Graviman,
True, but if you pull collective (like take-off and landing) the torque becomes imbalanced, unless you want to constrain the pilot to have to accelerate every time he wants to manouvre...
Not so.
The rpm of the propeller has a fixed relationship with the forward velocity of the craft.
No forward velocity = no rotation of the propeller.
This is the job of the Speed Controller.
During hover and slow forward flight, the Speed Controller has the propeller 'locked'.
All power (rpm and torque) is going to the rotor.
During transition, the Speed Controller allows some rpm to be removed from the rotor and transferred to the propeller.
During cruise, the Speed Controller is allowing the propeller to take its half of the power.
The differential is sending half of the power to the rotor and half the power to the propeller.
The rotor is turning at half the speed it was during hover.
The propeller is turning infinitely faster then it was during hover.
At any rate i don't understand why you want the prop to run slow in hover but fast at speed
The propeller does not have a variable pitch (constant-speed propeller) therefor the higher rpm is used, instead of the increased pitch, to provide increasing thrust during increasing forward velocity.
... for reasons given above system as drawn won't work
I beg to differ. Perhaps the action of the worm and gear is not fully understood.
Let's assume that we have a worm & gear that has a very large reduction ratio, say 70:1.
Let's also assume that the axle, which passes through the gear, is applying a large torque to the gear.
Now there is no way that this gear is going to turn because it is incapable, on its own, of turning the worm.
The force of the gear tooth on the worm is just about at 90º to the wall of the worm's thread.
All that the gear is doing is apply a lot of static friction against the wall of the worm's thread.
To allow the gear to turn, it will require a VERY large servomotor to TURN the worm.
Now let's assume that we have a worm & gear that has a very small reduction ratio, say 1:1. (Actual this would be called a pair of 90º helical gears)
Let's also assume that the axle, which passes through the gear, is applying a large torque to the gear.
At this ratio, it is extremely easy for the gear to turn the so-called worm.
There is very little static friction resisting the rotation of the gear.
To NOT allow the gear to turn, it will require a VERY large servomotor to RESIST THE TURNING of the worm.
It should be apparent that as the ratio of 70:1 is reduced the size of the servomotor required to TURN the worm will be smaller.
It should be apparent that as the ratio of 1:1 is increased the size of the servomotor required to RESIST THE TURNING the worm will be smaller.
At a ratio of approximately 10:1 it become a 'flip of the coin' whether the servomotor is needed to TURN the worm or RESIST THE TURNING of the worm. In other words, at this ratio the servomotor can be quite small. This is why the ratio of 10:1 was picked for the Speed Controller.
maxtork,
Thanks for the very valid comment about the weakness of conventional spider gears when the differential is spending a lot of its time transmitting unequal RPM's to the two outputs.
Dave