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Prop Weight and Balance
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4279 40 2015-2-14
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knisley.david.g
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While balancing my props, I used a jewelers scale and noticed that the weights varied upwards of 0.2 gram. At these rotating speeds (I saw a post at 10,000 rpm??), that could explain vibration and performance issues. I have seen postings indicating 1 gram variations, and carbon fiber props that are 3 grams heavier.

I adjusted the weights and balance to match, and then test flew the bird at over 32 mph, the sound and performance were noticable improved.

I am curious what the spec is for prop weights.

I did not record the weights of the first set of props, but used sterile gloves to weigh the unopened second set of props below.

18.275 grams
18.122 grams
18.246 grams
18.162 grams

variation 0.153 grams

I would be curious as to what weights others are seeing, and what affect the rotating mass variation has on stability, noise, and performance.
2015-2-14
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Bkackman
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I can be corrected, but the prop to prop weight variation isn't the critical feature. It's the unbalance of each individual blade that's related to any vibration. Do you have the equipment to measure blade balance?
2015-2-14
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dundee
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Bkackman Posted at 2015-2-15 13:52
I can be corrected, but the prop to prop weight variation isn't the critical feature. It's the unbal ...


I agree with you.
2015-2-14
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knisley.david.g
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Bkackman Posted at 2015-2-15 13:52
I can be corrected, but the prop to prop weight variation isn't the critical feature. It's the unbal ...

Dynamic balance is more critical than weight, but would also expect rotating mass affects
2015-2-14
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daninperth
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OK I couldn't resist. I've balanced these props but not sure I did a very good job. They seemed pretty close already.  As far as the weight difference between the silver and black it would seem to work out but open to suggestions.  These are the props I've been using and are not the new set.  

Silver Props
18.53 g
18.52 g
Black Props
18.15 g
18.10 g

What do you reckon?

Dan
2015-2-15
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knisley.david.g
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I think that anything over half a gram weight difference between props affects the energy needed to
speed up and slow down (Inertia) the blades.

2015-2-16
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bubo_bubo
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Can you recommend some equipment to enable me to balance my props please?
2015-2-16
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DJK
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I use a threaded rod from Orion to mount the props into a Du-Bro 499 Tru-Spin Prop Balancer. Both are available from multiple sources on amazon.
2015-2-16
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daninperth
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knisley.david.g Posted at 2015-2-17 01:29
I think that the nearly half a gram weight difference between props affects the energy needed to
spe ...

Hi David,

I see what you saying; even in view of the rotor speed compensation that the flight controller provides.  Maybe free floating or yaw wouldn't be affected as much.  But could roll and pitch over a longer stretch ... or that inevitable wobble on rapid altitude changes be affected in a way that you'd notice?  I have no idea.

I guess after you tested it you figured yes.
2015-2-16
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daver/m
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Anyone ever own a set of T props for thier phantom , I did they were exellent out of the box , hand finished T motor props ... Nothing else I had purchased in carbon props came close .. Maybe they will make a nice set for the inspire ? Although the price even for the phantom was the most expensive you'll see @ $189.99 a set of four .... Still have the same perfect set a year later on my p2.
2015-2-16
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DJK
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daninperth Posted at 2015-2-17 07:32
Hi David,

I see what you saying; even in view of the rotor speed compensation that the flight cont ...

Maybe an expert will shed some light for us.

I am not sure how fast the motors can turn, and of course the speed varies with throttle, but I think that the props all having the same weight helped the performance and smoothness of the flight.

I am also sure that the individual inertia would be slightly different based on the different weights at any given speed, and of course this is assuming any effects associated with blade balance have already been nulled.
2015-2-16
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DJK
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Never heard of T props, but will look them up.
2015-2-17
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InspiredOne
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DJK Posted at 2015-2-17 03:51
I use a threaded rod from Orion to mount the props into a Du-Bro 499 Tru-Spin Prop Balancer. Both ar ...


DJX, would you, please, be more specific about the threaded rods from Orion?

Thanks!

