Propellers, propellers, propellers ...

[afernan]

Propellers selection is always a headache. After sometime flying copters I´ve got many, many (maybe too much) propellers at home. So I decided to make a selection and keep only the "good" ones.

Propellers are the main source of vibrations, so it´s really worth to get the "lowest possible vibrations" from them. I decided to make a calibration of all propellers I had.

Calibration was done as follow:
1.- static callibration: this is known as "balancing". That is, each blade should induce same static moment around the rotation axis. We can correct it by using small masses added until a perfect balancing (thin Scotch tape)

2.- Dinamic callibration. This is more tricky because dynamic unbalance comes from aerodinamic effects derived mainly from diferential "shape" of each blade. This is almost impossible to correct. The idea is to test each propeller and through out the bad ones.

In order to test the Dynamic Callibration, my simple, cheap and quick system (yet a bit dangerous) is to take the motor mounted on a separated arm and keep it by hand while rotating the propeller. You can "feel" in your hand very preciselly the vibs induced by bad propellers (see image attached). Good propellers induce a very small micro-vibration on your hands. Obviously, I was using a good motor without any doubt of missalignement.

The results was very interesant. I mainly have only two types: RC-Time carbon and Flyduino plastic.
I´ve attached an Excel table with all results, but in summary:
- about 50% of the propellers I had were rejected
- 63% of the rejected propellers were CW . This is probably due to there are much less producction of CW tahn CCW
- Not all sizes has same results (obviously this depends of the quality of the mold). For instance 75% of the RCTimer 11x4.5 are good, while only the 36% of the RCTimer10x4.5 are good. Best RCTimer props are 15x5.5 (100% good)

At the end of the table I added the "weighted prize" per unit (Total prize/good propos only) and I´ve compared with the very good T-motor propellers (yet expensive!).

As a global conclussion is that RCTimer props are not so bad considering prize/quality and comparing with the refference price of T-motor (3x times the unit prize average). ... and buy the doble+ of RCTimer props you´d need in order to keep about 50% of them as good.

Comparing two propellers well calibrated (same size, material) from different manufacturers, makes really negligible performance in my experience.

Using well calibrated propellers on the copter (combined with good, calibrated motors) makes a BIG-BIG difference!. It worths the effort.

Hope this helps any of you

Angel

[afernan]

RCTimer new carbon propellers release called "TM"

RCTImer shown new carbon propellers called "TM" style ("Tiger Motor"? >>> yes!). They looks pretty nice the same to those of TigerM ( http://www.rctimer.com/product_919.html)

I´m just ordered a few ones to check quality. Of course the price is 1/4th of those of TigerM. I´ll report back the quality and calibrations. Keep tuned.

Angel

[Cookiemonsta]

Looking forward to your tests / experience with those props
Instead of mounting the motor on a extra bar I'd use one of my copters arms and put a mirror under the motor. Then you can use a laserpointer pointing at the mirror giving you a point at surface a few meters (1-3) away from the mirror while the motor stands still. While you throttle up this motor, obviously with the prop on, you'll may see that the point transforms into strange figures or so. Then you'll have to correct it. If it keeps being a point throughout the whole throttlerange than you're done

Long story short this a way to do it very precisely aaaand out of danger

[joebar.rc]

Hi angel,

I'm looking forward to the rc timer prop test, I also spend way to much money and time on props . They look great..
I hope they will do, because my previous carbon rc timer props did lack a lot of thrust compared to graupner/apc and therefor inefficient.
My current top selection is wood, the xoars are superb, they absorb some vibration and run both smooth and quiet but comes at a high price.
My 2nd are the new apc multirotor props, performing very good compared to the xoar but at a very low price. They now have 10,12 and 14" and are slightly heavier than the apc electro or apc slow props but lighter than apc gas props.

I also wend away from the plastic etc props, they are great to a 8" size but higher nah...

[kinderkram]

We're currently using Tarot 16" CF Props on a heavy lift Hexa with T-Motors 4014-11 33kV:
http://www.tarot-rc.com/index.php?main_ ... cts_id=223

They come at ~7€ each and they are manually balanced.
Only backdraw: 1 out of 6 pcs had the holes for the screws drilled wrong.

[teramax]

I am also on comparing the RCT Tiger clones with the original Tiger props.
First thing what jumped in my eyes is that the cinese are labeled wrong, the RCT 11" 5.5 are exact the same sice and pitch than the Tiger 11"x4.5.


Also weight is nearly the same.
Finish is glossy with scratch marks on the bottom. They tried to ballance by grinding of some material there. But only with little suxess. I had to rebalanze most of the RCT props by my selve.

Blade size also differs a little from one to the next piece but can be fixed with a little hand work.



Also the are a little softer than the original.

[afernan]

@Max:

did you test how is the dinamic calibration of RCT propellers?. This is a key factor because it can´t be solved in case they´re bad.

Angel

[teramax]

[plexus]

Very useful that thread.
Thanks men.

[afernan]

UPDATE:

I´ve received the batch of RC-Timer TM (Tiger Motor style) propellers:
8x units each of 10x3.8, 10x5.5, 11x5.5, 12x5.5 and 15x5.5

After staic and dynamic calibration (... it takes some time indeed), the results are in the table below.

Basically same ratios good/bad as other RC-Timer (with the exception of the very good´cheap: the old RCT15x 5.5):
small sizes about 50% bad/good and larger sices about 75%, except the 10x5.5 that it´s a real bull shit.

Finishing is not very good also. The winner wrt price its the RCTimer 15x5.5 (old style) with a 100% good.

Maybe some of you folks could add more data to the excel table to complete it (attached excell file)

Angel