Carbon Props Experiment

Hey Guys,

After going through a dozen wood props (they seem to splinter the minute you stare too hard at them), I decided to try out some carbon props. With the idea of reducing the RPM (and noise) of each prop, I ordered some 22x12 from Iris Engel.

After receiving the props, I went ahead and CNC machined the inverse shape of the prop shaft, 6 mm deep, so that I would not get issues with props slipping (see: Carbon Fiber Prop Bulk Order)

Doing some burst thrust tests against a wall, I got about 330A of current at max. throttle. The noise is generally lower pitch than wood props.

I went ahead and did a couple of flights. Everything ran smoothly until… about 10 mins in (and with 100-150 A of continuous current usage, which is pretty low) the motors all stopped rotating. In both cases, I had to perform un-powered landings.

To explain clearly: the motors just stop and go into the “beep-beep” mode. The throttle still shows “armed”. Doing a “disarm”/“arm” cycle has not effect. The only way to re-arm the system is to turn the big red knob on the side of the PPG (which can’t be done whilst flying).

To make sure nothing was damaged, I reverted to wood props, and sure enough a couple of flights went smoothly, without power cut-off.

I am guessing that the HUB or ESC do not like the 22x12 props, but I wonder why they shutdown when the current draw is only 100~150A (this is pretty much the same current I normally draw with the wooden props). Is there some setting in the HUB that can be changed to allow me flying with these (pretty sweet and expensive) carbon props???

I deleted my declaration but saved it. tarifachris explains very well how to reduce efficiency by adding more power. my ideology is completely different. i want to fly electrically with as little energy as possible. therefore my explanation does not fit here. if someone is interested in flying with little instead of a lot of electricity, we could make our own tread for efficient flying. It is important that people participate who can show what they explain.

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I deleted my declaration but saved it. tarifachris explains very well how to reduce efficiency by adding more power. my ideology is completely different. i want to fly electrically with as little energy as possible. therefore my explanation does not fit here. if someone is interested in flying with little instead of a lot of electricity, we could make our own tread for efficient flying. It is important that people participate who can show what they explain.

I have a few posts on this forum where I explained that you can only use
higher pitch props with higher amp ESC’s…

One example>

It is recommended that you have at least a 20% margin between the amp requirements of your motor and the rating of your ESC. This way you will know you will not be overloading the ESC’s.

How the ESC controls the Motor>

Motors are rated by Kv, which means the number of revolutions the motor will turn when you apply 1 volt of electricity. So our 180 Kv motor’s will spin at 8640 rpm if you apply 48 volts.

From this you might imply that the ESC changes the voltage to the motor in order to change the speed of the motor, but that is not the case. If you look at the specifications for our ESC you will probably see a frequency number. This might range from 2 KHz to 12 KHz or higher. This is related to how fast the ESC can pulse power to the motor. Our ESC’s are not a variable resistor that adjusts the voltage to the motor, it is a fast switch that pulses power to the motor.

You can think of this as a duty cycle control. How long will the ESC leave the power on till it turns it off? Then, how long will it be off before it turns it back on? There is no need for us to know this cycle time, only that on every on cycle your motor is getting the full voltage of your battery.

This is as well the reason the ESC’s have capacitors - this on/off switching leads to voltage spikes and
the capacitors are there to smooth this out! With longer battery wires there could be voltage spikes of 4-10 volts. More capacitors will smooth this out. BTW most voltage spikes are at half throttle ( more on/off)

In the end i recommended to use the 100A ESC’s with big capacitor banks and then it would work fine.

Actually, I’ve flipped that switch mid flight many times to reboot. Did you move yours to a location that can’t be reached?

I have a hard time believing that your props are causing the issue with the system disarming. If all 4 are disarming then the problem must reside in the hub or throttle controller. The ESCs wouldn’t just all decide to stop at the same time.

I recommend taking a couple more flights with the wood and if you don’t have issues switch back to the carbon and see if the problem comes back.

It is in the default location, sandwiched between the back CFRP plates. I can’t twist my arm to reach there…

Exactly!! That’s why I wonder whether the Hub has some protection setting that checks Voltage vs. Current, and decides to call it quit before the ESC gets damaged or something…

Thanks for this suggestion Chris, but is there some empirical evidence that this works out well in practice? (before I go and buy 4 new ESC)

And also… why would all 4 motors turn off at once? Does the Hub switch everything off if only 1 ESC reports overload??

