Bumpy blades

[scottessex]

OK I have noticed that the dominator seems to have alot more stick shake than the Soma did, I flew both sets of blades and they were very smooth on the soma, both sets were much less smooth on the doninator.
They are tracked correctly, like I said theses are the same baby butt smooth blades I have been flying for the last couple years on the soma,

Do I need to shim the side to side shims on the teeter towers to make sure the teeter block is centered in the rotorhead?

[GyroRon]

Yeap......

[dragonflyerthom]

Is there any slop in the head or control arms?

[Harry_S.]

I would say they're not in the same centered or off center spot, mast centered if you will, on the Dom, as they were on the Soma.

Trial and error shimming should find the sweet spot?!


Cheers :)

[Timchick]

What kind of blades are they?

[scottessex]

Tim, they are the dragon wings.

I measured and I have .236 on one side, and .217 clearance on the other, so I guess that is where I need to concentrate.

And there is no slop everything is tight.

[C. Beaty]

Could it be The Soma had a single 2 x 2 mast while the Dominator has a twin 1 x 2 mast? Makes an appreciable difference shakewise.

[chuter]

Undersling?

[13brv3]

Could it be The Soma had a single 2 x 2 mast while the Dominator has a twin 1 x 2 mast? Makes an appreciable difference shakewise.

My Dominator sure didn't come with a twin 1x2 mast :confused:

Rusty

[scottessex]

The dominator has a 2x2 mast and the soma had a 2 1x2.
I'll try the shimming first since it does seem to be a few thousanths off.

[C. Beaty]

Some do, some don’t; I don’t know where the transition happens to be.

I do know that on the two place Dominators, Ernie is now turning the 1 x 2s crosswise to minimize shake.

[scottessex]

Shimmed the blades, made a difference, still need to dial it in, Dang i miss the smoothness of the Soma! Not buyers remorse, just making adjustments etc. to make it mine.

[GyroRon]

Check the tracking of the blades too Scott. Your rotorhead could be off a slight amount in any direction and perfectly smooth on one gyro may not be the same on another due to misalignments of parts. Balance of the blades..... Stringing of the blades..... Tracking of the blades...... and centering in the towers...... all make difference in stick shake.

[Fl90]

Hi Scott, tracking is usually required, and I have to sling my blades. I suck at stringing and they are always smoother when I sling them. It's worth the effort to me, and you know what I go through to sling them. If your rotor head is off, after tracking the blades, you'll need to make sure the rotor is "clocked" to the head each time you remove and reinstall it. I have installed the rotor both ways, after I tracked my blades, and it doesn't make a difference.

Phil.

[scottessex]

Ok blades still shakey, I gues first i will try to rotate them 180 degree to the rotor head. Then I guess I will have to do the small shim under the teeter block, a little at a time.
I helped Phil R dial in the Skywheels but I have not had to adjust dragon wings,
How should I start? They look like they are tracked correctly when flying. But they don't feel it.
They were really really smooth on the soma, But both sets were smooth on the soma, and both sets shook on the dominator, so what should i look at on the rotorhead?

[gyromike]

Scott,

Does it feel like a 1/rev or a 2/rev?

[GyroRon]

Bring it to the Goose this saturday and I will smooth you out.... Big day at the Goose this saturday as were breaking in a new 582 that is on the back of a brand new Dominator that should be test flown after the break-in.... plus my gyro will be getting a RK-400 clutch installed and a new thermostat

[scottessex]

It is a side to side kinda shake, I would guess 1 rev at the frequency of it,

What's up Ron? spill the beans, Did you someone we know build another dominator?

I wish I could be there but I will be busy ALL day Saturday with some homeowners BS that has come up.

[GyroRon]

a new guy named Ken Ashely has built a Dominator with a pod and a 582 and it will hopefully fly this weekend. He will be keeping it in my hangar or one of the other ones at the Goose.... So that makes 3 Dominators at Goose Creek now!

your shake issue is either tracking or side to side in the towers most likely. Remember, perfectly centered in between the two towers may NOT be perfectly centered.... the rotorhead may not be perfectly made and could have some misalignment in it.

[scottessex]

Ok I guess I'll do some serious measurements, That is kind of what I was thinking since both sets of blades acted the same, smooth on the soma, both bumpy on the Dom.

[Harry_S.]

Scott;

Both sets are smooth on the soma and both are "bumpy" on another machine. IMO...don't mess with the blades...they're alright.

Did you perchance make centering measurements on your soma?

In my previous post, I suggested that you MAY have an off centered rotorhead on your new machine and it may take an extended trial and error exercise before you finally nail it, and, it could be a fore/aft problem rather than, or even with a side/side
problem.

