Help With Motor Timing and Poor Throttle Response (Gecko 120HV)

[Enterprise]

http://rcwebclub.com/PropEngine.aspx



I don't have the prop constant for a Xoar wide blade prop, but this is the info from your data. You batteries are sagging to 3.75V under load which is fairly normal. [MENTION=95]Aeroplayin[/MENTION] might be able to provide more help as this is his calculator.

In the end, I agree with Gyro that you should just go fly it as the system is working. There is some interaction with can diameter and length where shorter motors provide more low RPM torque. There are others here whom understand electric motor theory better than me that can explain the whys of that.

 

[AKfreak]

what your video showed me, is that everything is normal. Especially at 2:32, where you start pulsing it a little while it's spun up a some (similar to what you'll experience IN FLIGHT), and the response was aggressive and instantaneous, and again around the 2:49 mark. I think it's unrealistic to expect the throttle to spin up any more aggressively from ZERO power when you're only give it a quarter second pulse (earlier in the video).

I think your analysis of the throttle response is a little off.... especially since you haven't flown with it. Very hard to make a judgement about how it will perform in flight during static run-up bursts.

Also, I couldn't see what your amps went up to, and what voltage dropped to under load... the watt meter fell. The cells ability to maintain voltage under load will determine your power output. Are they new packs? How many C rating?

Sorry to disagree with you... please don't take it the wrong way!

First off, I highly appreciate and respect your opinion, I don't take offense, you taking your time to help me is much appreciated. However, I must insist that the throttle response is way less responsive that all of my other electric planes.

Moving on... until I fly this turd ... In the video, the amps at full power show as 2797 watts at 61.3A (@ 2:00) even when bliping the throttle, it was only 600-700 watts. The packs are new and have a burst rating of 100C but are rated as 50C.

I agree that flying it is the only way to make a true assessment, but again, based on the feel and my other stuff, it's way different.

 

[CrashTech]

Just want to add this. Maybe its been said before. Check your connections between esc and motor. I had coging problems do to a bad connection.

 

[Aeroplayin]

I just saw an [MENTION=95]Aeroplayin[/MENTION] email so I thought I'd drop by and add my 2 cents. I'm sorry I'm not caught up but I watched the video and also read a reference to a Xoar wide blade. If so, which Xoar wide blade is it?

Right now, I have two 12S setups in this size. With the A60-7S 215Kv and a 20x8 PJN, I'm getting peak readings between 3103W and 68.56A at 7785 RPMs, and 3115W and 67.22A at 7971 RPMs. With the DM4330-206 and a 21x8 PJN, I'm getting peaks between 2811W and 60.43A at 7531 RPMs, and 2953W and 64.94A at 7530 RPMs.

Watts off the meter are not going to tell you much because all the meter is doing is taking the peak current it samples and multiplies it by the volts at that time. It is also sampling about 1000 times slower than the ESC switch, which is where all the activity is taking place, so it really doesn't see the whole story, especially when you're blipping the throttle like that. RPMs with a specific prop are going to tell the real power story, along with the current as a safety check.

With that said, your throttle response is not a function of the motor. It is a function of the ESC and the battery health (EMF). The older Ice2 ESCs have the best throttle response I have seem so far on the older 3.27 version firmware. My Mezon 95 ca be programmed down to 0.5 seconds (acceleration) but that's a touch sluggish compared to the Ice2 IMO.

From your video, if that were a 20x8 PJN, I'm not sure I'm seeing something out of the ordinary. What I'm seeing is a very quick blip from idle to WOT back to idle. By the time the motor has a chance to respond, the signal is telling it to stop.

My son is the expert 3D pilot in the family, and he is constantly pulsing the throttle when timing his rollers, and he would never blip the throttle the way I see you blipping the throttle in the video. I'd guess you're asking for a 0.1 second full throttle response. I'm not sure that anyone would expect that with props this size. If you are doing that on your Slick, and your Slick is a 71, and swinging the same size prop to a much faster acceleration, please let me know what motor, prop, battery, and ESC you're using.

The next time I have the planes out, I'll try to get a quick video of the throttle response, but let's start with the prop... What prop are you using in that video?

 

[AKfreak]

I am using the Xoar 20x8 Beechwood Electric Prop SKU: XOAR 20X8E For example when i was flying the 64" MXS today, I tried to pulse the throttle to full and pull it back off as quickly as I could, and the plane took off and was in the air. The throttle response was instant, there was no time to build up speed, just BOOM and gone like a rocket. Once in the air I just applied 1/4-1/3 throttle and climbed out. If I tried that on the Extra with the 120 opto, the plane would move about 5 inches and the prop would be barley spinning. I am way past happy with my Gecko 85 and Motrolfly combo, so I know it's good stuff.

You see, there is Huge difference in the the Gecko 85, and the 120HV. It's truly night and day. The total amount of power I am getting is really amazing ( it pulls so hard), it's just so lazy. I am going to ask Kim Quenette (of Thunder Power/Hitech Pro) to see what he thinks. If he says the throttle response is slow, would you believe there might be a problem. If I cant figure it out, I might have to buy a Castle ESC just to test and see if there is any difference.

 

[3dNater]

I see what you want in an ideal world and I am not saying your point isnt valid, but at the end of the day I think it is just a matter of scale. The bigger a plane is the more it weighs. It is going to take a lot more energy to overcome the inertia of its static state. I would be a lot more concerned by how it feels going from 1/8 to 1/4 throttle and from 1/4 to full etc. Blipping it rapidly from zero to full and back down is basically an irrelevant measurement because it has no practical value in-flight.

When compared with your gas motor keep in mind that the prop is already turning at 1800 rpms before you hit the throttle... 2400 or so at a high idle. If you do the same thing with your electric setup how does it compare?

 

[gyro]

PLEASE.

FLY.

THE.

PLANE.



I'm anxiously awaiting a flight report....

 

[3dNater]

Me too... the suspense is killing me!

 

[gyro]

I mean, it's fun to discuss ground tests back and forth an all, but to me, it's somewhat useless.

Say someone in Manhattan buys a Ferrari and it's driven only on city streets downtown, so it never gets into high gear... The owner thinks it's slow... Would we spend all this time convincing the owner what it can do? No, we'd tell him to get it on the highway or the track!

So for the love of 3D... Please fly the plane

 

[AKfreak]

PLEASE.

FLY.

THE.

PLANE.



I'm anxiously awaiting a flight report....

I will fly it tomorrow. I just know in my heart, it's not right. Let me ask you somthing. If you know somthing is not right, will you do somthing just for the sake of doing it, or do you try to solve the problem. I have always been one to try to solve the problem. I guess it comes from the 3,000+ hours I have in fixed wing aircraft.

Also, have you ever heard of this, "if you want to get quicker throttle response from 0% throttle stick, just set up an idle up switch"