Ahem…
I just today experienced this exact same shut off issue. I’m flying with the stock wooden props and six cell batteries. I have a batch 4 unit with the 150kv motors) My full power draw is a paltry 240 amps with fresh batteries (I charge to only 4.1 volts/cell).

Was just doing landing practice, flying circuits. Dropped power to setup an approach and heard the beeping. Thought I’d inadvertently double tapped the button so I double tapped it again. No response. Double tapped again. Heard the armed signal and felt it vibrate. Still no power. Landed. I was flying a perfect approach any way. :grin::sweat_smile:

Reset power on the ground and all was fine. Flew again, staying close to the field anyway. Still all fine. I’ve had this happen once before when I was on the ground and had done multiple launch attempts disarming and rearming several times. I assumed it happened when I rearmed.

Any clues? I’m thinking tapping the arming button with the plunger down (at or near full power) might be triggering this.

Btw I can reach my switches (I have one on each side) in flight but sure didn’t have time today.

The same has happened to me on one occasion (with only 15 flights under my belts).
I suppose this is some bug in the HUB logics…

I’m a bit of a noob myself. That was flight #12 on my X4. I have another ten flights on a Blackhawk.

Looking at the main loop of the HUB (from line 233 of https://github.com/openppg/eppg-hub/blob/a97b0ff25535728922b90a92818bf0800b22eda2/Src/main.c), there is no condition that would stop the Hub from looping indefinitely.

There is a state called “ESC_STATUS_INVALID_DATA” (in case no data is received from an ESC), but it does not seem to be used anywhere…

I cannot see what would cause all four motors to stop suddenly… The controller, the voltage, current, throttle I/O, … info is not analyzed by either Hub or Controller (it is only passed around for display).

If the throttle controller chimes the arm tune and vibrates that means the controller did NOT lock up. The hub must be what is locking up and the only way to reboot it is by flipping the main power. The challenge is to figure out what is causing the hub to lock up.

Note: the first time you double tapped the controller it actually disarmed because the controller itself was still armed. The second double tap re-armed the controller but with the hub locked up that signal never reached the ESC.

If the ESCs stop receiving a PWM signal they will disarm and the motors will beep. Even though the controller was still armed the ESCs were disarmed because the hub wasn’t passing on the signal.

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That makes sense. Still though. What is triggering this glitch? Or is it hardware related? I’m a software guy so my experience is it’s almost never hardware.

My experience with these types of devices is that it’s usually hardware related but can be software too. Voltage spikes and noisy data can lockup these small processors. The system will develop lots of voltage spikes because of induction through the long main wires and switching of the ESC. I’m not sure how well the BEC handles those spikes as it reduces the voltage down to 5V to power the processor. There are also a lot of data lines running into and out of that hub which can be full of noise. Some of that noise can be caused by long unshielded data lines or bad quality connections.

I placed an order for 100A ESC. They are coming from Hong-Kong, so it may be a while before I see them… ■■■■ coronavirus.

The 100A ESCs arrived 2 days ago, and I spent half-a-day installing them on my X4.
The whole thing was a huge ball-ache (loads of wire cutting and soldering)!

Anyhow, I will find out tomorrow whether it was worth spending the time and money!!

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Last week-end was too windy to fly, but I emptied half a set of batteries at near full power without experiencing a shut down. So it looks promising…

Just one thing: Since upgrading to these 100A ESCs, I get no Voltage or Current reading on the throttle!! Is there some firmware update that needs to be programmed in to the ESCs for this?

Not sure but sounds like they changed the telemetry. The normal ESCs dont have any special firmware on them. You might be able to contact them and see what the latest documentation is and tweak the hub firmware. Once you have that figured out its pretty easy to update with an SD card.

Thanks for that Zach, I will look into it.

Had quick look at Hobbywing Website and they do have firmware updates for ESCs:
http://hobbywing.com/article.php?id=162

I am trying to dig further into the telemetry documentation, the website is not well organized…