Question on main-shaft drag

[Mark_NC]

Hello!

So I started assembly of my 766 last night

I got as far as completing installation of the main gear. I followed the directions meticulously, and Boto-lubed/oiled everything per the instructions.

However - I noticed when I spin the main shaft by hand it feels fairly resistive and hard to rotate. Not a lot - I can spin it and it will spin for a turn of two then stop. But it requires a lot of hand-force to get it moving. I checked meshing with the tail transmission - if I hold the transmission bevel gears and wiggle the main gear I have at least 0.1mm of movement, so I think meshing is good.

Any ideas?

Thanks!

Is this normal? I am stepping-up from a 500-size, so don't know how a bigger heli should feel.

[alan]

I would pull the main gear and shaft out. Install the shaft on the main gear outside the heli. Check for binding on the one way bearing and sleeve. Did you use oil or Boto Lube on the one way bearing (OWB)? Always use oil.
If you did use oil on the OWB and the sleeve is binding check the fit of the brass bushings on the sleeve. Also be sure the bushings are fully seated in the main gear hub and not canted. If they are not seated correctly they can cause binding. Did you use red loktite on them? If you did (which you should) and need they need to be reseated,  heat them up a bit and lay the gear flat on the workbench then gently tap them in.
If the main gear is fine just start working your way back to the tail.
Post your results for further guidance.

Cheers
Alan


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[Mark_NC]

Thanks for the suggestions!

I can't se anything obviously wrong.

The main-shaft on it's own in the three main bearings feels okay. It spins, but there is a little resistance. However the 12mm main shaft feel so "big and heavy" compared to my 500 that I think it is normal. Is that normal for a little resistance when you spin in?

The main gear has been lubed exactly as directions say. I used boto-lube on/under the two shims on the auto-hub sleeve, and regular lightweight oil on the rest of the sleeve. I was pretty sparing with the oil - I could try a lot more? I also noticed the whole main/auto gear assembly has some small resistance when I spin the two gears opposite directions. But then the gears are so heavy compared to what I am used to, is this normal? The two brass bushings seem seated fine - I had carefully red-loctited them per instruction, being very careful not to get any loctite into the rest of the mechanism. At this time I have not tried heating them and reseating them.

Everything seems fine - there is no obviously binding anywhere. The main shaft spins smoothly, just feels VERY heavy. I pulled the tail drive box back from the main gears, and the resistance felt the same so i don't think the tail was too tightly meshed.

So am I worried other nothing? If you took a 766 and pulled the motor back and pulled the head so you can grip the main-shaft and give it a spin by hand, does it feel heavy or slightly "tight"? Does it stop almost immediately after you let go? If the answer is "yes" then I think I am fine. If the answer is "no, it spins by itself and I feel zero resistance like it is perfectly floating on smooth bearings" then I must have a problem still! Thoughts?

[alan]

Sounds like you are fine. It will be a bit tighter than your 500. Tolerances are a bit tighter on Synergy versus some other makes. The resistance may be the Felton shims which will break in after a few flights. Doesn't sound like any errors in your build process.
Go Fly!

Cheers
Alan


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[Mark_NC]

Flew yesterday for the first time - all went very well! Just gentle circuits and figure-8's.... maximum current under load was about 20A with a head-speed of 1400. Need to start tweaking things up to about 1800, but everything feels good! Thanks everyone for the advice and help!

[Mike Spano]

20 Amps? that's is extremely low, even for circuit flying.

[Josh Easter]

Yeah that sounds low. What's your setup?


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[alan]

Was that from logs or telemetry? Unusually low even for circuits at that head speed.


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[Mark_NC]

I got the current and head-speed from the ESC log: I am using a CC EDGE HV 160. I am running stock 13T/139T, at 12S. I am using a CC Vetigo 700 (4540) motor, which is 490kV.

[Rodney Kirstine]

The first several ESC logs from the CC Edge 160 were stupid low on my 766, as well.  There's no way the current draw could have been as low as what my logs showed or I wouldn't have pulled as many mah's out of the packs as I did during the flights.  My 766 has definitely been surprisingly efficient, just not THAT efficient.

[Mark_NC]

I dont have the logs with me right now, but I would estimate I had a 3-minute flight and still had 60% LIPO according to my battery-checker. That suggests maybe 8 minutes of gentle figure-8's? Does that seem reasonable? I will check my next flight much more accurately and see.

[Mike Spano]

that sounds possible. the 766 is extremely efficient, as is that motor your running.

I would guess your pulling around 80-90 amps.

I sometimes get spikes of over 200-210 amps, and my average is around 130. flying hard of course.