Richard's Hovercraft
A log in (moving) pictures
Eppur si muove
She has no skirt. The friction of the board against the paving stones stops her running away.
Paint it black
One of the (many) things they don't teach you at school is how to attach plywood to polystyrene. Fortunately, thanks to the magic that is gaffer tape, I was able to secure the gash piece of ply I found on the way home from work to the surfboard I mentioned last time.
I seem to be missing the bits of Meccano that I used previously. Howewver, I had enough bits to assemble the frame that you can see in the second pic, and with any luck, in the next couple of days (after the second coat of paint dries) I'll be able to slot the engine into the hole and secure it in place.
Update, Sunday:
Monster downunder
After a long, long time not even running the engine, then dismantling the prototype and moving to Australia, something happened! Yesterday (Friday), I had to leave work early to pick up the girls from school, and wandered through Burwood, where — wonder of wonders! — I found a model shop. They sold me a litre of model fuel, and I took it home with joy in my heart.
That evening, I dug out the motor and the glow starter, clamped the engine, re-attached the prop and gave it a go. The starter was flat as a flat thing, but after a few minutes on charge there was enough of a splutter to encourage me that it would still work. So I left the starter on charge overnight.
And this morning, this. That's me priming the line, setting the throttle and starting up - for the first time in nearly two years. A few minutes of adjusting and warming up, and I was able to remove the starter. That's one hell of a draft, again, and now she runs until I want her to stop.
The next stage of the plan involves a surfboard.
Monster mark III
Got an even bigger push prop today.
That's a full 11/8", and she sounds much smoother for it. Doesn't rattle the nuts so much, and there is one hell of a draft!
Monster mark II
Spent $TOOMUCH on accessories yesterday. Found a new piece of board, did some drilling, cutting and screwing, and . . .
Fed her some petrol, on with the glowplug, flop, flop, twiddle the choke, flop, splutter, fiddle the mixture, put put put VROOOOOMMMMMMMMMMM. Woohoo. Only ran for a few seconds because the noise and the smoke in that confined area (the garage) was a bit much for me, but it was a real adrenaline rush. If I get chance tomorrow I'll bolt the petrol tank down, and make the firewall more secure, then on Boxing day I'll be able to show her off to Dad when the family descend in their hordes.
Happy Christmas to you all.
Update 16:30
750 kb movie. Wheeeeee!
Bigjobs
After the boss did his best to thwart me, I bought a new engine from eBay - the bid was accepted with one second remaining on the auction! This picture doesn't do it justice, but it's a meaty, grunty, leap tall buildings in a single bound engine. I may have to increase the size of the craft. . . but I can't do anything else until payday (need glow plug charger and fuel lines and fuel etc).
Bugger
Got a tuit and ordered the push prop (8/6) from an online place. It arrived quickly . . . and the bore is too large. Argh! Fortunately I know this guy who happens to be chief tech support guy at CIBA-Geigy. I love the smell of Araldite in the morning.
And if filling and drilling doesn't work (thanks to Rob for the idea) then I'm seriously consider getting a larger, petrol engine anyway. We shall see.
Achtung Spitfire!
Still waiting for my push-prop. In the meantime I finally got around to liverying up this model I started > 2 years ago . . .
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Meeeeow!
Backing up
Long time, no see. I've cut the board down a bit to reduce weight:
And here, you'll notice
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I've turned the
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engine around
She's now ready to take the 8/6 pusher prop that is on order. And yeah, that's D-2000 fuel. w00t.
An Oscar-winning performance
Stuck some drawing pins in the bottom of the bag to attach the bag to the underside of the body, and cut a couple of holes. The pins popped straight out, but I did get a couple of movies (876kb) (688kb). I really need to get some kind of widget to hold that compression screw in place.
And they said I was crazy . . .
Fitted the fuel tank holder tonight:
Again, the magic of Meccano.
You know, there's a reason Meccano is for small boys,
not grown up (hah) folk with whopping great fingers.
The tank has a sticky-outy bit that fits under that bar on the right.
Holds it in place quite nicely.
The deal with the masking tape and the bin bag
is the exciting part of tonight's tale, though.
I put tape onto the board, then taped the bin bag to it, to act as - well, think of it as a hot air balloon, but upside down. This is a test after all. Then I ironed the bag down onto the underside of the board to make a good seal.
It took me a long time to get the engine going, but when I did she inflated quite rapidly - too fast in fact, and she tipped and the fuel cut out before I could grab the camera.
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Going down. . .
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Flying! Actually staying up under her own steam.
Fortunately I was able to get her going again, and got an action shot of her in mid-'flight'; you can see my hand keeping her down. The camera had a fit and I didn't save the movie, unfortunately. But she flies!
Frankencraft
I had these sprung beech slats. Quite a bend on them, but the weight, thickness and material otherwise seemed perfect for the body of the hovercraft. I tried steaming them with a wallpaper stripper, soaking them in a water butt, bending them the other way in my vice, even quarter of a ton of Rover in the drizzle overnight: But they remained resolutely bent.
But what the heck, I thought, maybe I can get away with it. So I printed off my plan/template, got the mitre saw out and arranged the bits appropriately:
And it looked reasonably OK. A bit of warpage, but not too bad.
Here you can see them laid out with the engine in place,
but nothing's permanent at this stage.
The next step was to drill holes and countersinks,
and bolt the Mecanno onto the slats to hold
everything together and give me a frame.
It worked far better than I had any right to expect. A line of No more nails in the creases, and to seal the countersunk nuts, and it's actually pretty solid.
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Bolted down
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ready for gluing
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Stuck fast
You'll notice the engine block in that last picture, the hole and the yellow sheet that's a place-holder for the air intake to the skirt. That's the next part to think about, and I see lots of headaches ahead.
Steady progress
Sat down this evening, desperately recalled my tech. drawing training, and drafted the base plans for the hovercraft (someone I know said they liked the 'Frankenstein' effect. Hmm). Not much detail at the moment, but you can see the sort of thing I'm aiming at. And yes, I know the base/skirt haven't been drawn on yet. That's the next stage. At least, after I figure out how to straighten the sprung beech slats I'm going to use for the main body.
It lives!
I hinted (previously) at a project. Well, time to spill the beans. Dad and I are building working model hovercrafts; in my case at least, from bits and pieces to my own design. I have an idea in my head and some sketches in Appleworks. I'll post those at some point. I think Dad is going for a two-engined electric jobbie: I want to do it with a single, internal combustion engine (because that's cool, noisy, and there's lots of black smoke and it makes me feel like a pioneer).
I got a second hand PAW diesel engine off Ebay. It's a sweet little thing. I fitted a new muffler and gaskets, but I haven't got to the model shop yet to pick up the diesel fuel line matey had to order in for me. So I glommed a short length of silicon tubing (not ideal) and a dead reagent bottle and made a temporary fuel system. And guess what? It works!
That prop is actually spinning at a large number of revs per minute (~ 10 - 16 k I guess). The little Samsung digital camera is so good the prop appears stationary, but if you look closely you can see the cylinder cooling fins through the blade. And here it is, spinning. Woohoo!
Update: 04May04
From strength to strength. Got her started after only a minute or so this evening. Ran until I knocked the fuel bottle over - oops. But! I got her started again while still warm, and inflated a bin bag under the bench from the down draft. I also discovered that the vertical positioning of the fuel tank is critical. The top of the fuel needs to be below the carburettor, so that she runs by suction. Place the tank too high and the engine floods, and sputters. Lower it, and VROOM.