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View Full Version : Can I power a Hovercraft with a lawnmower engine?



mikeot
28-Jan-11, 02:03 PM
Hi,
I was wondering if someone would be able to tell me whether I could use a lawnmower engine as a lift fan on a homemade hovercraft and also where a good place to source a fan cheaply is.

JOHN STEAD
28-Jan-11, 05:00 PM
Hi,
I was wondering if someone would be able to tell me whether I could use a lawnmower engine as a lift fan on a homemade hovercraft and also where a good place to source a fan cheaply is.


hi
some do use lawn mower engines for lift, a little bit more detail will be needed before any usefull advice can be given,i.e what size and weight is the craft,what do you intend on using it for?

john

mikeot
28-Jan-11, 09:56 PM
Hi John,
I'm intending to build it from plywood, I'm not sure about the weight but I'm hoping to keep it under 200kg. I was just hoping to build it to try my hand and hopefully learn a bit about building them, I'll make improvements on the Mk2! I'm hoping to build it quite cheaply really that's why I wanted to use the lawnmower engine, it was being chucked out by my dad. I was also hoping to use finger skirts but I heard these need a more powerful engine. I was hoping to make it no bigger than 2440 x 1220mm so I can easily make it out of sheets of ply without too many joins.

Mike

JOHN STEAD
28-Jan-11, 10:20 PM
Mike
Have a Search of this forum for previous threads giving very good advice on taking on a project of this sort. There are a few members who have gone down this route. And I am sure one of them will be along shortly with some advice.
Where aboutís are you?
john

David Ryan
30-Jan-11, 09:24 PM
I have had a Vortex Evo with a 5.5 hp Briggs for lift and it did the job very well. At the moment, I am close to finishing a UH13 and it has a 6.75 hp Brigggs for lift. You can also use a lawnmower engine for thrust. The Evo had a 22hp Briggs and the UH has a 25 hp Tecumseh. The small Sevtec Scout will opperate with an 18-22 hp providing both lift and thrust. Good luck with the build.

Keith Oakley
31-Jan-11, 08:07 AM
It will need to be be bigger than a single sheet of ply (2.4m*1.2m) though. Thats a lift area of 8*4ft = 32 sq ft. Using the rule of thumb of 10lbs lifted by each square foot thats a total all up weight of 320lbs including driver. It probably needs to be a minimum of 10ft by 6 =60 sq ft and thus an all up weight of 600lbs.

You can still do it with 8*4 sheets of no more than 5mm thick ply (preferably 3-4mm). With sloping planing surfaces underneath most pieces will come out of a single sheet of ply. Joint them by drilling adjoining holes in both panels then use a loop of wire through the holes like a wire bound book. When its all in position apply a 50mm strip of glass cloth in grp resin on both sides.

As an alternative you could build a hovering wheel barrow project with a single 3.5-5bhp lawn mower engine 8*4ft and no thrust. It will lift a large child or similar payload and you can push it round the lawn. Graham Nutt even used one to move house!

You can find a useful 'Guide to Hovercraft Design Principles ' on this site - click on Forum above, then 'Free Downloads, Suppliers, & Links'. At least 2 of the companies listed here (Vortex & K&M) will sell you a fan and the hub adapter you need to fit it to the engine.

Good luck
Keith