I just got this helicopter today, and on the first take off it went up and back about 4 to 5 feet kind of diagonally, then just started spinning uncontrollably to the left. I checked everything and realized that when holding it and throttling up, the rear rotor spins till a certain point, then stops... There's no friction on the rear rotor when manually spinning the main. The gear that's connected to the shaft stops turning - which means that whatever connects the shaft to the motor is stripped. Has anyone else had this issue - or have any suggestions on fixing it, rather than shipping it back?
(Sorry if this has been discussed. I re-posted this over here after posting it in the General Discussion forum)

IntegrityHndywrk that Gaui X5 you have must be a blast. It sounds awesome & that video that said first crash, I'm so glad it wasn't bad & all is still flyable. Happy landings.

Originally Posted by Rain4LA

I just got this helicopter today, and on the first take off it went up and back about 4 to 5 feet kind of diagonally, then just started spinning uncontrollably to the left. I checked everything and realized that when holding it and throttling up, the rear rotor spins till a certain point, then stops... There's no friction on the rear rotor when manually spinning the main. The gear that's connected to the shaft stops turning - which means that whatever connects the shaft to the motor is stripped. Has anyone else had this issue - or have any suggestions on fixing it, rather than shipping it back?
(Sorry if this has been discussed. I re-posted this over here after posting it in the General Discussion forum)

One of the small gears on the ends of the tail drive shaft is probably rounded out or stripped...(odd that it was that way out of the box?). Anyway, your kit should have come with one spare set so just find out which one is slipping or stripped and replace it. You could always contact the vendor and ask them to send you another set of tail gears free of charge since it was apparently damaged before you ever got it. Nothing to bother with shipping it back for though imo.

Check for vertical play in the main shaft. If the main slides down, the A gear to the tailshaft may be separating from the main gear. Just slide it back up and readjust the locking collar below the swash.

If you crashed it, it is possible you broke a tail gear though. I suggest: http://www.rcgroups.com/forums/showthread.php?t=1649296

Originally Posted by LarsDennert

Check for vertical play in the main shaft. If the main slides down, the A gear to the tailshaft may be separating from the main gear. Just slide it back up and readjust the locking collar below the swash.

good point...hopefully that's all it is.

Originally Posted by Rain4LA

I just got this helicopter today, and on the first take off it went up and back about 4 to 5 feet kind of diagonally, then just started spinning uncontrollably to the left. I checked everything and realized that when holding it and throttling up, the rear rotor spins till a certain point, then stops... There's no friction on the rear rotor when manually spinning the main. The gear that's connected to the shaft stops turning - which means that whatever connects the shaft to the motor is stripped. Has anyone else had this issue - or have any suggestions on fixing it, rather than shipping it back?
(Sorry if this has been discussed. I re-posted this over here after posting it in the General Discussion forum)

You must have the new V2 V120. This is what I found out. But first to fly worry free install livonia bob slipper clutch. Did my first flips & a few crashes still going stronge.
http://www.rcgroups.com/forums/showthread.php?t=1577528
My first flight testing setup on rate mode 20% rudder mix it spun CCW & I crashed. Same problem you have now. Below is what I informed livonia bob about the new V2 V120D02s's after installing his great clutch.

I finally figured out why the tail was dragging so bad. The motor couldn't even spin the blades. I did make the mistake once & put another B gear on where the C gear went on a previous install, but even with that the motor could turn the blades on a V1 V120. Didn't want to post & say anything negative on your thread cause I love your clutch. But for your info the new gears have the same part number HM-V120D0S2-Z-11. Difference on package are V1 has 201205110012 & US1308, V2 has 226368500 & 201209110004 & HK2325. This is what I found the new V2 gear set B gear has a bigger tit on the tail boom side which makes it stick out farther up against the tail shaft against the fuel tubing & locking collar. By looking at V2 B gear on the tail drive shaft it doesn't flush up to the end of the D hole, thought I even got a defected tail drive shaft until I put a V1 B gear on it & it was flush which solved the problem. Everything spins great now. I figure for those who have a V2 V120 could sand the tit down some & make it work or put a V1 B gear on if they have one & if they don't it appears they are selling the new V2 cone gear set now & would be out of luck.

