New Propellers, New Life

Ansia · Oct 29, 2018

Hello all,

I recently purchased the props shown below, thanks to a recommendation from someone in these forums. I am amazed by them. They are a lot quieter and stronger than the original props. I don’t know how strong a 3 speed steel floor fan blows, but with the original props it would get pushed back and with the new props, the Tello stands his ground (this was in slow setting and with the fan in low). I in no way have a wind speed meter, but I’m guessing that the lowest speed must be around 10-15 knots. If any of you know, please correct me here. I beleive is around that speed, since yesterday I was flying in 11 knots winds (measured) and it would get pushed back in slow settings. These props are a bit heavier than the originals, so I don’t know how much stress they add to the motors. If anyone is knowledgeable in this area, please explain in details, so I can understand better.

Ansia · Oct 29, 2018

Did a flight time test with both props. In slow mode, no prop guards and in a closed room at around 27C. Here are the results.

New props:

Original Props:

As you can see, they take A LOT of flight time at the expense of thrust and response. I'm going to see if shaving off the head in the middle improves flight time. Going to consult a Aeronautical Engineer tomorrow, before anything. Let's see what happens.

stewe12 · Oct 30, 2018

Great test! You did much better job with testing, than I would be able to!

I am really glad that you have the same perception fo the noise level. I like them a lot. Regarding the flight time I was a disappointed, before I did the weight mod.

I would suggest using this kind of cutters for the job

, because the material is far superior to the original props and I wasn't able to cut it with any kind of knife. It might be carbon-nylon composite based on my small research.

And how to do this mod? I started cutting as low I as I could and going around multiple times with more and more pressure appliend on the cutter. This will produce nice and smooth finish of the cut and final height of the prop will be the same as original Tello props. If you would just squeeze it as hard as you coud, it would make weird squished line on top of the prop. How do I know? That it how I cut the first one...

EDIT: The stress from more weight/thrust of propeller on motor should work like this. If it is heavier to turn from weight, or more wind resistance (steeper angle, bigger working area), it needs more power. More power means it will draw more amps. It could also mean geting hotter if they are only heavier as they will need more power for the same thrust. But as long as our props have bit better thrust, I think, they can be a bit more effective.

raulvolador · Oct 30, 2018

Good work !

And a very interesting test.

Keep us informed.

Ansia · Oct 30, 2018

stewe12 said:
EDIT: The stress from more weight/thrust of propeller on motor should work like this. If it is heavier to turn from weight, or more wind resistance (steeper angle, bigger working area), it needs more power. More power means it will draw more amps. It could also mean geting hotter if they are only heavier as they will need more power for the same thrust. But as long as our props have bit better thrust, I think, they can be a bit more effective.

I thought of this, but to the touch, I found out they are about the same temperature with both props. Will have to get a Temperature gun and do further testing in this area.

stewe12 said:
And how to do this mod? I started cutting as low I as I could and going around multiple times with more and more pressure appliend on the cutter. This will produce nice and smooth finish of the cut and final height of the prop will be the same as original Tello props. If you would just squeeze it as hard as you coud, it would make weird squished line on top of the prop. How do I know? That it how I cut the first one...

You could try sanding down the excess material and get a smooth finish.

MBDonahue · Oct 30, 2018

Ansia said:
Hello all,

I recently purchased the props shown below, thanks to a recommendation from someone in these forums. I am amazed by them. They are a lot quieter and stronger than the original props. I don’t know how strong a 3 speed steel floor fan blows, but with the original props it would get pushed back and with the new props, the Tello stands his ground (this was in slow setting and with the fan in low). I in no way have a wind speed meter, but I’m guessing that the lowest speed must be around 10-15 knots. If any of you know, please correct me here. I beleive is around that speed, since yesterday I was flying in 11 knots winds (measured) and it would get pushed back in slow settings. These props are a bit heavier than the originals, so I don’t know how much stress they add to the motors. If anyone is knowledgeable in this area, please explain in details, so I can understand better.View attachment 1968 View attachment 1969

Interesting.... What brand are the new ones?

Ansia · Oct 30, 2018

MBDonahue said:
Interesting.... What brand are the new ones?

75mm DIY RC Quadcopter Spare Parts Blade Propeller Prop 2CW+2CCW

I spoke with the engineer today and he advised me against it. He says that the spinner (cone shaped center) serves a purpose in the propellers and that shaving it off will not increment flight time enough to see any benefit out of it.

He says that the purpose of the spinner is to reduce drag and making the drone more stable. If I were to shave it off, I may see a small increment of flight time in the best case scenario, due to weight loss, but if I don't cut into it with precision and it's not well balanced; it will decrease the motor's life exponentially.

He explained a lot of mumbo jumbo about how an unbalanced spinner at faster RPM will make the unbalanced weight increase, making the brush on the shaft hit the side of the casing, thus reducing life expectancy down to 1/4 or 1/8 of the 40 hours originally designed into the motors.

According to him, the real reason I am losing 1 minute and 12 seconds of flight time is in the design of the blades of the propellers. They are wider than the originals, therefore it needs more energy to spin them, thus draining the battery much faster (just like Stewe12 mentioned in the post above). If I wanted to get more battery life, then I would have to re-design the props and not worth the time. He says that the minute and 12 second compromise is actually not that bad, compared to the benefits of the blades on the drone. If I need to fly more than 10 minutes, I should consider getting another battery and to stop being cheap.

