How smooth a TDR looks to an SK-720

[Groucho_]

Here's a comparison between my T-Rex 550 and my TDR, with the TDR flown five minutes after the T-Rex, so same conditions...

(The spike towards the end of the 550 graph is when I flew through a tree as per my earlier thread in the Skookum forum - http://youtu.be/rRlx8-Zjzf0)

I have no idea what causes the spike to 9 in the TDR flight though. There's no extreme stick input or movement around that moment.

As I've stated a few times before, I believe that the gyro plate location on the TDR does contribute quite a bit towards these elevated vibe values.

T-Rex 550

TDR

[NRPY]

I finally got around to running a vibration spectrum analysis during my last flight. Looks like the Pyro 520 kV motor is the predominant source of vibes. There is some contribution from the tail, but not as much as I expected based on other peoples' comments. I also ran "motor only" bench tests at three different RPMs and the vibe magnitudes ranged from 7.5-10, all at the motor frequency.

Looks like I need a new motor.

[swalko]

For a comparison, my TDR with blue mini vbar, without main and tail, motor Xera 4530:

YouTube

YouTube

With Xera 4530 running only in frame (no contact with intermediate gear):

YouTube

YouTube

With Pyro 700-52 running only in frame (no contact with intermediate gear):

YouTube

YouTube

And in flight with Pyro 700-52:

YouTube

YouTube

In flight analysis the yellow line is in the bottom part of graph, then this graph is not directly comparable to previous graphs. Most vibrations are from head, most violent are from motor, what surprised me is that there are only few spikes from tail. I think that my replacement bearings in Pyro are the cause of high motor spikes, because if i run Pyro only in frame it is not noticeable in graph.

My TDR is almost all the time smooth in flight with vbar (other units which i tried had problems) and in flight analysis graph looks like earthquake if you fly 3D ... i dont like these high vibration conditions of TDR .

[marcosp]

I have not necessarily vibes but shakes. I think we are all doing something wrong here. The TDR has been around for 3 years and doesn't have a history of vibrations. Maybe it's because now we can measure them, who knows. I care because the shake sometimes upsets the heli before takeoff, making the Vbar crazy, and after landing on spool down. I still see the shake at low rpm but at mid and high it hovers very smoothly and only shakes with collective. I've had some weird reactions in flight as well, so I reached the point were I'm going to go deep into this until I solve it. The rotor disk doesn't look perfectly smooth in flight too, so in my case it could still be something in the head, either bearings, bent blade holder or something else I have not checked. To me at least it doesn't seem to be a tail problem, though further analysis will reveal were the problem is. The heli was smooth as glass when new and the shake only appeared after several crashes, even though I changed most of the components. Maybe the settling in of parts worsened the shake instead of improving it. We'll see. Maybe what I find is useful for everyone too.

[marcosp]

I always seem to write in two separate posts....... I have to stop this!

BTW, almost every E Trex I see is very very smooth in flight. I don't like that brand but I recognize they fly pretty good, different, but good.

[swalko]

I had shaking in hover on every rpms. On low rpms this was more violent, but slower. On higher rpms shaking was faster and not so noticeable. On resonance frequency rpms my TDR looked like it will kill self in air. Jointer know for how long time i tried to solve this. At the last this was caused by Pyro bearings. In that time i used G-T5 instead of VStabi. I replaced bearings with cheap "japanese bearings". First flight everything was fine. After that every flight it was worse. Not so bad as before, but no good. Currently i have problems with shaking if i use G-T5 and AC-3X. I am angry, because i really want to use AC-3X and i cant. Blue mini is OK. I will replace Pyro bearings with hybrid ceramic bearings and try AC-3X again, i hope it will help.

[ZuvieleTeile]

I've got a solution for you. . .
Get rid of the Pyro.

[NRPY]

What would you guys recommend for alternate motors? I have an HKIII 4035-560. Would that work? It has a long shaft.

[ZuvieleTeile]

HKIII 4035 is a good choice as is the Xera 4530 or the HK 4525 ultimate.
I fly alternatively the Xera 4035 2.5Y/480 as a low budget, but highly reliable alternative.

[marcosp]

Small Scorpions (4035) require frequent lubing every 8 to 10 flights and the bearings get shot after 200 flights aprox. So, you are almost in the same situation as with the Pyro. They are heavier too. Xera 4530 and HK4525 are another type of motor altogether. Any of these HK4035, Xera 4035, Pyro as regular motors and Xera 4530 and HK4525 as more powerful ones will work just fine.

[swalko]

I have Xera 4530, but when i installed it in my TDR everything (with G-T5 and AC-3X) was worse than with Pyro. I prefer Xera 4530, because it have a lot of torque and power and still is not so power hungry. But if you look at my graphs then you will see that running Pyro in frame only will produce almost zero vibrations from motor. Xera produce on every rpms spike. Then i think that my Xera 4530 is not well balanced. I replaced all bearings and almost all shafts (except intermediate shaft) in my TDR and i still can not use AC-3X. I like my TDR, but i am running out of ideas and i am already tired from that ... i currently realise my backup plan ... get Voodoo 700.

[johnjonfenomenon]

So the general consensus I would assume is if I want SL then dont switch out my HC3-SX for the skookum on the TDR?

[NRPY]

It seems so, but my results are intriguing. I originally thought the TDR inherently had high tail vibes, but it turns out my tail vibes are reasonable but my motor vibes are huge. So if I can get a smooth motor in there, SL may work fine at higher headspeeds.

[mkovalcson]

Originally Posted by NRPY

It seems so, but my results are intriguing. I originally thought the TDR inherently had high tail vibes, but it turns out my tail vibes are reasonable but my motor vibes are huge. So if I can get a smooth motor in there, SL may work fine at higher headspeeds.

So far my vibs look good. Of course I haven't gotten it up near 2000 rpm yet either.

[johnjonfenomenon]

Originally Posted by mkovalcson

So far my vibs look good. Of course I haven't gotten it up near 2000 rpm yet either.

How does it look around the recommended 1850 HS. Also when doing aggressive G manuevers like tic tocs. I have an sk720 on my 6HV right around 2150 HS and SL works throughout the entire flight with some aggressive tic tocs thrown in.

[NRPY]

I'm going to fit a smoother motor and do some more testing. I just need to find a smoother motor.

I'm hoping to run at least 1850 RPM. The TDR flies much better at 1850 than it does at 1700 imo.

[swalko]

Have someone video of TDR with SK720 flying?

[mkovalcson]

Originally Posted by swalko

Have someone video of TDR with SK720 flying?

What exactly are you looking to see from the video?

Unfortunately I'm not a 3D pilot yet, and my skills are still on the novice end of the spectrum.

[Danny_Swe]

seems to work

YouTube

YouTube

[johnjonfenomenon]

Ok, So I assume the general consensus is that we want to experiment with a different motor on a TDR combined with an sk720 to see if we can get the SL to work.. I have a scorpion 5020 - 450 motor. Will this be fitting for this machine. If so, I can send it out to a trust worthy memebr to conduct the experiment. Or you know what. I'll just get off my lazy ass and swap the motors and put a new 720 on and conduct the experiment.