700 DFC tail issue

[mtuccio]

Originally Posted by uragano47812

The hum is not constant. I have a brand new kit with all the upgrades and i hear the hum in one of the first flights and i was using bt with vbar and i saw spikes on tail rpm zone. Changed the tail blades with an old pairs of Edge no more hum. My Edge weight is 5.7 grams.

Do you have a way to check chord balance on the tails blades that you got with your kit? I would suspect that you got a bad set of tails in your kit. I am glad the Edge blades sorted your problems out though. If you want to send me your original tails I would be glad to check the chord balance for you. Let me know....

[rando]

I had a V2 with with all the v3 upgrades and stock Align blades and CF boom and never experienced the hum at 1950 or 2050. I've since converted it completely to v3 and still never had the hum with stock blades using the stock white tail gears/hub and now the newer black tail gear/hub. My original tail grip washers were cupped but still no hum. I now run with CY tails and still no hum at 1950, 2050 or 2150. It definitely seems to be a hit or miss problem and it's possible a combination of components none-of-which are strictly defective on their own interact together to start/feed the tail oscillation.

[beenflying]

Originally Posted by latte

A small improvement with 3rd bearing. Could fly in idleup1 (1900rpm) without hum, but it was there at 2150. Switching out the align blades for rail made it go away.

Interesting, thanks. Did you change your idle up 1 RPM? In an earlier post you said it was 1950.

I don't get the hum at 1900. I have it at 1950 and 2000, but it seems to be gone by 2100.

[beenflying]

FYI, tail blade cord balance has been ruled out by the use of some KBDD blades that were tested perfectly balanced (including the cord balance), but the heli still had the hum.

[latte]

Originally Posted by beenflying

Interesting, thanks. Did you change your idle up 1 RPM? In an earlier post you said it was 1950.

I don't get the hum at 1900. I have it at 1950 and 2000, but it seems to be gone by 2100.

Yes my mistake, I had to check and it was indeed 1950.

I have now changed to 1850, 1950 and 2100. Trying to get some airtime with them batteries..

Since I had to rewire my esc, I will check the bearings in the TT again, and maybe try relocating them a little bit. Putting them even closer to center.

[Trulsen]

Originally Posted by latte

A small improvement with 3rd bearing. Could fly in idleup1 (1900rpm) without hum, but it was there at 2150. Switching out the align blades for rail made it go away.

Reading forums often make me dont wanna maiden a new machine.

I have changed out torque tube gears in the tail with new black gears and everything else is stock on my Nitro DFC. Is there a place in Norway they sell rail blades latte? Have only two torque tube bearings. Planned to fly with kbdd blades. Am I safe?

[uragano47812]

Originally Posted by mtuccio

Do you have a way to check chord balance on the tails blades that you got with your kit? I would suspect that you got a bad set of tails in your kit. I am glad the Edge blades sorted your problems out though. If you want to send me your original tails I would be glad to check the chord balance for you. Let me know....

I checked the balance of the tails blades and they are fine. I don't have your balancer anyway. i said it is not constant because i have the hum only one time at the end of a flight and when i was near me landing i see that the tail fin vibrate and also you can see the tail boom with a strange vibration, so as i said i had the BT module on it and see the vibration.
At bench the heli is ok so i put a lighter bladesand i have done few other flights without problems. Probably is a problem in my tail blades and thanks for your offer but the shipping cost will be too much

[uragano47812]

Originally Posted by Trulsen

Reading forums often make me dont wanna maiden a new machine.

I have changed out torque tube gears in the tail with new black gears and everything else is stock on my Nitro DFC. Is there a place in Norway they sell rail blades latte? Have only two torque tube bearings. Planned to fly with kbdd blades. Am I safe?

KBDD are good blades but they are heavier. You can try the originals and if you hear the hum change for example with Edge or Rail or also Funtech are lighter.

[latte]

If you fly with a reasonable headspeed, which I would believe is a bit lower than what I assume is max below, then I think you should be fine.

The Nitro DFC has a ratio of 1:4.95
Which with an engine rpm of 16000 gives 2000rpm on the head, and 9900 rpm on the tail.

For the electric, the ratio is 1:4.73
Which will say that with 2000rpm on the head gives 9460rpm on the tail. 2150 means 10170 on the tail, and is where some begin to hear the hum with align-tailblades.

