START HERE |
|
Register | FAQ | PM | Events | Groups | Blogs | Calendar | Mark Forums Read |
Unregistered
|
Aerodynamics, Physics and Engineering Aerodynamics, Physics and Engineering Discussions |
|
LinkBack | Thread Tools | Display Modes |
12-01-2013, 09:38 PM | #1 (permalink) |
Registered Users
Join Date: Dec 2013
|
Possible? multiple length blades(Helis)
Hey. new here!
I'm working on a design project on helicopters, and I need to find some way to improve on them so i was looking at the wings. I saw some engineers working on extending blades, but would having matching pairs of long and short blades have any positive effect on the power generated or efficiency? given a top view, something like this -|- maybe an intermediate length passing diagonally as well ->|<- thoughts? |
Sponsored Links | |||
Advertisement |
|
12-03-2013, 01:19 PM | #2 (permalink) |
Registered Users
Join Date: Dec 2012
|
Possible? multiple length blades(Helis)
Why not make them the same length?
What would be the advantage? I would think the short blades would just be messing the air flow up for the main blades. Sent from my iPhone using Tapatalk - sorry for typos!!! |
05-08-2014, 11:43 AM | #3 (permalink) |
Registered Users
Join Date: Apr 2009
|
hey FatesFool, search on youtube for the following where Nick Maxwell talks a bit about what more blades will do :
Raptor E700 Tri-pop 3 blade head with Nick Maxwell
__________________
Gaui X7, Gaui X5, 360mm(6s) & 325mm(3s) rexies |
05-12-2014, 03:08 PM | #4 (permalink) |
Registered Users
Join Date: Nov 2010
|
So depressing to get such concrete evidence that those guys have no idea what they're talking about.
__________________
-Rob Former Managing Director of Maxxum Robotics Inc. |
05-12-2014, 07:02 PM | #5 (permalink) |
Registered Users
Join Date: Nov 2010
|
LOL, not a single technically correct answer there. The answer to every question is either "because better", or "because more expensive".
Special blades for a 3-blade head? Seriously? Remember back when everybody though FBL blades had to be special and more expensive? When's the last time you even saw a FB/FBL blade distinction anymore?
__________________
-Rob Former Managing Director of Maxxum Robotics Inc. |
05-12-2014, 07:59 PM | #6 (permalink) |
Registered Users
Join Date: Apr 2009
|
But they put the CG in different places.
FBL blades are more inherintly unstable are they not? So they would make your flybarred heli fly worse and FB blades would make your FBL heli react more slowly. I saw a bunch of FB blades being sold off dirt cheap in comparison to their FBL counterparts, just for stock clearance. That doesn't necessarily prove they're different I know. BTW; I'm not disagreeing with u on what was said bout that vid, cause I dont' know any better! ;P
__________________
Gaui X7, Gaui X5, 360mm(6s) & 325mm(3s) rexies |
05-13-2014, 03:49 AM | #7 (permalink) |
Registered Users
Join Date: Aug 2010
|
Laoch
In theory, FBL blades are more dynamically stable, because the FBL controller is too slow to address blade motions in real time; the FBL controller doesn’t even know if a rotor is attached to the machine. With FB, you have the direct linkage from the FB itself (which acts as a gyro reference plane)- to adjust the blade pitch in real-time.
__________________
"The problem with quotes found on the internet is you have no way of confirming their authenticity." - Abraham Lincoln |
05-13-2014, 03:50 AM | #8 (permalink) | |
Registered Users
Join Date: Aug 2010
|
Quote:
Its probably unfair to say there is no room for multi-bladed blade offerings ‘if’ someone were intent on a multi-blade head. For example, a 3+ bladed head will generally not have any lead/lag relief via spindle dampers. Likewise, absent a single spindle, the effective flap hinge is likely to be further out. In both cases, you are going to add to stresses on spindles/grips. There may be some benefit to offset some of this via lighter blades. Likewise, with higher solidity, there is probably some efficiency benefit in running thinner blades and/or reduced chord. Running CG further inboard may help a bit by altering the moment of inertia on the blade (less gyro torque for any given headspeed and pitch/roll rate). Hard to really understand the ‘why’ on the macro level though. Yea, you can increase peak thrust, which you use for perhaps .01% of the flight. For the rest of the flight, you are carrying significant extra mass, and adding significant drag. Plus, you add complexity and crash cost. Maybe a good trade in a couple of very specific niches, but hard to see otherwise.
__________________
"The problem with quotes found on the internet is you have no way of confirming their authenticity." - Abraham Lincoln |
|
05-14-2014, 08:55 AM | #9 (permalink) |
Registered Users
Join Date: Nov 2010
|
I'm not saying that there would be no need at all for specially designed blades on a 3-blade head. I just see no evidence that they've put any work at all into the engineering of it based on that video.
You suggest some relevant changes, but that's not what they have talked about. I was just waiting for him to say something completely nonsensical like "And the extra blade mass increases the gyroscopic precession forces which makes the heli more stable in a hover." I actually like the idea of 3 blade heads for acro, 4 or even 5 might be even better. In fact, I would bet a lot of money that in the search for "the next big thing" to force all the 3D guys to go out and buy all new equipment again, this is going to be it. They're up against the wall in terms of how high they can push rotor speeds in the search for even more control power. So increasing solidity ratio by running multiblade heads is the logical next step. Increasing solidity ratio will provide even more "pop" and control authority. And yes, will also require even more power because Ct/sigma will be driven even lower. But that just makes the motor and battery guys happy because they get to sell a whole new generation of those. 20S batteries and 10kW electric motors. 500 amp ESC's... ( I wonder how long before people start getting killed in electrical accidents...)
__________________
-Rob Former Managing Director of Maxxum Robotics Inc. |
Thread Tools | |
Display Modes | |
|
|