Inspection

Check the Blade Grips (037) for excessive axial play by grasping each Blade Grip as shown in Figure 1 and firmly push them toward one another and then pull them apart. Do this repeatedly to check for play. Ideally you would feel the slightest bit of play there. 0.002 inches would be great. You, however, will more than likely feel much more play - especially if you have a fair amount of flight hours on the Head. There is a shim kit available that relieves this problem. I recommend installing it. Excessive play here can cause lateral vibrations in the main rotor which rob the heli of power and shake the bajeebas out of your electronics, etc.

Using the same hand position as the last check, move your hands in a bending motion to check the Spindle (016) for straightness. Doing this with a bent Spindle will cause the Blade Grips (037) to move abruptly from one side to the other as the bent Spindle flips over. Be careful with this as you can bend the Spindle if you apply too much pressure. A bent Spindle will result in varying degrees of lateral vibration in the main rotor depending on the severity of the bend. A bent Spindle is more than likely the result of a main rotor Blade (042) strike. If after a crash or blade strike there is evidence of lateral vibration, perform this check.

Check the Center Hub Collective Sleeve (Figure) for wear and obvious damage. Ensure that the sleeve is lightly lubricated with Lubricant where it mates with the Rotor Head (034) inner sleeve.

Check the Retaining Pin (035) receiving-hole in the Center Hub for elongation and proper fit with the Retaining Pin.

Removal

To remove the Center Hub, Spindle and Blade Grips as an assembly, first remove the Main Rotor Blades (042) (see section 2-a.ii). Then follow the instructions in section 2-b.ii to remove the Flybar and Rotor Head Assembly.

Once the Main Rotor Blades and the Flybar and Rotor Head Assembly have been removed, disconnect the Paddle Control Pushrods (009) from the Swashplate (018).

Remove the Retaining Pin (035) by grasping with a pair of pliers and twisting while pulling. Figure 2.

The Center Hub, Spindle and Blade Grip Assembly can now be pulled off of the Main Shaft & Drive Gear (050). Under perfect circumstances, the Center Hub will easily pull off of the Main Shaft. Usually, however, the hole in the Main Shaft that receives the Retaining Pin (035) is slightly deformed for a myriad of reasons. This can cause the Center Hub to bind on the Main Shaft. If you have a "stuck" Center Hub, first make sure that the Hub will turn on the Main Shaft by twisting it. The only thing that would prevent it from turning is a broken Retaining Pin stuck in the hole. If this is the case you will have to use a very small punch and drive it through. If the Hub will turn on the shaft then you simply need to pull harder while twisting. Be cautious of how you are holding the heli and components while doing this. See Figure 3.

Disassembly

To disassemble the Center Hub, Spindle and Blade Grip Assembly use two 1.5 mm hex wrenches to loosen and then remove the Blade Grip attachment screws (013). Figure 4. Invariably only one screw will thread out of the Spindle (016). The other will remain tight in the Spindle. Once you have one screw removed, the Blade Grips (037) should pull apart. If the Grips will not separate from the Center Hub, the Spindle is more than likely bent. Pulling harder is about all you can do in this case.

If you would like to remove the remaining screw (013) from the Spindle (016), clamp the spindle in a vise with wood faces as shown in Figure 5 and then, using the 1.5 mm hex wrench, break it loose.

Repair

The most common repair in this area is the replacement or straightening of a bent Spindle (016). I have bent my share of Spindles and in about half of the cases I was able to straighten them. My favorite method is to insert the Spindle into a drill chuck so that the beginning of the bend is at the end of the chuck collet. Then I simply apply hand-pressure to straighten. Figure 6. Recheck the Spindle for bends by rolling on a flat surface or spinning in a drill press and checking for run-out. Repeat the straightening procedure as needed.

If you are not able to get the Spindle nearly perfect, don't use it. They are very inexpensive and you should always have a spare on hand. Bent feathering pins (Spindles) are a fact of life to every Blade owner.

Assembly

See Figure 7 to determine proper washer stacking order. Place a Large Washer (040) under the head of one of the Retaining Screws (013). Thread the screw into one end of the Spindle (016) and hand-tighten.

Lightly lubricate the outside surface of the Spindle (016) with Lubricant. Place a Small Washer (039) onto the free end of the Spindle with the shoulder facing away from the end of the Spindle with the screw in it. See Figure 7. Slide the free end of the Spindle through one of the Blade Grips (037). Slide an O-ring (038) onto the free end of the Spindle. Slide the Spindle and Blade Grip through the Center Hub (008). Slide the other O-ring (038) onto the free end of the Spindle. Then install a Small Washer (039) with the shoulder facing the free end of the Spindle. Slide on the other Blade Grip (037).

At this point you should ensure that the O-rings (038) are properly seated in the Center Hub (008).

Now all that's left to do is install the last two washers and the remaining Retaining Screw (013). You will need to stack the last Small Washer (039) and Large Washer (040) on the Screw (013) in the order shown in Figure 7. Thread the Screw (013), with the washer stack, into the free end of the Spindle (016). Now you must be very careful here to properly position the Small Washer (039) so that it fits OVER the Spindle (016). It is possible to pinch the Small Washer (039) between the Large Washer (040) and the end of the Spindle (016). You must visually determine that the Large and Small washer are centered on one another.

Use two 1.5 mm hex wrenches to tighten the Retaining Screws (013).

Check for axial play as outlined in the Inspection section and install shims as needed to reduce axial play to 0.002".

Installation

Remove any burrs from the Main shaft (050) by using a jeweler's file. Commonly the Retaining Pin (035) will elongate the hole in the Main Shaft causing a burr.

Test fit the Center Hub (008) on the Main Shaft (050). If it does not slide into position without binding continue to deburr the shaft until it does.

Slide the Center Hub (008) onto the Main Shaft (050) and align the Retaining Pin (035) holes.

Many experienced Blade owners use a brass pin instead of the stock Retaining Pin (035). Some even use a section of paper clip. The brass shears off easier, sparing other components from damage. If you choose to go this route the desired pin diameter is 0.032".

Grasp the Retaining Pin (035) with pliers and insert through the aligned holes in the Center Hub (008) and Main Shaft (050). Figure 8. For best results, twist the pin while inserting.