Help - Why Roll to Right

[rehler]

I need help fast. My gyro in flight wants to roll hard to the right. I have to fly with the stick about 6 inches to the left to stay straight, which means I only have a few degrees of left tilt available - very dangerous. If I release pressure on the stick it wants to go to the center and roll the gyro to the right - fast.

Please let me know any theory you can think of that could cause this problem.

If I can't find and fix it the problem the next couple of days I won't be able to use my new trailer to take my gyro to Mentone!! :( HELP.

[david holmes]

ken,
what power settings & a/s?

[rehler]

David,

At all speeds and power - from initial lift off, climb, level flight and landing.

An example today was 55 mph at around 4500 engine rpm in level flight.

[Friendly]

Ken , I am sure you probably checked to see if the head is centered correctly when the stick is in neutral position before it is flown, and the contol stick has no slippage of contol leavers and trim controls are not interferring, but this is going to be an interesting thread. Please advise us of what you find.

[rehler]

Mark,

I did check the rotor head position compared to the control stick. I made one push rod 1/4" longer and the other 1/4" shorter to try to fix the problem, but the roll is much greater than this little adjustment. It was after I did this that straight and level flight required the 6" to the left stick position to stay level.

You mentioned "interferring" which make me wonder if the Wunderlich prerotator shaft (which is new) could be putting some twisting force on the rotor head???

[rehler]

Question: If the teeter is not working properly or sticking does that make the gyro roll to the right or to the left?

[chuter]

I would say left. Seems like the advancing blade would then try to lift up on the right side. But wait till the experts chime in.

[GyroRon]

did you set your tail up in any special way when you first built the gyro? By that I mean some people put a offset in the rudders to help cancel P factor and since your gyro used a engine before that turned the other way the offset if you got any could be not helping cancel P factor but making it worse.

[david holmes]

Ken,
This is from a very vague memory:
If the teeter bolt is too tight, it will cause the roll. I had a similiar problem over a couple of years ago and I fixed by changing the torque on the teeter bolt as little as one face. I set my teeter bolt tightness so the bolt rotates with the blade -- but one has to start with it so loose that it doesn't rotate with the blade and tighten the bolt one face at a time until it rotates with the blade.

Check with Ernie B. He's my authority for light blades. His cell phone # is 813 294 7578.

Bubba says your problem is because you have more air in the left tire than the right tire. When was the last time you checked you tire pressure?

[CLS447]

Ken, you have to bring it regardless, please! I'm sure you will get good advice & help at Mentone.

[automan1223]

I read and spoke with the late Ken Brock about clearances for the teeter towers in the hub bar. He indicated that dirt could even collect up in the towers and cause what you are describing. 5 to 10 thousands is what you want I set mine to 5 thou.

You have a very dangerous situation right now, so please go thru everything before you fly it again. make sure the teeter towers are tight to the block, make sure the single 'jesus" bolt going thru the towers is tight and that the hub bar pivots about its axis with ease. You should also be able to feel a small bit of play when you push the hub bar side to side in between the teeter towers. If the hub bar is binding in the towers find out why. may need shims, but dont just losen the bolt to make it that way, the bolt should be torqued tight and makes the unit "1 piece"

Jonathan

[Rick Whittridge]

Mark,

I did check the rotor head position compared to the control stick. I made one push rod 1/4" longer and the other 1/4" shorter to try to fix the problem, but the roll is much greater than this little adjustment. It was after I did this that straight and level flight required the 6" to the left stick position to stay level.

You mentioned "interferring" which make me wonder if the Wunderlich prerotator shaft (which is new) could be putting some twisting force on the rotor head???

Ken, I think you might have answered your own question.I experienced this same thing on the GADGET only to find that the prerotator shaft was the problem. If you loosen it up,shift it the other way , hold it there & tighten it down it should take care of it. This might take several flights to get it RIGHT! You should see a improvement to let you know how much twist to counteract this problem.

[rehler]

Thanks to everyone. I'll try everything mentioned in the morning.

