I built my own prop balancer for blind hubbed props. I suitably sized plastic box and two burned out Phantom motors. Remove the magnets from each motor ans mount them at the top of either side of the box. Simply fix the props in the usual fashion and bingo one clockwise and anticlockwise prop balancing machine. I also have two new smaller motors which I was intending to fit on the other two sides of the box. but the scrooge in me won't allow the wrecking of two perfectly good and new motors.
I've slowly collected hundreds ot new props over many years, mainly because I always make a point of having at least 3 spares of each type I use, and with so many planes that really adds up. Plus the fact you need double the number for quadcopters. It wasn't that long ago when almost every prop I purchased required balancing, Some very badly out of balance and a few totally useless due to voids within the hubs, they got binned. More recently I noticed I wasn't having to balance every prop. At a guess about 60% good, 25% needing minor balancing and the remaining 15% needing more attention. Maybe I'm fussy, but I have come across a small number of DJI props which need attention. This is a great improvement over say 10 years ago. But then I wasn't flying DJI quadcopters until recently.
The only props to come into my workshop which I've never balanced are the new DJI props. They'd have to be dismantled for balancing. Only because I originally purchased one of those rods for balancing DJI props I'm considering mounting a couple of hobby knife blades with stops on each end to stop the rod from dropping off the blades. There are a few problems with using a rod to balance, at least the one I purchased from Amazon has them. It's way too light and unless the prop is almost touching the first rest the darned thing topples. So if you're thinking of buying one avoid the lightweight aluminium type. In my opinion the heavier the better. I'm considering extending the standard thread on one end to the center and weigh it down with nuts.
One final point, I don't like the Dubro balancer. I think there's too much added friction as the rod is wedged between four non-moving surfaces. For standard props I prefer a good quality magnetic suspension type where there's no friction. I'm also not a believer in using sandpaper to remove weight, now that there's less weight change between balanced and not balanced I use a special adhesive tape I discovered during a 9 week stay in hospital. It's used when a patient is prepped for surgery. It's a tape which is stuck to the surface of the skin where the surgeon is going to cut. It's very adhesive and helps to keep the edges of the skin in place for when it's being sutured. I was presented with a roll of it when I left the hospital. It has a protective cover on both sides of the tape so it takes a few goes to get used to it. You peel off one side, stick it down and I found simply rubbing the top surface with a finger makes it peel off.
It's called Opsite Flexifit and comes in rolls of 5cm x 10 meters. If you know a nurse or doctor ask them if they can cut you off a couple of feet, It also comes in larger sizes, but the easier to handle 5 cm I've found to be the best. Just one word of warning. There is also a new release which has thousands of small holes. I tried it and it works OK, but I'm unsure of how it will behave over time. The standard tape I've run for a couple of weeks on and off and at all speeds on my test rig and it displays no sign of lifting. Oh yes, and it's almost invisible especially on the white props. One thing I have noticed is how much quieter a properly balanced prop can be. Even props on my Phantom one and two which only needed a slight tweaking sounded much quieter after a good balance. Happy flying.
