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Thread: Lift problems

  1. #9
    gaz
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    Default Re: Lift problems

    Someone in the club once told me it is rare to get a hovercraft to work "out of the box" hang in there and ask those questions. Most people on here have been through what you are experiencing. Once your teething problems are ironed out you will soon forget there were ever any!

  2. #10
    Forum God > 400 posts Club Member
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    Mar 2009
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    Default Re: Lift problems

    Quote Originally Posted by gaz View Post
    Someone in the club once told me it is rare to get a hovercraft to work "out of the box" hang in there and ask those questions. Most people on here have been through what you are experiencing. Once your teething problems are ironed out you will soon forget there were ever any!

    I had teething problems with my surveyor for about a year. It come very close to going on ebay to join all the other hovers on there for sale that have teething problems

    Seriously as Gaz said keep asking questions as someone in the club will have the answer. Eventually it will all come together & you will wonder why it took so long to iron the little problems.

  3. #11
    Less than 10 posts so far!
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    Default Re: Lift problems

    Thanks for all your comments

    Had a go last night at re-setting the pitch,(Grinding in hub bearings) not good ! Will replace before next test, When I spoke to Ken he said there are four dots on the root of each blade 10 degrees to 50 degrees, Line the blades to 45 degrees inbetween the 40 & 50 dots with the split in the hub, is the 50 degree dot nearest the leading edge ? I've been looking for a diagram online to see how to set the pitch but can't seem to find one.

  4. #12
    gaz
    Guest

    Default Re: Lift problems

    I think your after this LINK for the Multi wing blades pdf, or this LINK for one from Hascon, just download hasconwing2008eng.pdf and you will hopefully have the data you need

  5. #13
    More than 30 posts!
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    Default Re: Lift problems

    Quote Originally Posted by keitht View Post
    ....if I increase the pitch would it give more lift and less revs, Can anyone help.
    No. You do have a poor ratio. The 900/9-9/5Z will absorb your engine power at approx max engine revs, but at 45 deg. the fan will be developing a large volume of air (good for top speed and into wind performance) but a marginal pressure (probably just sufficient to lift it reliably). ((This is a typical racing type choice.)) at lower revs the pressure will drop to inadequate levels as you have found.

    At a lower pitch (eg. 35 deg) for a given speed the fan will provide the similar pressure with lower volume and about 1/2 the power consumption. i.e it will allow the engine to rev further giving "emergency power", but the ratio needs to be changed to obtain this.
    Fanman_UK

  6. #14
    More than 10 posts! Club Member
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    Default Re: Lift problems

    Hi,
    A 900 mm 9/9 at 45 will absorb 51 Kw at 2500 rpm (+/- 70 HP).
    If your engine developpe such power, you must use a ration like 3.4 (2500 rpm on fan and 8500 rpm on engine).
    Have you try a lower pitch ?

  7. #15
    Very active > 100 posts Club Member
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    Default Re: Lift problems

    Hi i have used many bike engines in the past. Remember your have 6 gears in the box. Pitch those blades at 50 degrees and put the motor in sixth. Now thats your start point. Try the craft and take note to see if the motor pulls through upto max rpm. If not don,t alter the pitch just knock it down a gear and retry right through the gear range. Take some notes!!. If your engine red lines in 6th gear at full pitch then change your pullies.
    That craft of yours will be very rear heavy. This maybe a big part of the problem. But good luck and crack on.

  8. #16
    Less than 10 posts so far!
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    Red face Re: Lift problems

    Thanks for all your advice, Looks like I gave Ken the wrong info at the start regarding the gear ratio, 2 full turns of the crank ( which is the engine cycle) instead of 1 turn for the gearbox, so I'm out by 2 to 1, have ordered smaller top pulley & belt, fingers crossed.
    PS Photo's attached, It's getting there.
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