EDIT: Found the threaded rods, but they saying nothing about fitting the Inspire 1 props.
2015-2-19
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stuzphotos.gmai
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I purchased the STO prop balancers at http://www.infinity-hobby-jp.com ... amp;language=enthey are very good I use them with my Du Bro. you will be happy with bot
2015-2-19
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stuzphotos.gmai
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I ordered the STO prop balances at http://www.infinity-hobby-jp.com ... 252&language=en and use them with a Du-Bro.
2015-2-19
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rodger
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Sounds nice doesn't it. Just like a Jet engine. I have a Phantom that sounds like a jet when it is on the ground running in idle.
2015-2-19
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rodger
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I agree with both of you. If the balances bad enough you are going to get vibration and it is tough on the motor.
2015-2-19
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DJK
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T prop selling point.....lower weight means less inertia for faster control response and higher efficiency. Likewise same weight mean the same inertia for balanced control response.
2015-2-19
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Tahoe_Ed
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The E800 motors that are used on the Inspires are part of a tuned propulsion system.  I have flown 5 different Inspires and currently have 2 in my possession.  I have not balanced a prop yet.  I find the are sufficiently balanced "out of the box" and do not effect my video performance.  Right now I am testing the new E800 locking props.  I have not balanced them as well.  
2015-2-19
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mark.gray52
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I had 3 props out of balance. They are only slight, not as much as the phantom props. One prop was perfect so I will see how they go. I've used my own balancer rod which I make and the du-bro balancer.
2015-2-20
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InspiredOne
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What does one use to adjust the balance of a prop? Tape? If so, what kind?

I saw a video recently of a guy using small pieces of black tape that come in difference sizes (weights?).

EDIT: Found it. He was using vinyl stickers to balance his motors. Where do you get those?
2015-2-20
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GB44
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Tahoe_Ed Posted at 2015-2-20 13:20
The E800 motors that are used on the Inspires are part of a tuned propulsion system.  I have flown 5 ...

ED,

Will DJI be issuing the new Locking Props to existing Inspire owners ?  

I was of the opinion that the plastic lock props rushed out were only a temporary fix.  If so will the DJI dealers be sending them out automatically as they did with teh plastic prop locks.
2015-2-20
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dennis
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stuzphotos.gmai Posted at 2015-2-20 05:19
I ordered the STO prop balances at http://www.infinity-hobby-jp.com/product_info.php?products_id=112 ...

So after you find that its out of balance what is it you stick on the prop to balance it out??
2015-2-20
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daninperth
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dennis@aerialpe Posted at 2015-2-21 08:18
So after you find that its out of balance what is it you stick on the prop to balance it out??

There are all kinds of things people use.  

Sanding, transparent tape and vinyl tape are often used on blades.  Hot glue or cyanoacrylates are often used on hubs and sometimes blades too.

I didn't detect much imbalance in the stock props.  I'm a bit dubious about the efficiency of certain rod balance techniques used with capped props.  Maybe it's just a matter of practice.  I have the Orion rod.   Glad to hear that others found them well balanced too.   Any tips would be appreciated.

Dan

2015-2-20
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dennis
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daninperth Posted at 2015-2-21 08:36
There are all kinds of things people use.  

Sanding, transparent tape and vinyl tape are often use ...

Thanks daninperth
2015-2-20
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dennis
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Tahoe_Ed Posted at 2015-2-20 13:20
The E800 motors that are used on the Inspires are part of a tuned propulsion system.  I have flown 5 ...

Hey Ed I wanted to ask you a question on a different subject,  Is it normal for the status bar in the middle of the pilot app screen to be red and say no signal when the camera is not present.

and.....

If I am using dual remotes with the slave connected to a big screen for live broadcast, does the master remote dictate the image transmission settings or do I need to configure them independently.


Thanks,
2015-2-20
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Tahoe_Ed
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GB44 Posted at 2015-2-21 07:23
ED,

Will DJI be issuing the new Locking Props to existing Inspire owners ?  

I do not believe that they will.  I have no specific knowledge however.  The prop locks work perfectly well.  DJI recommends that they be used.  The E800 prop guards are more of a convenience that a requirement.
2015-2-20
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DJK
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daninperth Posted at 2015-2-21 08:36
There are all kinds of things people use.  

Sanding, transparent tape and vinyl tape are often use ...