Since you more than likely don't have the V1 B gear just sand the tit down till the shaft is flush with the front of the gear if the D hole looks good towards the front or sand your spare until it does. The A gear under the main gear has a lot more meat on the D hole that the shaft goes threw which will make it strong enough.

Originally Posted by LarsDennert

Everybody should check their travel adjust settings. Mine was set to 100% rudder and the linkage maxes out well before the sticks do. I set mine to 85% and now everything goes full travel at the same point. Elevator also bound up before the sticks do. Had to tweak those too. Piro is smoother after that. Maybe the linkage binding causes crazy stuff for some of you.

Just had to rotate gears in the aileron servo. Are there metal gear ones that swap?

Just my opinion, but i never use travel adjust or subtrims/trims if i can avoid it, which basically is always. So i never use them. The RX has 2 pots for "ext." of the rudder and cyclic. By adjusting those you can limit your rudder or cyclic throw. So you can use the Rudder EXT. pot to limit the rudder then readjust your rudder push rod to keep it setup correctly. Depending on if you have a slipper clutch installed or not your tail rudder setup might need to be one way or the other. But typically you want your tail blades at zero pitch and all of the servo arms and rockers at 90° angles from the boom. So you want to set zero pitch and adjust the pot to give you max equal throw. I often feel like adjusting the travel adjust induces odd behavior and it also seems to slow servo travel, not just range. Though i can't confirm that or verify it in any real way. I limit my pitch range to eliminate swash binding or interactions using the pitch curve in the TX and cyclic ext. pot.

Originally Posted by GTstrudl

My guessing is the link on the swash plate popped off first, and then heli took nose dive. This type of mechanical failure is very common if you have a worn/smaller ball on swash plate or enlarged link hole.

I took a snap shot. This thing hit smack into the ground. You can see the swash ball broken clear off but it's still attached to the linkage. If you look at the rotor head you can see the broken anti-rotation arm for the pitch linkage. I've been flying this heli with that broken for about 2 months now without any issue since it's only the one side. It broke the last flight/crash i had with the stock blades on the heli. Since then i've crashed the heli at least 30 or so times and if all i have broken so far is the swash in the last 4 months, i think i'm doing pretty good. I only had to replace the main gear once in as many as 30 crashes or so. Only because the sheer pin broke and the gear fell away from the pinion, but in the crash it got shoved back up against it and grinded the teeth a little. So i figured it's seen enough crashes with only sheer pins to replace. I suppose it's about time this heli cost me some money.

Edit: I didn't see these other posts

Originally Posted by IntegrityHndywrk

Just my opinion, but i never use travel adjust or subtrims/trims if i can avoid it, which basically is always. So i never use them. The RX has 2 pots for "ext." of the rudder and cyclic. By adjusting those you can limit your rudder or cyclic throw. So you can use the Rudder EXT. pot to limit the rudder then readjust your rudder push rod to keep it setup correctly. Depending on if you have a slipper clutch installed or not your tail rudder setup might need to be one way or the other. But typically you want your tail blades at zero pitch and all of the servo arms and rockers at 90° angles from the boom. So you want to set zero pitch and adjust the pot to give you max equal throw. I often feel like adjusting the travel adjust induces odd behavior and it also seems to slow servo travel, not just range. Though i can't confirm that or verify it in any real way. I limit my pitch range to eliminate swash binding or interactions using the pitch curve in the TX and cyclic ext. pot.

Thanks for that. I'll try it. Why would you want the tail pitch at zero when the linkage is in the middle? Wouldn't you want it set up for center of travel when hovering? Maybe there's not much difference to matter...

[.............

Originally Posted by LarsDennert

Check for vertical play in the main shaft. If the main slides down, the A gear to the tailshaft may be separating from the main gear. Just slide it back up and readjust the locking collar below the swash.

If you crashed it, it is possible you broke a tail gear though. I suggest: http://www.rcgroups.com/forums/showthread.php?t=1649296

I wish I was clear on exactly where you're talking about, but to tell if there's vertical movement in the main shaft, do I have to take the rear part of the tail assembly off? Or do I need to take the landing skids, main gear, and shaft holder off to figure this out?

