Stick shake

Brian Jackson

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If you were to allow the teeter block some small movement between the towers...wouldn't it centre up where it needs to be?
Probably a stupid question.
I am no expert on this, but am imagining that scenario like a kid on one of those old playground merry-go-rounds. If I stood perfectly centered on it while the neighbor kids revved it up, I just get dizzy. But if I was slightly off center I would tend to get slung outward with ever-greater force in an unstable feedback loop. I would think the rotor is similar to the kid on the merry-go-round. But if I'm wrong then we'll both learn something.
 

Mac

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Much like a slider head - advancing/retreating blades.
 

Mike G

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John H
To my knowledge there are two different types of teeter bearings for ELA rotors. The older design had two taper roller bearings housed in the teeter block (that’s the cube that is bolted to the hub bar). Later models had two NKX 15 combined radial and thrust bearings housed in a threaded "barrel" for chordwise adjustment. These had a needle roller bearing for the teeter bolt and a ball thrust bearing.
1628786178609.png
For me personally for 0.5 mm of axial play, I’d just tighten the teeter bolt to close the gap by deflecting the teeter towers. 0.5 mm is about 120° rotation of the nut on a 1.5 mm pitch thread (which is what the teeter bolt has from memory). If you don’t like that solution your plastic shims would be OK for me since they go between the stationary side of the thrust bearing and the stationary teeter tower so there shouldn’t be any rotation. No need for steel but there’s nothing wrong with using steel shims.

If you have the older design shims or tightening the teeter bolt should also work.

For tightening you need a little pre load on the thrust bearings and to fix your shims so I just tighten the nut by hand as hard as I can without using a spanner.

Don’t overdo it, I balanced a couple of ELAs and the local importer insisted on torqueing up the teeter bolt such that each time I found the thrust bearings damaged.
1628786223441.png
You can check if yours are damaged by rotating them with your finger while applying an axial load, if you feel it is “lumpy” as the balls pass over the dents in the race then you need to replace them.
I replaced the damaged ones I found with a NKXZ15-2-XL with roller thrust bearings having a higher load capacity.
1628786274601.png
As Abid said there should be no play in the ELA setup because any sliding along the teeter bolt would be done by the radial needle rollers and they aren’t designed for that it might even damage the rollers or the sleeve.

Mike G
 

Burrengyro

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John H
To my knowledge there are two different types of teeter bearings for ELA rotors. The older design had two taper roller bearings housed in the teeter block (that’s the cube that is bolted to the hub bar). Later models had two NKX 15 combined radial and thrust bearings housed in a threaded "barrel" for chordwise adjustment. These had a needle roller bearing for the teeter bolt and a ball thrust bearing.
View attachment 1153081
For me personally for 0.5 mm of axial play, I’d just tighten the teeter bolt to close the gap by deflecting the teeter towers. 0.5 mm is about 120° rotation of the nut on a 1.5 mm pitch thread (which is what the teeter bolt has from memory). If you don’t like that solution your plastic shims would be OK for me since they go between the stationary side of the thrust bearing and the stationary teeter tower so there shouldn’t be any rotation. No need for steel but there’s nothing wrong with using steel shims.

If you have the older design shims or tightening the teeter bolt should also work.

For tightening you need a little pre load on the thrust bearings and to fix your shims so I just tighten the nut by hand as hard as I can without using a spanner.

Don’t overdo it, I balanced a couple of ELAs and the local importer insisted on torqueing up the teeter bolt such that each time I found the thrust bearings damaged.
View attachment 1153082
You can check if yours are damaged by rotating them with your finger while applying an axial load, if you feel it is “lumpy” as the balls pass over the dents in the race then you need to replace them.
I replaced the damaged ones I found with a NKXZ15-2-XL with roller thrust bearings having a higher load capacity.
View attachment 1153083
As Abid said there should be no play in the ELA setup because any sliding along the teeter bolt would be done by the radial needle rollers and they aren’t designed for that it might even damage the rollers or the sleeve.

Mike G
Hello Mike,
Many thanks for your time and for the info. I have the new hub bar with the needle roller bearings. It has about 200 hours done now. The bearings seemed good when I checked them. I used the plastic shims for a couple of days to remove the slop between the tower sides and the hub cube. I replaced these plastic shims with stainless steel shims I machined to suite. (The plastic shims did not show any deterioration after flying for several hours doing tests.) No slop now as per Fara's and your info. I strung the blades, done the tracking using q-tips taped to the rotor ends dipped red and green paint. The gyro flies well up to 70mph but still getting some stick shake.

I have been using feeler gauges to centre the hub cube between the tower side walls using the ELA barrel adjustment. Is this just a starting point to get the blade mass centre in line with the tower / main bearing centre line or the optimum position? Would really love a PB4 balancer.

As always, thanks for the info and experience shared. John H.
 

Greg Vos

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Im always chasing vibration, me and my mate Dave are fiddling to get the best compromise ..here is a vid inside the cabin of the Xenon


 

Mike G

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Dave H

I just realised that I never answered your question "Is this just a starting point to get the blade mass centre in line with the tower / main bearing centre line ".

Greg and Scandtours videos in another thread show that you can get a good low level of vibration without electronics but I suspect that they have a lot of hands on experience and feel for what they are doing and it took them some considerable time to develop those skills

If you haven't got a balancer or their skills you can only do what you are doing by trying to get the CofG of the rotor as near to the centre of the bearing as possible. So the first thing is to track your rotor because, as I pointed out somewhere else, tracking with the traditional shim method introduces a chordwise shift. So there’s no point in trying to centralize the rotor chordwise by stringing and measurement as you are doing before tracking.