Light sanding with an black emory type is the easiest and most controllable way to tweek the balance. I am not going to advise anyone on how to adjust weight.

I have not seen poor or unacceptable performance with the props out of the box, but better, smoother performance with finer adjustments.


2015-2-20
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Blade_Strike
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You need to balance via a balancing rod. I just put all 10 props on my balancer and only 3 needed.work. Hub was perfect so it was an easy balance.
2015-2-20
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DJK
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Blade_Strike Posted at 2015-2-21 11:17
You need to balance via a balancing rod. I just put all 10 props on my balancer and only 3 needed.wo ...

What was your weight variation between the 10 props?
2015-2-20
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Blade_Strike
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I don't worry about the weight of the prop, just the balance. This is why I use a blade balancer and not a scale.
2015-2-20
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DJK
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I carefully go back and forth between the rod balancer and the scale to get a matched set. With 10 props, you could probably find a closely matched set and give us some feedback as to whether you observed any difference between them and say a set with a blade or two a half gram off.
2015-2-20
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DJK
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Does anyone know when/where props will be available?
2015-2-23
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JerryMutter
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pitch balance can cause issues as well make sure that your props are stored in a way not to cause any bending or other stress
2015-2-25
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DJK
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JerryMutter Posted at 2015-2-25 21:56
pitch balance can cause issues as well make sure that your props are stored in a way not to cause an ...

Thanks, I agree, would be nice if there was a way to compare shapes other that visual.
2015-2-25
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DJK
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Any recent news on DJI props?
2015-3-15
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DJK
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I have done a little more research, and racing engine pistons are weight balanced. I have read to less than 0.3 grams, and heard that some go as far as 0.0001 grams, but not found that documented yet.

I have read and measured the carbon fiber prop people are trying, and they are a few grams heavier.
2015-3-18
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markjacobs.talk
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DJK Posted at 2015-3-19 06:43
I have done a little more research, and racing engine pistons are weight balanced. I have read to le ...

The weight differential you are talking about is immaterial and will have zero effect on flight dynamics.

You cannot compare an engine which will have a rotational inertia connected by a single pivot - a crankshaft.
The E800 tuned propulsion system (or in fact any multirotor system) is not linked mechanically but electronically. Each esc will be independently controlled by the flight controller working on a closed feedback loop system taking into account aircraft attitude, acceleration and altitude and the props will be sped up or slowed down as necessary to maintain the correct attitude in flight (dependent on your stick input) or hover.
Even leaving the craft in a hover you will see the props constantly changing speed to maintain position and attitude.
0.0000000001 of a gram or even 1 or 2 grams will have ZERO effect on dynamics or performance.
You are chasing your tail if you are trying to match props to those sort of tolerances and wasting an awful lot of time for zero gain.
2015-3-18
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DJK
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I am not saying the craft won't fly acceptably, but I think performance and efficiency are affected.

I have a difficult time agreeing that 1 or 2 grams difference between props will not affect performance, since the inertial will be different in each motor/prop.

Lets take this concept to an extreme for the sake of discussion.

If you were to add 5 grams to both tips of one of the blades...
Assuming what you are saying is correct... "Each esc will be independently controlled by the flight controller working on a closed feedback loop system taking into account aircraft attitude, acceleration and altitude and the props will be sped up or slowed down as necessary to maintain the correct attitude in flight (dependent on your stick input) or hover."

How is the motor and control system going to seamlessly correct for the imbalance in the inertial of that one blade.  
                              F=ma    force = mass * acceleration
                              p=ma    momentum = inertial mass * velocity

I also think that it is fair to say that the quad's motor and prop do have rotational inertia around a single point, similar to the rotating components of an an engine, obviously much smaller.






2015-3-18
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DJK
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The new self locking props weigh around 20 grams, and the mount adapters weigh around 2.6 grams. this is 3.6 grams heavier than the original props.

I would be interested in hearing if there are any flight time differences with the heavier prop setup.

This new prop setup is also now similar in the weight to the full carbon fiber props commonly available from third parties. Not that I am recommending them.

I would assume that my questions about the range of prop weights acceptable  is somewhere from 18-19 on the original props to upwards of 22-23 grams on the new prop.

2015-4-5
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