Motor Losing Power at Mid-Throttle

[copterboy]

:confused:
My Belt-CP has had a new ESC after the stock one bumed out. I have replaced it with a SONIX 30a ESC UBEC, and soldered my own connectors (Male Deans and 5mm bullets to motor).
Problem is, when I'm about 45% throttle, the motor power starts fluctuating really badly and the tail also starts moving in-sync with the changes in power.

If I keep increasing the throttle slowly to about 60%, I get into a hover and the problem stops. It is only happening between about 45-60% throttle. I have searched threads and couldn't find a similar problem.

All I can guess is it could be my dodgy soldering, a dodgy new ESC or damage to motor from it's first crash (because throttle was not shut off straight away). Can anyone tell me if I am on the right track to solving this or am I barking up the wrong tree? :DOH
Ta v. much!

[tom dubya]

Mmm i'd think if your soldering was that bad it wouldn't make it off the ground. Hows your gear mesh to the motor pinion. Look for anything else that might be binding. Maybe some bad bearings. But the motor could be the reason also. The sonix 3550 motor is a great replacment for the esky and cheaper.

Edit:After thinking about it though might wanna give that soldering a second look,but somethings tellin me its somethin else, but i could be wrong.

[mnwizard]

I've been thinking about this for awhile and here's what I keep coming back to -

I don't think it's the motor. A faulty motor may slow down, lose power, or stop entirely, but I don't see any way that it could fluctuate, especially in just a small range of rpm.

It more likely is either a fluctuation in power to the motor, or an intermittent binding in the drive system occurring at a given rpm.

So if electrical, it must be battery, ESC, or connections. I think you can rule the battery out because of the fluctuation.

I would be less likely to suspect a mechanical problem because of the fluctuation. A bent or out of round shaft or gear might vibrate at a given rpm and smooth out at a higher or lower rpm, but it wouldn't fluctuate up and down.

Is it possible that what you're seeing is actually a pitch change which would speed up or slow down the motor? I'm thinking of a bad front servo fluctuating and cause a rapid pitch change.

I keep coming back to a bad connection that shakes at a particular rpm turning the power on and off rapidly.

Is it a rapid fluctuation? Does it appear to be faster or slower than head speed?

[copterboy]

Let me correct my terminology - it is the motor losing speed, as I haven't actually tested the power supply to it.
As I push the throttle another notch, the speed drops for about 1 1/2 seconds then kicks back in all on it's own with no more increase in throttle. I know it's this that is causing the tail to kick round. Maybe this does indicate some binding or further electrical problem. I'll get on with some more investigations and report back when I get some progress. It maybe a couple of weeks as it's still another week till payday & I need more cash!!

Cheers guys, any advice is much needed and appreciated. I've seen the vid with the folded paper to set the motor pinion, but I'll check for binding right through to the tail output whilst I've got the time on my hands. Thinking back, I struggled with the deans connection (even after watching bobs vid), so I will go back and check that one out too. If not then I may try swapping the ESC from my TREX to test against the old motor/esc, before spending any money on a new one.....
:thinking
The TRex was a bargain so I've skinted myself to get it - well it did come with a DX6i Tx...so I only need a Rx and the CP will be 2.4G ready...and hopefully upgrade servo's and TREX links & balls to try and get rid of some of that dreaded slop so often talked about...Hovering still has the occasional hairy moment, and I'm definately not ready to flick that switch yet.

[mnwizard]

Good luck with your trouble shooting and keep us posted!

One more thought - I've read that a battery that isn't supplying enough current, or a steady enough current (for instance using a 2 cell instead of a 3 cell) will cause the ESC to fluctuate. Might be worth trying a "known good" battery first.

[copterboy]

Thanks Jack - I can try the battery troubleshooting method with the t-rex batt but need a deans on it first - or maybe borrow one off my mate over the road!
I have been looking at the possibility of a binding problem tonight. It has had some success...I am still getting the motor glitch, but the improvement is that the tail doesn't kick round as much when the motor-jitters occur.:thumbup:

I found the motor shaft could be backed off a bit more.
The tail gear & belt pulley shaft were way to tight and bound badly, I moved it back as much as I can, but I think it could still move back some more - I may try elongating the holes with a file?
I wish to upgrade to CNC tail drive shaft mounts, as I have lost a thread in lower plastic shaft mount already. Also I want to find an ally pulley to go on the belt/shaft too - I have ruined 2 already (any suggestions?). Eureka moment...Maybe I fitted the new tail shaft to tight, which caused the binding and burned out the stock ESC!!:dontknow

Anyway, back to the plot, I still have the jitter problem and can't wait to 'checkout' the bits already in my 'shopping basket'. Will keep posting till I sort it out anyway...!