Still want to shave them off and see how it behaves.

Edit: I just ordered the props in the link below. They seem to be the love child between the original and the other props.

They don't have the spinner, so it will allow me to do the testing without altering my props. I will update when I get them within 7-19 days.
75mm DIY Mini Micro RC Quadcopter Blade Propeller Prop 2CW+2CCW

Ansia · Oct 30, 2018

I did a little bit of research. I found out the new props weight .9g and the other ones I mentioned in my last post weight .85g without the spinners and .99g with spinners. I wasn't able to find out how much the original props weight anywhere. Does anyone know?

stewe12 · Oct 31, 2018

I agree with all of the things your engeneering friend said. BUT! In our scale, it is almost nonexistent. For example in bigger quads, even smallest unbalanced weight on props is causing jello. And the cure is balancing them, which is normal thing in RC hobby. It is done with balancing stand and small pieces of tape you stick on end of the blades of the prop. On end because with bigger diameter it will have greater leverage(not sure if levereage is correct English term). I was checking balancing of Tello props and it is so small and light, that all unablanced weight would be in so small incerements of grams, that you will not be able to tell the difference. I wasn't on my balancer.

The shaving will happen in center. So if you proceed to cut it as I described, you will end with still balnced prop.

PS. I am afraid, that you will be disappointed with the ones you oredered. Based on about 10 reviews I read about them, when I was searching for props. They are heavy, unbalanced and uneffective. We will see, maybe they will surprise us.

Ansia · Oct 31, 2018

stewe12 said:
.
PS. I am afraid, that you will be disappointed with the ones you oredered. Based on about 10 reviews I read about them, when I was searching for props. They are heavy, unbalanced and uneffective. We will see, maybe they will surprise us.

You are doing a great job into convincing me to mutilate the props before this weekend is over. As for the ones I order. I’ll be honest. I ordered them, because I was afraid of damaging my motors. Never had in mind to male them my primary props. I will be using originals for normal light and indoor flying and the buffy ones for strong breeze, video filming flights. Just got my extra battery today. Can’t beleive I found it cheaper at the store, than online. So we are good to go. Thanks for your input. You keep giving me that nudge that I need to push things further.

stewe12 · Oct 31, 2018

I am just telling you my opinion. But the difference in shaved and non shaved props was almost as big as original props ve the new ones. Without shaving, I felt the same way as you. Using them only in wind. After shaving the weight off, I didn' took them down ever since. That big the difference is. Probably because the weight isn't affecting balance, but it is inertia, which the motor have to overcome - you will experience more nimble controls and tad better flight time.

Ansia · Oct 31, 2018

So after some mixed feelings and consideration, I ended cutting the spinners and did the flight time test. It was to my surprise and dissapointment, by removing the spinners, I cut in the flight time. I thought it was strange so I did a retest. Same results. So basically the spinner are necesary. Luckily I bought 2 sets of these props, so no harm done.

Edit: I did a third try. What I did different this time was I did an IMU and Gravity calibration prior to the test. Here are the results. Please bare in mind, I didn't do these calibrations for all the previous tests. Might retry them again when the third set of props arrive.

So I don't know what to think. Through my testing, it was concluded that with or without the spinner, the flight time is about the same, give or take a few seconds.

Stay tuned for the third set of props to arrive. Once I test those, I will post the results.

stewe12 · Nov 1, 2018

Sad to hear you didn't have the same result as me and needed to calibrate. Can you show us your result of shaved props? Is it possible, that some of props ended up being heavier than the others?

PS. I didn't put any gun anywhere

Ansia · Nov 1, 2018

stewe12 said:
PS. I didn't put any gun anywhere

Most of the times, I write stuff and edit them along the way. I'll keep in mind that you get an email with the original post.

Sadly, I got frustrated from spending hours cutting and later sanding them to get them down to blade height, that I ended up throwing them away.

I will look in the trash when I get back from work.

To the eye, they looked about the same height, but it's a possibility that one might've ended higher than the others.

stewe12 · Nov 4, 2018

Maybe different batch of props... It is weird, that I swear by them and you even had to calibrate your IMU to fly properly. I hoped you would have the same luck as me.

Sorry I made you ruin your perfectly fine props.

Ansia · Nov 4, 2018

stewe12 said:
Maybe different batch of props... It is weird, that I swear by them and you even had to calibrate your IMU to fly properly. I hoped you would have the same luck as me.

Sorry I made you ruin your perfectly fine props.

Don't get me wrong. I did the calibration, since the Tello kept spinning 45 degrees to the right every 3 minutes and I had to correct it. It was spinning jn the same manner on the original tests. Difference is I didn't correct it then. What was different is it kept going up and down and it didn't do that the first time. That was fixed with a simple gravity calibration.

As for the props. Don't feel bad. They are designed to to get destroyed. If it wasn't by me, definetly by a wall.

Ansia · Nov 5, 2018

So I was flying in fast mode today (got too cocky) inside my apartment. Well, the inevitable happened. I crashed straight into a wall. What amazed me was that the propellers didn’t suffer even a scratch. Don’t mind the cat. He just wanted to study the little demon who pesters him from the air.