Chris, you're right. I can get a lot of good advice at Mentone, so I will make the trip with my gyro even if I don't find the problem - but if it can't fix it I probably won't fly it at Mentone - not worth the risk.

If anyone has any more ideas, please post them. I'll check the forum during the day Sunday.

Thanks again!

[PW_Plack]

Ken,

Move your wallet from your right rear pocket to your left. :)

[CLS447]

That's great Ken! I hope you get this resolved quickly but you have come too far to ding her up, please be careful! I can't take any more bad news.

Everyone is sure giving some good ideas! I think Pauls' wallet suggestion may have merit! Maybe she's just begging for the Sport Rotors! Good luck & we'll see you at Mentone. Have a safe trip!

[rehler]

Paul, after getting my gyro back in the air I'm so broke my wallet now nas a negative weight. It should be lifting the right side of my gyro.

[rwr]

The pre-rotater shaft might be the culprit.

On my single-place Dominator, when I fooled around with the lower mount of the shaft, it would change the roll inputs. I was trying to get the drive wheel mounting for the prerotater tidied up so it would have less slop in it.

After quite a while, it finally donned on me that putting some torque or some different alignment on the prerotater shaft and housing was putting small forces on the rotor head.

The wunderlich shaft and housing is fairly heavy and stiff. When you realign it some way or another, you are almost always going to put some roll and/or pitch forces on the rotor head.

I finally verified all this by deliberately putting some torque loads and then some bending loads on the shaft and housing and, sure enough, it changed where the machine wanted to fly.

Good luck.

[rehler]

Well it's been a long day. I checked every idea posted and a few more. The good news is that it is much better. Flying straight and level now requires the stick to be only about 3 inches to the left of center.

I think the main problem (suggested by Bubba) was that I had 1 pound pressure more in the right tire making it heavier.

Ron's suggestion helped the most - thanks Ron. I re-adjusted my rudders to give left rudder while flying with the pedals centered. Perhaps I need to add a trim tab like I had on my air command to keep the rudders in the left position without any foot pressure. I never had to do this before but probably need to now with the larger engine and prop.

The other good news is that my rotorhead is now clean as new and operates as smooth as glass. It really had no problem but the parts were a little dirty.

The more I think about it trim tabs are probably my best bet to cure the problem.

Thanks very much for everyones help. Now I can pack up for the trip to Mentone. Hope to see all of you there.

[Friendly]

I'm glad to hear that, your gyro has always been one of my favorites.

[Aussie_Paul]

If the teeter is too tight it will roll to the left and have severe rotor shake.

The torque roll from more hp can be quite alarming particularly if you have changed from one prop direction to the other.

The pre rotator can have quite a force if it is "straining" one way or the other.

If you had a couple of these working together then it could feel quite serious.

With a 503 0r a 582 rotax powered single seat machine we always have the left (when sitting in the machine) control rod approx 1/2" longer than the right one. It seems that you already have that Ken, so I am backing that your problem is the pre rotator flexidrive pressure.

My thoughts.

Aussie Paul.

[GyroRon]

Ta Da! And see even if 2000+ of my posts are trash, I can still save the day every once in a while! :)

No It just dawned on me that most builders that use a short tail or tails on a gyro typically will have the rudder offset to help counter the P factor, some also use a trim tab. Since I remember Ken mentioning that his old engine turned the other way in his posts about props, I figured the tail was a good place to look, especially with all the power of that Rotax 912S.

A tall tail would make this problem go away. Having rudder above and below the prop centerline helps to cancel P factor.

[smckenna]

Ron,

I don't see why a "wide tail", such as Ken has, would be less effective in reducing P-factor than a tall tail. Assuming, of course, that it is centered on the prop axis. Am I missing something?

Steve

[Doug Riley]

Steve, no, you're right. Horizontal or vertical (or diagonal!), it will do the same job if it's symmetrical about the prop axis. Most HS's seem to be placed below the prop axis, though.