Lets say you are satisfied with the "pop" at around 1850rpm on your nitro, this only means 9157,5rpm on the tail, which should be fine even with aligns.


Nothing should happen anyways, with the 6mm shaft, so I wouldnt worry about flying it.

[Trulsen]

Originally Posted by latte

If you fly with a reasonable headspeed, which I would believe is a bit lower than what I assume is max below, then I think you should be fine.

The Nitro DFC has a ratio of 1:4.95
Which with an engine rpm of 16000 gives 2000rpm on the head, and 9900 rpm on the tail.

For the electric, the ratio is 1:4.73
Which will say that with 2000rpm on the head gives 9460rpm on the tail. 2150 means 10170 on the tail, and is where some begin to hear the hum with align-tailblades.

Lets say you are satisfied with the "pop" at around 1850rpm on your nitro, this only means 9157,5rpm on the tail, which should be fine even with aligns.


Nothing should happen anyways, with the 6mm shaft, so I wouldnt worry about flying it.

Makes sence. Thanks latte. I flew my 7HV @ 2050 and that was kinda perfect for me. Hope to fly this on same rpm safe.

[beenflying]

Originally Posted by latte

Yes my mistake, I had to check and it was indeed 1950.

I have now changed to 1850, 1950 and 2100. Trying to get some airtime with them batteries..

Since I had to rewire my esc, I will check the bearings in the TT again, and maybe try relocating them a little bit. Putting them even closer to center.

Thanks. That shows that it is torque tube related if the hum went away at 1950.

Yes, the bearings closer together, biased towards the front of the TT would be interesting to try. I'll look forward to any update you have.

Some TT bearing holders (not made by Align) turned up today. They are harder than the Align ones, that came with the 700 DFC. I'm going to try these at the stock bearing position and with one bearing moved forward so they are closer together.

I also have the X7 TT holders, but since the X5 and X7 boom has a smaller ID than the Align the bearing holder just falls into the Align boom. I will get some different orings so I can try these as well.

[latte]

I have planned to fly my DFC alot tomorrow, so I will do a little bit of testing, but I am dying to get comfy with my new bird!

[Trulsen]

Originally Posted by latte

I have planned to fly my DFC alot tomorrow, so I will do a little bit of testing, but I am dying to get comfy with my new bird!

Good luck!


Ordered rail 106 blades and lynx clutch as well.

[latte]

Originally Posted by Trulsen

Good luck!


Ordered rail 106 blades and lynx clutch as well.

Thanks buddy

I have only good things to say about both. My lynx clutch is on its 3rd season now.

[stevehof]

Originally Posted by latte

Nothing should happen anyways, with the 6mm shaft, so I wouldnt worry about flying it.

Just lurking here but I'm not sure that is a correct statement. One local guy flew quite a few complete flights with the hum. He wasn't aware of the problem. His old style tail shaft held together. When I told him what was going on, he ordered all the tail upgrades. When he installed the 6mm shaft he also took his tail blades apart and found that the thrust bearings were all ground up nearly to powder. YMMV.

[beenflying]

I just flew mine with the Align tail blades and it's now as good as it was with the Rail blades. I'm definitely heading in the right direction.

[504Rone]

Originally Posted by beenflying

I just flew mine with the Align tail blades and it's now as good as it was with the Rail blades. I'm definitely heading in the right direction.

What changes have you made? I never had the vibs but I changed over to the black gears anyway.

[latte]

Originally Posted by beenflying

I just flew mine with the Align tail blades and it's now as good as it was with the Rail blades. I'm definitely heading in the right direction.

Nice!

[johnjonfenomenon]

I tested today with edge 105 se. These produced no hum. There was a post earlier on indicating that the edge se and regular ones were the same. I dont think so as it indicates on the website that the se has a diiferent airfoil design.

[oleandro]

Guys,

for your kind information I am reporting my findings with my hum issue:

First flight with KBDD blades: terrible humming
Second flight after checking all mechanical parts with Edge: humming still there but only during deloading the head.

What I have done was changing Edge for Rail 105 and moving one torque tube bearing around 10 mm to center.

Today the day of truth and: HUM GONE in all head speeds, 1850, 2000 and 2100.

What a pleasure.

I don`t know how much or if the Rails are lighter than the Edge. Maybe someone has checked.

Best,
Michael