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Thread: to shaft or not to shaft - that is the question

  1. #1
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    Default to shaft or not to shaft - that is the question

    If, (hypothetically)one were to consider shaft driving a TZR powered F3, what ball park revs and lift fan size are we looking at to get things started rather than re-inventing the wheel



    any tips on what not to do would save time also



    thanks in advance



    Tony

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    Default Re: to shaft or not to shaft - that is the question

    Hypothetically eh...? Im doing this but im using a smaller duct and more blades than most- 8bladed 500 duct spinning at just below 4000rpm but its for a bag skirt.



    The usual approach has been 560mm duct with 5 blades spinning a lot faster.



    SO hypothetically would you be making a new hull? If so ours should both be ready about the same time...

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    Default Re: to shaft or not to shaft - that is the question

    I can't remember exactly what I ran RandomOrbit at but I think the lift fan span at about 3,500-3,750ish. I did the numbers for about 8hp to the front.



    As for things to look out for.... You will (hypothetically) have two pulleys on the engine output shaft, one going up for thrust, the other going across for lift with some kind of "outrigger" between the main bearing and the shaft bearing. Make sure that the "outrigger" is beefy anough for the job as the forces pulling on it are quite great. I had a couple of goes before I got it right.



    Also, Make sure you've got a good way of changing belts as when you have two, you're much more likely to need to change one and also one is bound to be in the way of the other. Avoid schemes that mean that to change the lift fan belt you have to take the duct guard of or similar.



    Having driven the same hull, first as an integrated craft and then with a lift fan, I wouldn't go back. It's great to have the lift air at the front where you need it rather than shoving it in the back and forcing it round to the front. RandomOrbit was always a pretty safe craft, even when integrated, but it never ploughed in after fitting the lift fan, not even once.



    If you do go for two fans, I'm sure you'll enjoy it.





    Come on in, the water's lovely







    Cheers.



    Andy.




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    Default Re: to shaft or not to shaft - that is the question

    I tend to agree with Andy's comments.

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    Default Re: to shaft or not to shaft - that is the question

    P.S. Remember to allow for the flex of the craft.

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    Default Re: to shaft or not to shaft - that is the question

    Dear Tony and of course the other chaps on the bourd, shaft drive for you ,im shocked nay surprised, all that complicated things running round at great revs, what are you thinking of, i surgest thearepy would be in order .



    Happy new year every body for tomorrow, looking forward to racing.


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    Default Re: to shaft or not to shaft - that is the question

    Happy New Ears to you Mick



    I've tried the back to basics approach Mick - now it's time to send the air the correct way through the thing and see what happens



    Tony

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    Default Re: to shaft or not to shaft - that is the question

    Quote Originally Posted by tonybroad
    now it's time to send the air the correct way through the thing and see what happens



    Yes, it seems crazy to be pumping the air forwards when you're trying to make the craft go faster.



    Happy New Year everyone.



    Nick




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