Weatherproofing

Preparing for Deployment

It has been nearly 5 months since I had the opportunity to do any work on this project. Tight deadlines at work, schooling committments, coast-to-coast cycles and repairing toys have conspired to keep me out of the garage. Fortunately, I did manage to complete the blades so the task that lies ahead is one of painting, greasing, tightening and wiring.

Frame Preparation

The Navy follows a philosophy "if it moves, grease it, if it doesn't paint it" which are wise words. So it was time to dismantle the machine and paint/grease all the parts. The startor and rotors were taken off as one unit after disconnecting the wires and unthreading from the stator brackets. The frame was painted using the same black metalic paint I used on the 12 watt design which served well last time. The tail boom was also painted at the same time. Thick layers of paint and I pushed it inside the ends of the open box sections as well. I had noticed on the 12 Watt machine, that this was a corrosion point.

Rotor Preparation

The rotors were separated from the stator using my trusty jacking bolts. Although a bit clunky, these work extremely well and make an otherwise impossible job managable. The rotors had collected a lot of swarf and iron filings which needed to be removed. This is a tedious job and I found the best option was to dab the magnets with masking tape to pull the swarf off. Once this was done, I superglued the magnets again - call me paranoid, this is the third time but I dont want a magnet flying off at speed. I believe the rim on the rotor discs and the strong magnetic attraction of the magnets to the disk make this unnecessary but you can't be too careful. Next the rotors were treated to the black paint. Again, spray-paint would probably have looked a lot better but this is what I had to hand and it works admirably. I marked both disks with a drill dimple so I could assemble them in the same way once they were painted.

From experience with 12 Watt machine, I found that the rotor shafts rusted very quickly so determined to paint these as well although I'm sure grease would be perfectly adequate. Here are the magnet rotors after a thick coat of black paint. Note the spacer washers and bolts have been treated to a coat of paint as well.

The bolts that clamp the two rotors together are standard mild steel. It would be possible to use stainless steel to help with rust-proofing but This would prevent a good magnetic circuit being made between the two rotors so I decided to stick with steel and use paint for rust-proofing. I suppose A2 stainless steel bolts could be used (as that is magnetic) but I'm sure paint will be good enough.

Before bolting the two rotors together for the final time, the grub screw on the sprocket was tighted down and bearing glue used to fix the rotor in place on the shaft. Perhaps this is not necessary but once reassembled, I can't see me taking the machine apart without damaging the shaft so I might as well make things as permananet as possible.

The stator was placed over the sproket-rotor and the top rotor lowered into place using the jacking bolts. The jacking bolts will wear away some of the paint so I dobbed some grease on the ends to help keep the weatherproof seal.

The whole assembly was then put back onto the frame and adjusted to see that everything was back in the right place. Now was the time to tighten everything, add locking bolds and thread lock to everything. Then the stator brackets were painted and the bearings bolted back into place.

Mounting the Blade Assembly

The hub is mounted on the shaft using two brackets, one at the rear of the hub and one at the front. These were made by welding a 12mm bolt onto a steel plate and tapping it for a grub screw. The steel plates are then mounted at right angles to each other and held in place by bolting right through the hubs and held on with locking bolts.

The first bracket was pushed onto the shaft and its/grub screw tightened securely. Next the blade assembly was put in place and bolted loosly to the bracket. The second bracket was then slid onto the shaft and bolted through the hub. All the bolts were tightened up, the grub screws secured and bearing glue used on the brackets to really fix them there. The grub screws were also treated with thread-lock so they could not vibrate loose. As an extra precaution, a collet was fitted over the end of the shaft, grub-screwed and glued. A collet was also placed over the shaft on the back of the machine so nothing can come off in that direction. All the parts of the blade assembly are a slight interference fit so I feel confident that nothing is going to fall off, if fact, getting the blades off the shaft again may be very difficult indeed.

Blade Balancing

It is very important to balance the whole machine as anything off-centre will shake the thing to pieces at high speed. The rotor is very easy to turn with no load, and with the weight of the blades it came to rest in a fixed position. The heaviest side (bottom) was rotated up to 9 o'clock and a weight added to the hub at the 3 o'clock position. The weight was moved in and out towards the shaft until the blade was balanced in that position. Slight rotation of the blades caused them to come to rest in a new fixed position. Repeating this procedure and moving the weight slightly ( in and out and around the hub) soon gave the result where the blades came to rest in any position when rotated gently. This procedure has balance the whole machine (rotors and blades) so we are ready to fly.

Final Preparations

The tail was mounted, the tail-vane painted after being bolted securely with locking bolts. The lead-weight and bracket assemblies for the hub were all treated to a coat of paint. The bearing housings and any untreated armature shaft were also painted, in short-anything shiney was painted ready for spending time out in the wind and rain.

The whole assembly is really quite heavy. So with the help of my long suffering wife, a workbench and a highchair, the completed machine was put onto the tilting tower, wired into the terminal blocks and raised to the upright position. The cables coming down the pole were all shorted to prevent the turbine from turning. The age-old wind-generator law then came into play stating that once you raise a wind-turbine, the wind will not blow for several days.