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Scratch Build – In Progress Project: Hovercraft - 23rd June - loads of pics *finished*

Discussion in 'Project Logs' started by profqwerty, 1 Sep 2007.

  1. profqwerty

    profqwerty New Member

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    Scroll to the end for decent pics :)

    Ignore these images....they don't matter too much..should have used a quality image hosting. smack on the wrists lesson learnt:p


    Here it is, the much anticipated hovercraft build log. I am making a cub scout promise to remember to take pictures of the building of. I usually forget, and when i do remember i think "i don't really want to touch the camera with hands this colour:p".

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    The hull upside down - laying some planks of Iroko to use as runners when it bottoms out. Also good if it stops on rocky ground as there is a degree of leinicy with the surface. Also good for stopping on concrete / tarmac as this wears out the GRP and skirt.

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    had to clear the crap out of the garage first

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    cut the wood with a hand buzz saw (vicious little bugger), then screwed it from wood>GRP with 6*1.25s screws (two each)


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    then turned it over

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    and put in zillions of 8*1s to make absolutely sure they don't rip off, especially when it hits the ground sideways. I am going to put something on the front of the wood and onto the angled bit of the plenum so the wood doesn't dig into soft ground.

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    Screwing them in. it takes a 2mm drill bit thru the grp and a little way into the iroko, then a 3.5mm bit thru the grp. This lets the screw turn in the grp without ripping it too much, whilst it can tighten into the wood. the large heads on the size 8 means the grp doesn't split.

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    nice little shot of the screws ready for screwing. i said i was going to do loads of pics!
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    and there it is! didn't have much time this afternoon. I spent a lot of it trying to get some bearings into the drive hub, but they're a damn tight fit!

    hopefully more tomorrow!

    profqwerty
     
    Last edited: 23 Jun 2008
  2. tranc3

    tranc3 ADHD Modder

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    wow i always wanted to drive a hover craft. how much is this coasting you?
    This looks amazing.. it looks like the one from GTA san Andreas
    What is that mean looking go cart in the second photo?
     
  3. TTmodder

    TTmodder Hammertime

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    Prolly a ghetto home build gocart. once build one myself with a 2 cylinder citroen engine and auto gearbox. the frame was too weak and sold the rest pieces
     
  4. Stonewall78

    Stonewall78 New Member

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    Wow that is an angle iron monstrosity lol Are you building a 2 fan hovercraft? By the looks of the tub there is one for lift and one for motion. Looks cool though, keep up with the pictures.
     
  5. Guest-23315

    Guest-23315 Guest

    We made a hovecraft at school. Good Fun!
     
  6. profqwerty

    profqwerty New Member

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    the go kart was meant to be based on the hl2 buggy, but something got lost in translation. It's a vw polo engine (1.1l) + bits. everything works except gearshifting. It needs to be out of the way so is free to anyone who can collect. otherwise it's going to the dump on monday.

    yep two engines, lift is a 20hp robin, thrust is a Rotax 447 atm but should hopefully be upgraded when funds replenish themselves (it should be able to cope with up to about 180hp).

    paid for from the insurance of the old one + it's trailer when they were stolen.
     
  7. mvagusta

    mvagusta Did a skid that went for two weeks.

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    cool hovercraft. what pc parts are you sticking in it? aircooling? or wc with a big rad infront of that huge fan?
     
  8. profqwerty

    profqwerty New Member

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    uhh. I need to figure that out.

    Any ideas anyone please say. I can do a bit-tech.net logo (do I have permission..?), as i have access to vinyl and laser cutters.

    I was thinking possibly a small computer, with music / wifi on it, but totally waterproofed etc. I can rip apart a small fan, and use the sensor wires to check engine / fan speeds, displayed on one of ch424's LCD screens.
     
  9. ComputerKing

    ComputerKing <img src="http://forums.bit-tech.net/images/smilie

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    HOLY ****! THis thing is SO awsome! you will put pc inside it? dude so nice. Can't wait to see more.

    Good luck.
     
  10. Kenny_McCormick

    Kenny_McCormick Member

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    [​IMG]

    This reminds me the HL2 car from the episode "Highway 17", I want one of those!!

    My idea: You can fit a plexi case inside (waterproof of course).

    Huge project dude, GL & HF
     
  11. profqwerty

    profqwerty New Member

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    Some more work done today.

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    Thrust fan fram temporaily mounted on the duct. It's just hanging at the moment, but will have bracing and supports later.


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    close up of the lower bearing block. the right hand end connects to a flexy coupling which mounts onto the engine PTO. red cap is the oil filler. It looks like the ally plate will have to be on the bottom of the hull, and long bolts all the way through.

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    Top pulley. the belt is held in position by the flanges on the bottom pulley. getting the bearing races into the hub was a slog - They're a VERY tight fit to prevent fretting, so i had to heat the hub in the over @ 200C for a bit to expand the casing.