Originally Posted by LarsDennert

Thanks for that. I'll try it. Why would you want the tail pitch at zero when the linkage is in the middle? Wouldn't you want it set up for center of travel when hovering? Maybe there's not much difference to matter...

Maybe i'm not explaining properly. The gyro is what will be doing the "trimming" for the tail, so the gyro needs to know the neutral and end points. The ext. pot for the rudder is what tells the gyro where the END of travel is. But you can only adjust BOTH extremes at the same time. But for it to hold the tail properly you have to set the tail properly. You do want it in the center of travel, if possible but the tail blades must be at zero pitch at the "neutral point", which is where the servo centers to after binding. So typically on the V120D02S if you put the servo horn at 90° and have the tail rocker at 90° the tail pitch should be set just about right. If you do that then the tail blade pitch will be nearly zero. So using a gyro setting of 70% or 80% should hold the tail solid if you set it correctly. If your using a slipper clutch you might need to use a little bit of counter thrust if your tail kicks a tiny bit, or possibly adjust the clutch depending on what is causing the tail kicking. Having the tail setup properly is essential for 3D. Otherwise you will spin out when you pitch too hard to go to flip. But you also don't want the steering slide to press or "bind" on the extremes of travel. Adjusting "traveladj" only adjusts the TX control's end of travel, NOT THE GYRO! This is important! Because while you might move the rudder stick back and forth and the servo does not bind on the ends, the gyro might still be capable of binding the servo. Binding a servo will cause premature burn out of the motor. I've seen the analogy used of closing an already closed door. If you keep pressing against it eventually your arm will get tired and quit too. So this is where you use the rudder ext. pot. After adjusting the tail's neutral point properly you would then adjust the rudder ext. pot to give it the max travel both ways without binding.

If you have any questions please ask. I'm trying to explain this in the best way possible. But sometimes i get too technical or just don't make sense. lol.

Originally Posted by Rain4LA

I wish I was clear on exactly where you're talking about, but to tell if there's vertical movement in the main shaft, do I have to take the rear part of the tail assembly off? Or do I need to take the landing skids, main gear, and shaft holder off to figure this out?

I think you should just have to lift up on the rotor head. See if there is any movement without the servos moving. if the shaft's locking collar moved there could be some shaft play. The main gear and everything should not wiggle up and down if you lift up on the rotor or push up on the shaft and main gear from the bottom.

Originally Posted by IntegrityHndywrk

I only take my 2 V120 size heli out every once in a while anymore. But lately i try to throw the heli around too much or something and the battery just cant keep up. The motor bogs and i end up crashing every time. It's a good thing i never strip servos or break gears or typically damage anything other than the canopy. The way i'm set up it's been pretty lucky. But this time the V120D02S took a nose dive that broke the elevator link off the swash plate. The servo still didn't strip. I'm positive the replacement gears are stronger than the original now, at least i'm damn sure.


http://youtu.be/zWLOdBtdqos


http://youtu.be/-djjKNRa-Qo

I just realized i double posted the same video, this was supposed to be the other.. Yeah, it's a D05, but who the hell is looking over in that thread?

V120D05CS08 - 3D Flight & crash - 11-25-12 (1 min 37 sec)

Hmm so my question might be a bit different. If you adjust the blades for no pitch at center of travel and then fly the heli, some pitch has to be added while flying to keep the heli from piro'ing. Then effectively you have less travel left on that side than the other. So it would seem that the max piro speed in one direction would be higher than the other. I was wondering if that has to be accounted for.

Maybe the geometry of the links as designed adds the right amount of pitch if the linkage is at 90 degrees as you stated.

Originally Posted by LarsDennert

Hmm so my question might be a bit different. If you adjust the blades for no pitch at center of travel and then fly the heli, some pitch has to be added while flying to keep the heli from piro'ing. Then effectively you have less travel left on that side than the other. So it would seem that the max piro speed in one direction would be higher than the other. I was wondering if that has to be accounted for.

Maybe the geometry of the links as designed adds the right amount of pitch if the linkage is at 90 degrees as you stated.

The heli will spin in one direction (opposite of the main blades) on it's own if the tail isn't holding it by pushing in the opposite direction. So you don't need near as much pitch in one direction as you do for the other to get the same speed piro in both directions if that makes sense.