Again, with tongue in cheek, I would say...don't mess with the blades.

Anyhoo...2 per rev would indicate tracking and you don't have that, right?!


Cheers :)

[scottessex]

I'm with you Harry, I think that it is a centering problem rather than tracking.

[bartc150]

Scott, when I flew Joe Pires' machine it had almost no shake, but mine has always had a little. It's something I live with, but would rather not have it at all. My blades look like they are in track, and I sling them instead of stringing. My shake seems to be fore and aft, and I also feel it in the seat and the pod shakes. I was going to experiment with the tracking too, but I'll let you figure it out and then you can hook me up.:help: :lol:

[scottessex]

Thanks Man, I'll let you know what I find out.

[scottessex]

OK I took measurements and moved some shims around to get the blades as close to center as possible, about .003" the shake was better but not acceptable, so i slung the blades, loosened them up and then just snugged ther nuts and prerotateda nd headed down the runway until the front wheel came off, about 260 RRPM then taxied back and let the blades spin down by themselves, and tightened up the nuts. Then I went and flew, much much better. now to get the trim dialed in....

[CLS447]

Good job Scott, glad to hear it !

I'm back to flying my SxS & I gotta say....my 28' DW's are so smooth that the only way I know their turning is by looking up !

I carried them out of the hangar by myself .....EASILY !

[scottessex]

I got everything sorted out, and then they started bumping again,
what has happened is the teeter block has moved,
kind of like it twisted opposite the direction of the blade rotation,
Took it off loosened it up, made sure it was square with the hub bar, Everything was great, after about 2 1/2 of flight time it has slightly moved again, Any one else ever have this problem? and yes i did tighten up the bolts. :)

[GyroRon]

Are you slamming the pre rotator in, or using the rotor brake very hard?

[dragonflyerthom]

Sounds like you need some locktight there buddy.

[scottessex]

Didn't think I was using the prerotator too hard, Not hard on the brake,
I should use locktite between the hub bar and teeter block!

[Harry_S.]

Scott;

You have ONE hubbar or TWO?

If you have two, are they both performing the same?

Pictures?


Cheers :)

[scottessex]

Sort of like this.

[Harry_S.]

Sorry, but I'm not familiar at all with the different brands of rotors, but wow...only two bolts on the block?!

I don't think locktite will solve this problem as you seem to have some slop in the bolt holes...maybe even out of round.

Any chance of adding two more bolts? Going oversize on the two holes and using close tolerance bolts? Go oversize and shim the holes? Drilling and driving roll pins to lock the block from twisting? Getting a new block?

Just suggestions Scott. What you now have is no good, needs corrective action.


Cheers

[scottessex]

I thought about the drilling and pinning, I did pick up some close tolerance bolts, but they were too long, I am going to try that first, They are dragon wing blades
I wonder if the Dominator pre rotator might be engaging a little hard, it does spin the blades up really fast.

It does not move much, just enough out of square to cause a shake, I used a machinist square to check it last time I tightened it up, and it was smooth, so I am sure this is the problem.

[CLS447]

Scott, what does Ernie B. have to say about this problem ?

[scottessex]

I put new close tolerance NAS bolts in the teeter block, made sure it was exactly 90 degrees and tightened everything up, then I slung the blades, flew tonight in gusty winds very little stick shake almost none, and I love the way this gyro handles the wind gusts.

[scottessex]

Went flying again yesterday, noticed the blades were smooth, until... I get ALOT of shake during certain flight envelopes, it seems to get worse as speed increases, and is definitely a front to back shake in the stick, about 2 inches worth. If I apply back pressure, and a little right stick and slow down it seems OK, very minimal shake at 40 mph, Also seems to shake in vertical decent. Very strange. :(

[Brent_Brown]

Mine shake the most at the start of a vertical decent at 55 mph they are happy.

[automan1223]

Scott,

I am having the same problems you are. After I came back from outer banks my raf's were really getting rough. I thought it might be the paint missing from the outer portions of the leading edges, seems the rain washed the paint off...

I put the new sport copters 30's on after reaching total frustration. You know what the sport copters shake as much or worse....... I had to center them with some effort and got them to behave. The flight envelope will change the amount and intensity of the shake.

I also noticed the out of phase of the hub bar with the teeter towers you posted with the graphic. I wonder if its my towers are twisted. Even with the new sport copters they dont measure square in equal amts at all 4 points.

Finally I eyeballed em and got lucky. I am still not happy. I am thinking about putting on the sport rotor head but I dont want to do too much rework only to need it back when I finish the other build.