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    the blades for the fans come in 3 sizes (these are the biggest), but have to be cut down to fit the size of your duct. the duct is 1100mm wide, and the blades in this hub are slightly larger. I made come bits of wood to 1100mm long, and measured the blades to the correct length. It also meant I could check the roundness of the duct (gravity makes it go oval:p).

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    rear view of the drive hub. the castle nut clamps two taper bearings with the hub inbetween, so it's only actually one bearing that takes the forwards push.

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    One question - is the belt tension good??!?!
    It can deflect slightly, and i can turn it about 45 degrees. the system turns fairly freely, it's not rediculously twangy tight, but certianly not loose.

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    the bits of wood in the duct. a system of "flow striagtheners" are used to convert the rotating airflow into a stright one. this supposedly increases performance, but also serves as an effect safety measure incase someone falls into the fan. they are, however, impossible to fit. i have been trying different methods all day. this is number 2 - hold the centre cone and try fit each one individually.

    I gave up and fitted the straighteners all onto the centre cone at roughyl equal intervals and jammed it into the duct. typically several of them don't actually touch teh duct. will have some sorting out to do.

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    most of them in the duct. they're not attached to the duct, but are pop-riveted to the centre cone.

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    they don't touch. they're also very effective at filling your hands and arms with fibreglass splinters.

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    the fan in all it's glory. only 3 blades for now, as the existing thrust engine is only 40hp. when i can i'm going to get a larger one and some more blades.

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    close up. each of those holes wants a small bolt, with a nyloc nut!

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    lovely boot-load of bits from the previous hovercraft.

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    one of the flow straighteners close up.

    more tomorrow (if the weather holds that is!)

    profqwerty
     
  12. IanJackson

    IanJackson Photographer & Modder

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    sweeeeeet get us a video of u driving it!!!
     
  13. profqwerty

    profqwerty New Member

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    Sorry about the long gap - work kind of got in the way :wallbash:

    I have missed a bit out o the log but, should be a bit more consistent now!


    Thrust engine in the back of the craft
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    The flexi-coupling from engine to fan frame - allows the engine to move/vibrate a bit on it's rubber mounts whilst the fan frame is secruely bolted to the craft.
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    This is the lift engine's position. This is a horizontal fan that draws air in a puts it under the hull for lift.
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    the different between lift/thrust:
    lift has to provide high pressure (like 0.03bar >atm pressure) and medium flow rates (higher craft speed = more air loss = higher air flow needed) (has lots of smaller fan blades)
    thrust provides large quantities of air moving back at high speed. ( has fewer longer blades)



    thrust engine mountings. my M10 bolts wouldn't go through the hull with enough spare for a nut, so i produced these:

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    a bolt welded on:

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    then these sit on the hull floor, with just enough poking through for a penny washer + lock-nut!

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    two clean strips of metal that can simply be welded onto.

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    found this which is peeeerrrrrfect for clearing drilled bits of fibreglass. It doesn't have enough power to suck up bolts/nuts/washers, so is ideal really. unfortunately i have no other bags, so i have to reuse the existing one by emptying it and re-stapling it again!

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    PS sorry for the c**ppy pictures - a lot of the work is done after work and the darkness mucks up the camera :roll:

    These flat plates will be welded onto the strips:

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    they have studs welded into them (max power top make sure the studs stick! each one is welded, then ground down, then put under high tension, welded + ground again.

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    an engine mount on the plate:
    locknuts onto those studs do nicely.
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    mounts+plates welded in place. bolted down tight. can turn over the engine and the flexi coupling looks to be flat!

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    a random one to put here, but this is the back of the duct. I was planning to cut off the back of the cone, leave the hole, and add a rudder mount in there.

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    making the fan hub
    luckily we found a 4" dia SOLID mild steel rod. it was about 4' long and weighed waaaaaay too much.

    it took about 10 minutes to cut through it on a cold cut saw
    made one HELL of a racket.
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    one of the technicians where i teach used to be a workshop lathe operator - so he was awesome at making these kind of things. did it for free aswell!
    It took ages to remove all the unwanted metal, but a very nice finish.
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    Took a while and many trail +errors, but he managed to create a damned near perfect taper in it!
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    The other side slots into the ring (6mm flat plate - cut on a 150mm hole saw!). the idea being the main boss bit is permanently attached to the engine, and the ring is attached to the fan hub with all those botls. then there are 4 bolts that hold the ring onto the boss (because we didn't have any sufficiently large dia rod to start with).
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    ring in the hub:
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    and assembled. there are no holes in it yet; drilled it later.
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    Drilling the ring. clamped it on the drill press and lined up +drilled each hole individually.
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    MEGA e-kudos points / e-pints for the first person to name this tool clamped to the drill press:

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    the final fan hub in place!
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    This is the engine frame I made. the legs are the rubber mounts extended.

