500 T-Rex 500 Odd behavior

[Doum066]

Greetings all,

I just finished rebuilding my 500, striped it doen to change most bearings and stuff since i bought it used.
I'm now having some problem, yesterday as i first tried to spool it up, the ended up spinning on her self, found out i crossed turn the belt drive the wrong way, so it made the tail rotor turn the wrong way, made them turn clockwise, so loose up the tail boom case to turn it the right way and spool it up after, no more spinnig on her self, but as i spool her up, just as she was getting light on the skid, she starts to til on her right, tried a few times and always does it.

As i was searching forums for any clues, mose was pointing out vibration issues... I decided to always replace the Microbeast with my AR7200BX and took off the receiver, might had been a damaged unit. The Microbeast was mounted on the plate behind the anti-rotation bracket as usual. So i tried to install my AR7200BX on the side... went for a try. So as i spool up, no more tendencies to tilt on take off, but she start again kinda wanna turn, and ended up with the Rudder wire poping out the AR72000BX, tried teo tiems, two times the wire poped out... guess i'm having lots of vibration? Any cluse what i should be looking for? Should i try without the main blades on? I'm absolutely out of clues what too look for, could it be the belt over tighhten or doubles crossed in the boom?

Thanks

 

[Doum066]

Well i just went outside and gave her a try without the main blades.... didn'T seem to be much vibration and i got the stick up to aprox. where she would get light on her skid, about 60 % stick and she never even turn, steady as hell.....

 

[Tony]

If you are looking at the tail blades from the right side, they should be spinning counter clockwise, not clockwise. the belt should be twisted 1/4 turn to the right when looking down the tail from front to back.

Weigh and CG your blades to make sure they are perfect. If you are getting no vibrations with the blades off, then that is the first place i would start.

 

[Westy]

yep +1 tony ....

I always look at it like this ..... no matter .... which side of the heli you are on .... the blades from 6 o'clock ..... should be sweeping forward toward the boom and up into the rotor wash .... not away and back.

hope tha makes sense ... I used to get confused with the left side ... right side thing .... so thought of it as a water wheel and sweeping the water up into the main rotor from underneath the tail boom

 

[Karubah]

Did you check to see how tight the servo wires are into your receiver, it seems to me that if vibration is removing a wire it is too tight. You have to have some slack in the wires or the vibes will upset you gyro and your heli will do funny things. Others on here will most likely jump in and explain it a lot better than i can.

 

[Doum066]

Thanks for the replies guys.

Tony: Yep hat was my first problem, i noticed at the firld i did twisted the wrong side the belt, making the tail rotor turning clockwise with the tail rotor on my side (making the heli bird on my right and tail on my left) so i removed casing, fix it so it turns counter clockwise, but it does turn even after that, that's why i don't get it, i did weighted the blades, diff was minor, so i haven't fixed the CG and Weight s i did with my 450, i always checked blades... i'ill fix this tonight and give a try, the other things i'm concerne is the tighten of the blades, they kinda get stiff in the blade holders even though i haven't yetput the crew in... i usualy make ight as i hold the bird sideways, the blades doesn't fall by themselv with gravity, but if i give a little jerk, they drop down... but it makes hard to do witht he blade grips being a bit tight.

Karubah: Wires arent that much tight, specialy the Rudder on, with the 7200BX ont he side, it makes the wire the closer to the unit/servo... Do you guys put hotglue on the connectors as i'Ve seen on some pictures?

I dunno why but this bird is giving me a hard time to set properly :S And i know it's minor issues, just got to put my hands on the prob. First heli with drive belt and normal FBL head, with the washout arms..

 

[Island Breeze]

I see a lot of people putting some hotglue to hold the wires to the controller so it wont come loose. give that a try

 

[Doum066]

Well i decided to take apart the tail tonight to see if there wasn't sorta more than 1 turn on the drive belt, even though i would had feel a tentions, but felt to take a look at everytrhing, no loose bearings etc.. But i do have a question, this is my first belt drive heli and a boom mounted rudder servo, how far from the end of the casing should the servo mount bracket should be, coulnd't find any info on this, if too close, or touching the boom gear case, could it create a vibration that could cause raisonance?

