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Thread: Mirage build - redone thrust frame

  1. #9
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    Default Re: Mirage build

    Yeah these are all very serious issues that do need addressing.



    The bottom/front of the engine will be pretty close to the FPS, so hitting anything solid head on would probably knock the engine (ofcourse wrecking the hull too) making the fan hit the duct.



    if crashing it would either be a slightly damaged hull or a total wrecked front.



    of course with careful driving (yeah right) there would be some decent advantages - more stability, and much neater.



    One possibity i looked at was hanging the engine frame from the existing mount points - essentially doing it normally, then turning it over.



    I had the day off of work today, so did some more - thrust engine mounted. Unfortunately my pc broke - a fan blade somehow snapped off so now it won't run (hopefully not a foretelling of things to come!). But therefore no pics.



    Toby




  2. #10
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    Default Re: Mirage build

    i can't see how there is any advantage mounting the engine like that! not sure how it will effect the stability, and as for neater, you won't be saying that when the engine gets wet, and you have to take the fan to bits to get to the engine. its all together a more complicated solution and far more clunky.



    As for hitting something, don't think you realise how much that front planing surface could deflect, even from a plough in. how do you fancy a heavy landing pushing the engine up, this would probably pop the fan!



    all for the cost of a set of fan blades! if not cut down, you might even swap them?

  3. #11
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    Default Re: Mirage build

    Quote :- Unfortunately my pc broke - a fan blade somehow snapped off so now it won't run.



    You should have mounted it above the CPU not under it.

  4. #12
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    Default Re: Mirage build

    I have changed the design slightly - instead of being sat on the bottom, it will have a frame, and will hang from the 4 mounting points on the hull.



    It would be as if it were on normally, then flipped over. I'll put some seat belt over the vibro-mounts incase one pulls apart.



    Without it's mounting plate, there would be about 3" of space (at least) between engine and hull. I'm making the fan boss, and it will have to be in 2 pieces as I don't have a large enough bit of metal - These would be tapped + bolted together so fan removal isn't tooo difficult!



    the fan blades - I'm not bothered about buying a new set. But if anyone does have a reverse set they're willing to part with do say. I've got a 22" duct (my blades are still uncut though).




  5. #13
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    Default Re: Mirage build

    you may very well have to wire lock the fixings on your two bits of boss, as you would not have a visual locking device.


  6. #14
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    Default Re: Mirage build

    Craft looks good so far, but just a question - how are you going to access the pull start or start the engine?



    Mounting the engine in the plenum could be good for looks and for maybe a lower centre of gravity.



    But its going to be a real pain if you need to access the spark plug or carby and if you get water coming in through your air feed holes or over the deck its going to drown the engine.

  7. #15
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    Default Re: Mirage build

    These are all issues that would need addressing!



    I am happy to fiddle with it to the end of time, so I think i will TRY it, and put the craft through it's paces.



    I can fiddle with it to try and iron out the problems, but if it is really impossible I can turn the engine the normal way up!



    The frame I've almost finished is reversible (H shape with legs), so would support the engine inverted or normally using the same fixing points.



    As for starting it - feed the pull start through some metal pipe from the engine to the cockpit.

  8. #16
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    Default Re: Mirage build

    OK, insane update here! the new bit for my computer got lost in the post, so i gave up and snapped the fan blade opposite the already broken one off. seems to work:p

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







    a bolt welded on:







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







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













    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!









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






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