Triple blade props

[solentlife]

Meta4 ... with the birds ... and others have nailed it down by stating Flight Controller. You cannot make the P3 fly faster as explained.

Speed is based on PITCH, thrust on DIAMETER.

If a blade is stiffer and pitch stays as designed better - then Flight Controller will slightly reduce RPM to compensate - maintaining designed AC tilt / attitude - which governs its speed.
If blade flexs and pitch reduces - Flight Controller will detect the instant tilt / attitude starts to change and increase that props RPM to maintain AC tilt / attitude - same speed......

The only time speed will be different at max - is if the props are so flexible in pitch ... or ... smaller props - so Flight Controller is maxing out trying to get to designed speed / tilt etc. It will then fly slower.

As others say - it is most likely that given DJI's design team - that the OEM props are the best compromise in rigidity, pitch, diameter and blade form. Any change to that and Flight Controller will adjust..... so in effect no nett gain. If a 3 blade was better - maybe they would have offered that ?

There is also a misconception about 3 bladers vs 2 bladers by some ... a 3 blader is not necessarily a greater thruster and certainly will not increase speed in normal model use to any real extent. Increasing blade count gets into RPM and dirty air factors - where as RPM goes up - the blades affect each following blade ... causing a loss in additional thrust. On high RPM setups such as the small diameter but high KV racers .. 2 bladers are prime and outspeed 3 bladers easily. 3 Bladers are better in lower RPM applications where blade interaction is less and then you can see 1.5x thrust performance or similar.

But increased thrust does not mean significant increased speed .. it means that the prop will cause the model its fitted to - to accelerate quicker to as close to Pitch speed as drag will allow.

There is one area that could happen though - NOISE level of props. Compare an APC prop to a Master Airscrew Scimitar for example ... same pitch, same diameter, similar thrust - but the Scimitar has a different sound and noise level to it.

I apologise for the 'novel' but its a subject that is close to heart having been involved in Speed Records etc.

Nigel

 

[Mark The Droner]

Interestingly, the Hover Camera Passport was deliberately designed with a 3-winged prop - apparently due to its smaller prop diameter... and maybe weight is a factor too? This one is so light it doesn't have to be registered with FAA

Hover Camera

 

[N017RW]

Yes. Likely a design consideration for compact size.

 

[solentlife]

Interestingly - I was looking at various Camera systems other day - I have the Soloshot 3 system and its not performing as it should, no-ones getting as promised !
Searching for alternative autonomous robot cameras brought the Hover Camera up.

Looking at the 'test review' drones I still have .. the smaller ones have 3 and 4 blade while the larger have 2 blade props ...

Nigel

 

[joeyjan19]

Because it's carbon fiber!

(yeah, just a little sarcasm as it seems people always think because it's CF that it's better... despite all of the testing showing it does not make a Phantom fly any better).

Remember the propeller is a wing going round and round producing lift. What it’s made of is not as important as the shape of the blade.And these, however many blades engineers figure will give performance desired when connected to the motor. Stick with OEM equipment.

 

[AndrewCCM]

Well I am sure msinger will reply, but props are one of the single source of failure, you lose a prop, and you are down, same with batteries, so..
I do not take a risk with these items. I also think a huge amount of research has gone into the OEM stuff, so for props, I stay with DJI ,OEM.

Well the OEM batteries certainly don’t have a great track record, so there’s that.

 

[With The Birds]

Well the OEM batteries certainly don’t have a great track record, so there’s that.

Have you had bad experiences with the DJI OEM batteries? There have been a fair few reports of DOA packs for P4 AC however the ones that work out of the box seem very good.

 

[AndrewCCM]

Have you had bad experiences with the DJI OEM batteries? There have been a fair few reports of DOA packs for P4 AC however the ones that work out of the box seem very good.

Yep. DOA battery with my P4P... I got a free extra battery and it works fine... Also using a PowerExtra battery which works well. My replacement battery took about 10 days to receive (was leaving for vacation which is why I took a flyer on the PowerExtra)...the DOA replacement arrived while I was (still am) out of town. Crossing fingers it’ll charge once I get home to test.

Did a lot of research and found that there are tons of people with the same DOA included battery with the P4Ps. Mine came from B&H Photo...

 

[AndrewCCM]

Interestingly - I was looking at various Camera systems other day - I have the Soloshot 3 system and its not performing as it should, no-ones getting as promised !
Searching for alternative autonomous robot cameras brought the Hover Camera up.

Looking at the 'test review' drones I still have .. the smaller ones have 3 and 4 blade while the larger have 2 blade props ...

