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HelicopterAerial Photography and Video › Ergo60 head wobble problem - video
09-02-2003 04:19 PM  14 years agoPost 1
MPA

rrElite Veteran

Australia

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I appear to be having stuff all progress in isolating the cause of what appears to be a rotor head shake.

It starts and stops.
As to what Ive done to rid the problem.
Increasing head speed does seem to have some effect, it cleans up at 1750 or therabouts.
I would like to be able to run lower head speeds.

I replaced 680 rotors for 700 NHP razors.
It has a 9th eng gear I went to 10th
At 1750 head speed it was revving its ring off.
Now the rpm is reasonable although for some reason Ive had to lean it off quite a bit to get power back it seemed to run rich on the main tooth gear change to 10th.
Im down to under 1 turn on main and closed middle range tap.
Engine is 61WC
3 screw carb
Ergo60 sport

No results doing the above
Added flybar weights and ran them out at the paddle ends, now to centre as normal.
Still no change to the shake.

Appart from having to run a very high head speed to clean up the shake under load it loses some speed and the wobble does come back for a period in so it doesnt totally solve the problem.

When it originally occured I asked the LHS JR guy and he said he heard of it before and it was the rotor spindle shaft washers are too thick.
Take 2 thou off each one and refit them, apparently this will cure the intermitant head shake, anyway it didnt but there is a chance I didnt take enough off them.
How far can I go sliming the washers as far as the rotor grip clearance to the rubber the washer fills up.

In all the change to longer rotors and moving gear around, flybar weights here and there, new paddles, spindle, new bearings in mast, eng starter and tail drive gear.
The problem has not changed at all it is the same as the first time.

Ive managed to sort all the issue Ive come upon to date with helis but this one has me utterly flumexed.

I am fitting a mini CCD cam on the tail pointing at the mast with a wide angle lens and will run it tomorrow and record that on VCR as well as the TVR on board with front view..

Anyone clues on the cause and cure of this.
TIA

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09-03-2003 07:28 PM  14 years agoPost 2
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rrElite Veteran

Australia

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Next installment.

I had a close inspection of the spindle shaft after removing it to shave some more off the damper washers or go to shims instead as was suggested elswhere.

I think Ive found the cause and it not anything Ive considered or been suggested so far but Im sure it is the culprit

It appears looking at the new spindle to the old that there are makrs on it that should not be there.

The marks are the plastic rotor head comming into contact with the spindle shaft, under power lifting off or iff a guast hits it, any reason it loads up the spindle can twist in the head damper rubber far enough to touch the plastic head.

I would think this could potentially be destructive to the head but looking at the old shaft it sems it doesnt rub that hard on it.

BUT
It could be enough contact to cause a vibration to be transmitted to the shaft bypassing the dampers.

I was going to remove more off the damper washers as was suggested by a few people.
At this point I think removing more off the washers will allow the spindle shaft to have more of an excursion under load conditions to touch the rotor head than it does already.
It looks as if the best course of action here would be to grind a small recess right on the edge of plastic head corner where the shaft contacts under power.
Maybe just a chamfer along the sharp edge.
You can see a small dent in it now.

But Id like another opinion on it.

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09-03-2003 08:48 PM  14 years agoPost 3
SteveH

rrProfessor

Texas

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Had a simular problem on an X-Cell and the cure for it was adding more damper washer shims, or tightening the damping. The wobble never showed up unless I was flying with the camera and mount and the faster I ran the rotor, the worse it was.

The government cannot give you anything without first taking it from someone else.

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09-03-2003 09:15 PM  14 years agoPost 4
MPA

rrElite Veteran

Australia

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I thought about adding another washer but the one there cuts into the damper rubber a bit, adding another may cause it to chew out a bit.

Its a bit of a chuck up whether to stiffen dampening by stiffer rubbers or as you did adding washers.
or allow it to move that much, and like I was considering, provide some more clearance from the plastic rotor head to the shaft.

The head speed increase does seem to improve this which is the reverse of what you had as I read it, that may indicate some diff in the causes here but it certainly points to the head dampening in both our cases being the common cause of this shake.

Thanks for the input.
It helps.

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09-04-2003 06:15 AM  14 years agoPost 5
MPA

rrElite Veteran

Australia

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Looks like what I need
Apparently the 45 deg rubbers are the ones the LHS guy has ordered so they are on the way.
The shaft however he tells me they dont sell in Aus, he tried to get one and no go so Ill have to mail order that one but I will grab one for sure.
Looks good.
Sounds like it will do the job to keep to spindle in place better..

