A087
DESIGN: GyroHeli ~
RotorOverview:
Tri-teetering rotor hub; with offset and undersling,
Outside Helicopters
xx.
GyroHeli
Quick Disconnect for Blades:
Rick A. says that the Hughes hub has a type of quick disconnect pins at the blade root and the drag link connection. Perhaps BCIT has a manual on this craft. Quick disconnect blades and tail would make the helicopter truly transportable.
Hub Spring:
There are two tie-bar assemblies. One is for the lead, the other is for lag and both work together for teetering. Location a
Hub Spring at the central intersection of the three bars on each assembly will act as a lead-lag spring and also as a teetering spring.The elastomerics should be located outside the tie-bar centers, between them and the mast. Because, they cannot be located inside and press against the control stick. Note the the elastomeric must leave room for the three collective rods to pass through.
I do not think that there is any reason for a hub spring.
Negative thrust, Droop Stops & Tie-rods:
The current design of the tie-bar assembly will not allow it to handle compression. Therefore, it cannot serve in any way to resist droop or negative thrust. Consider the idea of elastic droop stops, witch are permently in position. They could start resisting negative flap at a some to-be-determined angle.
Drag Link:
???Consider drag links with some elasticity. This is to accept the lead/lag caused by the variation in drag at forward speeds. It might also reduce any 'shock loading' on the gears. Better yet, put elasticity in the arms of the rotor head [composite head?] that go out to the grips.
Alternatively: Consider locating the provision for lead/lag in the vertical blade attachment bolt assembly, if the amount of lead/lag is quite small. Basically the conection will have a 'sloppy spline and the gap between the two spline segments will be 'filled' with an elastomeric. Bushings will be required to maintain blade alignment.
May be a dumb idea.
Folding Blades:
For view of SynchroLite folded blades, see:
Design: SynchroLite ~ Rotor Disk - Folded Blades - View 2 The dragonfly has the blade pivot points spaced further apart and there are three blades per rotor. The dragonfly's blades will probably have to be folded both forward and aft; or removed.
Additional information
OTHER: Flight Dynamics - Rotor Hub - Offset Teetering Hinge Concept
Interesting & Relevant Post by Vfrpilotpb on PPRuNe:
Mast bumping can occur on any "Teetering Head" system the R22, R44 B206 the Huey and many other well known Helicopters have that sort of head, Lu is quiet right in his explanation of the way to cause mast bumping, it is something that is normally drummed into most Helo pilots to avoid at all costs(the cost being your life and or that of your pax) with the rotor going one way and you and the heli going the other, it is apparently a problem that is easier for converted fixed wing pilots to get into than pilots trained on Helo from scratch, the main reason being a fixed wing pilots reactions are to push the stick forward at the sign of any problems this action will cause the Teetering head Heli to get into the condition of Negative G, this is a most dangerous position to get into and requires quick but accurate action to recover, it has been demonstrated to me by a very experienced Heli pilot, with the cyclic loosing all feeling of being attached to anything, very dangerous don't go there!
Very Miscellaneous Working Notes:
To be used then removed
Rotor bearing:
For consideration when selecting the rotor bearing(s) for this craft.
MRC5206MZZ bearings as they were standard equipment on Air Commands
The Air Commands have Gross Weighs from 552 lbs to 750 lbs
MRC 5206CZZ-1 Bearing
From the MRC catalog:
MRC double-row ball bearings are manufactured in
two main types: C-type (conrad construction) and
M-type (maximum capacity with filling notches). Each
row has a 30° contact angle.
C-type
Conrad construction, or C-type, double-row ball
bearings have contact angles that converge outside
the bearing, thereby increasing resistance to
misalignment. This type does not have filling notches.
These bearings are recommended for applications
where single-row bearings are inadequate, but radial
loads are not so great as to suggest a filling-notch
bearing. They will take heavy radial loads, and axial
loads equally in either direction. The C-type design
fully meets the requirements of American Petroleum
Institute Specification 610.
Both the inner and the outer rings have closure
grooves. These bearings are available with seals,
shields, and snap-rings.
M-type
This type has filling notches on one side to permit
assembling the maximum number of balls into the
bearing. Contact angles converge outside the
bearing. All inner and outer rings have closure
grooves. These bearings may be equipped with seals,
shields, or snap-rings; or a combination of these. The
M-type bearing has very heavy radial capacity. It also
has thrust capacity in one direction, with the ability to
accommodate light thrust load in the reversing
direction.
Part numbers on M-type double-row bearings are
normally located on either the side face or the O.D.
The side face marking is always on the side opposite
the filling notch and the O.D. marking is offset from
the center away from the filling notch. Therefore,
double sealed or shielded bearings with the filling
notch covered from view can be oriented correctly.
Ball Cages and Types
The cage supplied with C-type and M-type bearings is
one-piece, heat-treated steel for maximum retention. It
is snapped into place after the full quota of balls has
been introduced between the inner and outer ring.
Load Ratings (lbf):
Dynmaic Radial = 6,430
Dynmaic Axial (thrust load)= 5,208
Static Radial = 4,590
Static Axial (thrust load) = 3,029
To me, it looks like the NTN 5206 MAY be the same.
Material:
Zeeoo ~ i read D. Degraw used 2024 instead of 6061 on his hub.. do you have the answer why ?
skyguynca ~ I think he used 2024 because the stresses in a articulated hub are more than what I will see. We use 6061 in our teetering heads and my loads won't be anymore than usual compared to the teetering head. 2024 is also harder and alot more expensive.
DeGraw's DeBird
from Dean Dolph on Rotary Wing Forum, January 7, 2005The interview write up is a little ambiguous in this area but Dick is driving the rotors thru a differential off of the prop with 14% of the engine power going thru a right angle gear drive to the rotor. He alludes to the fact that this is more than he provided the Gyrhino rotor. He doesn't provide any details on the differential other than "at the normal flight RRPM of 350, the differential internal parts do not turn, just like a car going down the road - both barrels turn at the same speed"
He is quoted as saying they can get 260 RRPM but usually takeoff when it reaches 220 - 230. He goes on to say that since the rotor is always powered it won't slow down 'catastrophically' (my interpretation!) during negative 'G' or in a full power push over situation and as such is an inherently safe design. He also mentions that with the driven rotor they cruise at 85 mph versus 70 mph when it is not driven. Top speed is around 100 mph but the fuel burn at 90 mph is 6 gph vs. 5 at 85 mph. The DeBird's powered rotor flies at a 4 degree angle of attack vs. 8 - 10 degrees unpowered like a standard gyro. The power to the rotor increases the RRPM by only 10 rpm over unpowered.
Same Page ~ Different Craft:
~ DESIGN: SynchroLite ~ Rotor ~ DESIGN: UniCopter ~ Rotor
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Last Revised: January 7, 2005