Hi all! :-)
A few weeks back (probably a month or more) my 9 foot 2 blade prop had exploded during a severe wind storm. Inspection showed that there was a large dent on the prop which was caused from hitting the tower. What i found on top of the tower was that the DC genny base had broken along with one bolt. Actually the base was broken in several spots, allowing the genny to tip forward. Thats when the prop hit the tower. After discussion with a few people about the prop, i do put some of the blame on the (apparent) problems that exist with 2 bladers when passing the tower. I guess there is some type of vibration that sets up and causes problems. I never did like the performance of the 2 blade as start up was not that good and got "nothing" at all in low winds. No more 2 bladers for me.
I welded on a new base to the genny ( an industrial duty 1 1/2 hp Leeson 180 volt DC permanent magnet motor). The shaft and bearings had no damage from the previous hit on the 2 blader. Mounted everything back on top of tower and put the new 3 blade on.
Performance is excellent, starts to spin in the least detectible breeze, and got peaks last night of 36 amp. It was windy, but not severe winds.
There are 8 pictures to this post, plus a small movie clip of it spinning on the tower (not sure if it will work here or not).
Here is a picture of the destroyed 2 blade prop
The new blades are made from bass wood (nice stuff to carve, very tight and straight grain, similar to pine ). The stock was planed down to 1 7/8 inches thick by 6 inches wide. Length of each blade is 4 foot to make an eight foot blade. I used outdoor wood glue and biscuits to glue on an extension to the root for better start-up. The blade is now 12 inches wide at the root. TSR is 7.
Finished carving
My son Chris holding the finished prop
The hub is made from 2 steel discs. 3/16 thick and 10 inches wide, held together with five 1/4 inch grade 8 bolts per blade.
The rear side view of the blade hub. I like to use "weld on hubs", and weld it directly to the rear hub. This hub has a 7/8 inch bore for the genny shaft, has a keyway, 2 set screws, and is mounted to shaft with a 3/8 bolt through from the front hub directly into the genny shaft which i had drilled and threaded.
The blade is perfectly balanced, and here you can see the balancing weight i used bolted directly from one of the hub plates.
Here are 2 sky shots with the new prop installed.
Here is a short movie clip of the prop spinning. The digi cam seems to give it an appearance of having 6 blades LOL. Not sure if this posting of the movie clip will work.
Well, hope you enjoyed the update of the old 9 foot exploded prop :)
have fun, zubbly
