What causes surging?

[Jonathan Ott]

Not necessarily a Mini Titan question, other than I have a Mini Tiatan.

I was test flying my MT yesterday: spool it up, swash check 'okay', bring the throttle/pitch up some more and break ground. The HH gyro catches and I get about knee high and it started 'surging' did a quick 1/4 piro and drug the gear, blade scrape leading to a boom strike.

No real damage other than a blade grip, sliightly tweeked mainshaft, and boom, but the surging has me concerned. (replaced the mainshaft and blade grip, gotta order a new boom and another set of blades)

Battery is/was fully charged (Thunder Power 2100 3 cell).

Align 35A esc, Align 3550 Kv brushless. Throttle & pitch curves not set yet, straight linear, but that wouldn't cause it to start surging at 75% throttle, would it? (I'm 0° pich at mid stick).

Jon

[comeflywithme]

First thing I would check is that you are not running in governor mode (if your ESC allows it). I have noticed this type of surging when I started using governor mode and once one of my lipo started to get a bit older. I might be corrected on this but what seems to happen is that as lipo's get older they take longer to reach their optimum operating temperature. Untill this temperature is reached the lipo will struggle to deliver high currents resulting in a big drop of voltage. This is most significant in governor mode because if your esc cannot deliver the RPM that you want, then it will bog down big time.

I have also found simillar power surges with electric fixed wings where a lot of power was demanded almost emideatly after take off - even with brand new packs.

What I tend to do when flying my mini titan is to spool it up and give it 10-20 secs to warm up on 1/3rd stick. Then hover it a further 20 secs (whilst remaining ready to land if it does surge) and then finally switch into idle up where lots of power is required. If you are a beginner and worried about landing when the heli surges then just give it at least 30secs at about 1/3rd stick on the ground before taking off. Unless your problem is something completely different than I described, you should be fine.

Hope this helps

[comeflywithme]

I just noticed that you mentioned having 0% pitch at mid stick. If you are running in normal mode flight mode you would want to have a pitch curve something like -3, 5/6, 9 ie about 6deg at mid stick. Its in idle up where you normally have 0deg mid stick (typically something like -10,0,10).

For throttle curve I normally set something like 0,40,65,75,85,95 but this can vary from heli to heli.

This might not have been the cause of your surge but getting the pitch curve right should help in general flying

[Jonathan Ott]

I'm going to check it out tonight or tomorrow. I'm thinking the guy I bought it from may have been flying on 4 cells and set the voltage cut at "high" instead of "med".

Once I enter the programming mode and listen to the beeps I'll know. Until then I gotta wait for my new set of blades and boom.

Thanks!

Jon

[mkoutnik]

I've got the same thing happening...I noticed last night that I've got two different problems with my MT...

1) Motor constantly sounds as if is surging / revving up and down (not sure how else to describe it). It only seems to happen at higher head speeds...

I'm using the stock Ace BLC-40 ESC, stock motor, and TP 2070 mAh battery...I've tried to reprogram the high and low throttle ESC settings. Other than that, I use all of the ESC default values (standard battery discharge, auto motor timing, no brake, standard throttle response, and no governor).
NORM throttle curve is 0 - INHB - 80 - INHB - 100
NORM pitch curve is 25% (-3 deg) - INHB - 50%(0 deg) - INHB - 80% (+6 deg)

Any ideas why the ESC/motor is doing this? Am I over speeding the head? Or, is the ESC bad?

2) The blade tracking is totally screwed.

No matter what I do, I can't get the blades to track perfectly. This was never a problem until recently, after 1 "minor" crash. Since then I've replaced...main gear, main shaft, rotor blades, mixing arms, feathering shaft, flybar, flap dampeners, added main grip spacers.

I've read on another forum the MT has problems with the plastic head pieces and tracking becomes an issue. It seems the only way to resolve is to replace plastic head with aluminum upgrades. Anyone else have this issue/problem? I'm very frustrated and confused.

I greatly appreciate any help...