I will have a blade report later.

J

[Harry_S.]

Scott, do you have a stabilizing bar at the top of the teeter towers?


Cheers :)

[scottessex]

No Harry I do not, It is an RFD head with the short towers.

[13brv3]

You guys are really depressing me with all these horror stories of trying to get the blades smooth. I sure hope that's not how I spend my Summer...

Does Ernie balance these blades dynamically? I know Scott's blades felt smooth on Soma, but I wonder if it was just better able to damp the vibration :noidea:

Rusty (has a dynamic balancer, and isn't afraid to use it)

[GyroRon]

Scott has a bad habit of sticking his chewing gum on the end of the rotorblade as he does his preflight inspections and that is what is giving him the shaky rotorblades!

[scottessex]

Dang Ron you nailed it!

I spun the rotorhead 180 degrees, got smoother, I'll try a few shims this week.
How often should the rotorhead bearing be changed? shows 117 hours on the gyro, but I know it has been in there since it was built around 2002, The head is tight, but I s'pose it wouldn't hurt to change it.

[devon532]

Scott,

So don't leave us in suspense. Did you change the bearing? How are the blades now. I'm interested because I seemed to have developed a stick shake "out of nowhere". I lifted off yesterday (it was to be my first flight away from the airport no less!) . At first I thought the still spinning tires were the cause so I hit the brakes. The wheels stopped but the shake continued. It is a wobbling sensation - an "off balance" feeling of the rotor. I had done all kinds of maneuvers over the runway in the past and even remarked to myself how happy I was that there was never a shake and everything was smooth. Well, like I said, that ended yesterday, so I'm curious as to how you solved your problem.

[scottessex]

OK first of all make sure the blades are clean, I mean really clean.
What I did was make taller towers, just like Ernie makes now, that way you can hang the blades from the top hole in the teeter block.
I also added 2 shims under the teeter block, it is very good now.

BUT I also believe that having a scissors arrangement in the control system adds just a little bit of extra slop, that dampens the vibration in the stick.
I still have some slight stick shake, nothing major, but when I look up at the rotor head in flight, it sure has smoothed out.

Most of the minor shake is now at low speed, before all the shake was at 60 mph plus. Now they are really smooth at high speed. plus I did a few High G turns and had the rotors up to 486 RRPMs! sounded like a Huey H-1 and still smooth!

[Passin' Thru]

Scott, so you increased the under-sling. Could you share the dimension?

[GrantR]

486 rpms! Is that safe?

Just after reading this crash report http://mentone98.8m.com/ I am a bit weary of fast spinning blades.

equation we might find out why the nose of the aircraft violently dropped down and to the right. According to Ernie, the airfoil he uses in the wide chord blade, which is different than his narrow chord blade, stalls or goes into something similar called a Mach Tuck at about .7 MACH, which is about 525 MPH. Now if you do the math on a set of 28 ft diameter rotor blades, you will see that 1 RPM of blade rotation gives you approximately 1 MPH of tip speed on the rotor blade, and I am sure that if I have done the math wrong somebody will check it. Now, if I had rotor blades that were accelerating at 485 RPM (485 MPH), and an aircraft with 40 MPH of airspeed and probably increasing, if you add the forward speed of the aircraft to the advancing blade speed, bingo, you blow right past that 525 MPH of advancing blade speed at just the point where the nose of the aircraft dropped violently down and to the right. Couple all of this with the fact that there were less than three hours of flight time on the rotor blades at the time of impact and all reasonable information points to a rotor blade failure.

[scottessex]

Scott, so you increased the under-sling. Could you share the dimension?
I raised the tower height by 1 1/2"

Grant, during a high G maneuver, the rotor blades will speed up just for an instant only a few seconds, and then rapidly drop in RRPM back to normal flight RPM, That is why negative G's should be avoided, they will slow down.

[Fl90]

GrantR, that's a different airfoil. Also, about 2 feet larger diameter.

That's why I don't have instruments, too many things to wory about. My gyro makes a specific noise when it's flying. If it makes a different noise, or stops making noise, I land.

Phil.

[scottessex]

My blades are 23 ft. I just happened to look at the rotor tach during the wop wop wop .
I was in a dive and then pulled back and to the right, nice little spiral similar to this one I did at ROC.

[Fl90]

486rrpm on 23' is less than 400mph on the tip....means your blades were seeing about 1000lbs.

[GyroRon]

Scott, looks like your mastering the " Death Spiral! "


I never saw the post above from a few months ago about the rotorhead bearing. I would advise you to change it out simply due to Tim trailering the gyro in a heavy duty trailer with the blades on.