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    i spent ages making the damn things so here's a close up:
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    mounting points for the engine on the frame:
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    side shot - yummy welds!
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    how it looked - it looks quite good i thought, just the mechanics are stupidly awkward.

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    got the day off tomorrow - so should get some more done!

    profqwerty
     
  14. Rocket733

    Rocket733 Austerity - It's the only way

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    Looks like a specialized rotary table to me. Nice looking project and :jawdrop: at the steel stock.
     
  15. Guest-23315

    Guest-23315 Guest

    very nice craftsmanship
     
  16. mr_carl

    mr_carl New Member

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    excellent work, 2 thumbs up :D
     
  17. profqwerty

    profqwerty New Member

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    Sorry for another time gap. Fast forward to the future:

    [​IMG]

    This is almost how it looks now. Some notable things:
    -The lift engine is now mounted on top. This is because of safety concerns - if something hit the bottom of the bow, which is close to the engine, the shock could cause the engine and fan to jerk, causing the fan to impact on the duct (NOT good!)
    Has also made mounting logistics easier:p
    -Trailer is now road worthy

    [​IMG]

    Thrust engine in the back...you can see where I have removed the old engine frame there are some largish holes. I filled the smaller holes in the bottom of the hull with sealant and gaffa tape:) have to make the cockpit water proof for stopping on water!

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    The seat on this one has a higher console than the last one did...and the seat is a whole single unit from fibreglass. therefore to get at the electronics / controls / fuel tanks the entire seat unit has to be removed; and the handle bars need a long stem.

    By sheer luck (love it!) there was a short length of metal tube with an ID a teensy bit more than the OD of the handle bars. This was welded onto the bottom half; i put a bolt through this, and the top half can slide into the tube and nestle on the bolt:)

    yes they are bent...my brother crashed the previous hovercraft (on it's first bloody outing!!!!) and held onto the handle bars too tight!

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    The rudder being poisitioned. 3 hinges for extra rigidity. The metal work is a back stay for the engine frame, I've hidden it inthe duct so it's a bit neater:)

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    The throttle for the lift engine. I bought a very simple outboard motor controller, with separate throttle/gear levers. One lever does the elevators and one does the lift throttle. I had to modify the throw to fit the lift engine carb though.

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    ah yes the fitting together of the handlebars. showing how they go together...

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    close up of the lift engine frame and mountings. The engine idles at about 1800rpm...it lifts at 2300rpm...at full blast you can see clearly underneath the front of the craft (the bottom of the skirt is a good 3" from the ground!!). suffice to say..it is shifting a HUGE amount of air.

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    The control surfaces. Those bits that look like something's hit the rudder...I think it's just the camera and how the preserver has gone on. Rudder and elevators for superior cornering etc. Controlled by some bike handle bars and a lever.

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    I've been testing it today...The exhaust is smaller than it looks! Cardboard a temporary thing to stop it burning/scratching the fibreglass. I changed the engine mounts for something a bit lighter. The rubber flexi coupling holds the crankshaft onto the bearing block. I think the belt tension is slightly off so I'm doing trial and error to get it right.

    The engine has been a pig to start...It looks totally crapped up inside so when the flood's have gone i'll ditch it and get a bigger one.

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    Lift engine heat deflector..the exhaust gets pretty hot pretty quick. although the constant stream of air keeps most of it cool, the crap the comes out of the exhaust makes the fibreglass go a funny colour. You can sort of see where I put some all tape on, ran it for a bit then put some more on.

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    As it stands today. the fan guards are on for testing; the fuel lines are properly sorted and neither are the kill switches etc. The fuel tanks will ultimately be inside the seat..I have some custom ally ones coming at some point this month:clap:
     
    Last edited: 12 Jan 2008
  18. widmod

    widmod Member

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    cool self built hovercraft!!! :jawdrop::jawdrop:
    is it for water driving only or will you drive on land too?
    hovercrafts have no brakes to stop on land?
     
  19. rytmehunden

    rytmehunden I love glory and fame

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    goodness what a nice machine you got there!! :rock:
    And it even looks cool!!

    Just a question.. if you were to put that big fan in a computer, would that be effective cooling? :naughty:
     
  20. Moriquendi

    Moriquendi Bit Tech Biker

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    Umm... if you swapped the lift engine from below the fan to above the fan wont the direction of rotation need reversing? How did you get round that? I can see that the incidence of the blades is adjustable but it seems to me that a whole new set would be required or the engine crankshaft modified to rotate the other way. Alternativley I could just be being really really stupid...

    The thing in the picture clamped to the drill press, it looks to me like a three jaw self centering chuck mounted on an indexing head.

    Really like the hovercraft, looks like its going to be a whole lot of fun when youre done.

    Moriquendi
     

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