[EricW]

I had the same problems and didn't waste much time on frustrations ;)
You don't mention what kind of blades you use now, but i guess they are not the stock woodies..
This was mentioned many times before on all the forums:
When you replace the stock woodies with carbon or a other brand of blades it's advised to also change the upper mixer-arms to allu to fix the main blade tracking and use the TT spacers.
I replaced the head with a Kasama upgrade and that did much more than just the tracking, great upgrade.
I also had the exact same problems with the ESC and motor, the surging...
It's a setup problem, i tried many different settings.
It's worse with low C rated lipo's (<20C).

ended up with these ESC settings and it's working great since:

-discharge protection disabled (also surges when activated)
-standard timing
-no brake
-fast throttle
-heli mode with governor

Tx settings:
(90% flat curve in idle-up, I always fly in idle-up and use the throttlehold to start and stop.)
Always use high curves, flying below 85% is less efficient and heats up your ESC.

Hope this helps
Eric

[mkoutnik]

I scrapped the stock wood baldes. I now use Align 315 mm and/or 325 mm wood blades (Still learning to get the hang of this thing.) I also use the TT spacers for the main blade grips. I'll have to look into the Kasama upgrades. At a minimum, it sounds as if I'll upgrade the main hub and upper mixing arms with aluminum.

I'll try your ESC settings tonight...I hope that solves it.

[mkoutnik]

So, I got to thinking...and I called Thunder Power. Talked to a really nice guy (Mark) in the warranty department. He told me TP has had some probs with the extreme V1 series 2070 mAh batteries, and I'm the second customer that's called with this "surging" problem with this battery...

The best part is he's going to send me a brand new Extreme V2 series 2200 mAh battery....SWEET! Once again, TP provides EXCELLENT customer service! So, if anyone else is experiencing this problem, let them know before the warranty expires. TP's phone number: 702.228.8883.

[EricW]

:)
That's even better.
Most of the problems I had were caused by low quality or bad lipo's, the stock motor/ESC combo really needs quality lipo's to perform for seven minutes (put back 80% ,+- 1750 mah).
All the major brands work great now on my MT.

[Jonathan Ott]

I reprogrammed my ESC tonight, and was not getting any surging while I had it clamped down and spinning it up 75% and a touch higher. I got my blades in track and just need to hook up with a buddy here in town to borrow a balancer to get rid of the shakes (new blades).

(I guess I could pull the head and mount it on my spare main shaft and put it in my Dubro prop balancer, but that is a PITA)

Jon

[chuckk]

I just noticed that you mentioned having 0% pitch at mid stick. If you are running in normal mode flight mode you would want to have a pitch curve something like -3, 5/6, 9 ie about 6deg at mid stick. Its in idle up where you normally have 0deg mid stick (typically something like -10,0,10).

For throttle curve I normally set something like 0,40,65,75,85,95 but this can vary from heli to heli.

This might not have been the cause of your surge but getting the pitch curve right should help in general flying

as far as 0 degrees pitch as mid stick is concerned...wouldn't you want 0 degrees at mid stick? mid stick all the way to high stick should have the same degree of pitch in every flight mode so when you flip to idle 1, idle 2 the heli won't jump.

[EricW]

It all depends on how you set it up, and how you like to fly a heli.
If you fly in normal mode with +5º at mid stick and a low throttle (65-70%), it can be a bit difficult to program a soft transition to idle-1.
Pitch/head speed should be equal somewhere in the crossing curves, preferably in a hover (switch point).
I only use normal mode to spin up the blades on my first flight and have everything equalised from mid stick to 100%.
After the first flight i only use throttle-hold (still in idle-up mode)to switch it on and off.

Mine (with governor) looks like:
Throttle curves:
Normal: 0-70-90-90-90
Idle 1: 90-90-90-90-90
idle 2: 100-100-100-100-100
Throttle hold: 0-0-0-0-0
Pitch curves:
Normal: 25-37-50-75-100
idle 1: 0-25-50-75-100
idle 2: 0-25-50-75-100
Throttle hold: 0-25-50-75-100

Eric