Maintenance Manual Table of Contents > Main Rotor Modifications > Installing the Bell Hiller Head
Parts Needed
All parts are E-flite brand.
The parts needed to implement this upgrade are:
Part Name: Bell Mixer Upgrade Kit: BCP
Mfg Part Number: EFLH1170
Purchased from: HorizonHobby
Purchase link: link
Cost: $24.99 USD
Figure 1 shows the parts.
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Figure 1
Out with the old...
If you have a pitch gauge I recommend you take a neutral reading prior to the upgrade and then adjust the Pitch Control Links (006/007) to return to neutral after the upgrade.
Remove both Main Rotor Blades (042).
Disconnect Pitch Control Links (006/007) from the Blade Grips (037).
Disconnect both upper and lower ball connections on the Paddle Control Pushrods (009) and slide the Pushrods (009) over the Blade Grips (037) to remove them.
Using two 1.5mm hex wrenches remove one of the Blade Grip retaining screws (013) and then remove both Blade Grips, Spindle (016), O-rings (038) and Washers (015, 039 and 040). If you had Head Dampening Shims installed remove them too. If at all possible you should replace the O-rings (038) at this time also.
Exploded View
...and on with the new.
Disassemble the new upgrade kit and install two of the included Head Dampening Shims and an O-ring (038) onto the Spindle (016) as shown in Figure 2. Make sure that these parts have a light coat of silicone lube during assembly. This is especially important for the O-rings (038) to prevent "sticky collective". Don't forget that the step on Washer (015) always goes against the Blade Grip bearings.
Now install the other O-ring (038), shims and Washer (015) to the other end of the Spindle as shown in Figure 3.
Slide the other Blade Grip (037) onto the exposed Spindle (016). Do not push the O-rings (038) into the Center Hub (008) opening as this will diminish the dampening effect of the o-rings. Install the remaining Blade Grip retaining screw (013), but do not tighten. Before proceeding make sure that your Blade Grips are installed correctly as shown in Figure 4. When you are sure that the Grips are installed correctly tighten the Blade Grip retaining screws (013) using two 1.5mm hex wrenches.
The manufacturer suggests shortening the Pitch Control Links (006/007) 1-1/4 to 2-1/4 turns (depending on setup). Attach the adjustable Pitch Control Links (006/007) to the short end of the mixer arm first. Then attach the fixed-length control rods to the Upper Swashplate (044). Figure 5.
Reinstall the Paddle Control Pushrods (009).
Exploded View
Figure 2
Figure 3
Figure 4
Figure 5
Wrapping it up!
If you were not able to get an initial neutral reading with a pitch gauge then follow these instructions:
Before proceeding you should unplug both Main and Tail motors from the 4-in-1, arm it and move the collective and cyclic through all ranges to check for binding. Correct any binding before continuing.
Check and adjust Main Rotor Blade tracking.
That's it! You're ready for a maintenance test flight.
This was a very easy upgrade to install. Follow these instructions carefully and you should have no problems.
When weather permits a flight I'll report back how it differs from the stock head.