I think my next step is to order a new belt and another pulley. I could still be getting some binding there...
I'm thinking now, that the first or second crash damaged the belt when I snapped & stripped the 2 pulley's).
I'm only guessing at this point, but I think it could be why the problem goes away once you get to a certain throttle speed/rpm, I.e. When the belt is streched under drive from the motor at almost 3,000 rpm?!

[DierWolf]

stock transmitter???
coper connectors inside the pot could be dirty or going bad in that spot. (very common)

[mnwizard]

Ah, good one D, I forgot about that.

CopterBoy - Shoot some electrical cleaner (any hardware store has it) in the pots. If they're dirty, that will clean 'em out.

[copterboy]

Electrical cleaner - need a UK translation - is it WD40?

Might have some lying around...my battery is charged and I'm off to find some. Will be back with a reply to that one soon.

[rapidgaz]

hi dennis sure its u. have found this manual sure these 2 controllers are the same meaning the 1 you have and this 1 here is the link so you can set up the tthrottle calibration.http://www.hobbywing.com/upload/manual/ESC_e.pdf. hope this helps

[copterboy]

Thank you freaks &RAPIDGAZ...have lift-off glitch free!!!
:)
Checked for binding & removed from inbetween motor&main gear, and main tail gear&pulley shaft (I may still elongate holes as I think it could back off some more).
Ruled out dodgy motor, dirty copper pots on tx, soldering & battery (my mate's back from grand-prix and I borrowed a spare).

I have only had this problem since the new ESC was installed. So rapidgaz is right to suggest checking ESC manual again for throttle calibration or throttle range for the Tx, and this needs to be done everytime you use a new Tx or ESC on your Tx!!! I have now set the range and turned up the pitch trim a bit - so I now get roughly 50/60% throttle, at 50% stick, with about +5degree's pitch in normal/hover mode.

I must have been getting something like 100% throttle at 50% stick - far to much head speed and not enough pitch making the motor over-rev and giving the apperance of it slowing down. (Is that the correct term over-rev?). Soooo - why did it stop at 60% stick - it's because the pitch is increasing as you give it more stick, so the extra load on the blades was then reducing the head speed/rpm and making it hover ok, but very hard to control due to the high head speed.

The last battery was the best one yet, nice smooth movement and stable hover with much less head speed.

I've still got other issue's so I'm off to read the one about it going backwards and too the right.
A new belt, pulley shaft, 4xSG90's and a Spektrum 6200 2.4G should arrive in about a weeks time, so can't wait to get them on board too.:clappp
Just wanted to say thanks to all contributors on my first thread - DW for a couple of PM's, Tom Dubya&MN Wizard - first respondee's and rapidgaz pointing me towards the solution.

[mnwizard]

Electrical cleaner - need a UK translation - is it WD40?

Might have some lying around...my battery is charged and I'm off to find some. Will be back with a reply to that one soon.

WD 40 would probably do it.

This is the stuff I use -

http://i31.tinypic.com/2vskj0k.jpg

http://i28.tinypic.com/ipv71g.jpg

[copterboy]

I couldn't find any WD40, and my friend (who I borrowed battery from) recommended not to...would probably go with your stuff....the label says it all!

The dirty pots weren't the cause anyway, but now I know for future reference thanks...it was not setting the throttle range when installing new ESC that was the main problem.

[mnwizard]

Glad you got it sorted out!

[sutty]

I'm glad you couldn't find any WD40, I don't think it is a helpful solution long term even if it works in the short term. WD40 is a lubricant and it is a good electrical insulator, not something you want to be coating the tracks of your pot with. In addition to that it will leave a residue, it is designed to, and that will collect dust, thereby storing up problems for the future. Switch cleaner or similar as shown in the picture is volatile and leaves no residue. They clean and then evaporate which is what you need it to do.

[rapidgaz]

if you crash, just see it as an upgrade so be positive and get ya self a bigun