 

[Westy]

For the Tail Slider?

you position it loose until you connect up your tail slider and get it to mechanical and lock it up. If you have the correct length tail servo rod .... you will be a little off the housing... about 10 - 30 mm

 

[Doum066]

For the Tail Slider?

you position it loose until you connect up your tail slider and get it to mechanical and lock it up. If you have the correct length tail servo rod .... you will be a little off the housing... about 10 - 30 mm

Well that's the thing, in the manual they say 396mm from ballink bottom to ballink bottom, which is way too much, no way i end up with enough space that far for the servo being 90 deg centered... Well tonight will be a try with the belt a bit less tight, the servo bracket a bit futher from the tail boom front drive casing, if this doesn'T work next try will be taking off the Fusono tail rotor blades and put back the CF ones i had before rebuilding it with upgrades. But first i'll also try balacing the blades, matching CGs on both as i was doing with my 450.

 

[Doum066]

Well, we'll see tomorow how it goes with the stuff i've made tonight, but i think i might have found something that could have also cause all this.. might be one factor... I'm still new with my DX8 and it's interface, and i just realise tonight that for some reason, had some trim set, i'Ve never paid attention, i thought empty scare meant centered, which in face, full black square means center.. so i had about +3 trim on most axes for some reason.... and as i remember, the AR7200BX or directly Microbeast manual sates a few places, « NEVER USE TX TRIMS WITH THE AR7200BX! The AR7200BX will interpret the trim as a control commant, NOT as servo trim » :S Guess that could be part of unwanted behavior....

 

[Westy]

have you turned the servo so the output shaft is closest to the tail transmission box? .... I know you have .... but ... just in case!... ya know we all get flustered from time to time and miss some things

 

[Doum066]

have you turned the servo so the output shaft is closest to the tail transmission box? .... I know you have .... but ... just in case!... ya know we all get flustered from time to time and miss some things

Yes i did

But.. i just got back from tonight's testing to se if what i did last night was the problem, first spool, dunno how properly say this in english, but i got disapointed, started to have a tendency to spin, when softer wanna tilt around 60 % stick, clsoe to take off, same as before, rudder wire got loose again.. tried a second time, same thing... so i decided to try out the next possibility, i brought my old white CF tail blade with the black stripe on it..... changed them, gave another try... well, around 60% stick, no spin around unusual, no tendency to tilt, soft and nice take off, did a few secon hover, land back, checked the wire, not loose at all, tooke her back in the air, finished the pack hovering real close to the ground incase something happends, finished the 4-5 min time, wire was still perfectly in it's socket, flew the second pack, same, low altitude, and switched to idle 1.. after 2 packs, no loose wire, no more spining.... so all this so far, i cross my fingers, it was Fusuno's Plastoc 72mm tail blades. I''m for sure fly a few packs softly to make sure all is good.

 

[Westy]

sounds like the blades are out of balance... did you weigh them and CG them?

 

[Doum066]

Blade balancing on tail rotor blades? That'S way too small to do on 500 size heli :S

 

[Westy]

never too small .....

you can weigh them to 0.1grm ... and CG them ... that is balancing them

 

[Doum066]

To be honest i don't think it's the weight, since i never had problem with tail rotor blades, i never balanced them, the CF ones aren't and no prob, but one thing that might me the prob is, the hole in each blades that the screw goes to to hold them to the blade grips, is maybe too small, at the point that when i unscew them to take the blades off, the screw is so tight in it,t hat it doesnt fall by itselt, i got to take long noses or twizzer to take it out and even with it, it's tough, so maybe they are so tight that it created vibration on each blade, i mgiht try to simply wider the hole a bit to fit the one on the CF blades, we'll see, if it does nothing, i will owe you appologies Westy and admit you were right.

- - - Updated - - -

Here's some side to side pics, as you can see the White CF blades hole is way bigger thans the orange ones, you can see the white CF blades, the screw goes softly, loose all the way in, on the orange one, i can't get it in pass the threads without forcing it, and i mean force it. Guess that doesn't help.

 

[Tony]

Those holes look exactly the same size to me. I even measured the screen and they are the same.

 

[Doum066]

Those holes look exactly the same size to me. I even measured the screen and they are the same.

They look, but they weren't, believe me, the only way i could get the screw through was to shim the hole with a small round file, if not i had to force it through and blade were so tight they weren't pivoting. But that didn't changed anything, the heli still wants to turn on itself when getting light on skids, so i guess it was indeed balance, but i haven't found a proper vid on how to balance tail blades.

 

[Tony]

post a video on what it's doing. And I keep my tail blades pretty tight on my 450 and on the 600. They don't need to flop around. But post that video and we will be able to help more.