to hold the two pieces together. Then I wrapped more aluminum flashing around the whole thing to make the duct.

The fan was mounted to a 1/2in shaft that ran through two brass bushings with a pulley on the other side. This was all mounted on a 2x4 and plywood frame. Then a smaller frame was made to hold the engine up so that the belt would fit. No type of clutch was used on the engine which is typical for most hovercraft. This finished the thrust engine and fan.
 
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pavilion891 year ago
My craft is about 8 icnh height, 8feet length, 4 feet wide and capacity for a person only. is 2.8hp enough ?
dbc1218 (author)  pavilion891 year ago
I don't think that will be enough unless the craft is very light. check out this http://www.instructables.com/id/10-HP-Hovercraft/ same size but uses a 10hp engine
pavilion891 year ago
what is the suitable material to built a fan for engine of 2.8hp?
dbc1218 (author)  pavilion891 year ago
I would not recommend building your own fan, especially not like the steel fan I built for this craft. Most fans/props I've seen are made from wood or have plastic baldes connected to a center metal hub. Also, if your building a craft similar in size to mine, 2.8hp won't be enough power.
charles615 years ago
Propeller has flat blades : much noise , bad aerodynamic and poor thrust.
You have to wharp the blades so that they have the same diametral pitch (at any distance of the center) . Furthermore, it shoud be good too to give the blades some curve (put a look on an airplane wing ) and to sharpen sligtly their trailig edge ...and make the leading egde 'round' . As a result you will obtain MUCH better performances : much thrust for less power !
a safety gaurd would be a really good idea . safety first n all that. nice project
bayaan196 years ago
what did you use to make sure your carborator is facig upward?
yrmoma6 years ago
I wonder if you could make this fan Collective Pitch, that way you could have a way to better control the speed as well as have reverse... Anyone ever try this or have an idea how feasible it would be?
Nfiltr86 years ago
In order to have a duct that affects the air flow significantly, the margin between the fan and duct has to be under .25". You would have been better off putting the aluminum flashing on the inside of the duct's frame.
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