Item 0736
DESIGN:
SynchroLite ~ Rotor - Disk - Blade Lag Angle (2-blade rotor)
Outside Information
Drawing:
~ Borrowed, temporarily, and without permission from Colin Mill and Lance Electronic Publishing ~
Notes:
Blade Lag Angle
is the angle about the lead-lag hinge between the centerline of the blade and the centerline of hub when looked at in the plan view.Centrifugal (centripetal) Force:
The centripetal force F [in lbs] acting on a body of mass m [in slugs] is given by the equation F = (m*v^2)/r, where v is its velocity [in ft/sec] and r is the radius [in feet] of its path. Might be more efficient for future changes to put into Access
Mass:
1 slug = 32.175 pounds
Movement:
The forward blade stop should permit the blade to move to a position at least 3 degrees and preferably 5 degrees ahead of the autorotational position which is the true radial with the blade c.g. passing through the center of rotation. The lag stop should, be located 3 to 5 degrees behind the worst operating position of the blade. This maybe determined by combining the maximum torque developed, at each blade with the centrifugal (centripetal) force for the slowest operational speed of the rotor.
The article goes on to say that 2 degrees each side of the average position is a good assumption.
______________________________________________
Eric Hollmann also mentioned + & - 2 degrees a while back.
Synchropter
|
Blade Element |
Weight |
Mass [slug] |
Radius (in) |
Radius (feet) |
Velocity (ft/min) |
Force (lbs) |
|||||||||
|
1 |
4.124 |
0.128 |
5.2 |
0.4333 |
27.23 |
219 |
|||||||||
|
2 |
0.374 |
0.012 |
15.6 |
1.3000 |
81.71 |
62 |
|||||||||
|
3 |
0.374 |
0.012 |
26.0 |
2.1666 |
136.17 |
103 |
|||||||||
|
4 |
0.374 |
0.012 |
36.4 |
3.0333 |
190.64 |
144 |
|||||||||
|
5 |
0.374 |
0.012 |
46.8 |
3.9000 |
245.12 |
185 |
|||||||||
|
6 |
0.499 |
0.016 |
57.2 |
4.7666 |
299.59 |
301 |
|||||||||
|
7 |
0.499 |
0.016 |
67.6 |
5.6333 |
354.06 |
356 |
|||||||||
|
8 |
0.499 |
0.016 |
78.0 |
6.5000 |
408.53 |
411 |
|||||||||
|
9 |
0.499 |
0.016 |
88.4 |
7.3666 |
463.00 |
466 |
|||||||||
|
10 |
1.299 |
0.040 |
98.8 |
8.2333 |
517.47 |
1301* |
|||||||||
|
Total |
|
|
|
|
|
3548* |
|||||||||
|
10 @ tip |
1.299 |
0.040 |
104 |
8.666 |
600 |
1662 |
|||||||||
* Will be a little greater since most of weight is at tip end of element 10. See 10 @ tip for values if weight of element 10 was concentrated at the tip.
Thrust:
Lead-Lag hinge offset = 8" = 0.66 ft
The maximum torque at each rotor = 254.2 lb-ft. / 2 blades = 127.1 lb-ft. [Note this is based on 30 hp engines. The value at hover and cruise will be about 70% of this]
Thrust transmitted to blade at lead-lag hinge = 127.1 / .66 = 190.67 lbs.
I think that the following maybe based on the lead-lag hinge having no ability to lead-lag. ~ March 15, 2009
Coefficient of Thrust is 0.002302.
Coefficient of Profile is 0.0000657.
Coefficient of Induced is 0.0000823.
Induced is therefore 2.68%.
190.67 * 2.68% = 5.1 lbs
Centrifugal (centripetal) force = 3548 lbs
Lag angle = 0.0824º. 0.0747º if using 10 @ tip
. If the above thinking is correct.Note:- In autorotation, with no power, the angle will want to be 0 degrees.
It actually might want to be slightly negative because one portion of the disk is driving the other portion.
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Last Revised: March 15, 2009