Time has come to start setting up the geometry and controls - Rigging the ship.

TAIL ROTOR BLADES

 I’ve been thinking of a way to mount the Rotorway Digital Protractor Tangentially to the Chord Line of the Tail Rotor Blades. I wanted a jig that would be accurate and simple to use and install without damaging the paint finish. The blade profile is symmetrical which make things a lot easier.

I started by milling a slot the same width as the thickness of the blades in a billet of aluminium - My blades measure 19 mm (3/4 inch) maximum thickness. Without removing the material from the chuck I also took a cut across the end of the billet at 90 degrees to the slot.

I then machined a smaller block exactly the same width as the slot and milled a 1.5 mm (1/16 in ) slot dead centre at one end to fit over the trailing edge of the blades.

I milled the slot through to one end to make a fork, secured the Protractor across the end with a couple of ties through some drilled holes and wedged the small block in the open end straddling the trailing edge. A layer of Sellotape all round the blade protects the paint from scratches. I guess I could have just as easily made the thing from a piece of hardwood.

Setting the pitch angles is pretty-much as detailed in the manual but I discovered a couple of additional potential pitfalls. On my first attempt to achieve the 2 7/8 in cable travel dimension I found the cable on its full travel limit at full right pedal. I adjusted the stops and Rod Ends so that the required travel dimension still left some cable travel available on each stroke.

I also discovered that in order to achieve consistent results when measuring the 24 degree and 8 degree blade pitch angles, it’s important to keep the blades perfectly horizontal for each reading. I used a small spirit level on the leading edge.

MAIN ROTOR BLADES

I found this combination ladder to be a perfect working platform for installing and adjusting the blades.

Balancing the blades necessitates reducing the internal friction of the Rotor Head so that it can rock freely. The head arrives pre-assembled from the factory and centralised to within .001 “ on the main shaft. This is achieved by shimming between the bearings and pre-loading the Teeter Blocks. (These are the triangular pieces in the picture that house the needle roller bearings). The bolts that secure the teeter blocks are precision ground to be a perfect fit through the holes in both the blocks and the head plate below. In order for the head to rock freely the teeter blocks must be released of their preload tension. This is achieved by replacing the two bolts in one teeter block for smaller diameter ones. However, because of the preload, the blocks must first be clamped tightly to make the bolts easy to remove, otherwise there is a risk of shaving material from the holes with the thread of the bolts as they are removed and reinserted.

Rotorway recommend clamping  across the blocks at bolt level using a simple, carpenters ‘F’ clamp (one with a screwdriver-type handle). My assembly needed two hefty rack clamps (pictured) to exert enough pressure to allow the bolts to be removed easily. Also, I’m not convinced that ‘bolt level’ is the place to clamp. Seems to me that the pre-load pressure is acting at the top of the blocks, in line with the bearings and cross shaft so here should be the place to clamp. I could be wrong but the job’s done now, as recommended. Oh, and I drilled one blade weight to reduce its weight by one 3/16” washer

First time outside and here I am setting the blade pitch.

I couldn’t work out why the collective travel was being restricted when I applied full left or right cyclic and vice-versa. A quick call to Southern Helicopters solved the problem. The two 3/16 bolts that help secure the pitch horns to the blade straps are too long, limiting pitch angle. Putting both washers on top sorted it.

Blade tracking is adjusted until both blades rotate exactly on the same path. A favourite and proven method is to fix a red led light on one blade tip and a green one on the other. These can be easily seen as a red and green line from the pilots seat when the blades are turning at 100% rpm.  When the green and red lines merge, the tracking is perfect. I didn’t fancy spending fifty quid or so on a pair of tracking lights so I bought a bunch of LED keyrings from ebay for 75 pence each.

Fortunately, they’re held together with four tiny screws so I made some aluminium mounting brackets, changed the LEDs for a red and a green one, cut a slot in the side where I could slide in a piece of credit card between the batteries and glued them together. All for a fiver.

[Home] [Specifications] [Frame] [Tub Split] [Body Assembly] [Roof Panel Modifications] [More Body Mods] [Interior Finishing] [Painting] [Screen] [Doors] [Skid Pants] [Controls] [Tail Boom & Fins] [Tail Rotor & Drive] [Chain Oil Bath] [Drive Train] [Rigging] [Cooling] [Instruments & Wiring] [Cabin Comfort] [Exhaust] [Silencer] [Heat Shield] [Fuel Tanks] [IT LIVES!! &Teething Troubles] [Testing] [Main Rotor Blades] [Miscellaneous] [Tools] [Parts Supply] [Build Diary] [Events] [Flight Training] [Links] [Toys and Dogs]