I removed some of the plastic inside (a chamfer) so the spindle cant hit the head as it flexes sideways under power.
Just on the power side where the mark was from it hitting before.

Went and tested it with the video, just got back.
Seems now its not_touchng the head inside the dampers are showing their weakness being too soft and the effect is quite bad now compared to before.

It was a good 24knot wind and quite gusty, it shakes badly on any load from gusting (I can hear revs on the video and blades, high or low it does it)

Stiffening up the dampers and using this shaft you suggested I think will bring it back in trim.
Importantly, not bottoming into head inside like was before with stiffer rubbers and a more central pinning like this spindle has.

Ill have to go back to the thicker washers and perhaps as suggested use the aluminium ferals that Ive got on my 46 rotor head to stiffen the dampers up without chewing them out, the alu sleeve has a taper on it that is kinder the the rubbers.. (Im sure youve seen them before)

Im also going back to 9 tooth engine and 84 main instead of 88
Needs a few more revs to keep the head speed up to speed but not too much like it had earlier.

Ill check out these others and test out the harder rubbers I get tomorrow and more revs with gear change in the mean time till I get the shaft by post.
Thank you for that tip on it.

(I have the silicone spray, its an old fav from time as road service patrol, my car "lockout" tools slip in the gaps easy with a squirt on the door rubber, save tearing them)

Cheers

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09-05-2003 07:27 AM  14 years agoPost 6
MPA

rrElite Veteran

Australia

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Latest on the jr shaft.

Cant get the shaft here
Can get the 45deg rubbers

Beav suggested fit some silicone rubber tube over the shaft at the centre so it support the centre like the ball type shaft, or close to it..
Apparently worked on a few Xcells for him.

Ill see how it goes with some tube over the shaft when I get the grey 45deg dampers and 9/84 gears.
Dampers and gears ordered not in yet.

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09-05-2003 03:39 PM  14 years agoPost 7
Smithprod

rrVeteran

Oklahoma

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The new shaft John is talking about makes a HUGE difference. On my Z230 the old spindle was actually changing the pitch about two degrees in the air! Also, with the new spindle the dampners seem to last forever if you keep them lubed.

The ball on the new spindle is actually not round, it's more tall than wide, kind of diamond shaped. The rubber tubing idea will definitely be better but not as good as the spindle. What about ordering it from someone like Cyberheli?

Brad

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09-05-2003 09:48 PM  14 years agoPost 8
MPA

rrElite Veteran

Australia

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Ive considered doing that (order shaft OS) and just use the tube in the mean time (which will wear out unlike the ball) till I get the JR part.

Have the JR alloy upgrade boom mount & fin / stay support as well as alloy jr tail case.
I got the tail from Cyber, same deal as with the shaft they had none here in Aus and cant get.
I prefer the o.e.m. upgrades, the ball shaft sounds like the job for it..
Mixing arms and swash are the purple ones/non oem they carry here in Aus.

I was thinking of trying Walter Lee in Singapore as well, Walter gets the Emails out fast I know that..
Last time I got a reply same day so I might try him.
Things went a bit pear shaped on the last JR upgrade from cyb, it threw him a bit being a non regular stocked part and ended up 2 weeks in the getting, the shaft is an odd bit Ill give Walter a go.

Either way Ill get the JR shaft, the tubing should do me in between..
As well as answer some questions to the problem for my satisfaction before I get the shaft, I cant wait to find out if its solved..

4 solid jobs, waiting for the_fix, being when there is no shake at all I can get these jobs done.

Looks like Im in for a nice weekend of thumb twirling and giving the telephone the evil eye.
Having yanked out said gears and dampers waiting for new ones.
Cant get them for more day_s
not a_day as I beleived I heard the LHS man say he was told by JR Aus in Sin city (Sydney)

Im sold on the JR shaft, the right dampers are in transit somewhere between me and japan to arrive imminentely, in theory.

Thanks for the tip/s

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09-08-2003 03:50 PM  14 years agoPost 9
MPArrElite Veteran - Australia - My Posts: All  Forum  Topic

Well ma gear arrived from JR.
(gears and Dampers).

Ive ended up with the 50 degree rubbers instead of the 45, apparently the 50 are the stiffest.

The 9 t and 84 tooth main dropping me back to 9.33:1 from 8.8:1.
The price of the main gear from JR 84T was (suck me sideways) three times the price of the 88T main.

