FYI Prop+Hub Balancing

[nuggetz]

To be technically accurate, you are not balancing them separately, you're balancing them both at the same time along two different axes. Let me set up a system so I can type this with a chance of being understood. Visualize the prop horizontal. Now think of it in three pieces - the left blade, the hub, and the right blade. Now:

Case 1: Let's say the left blade is "heavy." In that case, we'd sand a little behind the blade until it balanced out. Since everything else was OK, it will not spin in the balancer no matter what orientation it starts from - a perfectly balanced prop.

Case 2: Left blade heavy, bottom of hub heavy. We would need to sand the heavy blade until it stayed horizontal in the balancer. Then we would add some glue (or whatever your fav method is) to the top side of the hub so that when you orient the prop vertically in the balancer, it stays put.

Case 3: Left blade heavy, left side of hub heavy. In this case, you would sand extra on the blade to get it to stay level. You think that it's just a blade badly out of balance - but you have no way of knowing that the hub was contributing. It doesn't matter. It will be balanced and not vibrate due to imbalance.

Case 4: The bottom edge of the left blade is heavy, hub balanced. Again, you can't know what part of the blade is heavy. You sand the blade to fix it horizontally, then you add glue to the hub to fix it vertically, not knowing that it was the blade that was making it not stay vertical in the balancer. Again, it doesn't matter as far as the shaft is concerned.

Well, I've probably confused things tremendously, but all I'm trying to say is that "prop" then "hub" balancing is just making sure that the whole system is balanced about the shaft while rotating.

Yep that's the way I understand it. That was a good write up.

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[RichWest]

With out the proper tools, prop balancing is a pain in the... Managed to find a Du-Bro this weekend, however no threaded prop rod available. I defaulted to using the supplied rod and use the silicon gas tube as a centering/retainer when placed into the hub. Battled with keeping the prop centered from this improvised method. Eventually I created a point on the rod to take advantage of the hub's centering point. Improved the repeat ability, but still no cigar.

At this point the current method is not reliable, at least for me. For those that have the EJH rod, how repeatable is the balancing? Can you actually take a balanced prop off and then re-install and the prop remains balanced?

Still a lot to learn...TIA

 

[mcneely19]

It is very repeatable at least for me.

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[Acroduster]

Yes - with the rod it is repeatable. I tipped it on its side this weekend as the props were winding down and was worried that I may have boogered one. It checked out fine, though.

 

[RichWest]

Thanks for the replies, just finished ordering the Solo rod.... Now to order the replacement idler wheels for the dryer....priorities are in order.

 

[User Name]

however no threaded prop rod available.

Solo's props use the same thread as DJI's, so any balance rod for a Phantom should work on the Solo. Hobby King sells a set for $5, which I purchased and can verify works: Balance Shaft with Adapter for DJI Propellers 1 pair (CW & CCW)

 

[RichWest]

Solo's props use the same thread as DJI's, so any balance rod for a Phantom should work on the Solo. Hobby King sells a set for $5, which I purchased and can verify works: Balance Shaft with Adapter for DJI Propellers 1 pair (CW & CCW)

That's a pretty slick design. If the EJH has errors, I'll reach for your recommendation...Thanks!

 

[nuggetz]

Well for my the EJH rods are pretty repeatable. I tested just the rod and I was able to rotate it to any position so it seems that the rod itself was pretty well made. I know what you're saying about using that piece that came with the DuBro. Sometimes even with a proper rod there can be things that affect your readings. I've seen people on youtube slam their rods ahem...slam the rods against the balancer when taking it on and off and I would imagine it would be really easy to dent the delicate metal wheels in the balancer. I think that with any system you might hit some of these little points of friction but in the end its always better to start with the right tools. Can't speak for the DJI ones. Didn't even know the threads were the same. I will say that you want thin rods. I know the EJH ones are the same diameter as the rod that comes with the DuBro. Larger rods will cause problems unless they spin 100% true and are polished.


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[RichWest]

Well for my the EJH rods are pretty repeatable.

Thanks for the further confirmation. I mean if we are to spend several minutes balancing a prop, I want it to be consistent...

 

[Matt Chevalier]

Is there a DIY way to make a balancing system? I saw someone using a soup can and putting tape on the end of a rod to go into the threads of the hub.

But to me the tape wouldn't be balanced.

 

[nuggetz]

Is there a DIY way to make a balancing system? I saw someone using a soup can and putting tape on the end of a rod to go into the threads of the hub.

But to me the tape wouldn't be balanced.

Theres a video where a guy takes a glass vase or jar with very smooth lips and just lays the rod on the jar. You rotate the jar to ensure that the rod is level and won't roll by itself and then just use that.

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[RichWest]

Reporting back, received EJH prop rod from Carolina Drones within two days via USPS, wow...

Balanced 4 props, hub balance was off on 3 of the 4. And to confirm the EJH rod is repeatable, really nice quality and worth the expense. Just need to get some flying time in before the weekend.

I choose hot glue to balance the hub. It makes quick work for the effort. Tape on the blades.

I appreciate everyone's help. Eight more props to balance....

Still waiting on motor pods from 3DR....

 

[z-axis]

Overall, it should become a priority of 3DR to address this QC issue. These props are relatively very out of balance compared to the APCs I used to fly. This means that w/o balancing, a LOT of people are fighting jello issues, adding an almost unfixable variable of why the video isn't perfect.

By the way, Rich, when you flew my prop set the other day on your bird, indeed, my son had "fixed" two of the props by removing the different material on the hubs (the silver tape). So I hub re-balanced those two and now the whole set is balanced, instead of just two of the four.

 

[RichWest]

Overall, it should become a priority of 3DR to address this QC issue.

By the way, Rich, when you flew my prop set the other day on your bird, indeed, my son had "fixed" two of the props by removing the different material on the hubs (the silver tape). So I hub re-balanced those two and now the whole set is balanced, instead of just two of the four.

I agree with your first comment, on a variety of issues related to propulsion.

You had mentioned that they may have been "adjusted", dang kids. The short video comparison did reveal better performance with your set of props, blaming you for the tools I have purchased.... If it doesn't rain this evening I'll be able to test out my balanced prop set. They are spot on now, the right tools makes the job very easy.

 

[FlyXlsa]

Interesting reading this post and checking out a few different techniques for all of us Noobs out here with our new BB Solo(s) looking for REALLY stable flight. Good Vimeo video here I didn't see posted elsewhere?

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[nikono]

You can easily check the prop's balance with a ballpoint pen.

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[SARDG]

You can easily check the prop's balance with a ballpoint pen.

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I would be worried that the tape wouldn't hold under water or when flying through tree branches...

 

[FlyXlsa]

The other option I saw was trimming or filing off a bit which seems easy enough and more permanent. That being said... It was > 50F and a little breezy here in Hershey, PA today - 7mph SW with Gusts to 18mph. The new Solo with Gimbal Installed (my second Solo from BB) flew very nice and steady. I did double check the prop(s) balance using the "pen method" suggested above, but they were pretty good out of the box - not perfect but no bad. Quick up, 360 rotate and down. Tested the Gimbal features a bit after this video. VERY COOL! So easy to fly this thing... I love it!

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