A control hub is located in the center of the rotor hub. It is rigidly attached to the roof of the rotor hub. On this control hub are mounted three self aligning bearings, which are at 120º around the periphery and are tilted up slightly from the horizontal. They are axially aligned with the torque tubes. To these bearings is mounted the splined pitch controller, with its pitch horn. This controller is joined to the splined end of the torque tube. The movement of the pitch horn will, via the spline, torque tube and universal joint, change the pitch of the blade

The upper end of the control stick is mounted in a gimbal in the center of the control hub. Outside the lower portion of the control stick is a control sleeve, which can slide up and down the control stick. Three pitch links connect the pitch horns to this control sleeve.

A Bowden cable is attached to the control stick and the control sleeve. AS the collective lever is moved, the control sleave will move axially on the control stick and change the collective pitch of all three blades. A hydraulic system could be substituted for the Bowden cable, particularly if the rotor governor is incorporated.

Moving the bottom of the control stick for & aft and side-to-side will result in longitudinal and lateral cyclic being transmitted to the blades

The hub yoke has undersling, in that the feathering axis is located below the teetering hinge. The universal joint, which connects the outer end of the torque tube and the base of the blade grip, is located directly below this teetering hinge. Therefore, as the blade flaps up it pulls the torque tube slightly outward from the control yoke. Between the control yoke and the torque tube is a slip fit spline.

The control stick could rotate with the rotor. In which case, the collective and cyclic controls must have bearings between them and the control stick. Alternatively, the control stick could be non rotating and in this case there must be a bearing in the control hub and another bearing between the control sleave and the control stick.

It appears that the exact cyclic inputs from the pilot's stick can be output at the blade. I.e. a linear relationship. The collective inputs will not be purely linier, but this is not a big problem.

One slight deviation from this purity is the universal joint. It will give a slight non-linearity, but this may be slightly good, slightly bad or indifferent.

Everything rotates with the rotor. The two pitch arms and the collective arm are connected to the control stick via bearings.

Remember to leave passage from control stick base to blade tip. For tip brakes, lights, whistle etc. etc.

The gimbal is not subjected to axial rotation but it is subjected to axial displacement, due to cyclic inputs. The greater the cyclic the greater the displacement. It will be a 'stirring' motion, at RRPM.

The bearing Item 0817 can only accept 8º of self-aligning in either direct. Other KS bearings can accept 10º of self-aligning in either direct, but the KS6 weighs 0.12 lbs more than the KS6A.

Consider using the cylinder's rod as the control stick and mount the control sleeve to the barrel of the cylinder. Note that the barrel and the control hub must rotate on the non-rotating cylinder.

Consider Torrington control bearing (item 0705) v.s. bushing (item 0271). Inner rocker bearings only move to collective input. The bearings at the end rotate with the cyclic also.

There is a very little angular movement on these bearings, caused by movement of the universal joint and the radial orientation of its 'X'.

Note that the control hub could be attached to the rotor hub at locations other than the roof.

The current bearing (Item 1245) is not a self aligning, and there is a very small amount of vertical motion at the yoke, caused by flapping.

Use thinner Kaydon bearings for the two bearings, which allow the pitch boss to rotate with the rotor.

The pitch horn, pitch links and the control sleeve will be connected to the stick via bearing, which will allow the stick to rotate and 'stir' rock & roll within the bearing.

The stick will probably rotate with the rotor. This is because the friction in the gimbal at the top will be greater than the control rod bearings at the bottom. There does not appear to be an advantage or a disadvantage to the stick rotating.

The maximum rocking of the stick will be that of the maximum cyclic.

The hub spring will be located between the tie-bar central pieces and the mast. Make sure there is room for the collective rods to pass through.

Consider the possibility of seals, which take axial motion, on both ends. This may allow for all flight control items to be sealed.

For 10º of flap, the control tube moves axially 0.22". If the desire is to pull, via delta-3, 25% of the pitch when the blade flaps then the linear movement of the twisted ball track must be 10º of twist for 1" of travel.

Vancouver Gear cannot cut spiral bevel gears so they doubt that they could produce the spiral spline.