AU$63 for 84T main. (4 teeth less for triple the price)
Oh well **** happpens.

To the inner spindle support mentioned above.

I read some info that concerned me and not sure if the validity but they claimed that some used the ball type spindle and it ended up in some nasty "disconnections" in mid air and a JR note on it to stop using them. Odd thing is you can still get them.
It spooked me a bit on that.

In the mean time the inner support as suggested is done with silcone tube, which is the same suggeston as the person who mentioned the ball shaft issue. (found on google)
Due the the load here Ive elected to try using a set of dampers ground down to fit into the centre of the head.

The ID is right for the job.
2 fit in the centre just right side by side but Ill need to add some thin tube to the shaft between the inner dampers and the original outer damper rubbers to stop the ones in the centre displacing or "walking" down the shaft.

Ill see what I can find I may have to go get some silicone tube across town. I dont want to glue or bond anything in there.

Anyway thats the latest Ill see how the video goes.
Perhaps tommorow, just came into spring here so weather is still a bit wintery and odd days.

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09-08-2003 07:21 PM  14 years agoPost 10
Lwnemesis

rrVeteran

Seattle, WA

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The reason that 84 tooth gear was that much more expensive is because its CNC machined. The standard Vigor 84 tooth gear is molded. next time buy the molded 84 gear

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09-08-2003 09:00 PM  14 years agoPost 11
MPA

rrElite Veteran

Australia

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Ill keep it mind if I have to replace it.

Seems the new 9 tooth gear has the same issue as the old one, the bearing slips on too easy, hope the loctite works.

The 10 tooth, the bearing fit on snug on the journal.

The old 9 tooth fell to bits becuase it wasnt tight enough in the bearing to begin with.

Not good machining tollerances there.

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09-09-2003 02:49 PM  14 years agoPost 12
Smithprod

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Oklahoma

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These pinions from JR are of very poor tolerance. I use a 11 tooth in my Z230 and they vary greatly from one to another as far as fitting tight or loose. One trick that helps (thanks to John) is to use Loctite Sleeve Lock. I can't remember the number, I'll have to look later at the house, but this stuff is STRONG and highly heat tolerant.

Brad

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09-09-2003 03:18 PM  14 years agoPost 13
MPA

rrElite Veteran

Australia

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Brad

Seems to be the concensus on them
for the 9 tooth anyway.

I tried shaft lock to begin with but too thin so went to a hard threadlock.
its on good and solid now but Ill keep an eye on it.

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09-09-2003 07:43 PM  14 years agoPost 14
MPA

rrElite Veteran

Australia

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John
Yes that is a nicer looking job than the JR one, the top journal is a better finish too.
Ill get a hold of one for spare and swap it over at the next refit.
Thank's for that and the link..

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09-12-2003 12:54 AM  14 years agoPost 15
MPArrElite Veteran - Australia - My Posts: All  Forum  Topic

After the first run with some loose fitting rubber in the middle of the spindle it is improved but not cured.

The gear ratio changes allow the head speed to stay higher but still sags.
Leaned it off and its better but not full power.
I will add some more Nitro to cure that.

Ive removed the inner dampers and made new ones to the size of the hole which is oval shaped.

The head showing the material removed to stop the shaft hitting the bead block.
This revealed the large wobble going on Im now resolving with the stiffening of dampers using 50 deg dampers and the fitting of inner dampers.

About to head out and test the tighter inner dampers.

Next is to shim the grips to dampers to squeeze the dampers more in the head which it needs.

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09-12-2003 03:35 PM  14 years agoPost 16
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Australia

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Well tested that and no diff, still wobbles on and off.

Its got plenty of support in there now and the hardest dampers.

Not as bad as when I first removed some plastic to stop it knocking inside so in that respect it is improved but only back to what I originally had with it knocking the head inside.

At least the spindle not bumping the plastic head so Im happy about that but still shakes.

Next is to throw another 5 Nitro in the Mix to get the revs to speed, still sagging with the 9 tooth 84 tooth but not going back to 9/88 as Im certain this needs at least 1650 under load to stop the wobbles and 9/88 leaves it close to peak revs..

Plus shim up the dampers to make the head tighter out at the dampers.

Considering ways to do this without throwing more cash at it for now.
Ive seen the ORing setup at Ricks and other places but Id need to order it and pay for it and then wait only to find its perhaps no solution at all as Ive done so far.
Considering using a not just thicker washer in there but much large OD, a plastic rotor bolt shim looks about right for it.
The one on it now is very small.

