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T100 thrust drops dramatically with quick application of power (1500 to 1680 ms input)


(Daniel Plale) #1

I’m having an issue with my thrusters. They work fine and provide what I believe is the documented thrust if I slowly (1500 ms to 1680 ms change in 1.5-2 seconds) apply power. If I apply the power quickly, the noise from the thruster increases in pitch and the thrust dramatically drops. I can drop back to 1500 ms and then slowly come back up to full power. I haven’t pulled the motors apart yet.

Really appreciate any help you can give.

Thanks
FSTgeek


(Adam) #2

Hi FSTgeek,

What ESC and power supply are you using with your T100? Let me know what you find inside, but I suspect the issues lies with one of those other two components.

-Adam


(Daniel Plale) #3

Adam,
I’m using your current Bluerobotics ESC and a Rigid tools 18V NiCad battery.

I don’t believe that’s the issue. This sounds and feels like a mechanical issue (I’m a Sr. Aerospace Engineer with 20 years of in service support experience - not my first rodeo but it is my first experience with your product) It seems as if the prop is entering into a sustained Euiler’s vibration / rotation. Check out this vid for an example of Euiler’s rotation. https://www.youtube.com/watch?v=ug2bKCG4gZY


(Adam) #4

Daniel,

That’s a very satisfying video to watch all the way to the end- I see what you’re saying about the vibration. Our thrusters do not use ball bearings, rather plastic bushings for corrosion resistance, so this is possible if the fit is overly loose. We’ve never seen this before, but I suppose it could happen under the right combination of conditions. When you take apart the thruster, let me know if the bushing/shaft fit feels excessively loose.

Do you know what the discharge capability of the NiCd battery you’re using is? The T100 can draw up to 20-22A at full throttle (16V), and other issues can happen if your battery is not up to the task. The T100 is rated to run at a maximum of 16V, 18V is pushing it. I would recommend avoiding sustained full throttle operation at 18V, or damage may occur.

-Adam


(Daniel Plale) #5

Yeah, I’m not thinking discharge capacity is an issue. I’m running the motors on the very low end. 1500 ms to 1680 ms (fwd) and those Rigid batteries are beasts. I hope to be able to break into the thrusters tomorrow and will let you know what I find.


(k.deboer) #6

Cavitation, maybe?


(Daniel Plale) #7

Nope - keeping it low speed. Using less than 1/3 power.


(Jacob) #8

You should open the motor and check that the bushings have not melted. The motors are not designed to run in air.

I also suspect the battery can’t keep up with the load as @adam suggested.

If you make a video, it will be more clear what the problem is.


(Daniel Plale) #9

Finally was able to open up the thruster. Found significant non-axial play in the shaft. Suspect bad bushings. Contacted customer support requesting warranty replacement.