Rotor Blades, Why...
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Rotor Blades, Why...| Kyiv |
Posted: Apr 10 2012, 06:28 AM
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 My tank is umbrella! Group: Members Posts: 2,903 Member No.: 401 Joined: 3-June 08  |
So how is the number of blades on a rotor determined? I'm thinking mainly about helicopter rotors, but I suppose this is just as valid for other rotors.
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| Vault X |
Posted: Apr 10 2012, 11:37 AM
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 Designer Group: Members Posts: 6,416 Member No.: 937 Joined: 16-July 10 |
2 is very simple and always balanced, 3 is much harder to balance, 4 is easier than 3, 5 is harder to balance, 6 or more idk. Fewer but longer blades can be more efficient (more eff. wingspan), but take more space, odd blade count is quieter, even count has balance advantage.
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| Trinary |
Posted: Apr 10 2012, 01:10 PM
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38% Armaments Designer Group: Members Posts: 773 Member No.: 1,004 Joined: 21-October 10 |
For fast crafts you migh also whant to think about rpm and length to allow higher speeds without retreating blade stall.
If i rember it correctly the US military has some nice course mterial for helicopter aerodynamics avalible from one of the sites in this forums library section |
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| no endorse |
Posted: Apr 10 2012, 02:37 PM
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 You have way too much time on your hands ... Group: Moderators Posts: 4,164 Member No.: 22 Joined: 11-April 07 |
More blades runs smoother, is quieter, better balanced, and can carry more load better. Two blades are really easy and simple. Imagine the swashplate for a Cobra, and then for a Blackhawk. Yup. A dominant force in helicopters is tail rotor interaction. In prop planes, it's all about propulsive efficiency at cruise, so you get them curved rotors. --------------------  
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| Forza |
Posted: Apr 10 2012, 03:31 PM
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 36% Armaments Designer Group: Members Posts: 724 Member No.: 1,006 Joined: 22-October 10 |
Would it not also have something to do with the amount of power available against the range of weights to be lifted?
-------------------- Qui Patitur Vincit - Who perseveres, conquers.
You'll Never Walk Alone |
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| Samozaryadnyastan |
Posted: Apr 10 2012, 04:53 PM
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 85% Armaments Designer Group: Members Posts: 1,701 Member No.: 1,101 Joined: 13-April 11 |
So, the viability of a 7-blade rotor would depend significantly upon the extent to which the tail rotor was geared to evade the main rotor? I take it that simply moving the tail rotor away from the main rotor so they don't intersect poses a variety of issues in flight and generally engineering wise? -------------------- One day, I will actually know what the fuck I'm talking about. Samozniy Military Industries Starting alliances and ending wars since 2011.
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| no endorse |
Posted: Apr 10 2012, 07:04 PM
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You have way too much time on your hands ... Group: Moderators Posts: 4,164 Member No.: 22 Joined: 11-April 07 |
Moving the tail that far out is heavy. Weight is your mortal enemy in an airplane, but a helicopter is the sort of thing where you'll commit a murder for each pound you can drop. The tail rotor interaction has a lot to do with stability, noise, and the sheer geometry of it (can't work if the blades will intersect)
It's just structurally and aerodynamically more efficient in many ways, though you pay one hell of a complexity penalty. --------------------
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