I bought a 10.5mm (3/8") square stick from Home Depot and sanded two pieces out of it until the wood measured 14.5mm x 7mm x 10.5mm which fit snuggly into the prop.  Drilled a snug center hole in them for some 1/8" (Cut to 11 inches long.) spring steel wire from the hobby shop.  Pushed the wood blocks onto the ends so they are 90 degrees to each other for static balance on the "DuBro Prop Balancer" and sanded the opposite end from the prop one so it would freely spin and balance at a different point each time (Static balancing.).

Put on the prop and see where the heavy side falls and sanded a bit off the underside or trailing edge to balance.  Some add tape as a weight too.

Two of mine were heavy and the others were passable.  Didn't take much sanding to balance.

Awesome to see a balancer for I2 props... had a similar idea recently. Great job !

how can you be sure you've properly centered the shaft in the blocks?
...and the blocks on the props?
If you did it by eye, that's not gonna be good enough.

raven4 Posted at 2017-8-17 16:31
how can you be sure you've properly centered the shaft in the blocks?
...and the blocks on the props?
If you did it by eye, that's not gonna be good enough.

I have a drill press with an X-Y axis machinist's vise.  Not that hard, along with vernier calipers to mark the center of the block.

The wooden block fits snug into the middle of the rectangular prop cutout so it is centered.  It takes some sanding of the end block (Opposite prop end.) to get the shaft to spin and into balance without a prop attached, but not that hard.  The 1/8" shaft has to be more than 10 inches else the weight of the prop will tilt the shaft up off the balancer's wheels.  My error was the first one was 6" (Too short.) and it tilted up when the prop was on.  You can roll the shaft on glass to see if it is straight.

The DuBro balancer needs to be up on a 25mm tall block as it was made maybe for 14" props at most.  Inspire props will hit the table otherwise when spinning.  

In the yard, the slight wind gusts blew the thing like a windmill and I could watch if it stopped at a new spot indicating it was balanced.  Same heavy spot down and it took some sanding.

Better than nothing, which is what it was.

Great approach. And have you flown the balanced props? Do you notice a difference?

raven4 Posted at 2017-8-17 17:46
Great approach. And have you flown the balanced props? Do you notice a difference?

Haven't tried it yet on the I2.  It has other issues like disconnecting from the RC right now maybe due to firmware.

Fwiw, I've done the same balance on the old P4 last year and it worked for that model too.  The web speculators were claiming any prop imbalance was causing jello with them.  I haven't seen jello with that P4 ever.  More odd is it hasn't cracked the shell yet either so maybe it is smoother?  Dunno.

The hottest setup would be to turn the wood block; and, simultaneously bore the center hole while the whole thing is chucked up on a lathe.

raven4 Posted at 2017-8-18 06:20
The hottest setup would be to turn the wood block; and, simultaneously bore the center hole while the whole thing is chucked up on a lathe.

Many times I wish I had a lathe.  For this, one would need a four-jaw chuck as the block fitting into the prop is rectangular in shape.  Then maybe I could have used aluminum instead of wood, but wood has some give as some props fit tight while others are looser (DJI ill-fitting props again!).  Aluminum may exacerbate the prop molding matter by being too loose on some props.  Wood, being light, doesn't impose a lot of arm or moment weight from the center of the shaft either so not super-critical as if it were at the ends of the 15" props, plus it is easy to sand down to fit and balance.

Least it gave me some assurance that the things are better balanced than stock.  They weren't really bad and maybe better than my P4 props were, but they still could use some tweaking.  A couple would not spin with the yard's wind gusts and always were one side heavy.  Others would windmill a very long time and stop at different spots so they passed.

If I doubted their balance, I could remount it 180 degrees on the block and double-check.  I do the same static balance with my motorcycle tires too on the balance mandrel made for them.  I balance them down to one penny in weight which is probably overkill for them, but sort of fun to see how well I can balance them.

With your tooling chances to get it right are very, very slim, my friend. You need to be within at least  .001" accuracy and CNC machinery or you may make things worst. DJI props are good enough to be left untouched, rattling issue aside. Sorry ...