I posted todays Video off the tail cam
Found the exhaust touching the AV Tx mount as Ive got it running to the tail camera, replced foam for camera moutn rubber sheet and tighter strap, no vibe and better pic than last one.


Another day.

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09-12-2003 09:50 PM  14 years agoPost 17
daggit

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Claremont, MN

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Interesting video... the frame rate is such that it makes the blades and head look like they are nearly standing still. I couldn't see the wobble. Is it easier to see uncompressed?

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09-13-2003 08:09 AM  14 years agoPost 18
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rrElite Veteran

Australia

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The wobble doesnt show up on the tail cam its a solid pictutre
On Sony its only just noticable at the edges running at normall speed.

I can only see the wobble visibly on slow motion on the Sony cam.
I didnt till I got the Sony cam on there and slowed it down.

If you stood there looking at the heli you would swear it looks like it was hovering like glass.

In the video off the Sony I have Chris gives the thumbs up from the ground as he was certain it was fixed and hover perfect.
We got it down and look at the video to see it having the on off shake on slow motion, It did.
On normal speed it looks ok except you can see the vibration twist on the edges if you look close..

No ones picked in any Video Ive showed them till I slow it down with slow motion playback.

When I look at full size helis doing video you can see they nearly all have a slight twisting shake.
The thing with this is it is not constant and to my thinking this means in my case it is not an intrinsic problem to helis, the on_and_off of the wobble indicates a "condition" which I should be able to solve.

The wobble is there on slow motion and so long as it is there to my mind at can be better vid and stills if its not doing it.

No tests today its blowing a gale and raining.

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09-14-2003 08:07 AM  14 years agoPost 19
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rrElite Veteran

Australia

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more rain, more wind today.
Getting edgy for a test run.

I was thinking about the frame rate.
thats VHS PAL = 25fps
Means that the rotor head stationary at 25fps would be 1500RPM head speed.
This means the motor is loosing 230RPM as soon as I feed it collective.
I knew it was loosing some but didnt think it was that much.

Mixed some more Nitro to the latest batch to get the head speed up again with the 9/84 gears.
I want to see if 1750 is good for it and the 9/88 wont get it there without the engine busting a nut.
If with the dampening fixes its ok at 1650 I might drop back to 9/88

Picked up a fresh batch of Nitro yesterday, AU$20 a litre now.
Man we need a gasser sooner than later.
See what happens tommorrow if it stops blowing a gale and raining.

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09-20-2003 05:10 PM  14 years agoPost 20
MPArrElite Veteran - Australia - My Posts: All  Forum  Topic

The latest on WobbleCam

Well after my last post on it I made these and stuffed them in.

(pics removed)

Well the camera is still shakin like Elvis

Cant see it on the tail camera.

In all the mods above it does increase the responsiveness of it and
the spindle doesnt hit the head block anymore inside so that good.
But the shakes it seems have no relationship to head dampening at all.

The oscillation I have concluded is the head shakes but that is induced by something else on the heli.
I suspect the rubber mounting parts to the damper frame off the heli
frame are too soft.
The liquid dampers between the pan tilt frame soak up
vibration well but the rubber spacers on the frame that hold them to heli
frame are allowing some elasticity in the support frame and its the part vibrating in time with the rotor head.
Like a set of trainer legs do when they are the wrong length only they are more violent.

The 9/84 main gear is not up to much for the motor with 30% Nitro and
leaned out so Im back to 9/88 main.
I went out today with the 9/88 main gears back in it and some revs on it back to the peak it should be.

Now it is back up to full speed with the gears the dampening improvement seem to have have some benefit to it, it is very hard to detect any wobble on slow motion now and only now and then, and cant see it on normal video speed.
But at some points I can still pick it if I look hard so to me its still there and not fixed till its glass on all speeds.

Next is to change the top 2 frame grommets for a much stiffer rubber grommet and a plate mount to include an extra securing point to make 4 sleeve and grommet points instead of 3 like now..

If that doesnt clean up the rest Ill go to the new single pivot liquid silicone mount head with the camera free to pivot and that will decouple the mass of the camera considerably from the heli frame to the roll axis...whilst dampeing movement with the silicone liquid head.
That kills two birds with one stone, the existing mount was for stills and needs to be free for video and this will solve that as well as the above issues.
We have found someone who makes the liquid silicone mounts locally and has many types for us to try on it so we can get one to suit what I need instead of working to use CD player buttons being the only other option I had till now..

Another day passes.

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