Tips for balancing props?

[cahutch]

I got a DuBro prop balancer and a threaded rod for balancing P2 props.
I know to remove material from the underside of the prop but I have a few questions for anyone who has experience doing it.

Should I sand lengthwise or sideways? Or does it matter?
Should I sand toward the tip or closer to the hub?
Should I try to stay away from the edges and only remove material from the middle?
What kind of sandpaper grain do you start with?

I'm using fine grain sandpaper and sanding a little at a time and re-checking but it's taking forever to see any difference.
When I do see a difference, instead of settling straight down, the heavy side starts to settle at a 45 degree angle. Does this mean I need to remove more toward the inside of the prop or should I try to remove material from one side of the hub?

How close is close enough? Even though it's settling to one side still, it settles slowly and spins freely if I blow on it gently.

Thanks

 

[bergenfelter]

I have the same balancer - I use 220 grit sandpaper - sand radially on the concave side (bottom side) of the prop usually starting about 1/3 of the way from the prop hub outward and avoiding the edges. Hope that makes sense - it usually does not much take much material to remove to balance things - at least with the stock DJI props - they are usually pretty close. If the blade stops horizontal or within 30 degrees of horizontal - I would call it close enough. Hope that helps.

 

[LuvMyTJ]

I do it the same way. Take about 3 scrubs with the sand paper across the underside and check it, then re-check it.

 

[MRSpyder2U]

I'd like to offer yet another way to balance props. I shy away from sanding the blades because this can induce subtle changes to the shape of the prop and lessen its efficiency. Instead, I apply the lightest of coatings of clear, spray-on polyurethane to both sides of the "light" blade. I then hold it in front of a fan to speed the drying time. (The lower the humidity the better.) Then I put it on the balancer. I repeat the procedure until the prop is balanced. This will maintain the intended shape of the prop without removing any of the surface area which might weaken the prop. I haven't had a vibration induced failure yet with this procedure and I've used this method several years with electric fixed-wings.
Thanks for letting me prattle on, and fair skys and light breezes to you.

 

[LuvMyTJ]

Sanding or spraying something on = no difference. The amount removed by sanding is minuscule and will have zero effect on the prop.
Different strokes for different folks I suppose.

 

[robinb]

I use some very small pieces of stick on plastic paper (clear same thickness as paper) and put that in the well on the centre of underside.
Normaly the little strip is around 15mm long by 5 mm wide.

 

[Fplvert]

Another way is to use a bit of magic transparent tape on the light blade. I like this method since I can tell which props are balanced, and no chance of changing pitch. I cut a small strip that will just wrap once with no overlap and place it close to the tip. I've only found one dji prop that balanced with no correction. :lol:

 

[BlackTracer]

Just curious do you balancers see a before and after difference and if so (which is obviously the case) what diffs do you see?

I have never balanced a prop for my phantom but could be convinced after someone explains.

 

[Phantom_Menace66]

After balancing the props, the prop should remain stationary in any position you place it on the balancer... If it settles horizontally, the centre hub is out of balance which can create as much vibration as the unbalanced prop did. Effectively rendering the efforts to balance them useless....

 

[robinb]

Just curious do you balancers see a before and after difference and if so (which is obviously the case) what diffs do you see?

I have never balanced a prop for my phantom but could be convinced after someone explains.

I used to fly Nitro powered heli's a long time ago.
The blades are much longer and flex.
The lighter blade used to fly a little higher, this meant it cut into the vortex created by the heavy blade which would cause a sort of flutter.
This reduces efficiency and can cause instability in the worst cases.
It was also essential to balance the blades then and to an extent now.
I bought a balancing rod with opposing screws each end so you can check both blades.
This only cost £10 inc delivery around EU.
The trick is to have a level table a quality whiskey tumbler and roll the rod with blade on that to do the balance, works really well.

 

[Phantom_Menace66]

Just curious do you balancers see a before and after difference and if so (which is obviously the case) what diffs do you see?

I have never balanced a prop for my phantom but could be convinced after someone explains.

To be perfectly honest, I have seen no difference in flight characteristics although there is definitely less vibration. It just seemed logical that something spinning at a great rate of knots should be balanced. It's a poor analogy I know, but as a wheel wobbles on a car when it is out of balance, or as a washing machine shudders on the spin cycle when all the clothes are stuck to one side, can the same not occur with a propeller that is heavier on one side?

 

[Luap]

I balance blades to get rid of vibrations and jello in the video - but don't feel any difference in flying performance (unless blades are ruined) - probably a touch more quiet as well.
But then I do not fly 3d

 

[GerdS]

I have just described dynamic balancing here on page 3: viewtopic.php?f=4&t=22911&start=20

Regards, Gerd

 

[Jetfixer]

I haven't any unbalanced blades in 4 complete sets of new blades. However, I have found a couple that due not track true. To me, this is a far more serious issue than static balance. Checking your tracking is easy. Place the blades on the phantom at normal tightness on the motors. Set the Phantom on your bench and hold a ruler up just outside the arc of the blade tips. Without pushing down on the rubber pads on the landing gear, slowly turn the motor by hand and make sure that each blade tip passes the ruler at the exact same mark. Repeat for each blade. If a blade is bent up or down, it's better to replace it than to try to re-bend it. This will cause more destructive shaking than a slight spinning imbalance.