View Full Version : Gordie/David- Help please.
Gary O
08-15-2006, 10:45 AM
I have a Tempest FAI that I've been flying for the better part of a year now. I had a YS 91 in it originally and the helicopter was very smooth and was great for the FAI type flying that I was using it for. When I got the kit from Ron, (Rick's) it said it was a 7.75 gear ratio. when i assembled the kit I had to re work almost every slot on the mounting plates to get it to work. It had a 93 main gear and what I thought was a 12T pinion. when I started flying it it was as smooth as glass but very boggy and under powered feeling. After checking everything I could think of, I thought I had a bad motor until I checked the pinion. The kit was packaged with a 13T pinion instead of a 12. That explains why the holes didn't fit. I changed the pinion and now it is a 7.75 like it should be. Now to the actual problem:
I now have a wobble that I can not get out. I am turning the head at 1550 in normal mode, 1850 in idle 1 and 1950 in idle 2. It doesn't matter what the head speed it wobbles, not just a little either. I have changed clutch dampners, head dampners, fly bar ratios, delta set ups, and no matter what I do it still wobbles. I'm at a loss of where else to look. The fan is less than 1 thousandth run out so I'm pretty sure it's not that. Any thing you guys can think of?
Dr.Ben
08-15-2006, 12:43 PM
PM sent.
Ben
Gary O
08-23-2006, 11:11 AM
This helicopter has just about gotten me at my last nerve. After trying a new head from a new FAI build I was in the process of building it still didn't cure the wobble. I put the head back on that has always been on it and started trying other things. I put a new main shaft in it, that didn't stop it. I even put a brand new YS 91 in it with a new fan balanced and less than a thousandth of runout, that didn't even stop it. I've put new bearings in all the bearing blocks. I've almost rebuilt the heli and it just won't stop the wobble. Any ideas? at this point I'm open to just about anything. :arggg:
DavidH
08-23-2006, 11:47 AM
Has this been the same set of blades ?
David
Gary O
08-23-2006, 12:17 PM
No, I've had Radix, V's and SAB's on it with the same result. Anything you can think of that is fairly obvious, I've changed. That's why I am out of things to try.
What durometer O Rings are in the head?
Gordie
Gary O
08-23-2006, 02:40 PM
I have tried every combination. I even tried the one pc. still the same thing. I'm really at a loss as to what to do next. I've almost re-built the thing already. The only thing I haven't tried is a new auto hub.
Wobbles? I need more info. Mast Bump or vibration? A mast bump is caused by too much damping at too low an rpm. A vibration is caused by alignment or balance. After flying is the blade axle still in the exact center of the head block?
Gordie
Gary O
08-23-2006, 03:33 PM
This has to be the wobbles. The spindle is fine, but I can't let it go for more than a few seconds after it lifts off. It starts to wobble side to side and it starts out very slight and then after just a few seconds it gets pretty violent.
DavidH
08-23-2006, 03:52 PM
If the wobbles are still there at 1950 rpm as you mentioned in the first post. I don't think it is head dampening. I have installed the 90 durometer one piece dampeners in a Tempest FAI head just to try them. I had to get the rpm above 1800 before the heli would smooth out. Put the combination of 60/60 dampeners back in and the heli would hover smooth at 1500 rpm. This is a hard one to diagnose without actually seeing what is happening.
David
Gary O
08-23-2006, 04:13 PM
David,
Yeah, I flipped it to idle 2 where I had it at 1950, while it was still on the ground and it did the same thing. The one thing I did notice last night that I haven't seen before is that with it sitting on the ground spooled up but just barely light on the skids, it looked like the disc was trying to oscillate. It wasn't a lot but I could see it. The only reaon I could see it was I had the SAB's on it and they showed up a lot better under the lights.
Spawndn72
08-23-2006, 04:18 PM
Gary, I have been following this thread, hope you don't mind me jumping in. Just wanted to get one thing clear in my head.
It was flying smooth, then you changed the pinion from a 13t to a 12t. And then all hell broke loose. Nothing else changed, right?
Todd
Gary O
08-23-2006, 04:27 PM
Right, All I did was change the gear ratio. This helicopter was smooth as glass from day one. I had been flying it for right at 8 or 9 months I guess. MA had it boxed as a 7.75 which would be 7.75. When I decided to change the ratio to suit the YS 91 better that's when I discovered the 13t pinion. That's a 7.15 ratio, way too low, especially for a YS. It was just an error at packaging because to get 7.75 it would take over a 100t main gear.
DavidH
08-23-2006, 05:28 PM
Yeah, I flipped it to idle 2 where I had it at 1950, while it was still on the ground and it did the same thing. The one thing I did notice last night that I haven't seen before is that with it sitting on the ground spooled up but just barely light on the skids, it looked like the disc was trying to oscillate
Has all this been happening with the model on the ground. Always will get some osicilation when the model is on the ground and spooled up.
David
Gary O
08-23-2006, 10:41 PM
David,
No, I only noticed it when it was spooling up with the SAB's since they are white and more noticeable under the lights.
Is this happening on the ground or after lift off or both? Is the blade axle still centered after you land ? Are the blades loose in the grips or tight? You don't have the pitch arms tailing do you? I doubt it but thought I'd ask.
Gordie