Nigel

I’ve been following your saga over at the SoloShot Yahoo group for a few weeks..

Kept me from buying it and led me to spend the $ on the P4P instead. After the DJI purchase, I saw you were here too.. LOL

Of course, several of my son’s soccer teammates use that SoloShot 3 with decent luck. Probably fine for field sport and I’ll probably end up purchasing one eventually.

 

[solentlife]

The SS3 is OK for slow action ... but with the model planes it gets out of synch in tracking. The pan and tilt is not quick enough, why ? Because it uses GPS positional info between the two units (tag and base). If it was RADAR / RF based - then it react quicker.

Here's latest tests :

Getting there slowly ...

Nigel

 

[je2854]

Normally you'd expect that the flight controller won't allow the Phantom to go faster with non-standard props.
Do you have any testing data to show that isn't simply riding the wind?
Like a flight record showing a 500 metre run in both directions?

Once work slows down I'll be able to do more testing.

I definitely feel as if it has faster response timing though...

Different noise as well...

 

[With The Birds]

Once work slows down I'll be able to do more testing.

I definitely feel as if it has faster response timing though...

Different noise as well...

The three inch straight through exhaust input in my car made it sound faster- it made less power on the dyno though.

The props may be spinning faster as they have less thrust for a given rpm...

 

[je2854]

The three inch straight through exhaust input in my car made it sound faster- it made less power on the dyno though.

The props may be spinning faster as they have less thrust for a given rpm...

You right, you sho right...

They are "9450".

As stated before, they are actually heavier so it might actually hinder the bird instead of helping...

Though I did get an increase of flight time by about a minute or two if I didn't gas pedal it hard. If I shot it straight up it took off faster upwards...

Noises were louder (hear it a lot farther away)

I actually have put back the "flimsy plastic" ones :/

On a side note.... Don't get fingers close, ask me why lol

 

[Meta4]

If I shot it straight up it took off faster upwards..

That sort of assessment only means something when there are numbers to compare.

It's possible that stiffer props make the Phantom respond a little quicker because they don't flex like the originals.
But that's not necessarily better.
The flex is intentional to provide a bit of cushioning - sort of aerial shock absorbers.

 

[ImACarbonCopy]

I have noticed in my years of flying R/C aircraft is three blade props are a bit quieter than two blade props.
I have only used DJI props so I have no extra info on that I would say always balance the props before using them.

 

[N017RW]

I have noticed in my years of flying R/C aircraft is three blade props are a bit quieter than two blade props.
I have only used DJI props so I have no extra info on that I would say always balance the props before using them.

Yes. This is consistent with the physics.

Given the same amount of thrust per revolution... three smaller pressure pulses will be quieter that two larger ones.

It has been stated many times here what the advent of multi-bladed props is/was based on.
But to take a system tuned for a specific two blade prop and simply substituting three (or more) will result in performance trade-offs in addition to less efficiency.

 

[ETC]

Three is the most efficient blade design as you notice all wind turbines are 3 bladed however the DJI units are calibrated for 2 so adding a more efficient blade may seem to make more sense but if the IMU is not programed for the performance dynamics there will more than likely be a detrimental result. It's like taking the mufflers off your motorcycle thinking it will make more power however just the opposite will happen unless the computer operations are remapped.

 

[N017RW]

Three is the most efficient blade design as you notice all wind turbines are 3 bladed however the DJI units are calibrated for 2 so adding a more efficient blade may seem to make more sense but if the IMU is not programed for the performance dynamics there will more than likely be a detrimental result. It's like taking the mufflers off your motorcycle thinking it will make more power however just the opposite will happen unless the computer operations are remapped.

More blades = less efficiency.

Thus, a single blade is the most efficient.

Simply basing efficiency on this (i.e. a wind turbine) or on any single example is a logical fallacy (Faulty generalization).

 

[Twinscrollgt35r]

Ok, gotcha- re the weight.....

Would be very interested to see any evidence of increased sustained flight speed.

I have also seen a increase of 3-4 mph top speed and faster acceleration.
I can explain this in motorcycle or automotive terms, as one of my bikes has carbon fiber wheels. And rotational mass was reduced. I don't think tilt angle on a drone is the whole story here.
I was using the same blades as the other guy. On my P3SE

 

[Twinscrollgt35r]

Also, the carbon blades, the length on the blade to the tip is less weight, the extra weight is in the hub area. This is one of the reasons they are quicker.

This combination with less weight and stiffer materials, is why the carbon blades are more responsive.