In your experiences have you found the carbon propellers need balancing?
If so can you suggest a good tutorial, thanks
If so can you suggest a good tutorial, thanks
Prop balancing
- Thread starter OnTheRopes
- Start date
PatR
Premium Pilot
I’m going to generalize for a moment and state all carbon props should be balance checked.
To be model specific, both Seabee and I both found our 920 props be out of balance as delivered. Some considerably. That condition was also evident with the spares I purchased from a different vendor.
For our purposes, blade balancing is, IMO, sufficient, and hubs do not need balancing because of their low mass, the addition of a quick release, and because the motors are not smooth in their rotation.
I’ll be back shortly with a text and photo tutorial.
The only video tutorials I am familiar with are quite old and applicable to gas or glow engine models using much larger and thicker propellers where sanding is employed to balance. We should not sand thin carbon props consisting of only a couple layers of carbon fabric to remove weight. It’s much too easy to violate the structure of the fabric. In fact, we should not sand any carbon prop. Instead we add mass to the light side.
To be model specific, both Seabee and I both found our 920 props be out of balance as delivered. Some considerably. That condition was also evident with the spares I purchased from a different vendor.
For our purposes, blade balancing is, IMO, sufficient, and hubs do not need balancing because of their low mass, the addition of a quick release, and because the motors are not smooth in their rotation.
I’ll be back shortly with a text and photo tutorial.
The only video tutorials I am familiar with are quite old and applicable to gas or glow engine models using much larger and thicker propellers where sanding is employed to balance. We should not sand thin carbon props consisting of only a couple layers of carbon fabric to remove weight. It’s much too easy to violate the structure of the fabric. In fact, we should not sand any carbon prop. Instead we add mass to the light side.
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Thank you for your reply Pat and it is interesting that you point out the glow engine tutorials as I already watched a couple and balked a little at the idea of sanding a carbon prop.
I look forward to your tutorial, perhaps you can suggest a way to make a jig or a suitable one to purchase too.
Regards
PatR
Premium Pilot
Prop balancing instructions. The instruction is for blade balancing and does not include instructions for hub balancing. All the photos and a few more can be downloaded from the Dropbox folder by anyone with the link. Links to balancing tools are in the PDF.
Dropbox - 920 Prop Balance - Simplify your life
Dropbox - 920 Prop Balance - Simplify your life
Cheers Pat, it's late now so can't focus and Ive had a couple of beers so I will d/l and take a closer look tomorrow. Thanks for putting this together.
PatR
Premium Pilot
Brilliant, very clear and concise. I have ordered what I need and will give it a try in a week or so. I will let you know how it goes.
Thanks again for the help.
Thanks again for the help.
PatR
Premium Pilot
I would never, ever use a thin multirotor prop he had balanced. The cardinal sin with balancing this kind of prop is sanding the blade. This is even more of an issue with the very flexible slow flyer props as the area sanded induces failures at that location. In other respects he is usually very fastidious and gives good advice, but not this time.
You can sand props and hubs but only when they have an amount of material thickness that will permit a limited amount of sanding. Wood and fiber filled props having considerable thickness handle sanding quite well. OTOH, props only a millimeter to a few millimeters thick do not possess a structure that will tolerate adding a stress riser.
I won’t mention my opinion of the RC Timer props other than to say his experience with them is a lot different than mine. Anyone needing a hex set of 15x5.5 can have mine for postage costs.
You can sand props and hubs but only when they have an amount of material thickness that will permit a limited amount of sanding. Wood and fiber filled props having considerable thickness handle sanding quite well. OTOH, props only a millimeter to a few millimeters thick do not possess a structure that will tolerate adding a stress riser.
I won’t mention my opinion of the RC Timer props other than to say his experience with them is a lot different than mine. Anyone needing a hex set of 15x5.5 can have mine for postage costs.
I found it odd that he took a file and started taking material off the hub .he had a lot of debris from that prop on the table
PatR
Premium Pilot
Rotational force is pretty powerful stuff. That hub is all there is to keep the blades on. They don’t just go round and round, they also flap a little bit during thrust and vertical maneuvers. That poor little hub is the mass dampener for all the forces the blades experience.
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Yea I would be afraid to do all that to a prop.I build aircraft engines some times for airboat and if you stand next to that prop when they hammer the throttle that prop moves forward and backward when accelerating and decelerating. It gives you a not so trusting feeling
PatR
Premium Pilot
Thrust loading. Props are designed to flex some amount. While still employed I got to watch a few 26” props made of wood, carbon, and carbon laminated over wood explode after the hubs were weakened by foolish engineers. They were surrounded by a safety cage but it was still pretty dramatic.
With these guys they want to take it to the max. And I've seen a 6 blade carbon fiber prop let go of its blades. Sending them about a 100 yards but the prop was rated at 3000 rpms max and he was running it at about. 3500 instantly
PatR
Premium Pilot
@PatR I did the prop balance today following your instructions. It took a while to get a feel for it but hopefully now i have some better balanced props. There was quite a variance from one being pretty spot on to one needing 5 strips. I did find that when it was getting close that tapping the table would send the heavier to the bottom allowing me to make the final adjustments.
Thanks again for going to the trouble of putting the tutorial together.
Thanks again for going to the trouble of putting the tutorial together.
