Blade400 - Tail Drive/Pulley

[dam74]

Hi, just gone through the process of replacing my tail drive/pulley gear which was a job in itself. It seemed to work without hassle for a while then when I stopped and started again the motor was having difficulty driving the main blades and driving the tail rotor. I stopped immediately as I didn't want to burn out the motor or have any overamp cutout in the ESC (if they have them). I then rotated the mainshaft and it felt notchy caused vibrations to go through the body. I think it was coming from the tail drive/pulley gear. Now I've stripped out the tail drive/pulley again and removed tailboom and belt. Turned the mainshaft and it seemed to rotate smoothly. Put the heli pitch curves to a safe level and started up the heli without tailboom and it sounded like it was running fine and smoothly. So the question is should I change out the top/bottom bearings on the tail drive/pulley? The top bearing is a right pain and requires cracking the case open. Was thinking about giving it one more last go before biting the bullet.

[Geek]

Are you sure you didn't have a extra twist in the belt?
thats my thoughts
Cheers paul

[dam74]

I'm wondering Paul as there was a bit of what I call of a rattle noise eminating from the tailboom like something was knocking against the wall of the tube. I could do with a nice little penlight to check it

[Geek]

I hook the belt on a long small shaft like a boom surport from a bigger heli
then push it up the boom.
I hope that was it
Paul

[dam74]

Paul I use a bit of string with a weight, then attach it to the belt and drop it through but I have used the hook method before.

[spunkmyer]

Are you sure you didn't have a extra twist in the belt?
thats my thoughts
Cheers paul

I agree with this, also the belt was not loose was it?

[dam74]

Mike, the belt is a new belt and from the way it's been packed in the bags has all of these twists and kinks in it. I've reassembled it for the second time and it made the noise again so I dropped off the tail gear box assembly. Turned it in the direction it wanted to go naturally twice. Put the tail gear box assembly back on and gave the main blades a turn. It seems to turn now without being stiff and sending vibrations through the tailboom/body. However there is a whistling noise when I ran the motor, I'm wondering if it's a tracking issue but the blades and paddles look straight when viewed side on. Could it be bad bearings making this sound? I was going to take the head off and see if the noise goes away. That way I'll know if it's a tracking issue or not.

[Geek]

Another thought is it twisted the wrong way
this would make it touch if you had it setup up to do a 90 deg twist one way but then twist it 270 deg.

by doing that the tail would spin the wrong way
good luck

[spunkmyer]

Heard a trex 600 with bad tail bearings down the field yesterday it sounded a bit like a whistle/whine. Take the head off and run it up and listen to all areas with bearings to see if the noise goes. then replace the head with out blades and do the same again.

[dam74]

Mike, something else doesn't look quite right either. The smaller gear on the tail drive/pulley has a gap between the guides. Like it's not pushing up hard against the top bearing block to compress the guide onto the gear.

Update: just tried a headless spool up and it's sounds like there is a high pitch whine. I could try and record it with my mobile so that you guys could give an opinion.

[dam74]

Here is a video clip of the B400 starting up to 50-60% with no head.

[ame=http://www.youtube.com/watch?v=lTGfMLwglOw]YouTube - Blade 400 - Post Repair Test - Possible bearing issue[/ame]

[Geek]

it's difficult to say but it sounds like the motor to the main gear is a little tight
There should be a very small gap between the pinion and main gear.
like if you was to trap a small thin piece of paper between do it up then remove the thin paper.
there should be a small rocking of the main gear this is called backlash
if this is a problem it will save power so heli will be alot better to fly just like having the belt to tight
hope this helps

[spunkmyer]

Hmm the motor at the start sounds like its struggles to over come some friction. Defo sounds like something is binding. Have you adjusted the pinon mesh as advised?

What was the reason for replacing the tail drive gear in the frame?

The new tail drive dear is the gap between the gears the same as the old one?

[dam74]

Yeah I checked the binding of the pinion to main gear, it was a little loose if anything. I've also had the motor out and checked it, according to Boggy the description of it running in my hand is perfectly normal. Found a couple of main shaft bearings that were a bit notch and not as smooth as some new ones that I tried rotating by hand. So have replaced those aswell as the tail drive pulley bearings.

Reason for changing the tail drive was the belt was overly tight and caused the small gear to shear/burn itself around the shaft and the brass spacer became wedge inside the gear. I discovered it the other day when I went to fly the heli and even though the tail rotor was going it resulted in the heli spinning uncontrollably. I figured it wasn't getting enough tail rotor head speed so started to look for causes and noticed something visually NQR about the tail drive so stripped it out and discovered it looking a bit of a mess

[spunkmyer]

Sounds like a bit of a mess. At least you found out before a crash. So you checked all bearings for the main shaft, tail drive etc. I would rebuild the heli running it up at each stage ie put motor back in with main shaft, tail drive, belt, tail rotor gear then run it up with out any rotors including the tail. If all is ok then carry on if not you should be able to hear which bearings are causing problems?