I presume from your explanation use “Q tips” that you’re using the “flag” method during pre rotation. This is better than nothing but, if you can’t afford a PB4, I’d recommend that you invest in a pair of Tip LEDs from Smart Avionics, they’re cheap and you can track in flight.

Next you have to align/string the blades followed by a static rotor balance to establish the best spanwise balance. Perhaps stringing before tracking, it means the blade bolts are tightened for good. Then set the rotor chordwise to the centre of the teeter towers as you seem to be doing.

All this should get you into the ballpark and with a bit of luck you may get an acceptable result. However you must realise that all you are doing is theoretical and assumes that the manufacturer has made and machined all the parts perfectly, which he hasn’t. Also tracking using tip LEDS or any method that implies getting the tips of each blade to fly at the same height is also theoretical and any good helicopter mechanic will tell you that you often have to de-track the blade tips to get the smoothest ride.

You could also look at the frequency spectrum discussions here about using a smartphone to make sure that you really do have a 1/rev vibration, again I repeat myself but if you don't have a 1/rev leave the rotor alone.

Helipaddy and I tried to organise a visit to Ireland but we could never get it to work. With a country the size of Ireland if all the gyro owners got together you could buy a PB4 and a group training session between you, that way you’d have the balancer and a few guys who knew how to use it.

Mike G
 

Mike G

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Brian Jackson & Brian P

Your explanation is an over-simplification of part of what happens but a good one (guys don't need to have a degree in physics they just need to get a picture of what happens that works for them). I use a similar sort of description when I’m doing the rotor balance training.
If the rotor was offset to one side along the teeter (like your kid “slightly off centre”) as the rotor accelerates the centrifugal/petal force would throw it to the end of the play/clearance along the teeter bolt and the vibration would get worse and worse as the Rrpm increased. However at a certain speed, as Brian P said, the inertia of the rotating rotor takes over and dominates the situation such that it (the rotor) rotates about it’s CofG forcing the gyro mast to rotate about it.

Whether it would then move back along the teeter bolt to align its CofG with the rotor bearing axis and reduce the 1/rev is debatable but Chuck Beaty has explained that Ernie Boyette built some “slider teeter” systems (as MAC mentioned) and he reckons that this reduced the 2/rev vibration.

Mike G
 
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Burrengyro

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Dave H

I just realised that I never answered your question "Is this just a starting point to get the blade mass centre in line with the tower / main bearing centre line ".

Greg and Scandtours videos in another thread show that you can get a good low level of vibration without electronics but I suspect that they have a lot of hands on experience and feel for what they are doing and it took them some considerable time to develop those skills

If you haven't got a balancer or their skills you can only do what you are doing by trying to get the CofG of the rotor as near to the centre of the bearing as possible. So the first thing is to track your rotor because, as I pointed out somewhere else, tracking with the traditional shim method introduces a chordwise shift. So there’s no point in trying to centralize the rotor chordwise by stringing and measurement as you are doing before tracking.

I presume from your explanation use “Q tips” that you’re using the “flag” method during pre rotation. This is better than nothing but, if you can’t afford a PB4, I’d recommend that you invest in a pair of Tip LEDs from Smart Avionics, they’re cheap and you can track in flight.

Next you have to align/string the blades followed by a static rotor balance to establish the best spanwise balance. Perhaps stringing before tracking, it means the blade bolts are tightened for good. Then set the rotor chordwise to the centre of the teeter towers as you seem to be doing.

All this should get you into the ballpark and with a bit of luck you may get an acceptable result. However you must realise that all you are doing is theoretical and assumes that the manufacturer has made and machined all the parts perfectly, which he hasn’t. Also tracking using tip LEDS or any method that implies getting the tips of each blade to fly at the same height is also theoretical and any good helicopter mechanic will tell you that you often have to de-track the blade tips to get the smoothest ride.

You could also look at the frequency spectrum discussions here about using a smartphone to make sure that you really do have a 1/rev vibration, again I repeat myself but if you don't have a 1/rev leave the rotor alone.

Helipaddy and I tried to organise a visit to Ireland but we could never get it to work. With a country the size of Ireland if all the gyro owners got together you could buy a PB4 and a group training session between you, that way you’d have the balancer and a few guys who knew how to use it.

Mike G
Hello Mike,
Many thanks for the comprehensive reply. I am doing the trial and error method to get a better understanding of all the variables involved before going down the route of buying a PB4. I am a novice at rotor balancing, but, test by test, I am getting there and also getting a great appreciation for all the time and effort you have invested and shared to come to your level of expertise in this very difficult area.

Yes, I am using the flag method for now, basically trimming off the wick end of 2 q-tips, taping them onto the ends of the blades and wetting the plastic ends with artists oil paint to mark the flag. The more we do it, the closer we get. Thanks for the info on the Tip Leds from Smart Avionics. It's difficult to do the flag method without a helper. The Tip Leds could be a big help when working solo. I do a trial flight after every incremental change to get some measure of progress. I have to admit that I am finding the flag method gives only a rough idea of tracking accuracy. I have followed your posts and Scandtours and Gregs and all the posts on this topic for several years. Going through all the steps seems to be the best way for my "training" for now.

I have also followed with interest your GWS progress. Very impressive. If I recall correctly, you said you had a trim compressor failure during the trials. Same happened to me. The solution was cleaning the connections to the trim relay under the front seat of the ELA07S.

Thanks, John H.
 

Burrengyro

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Brian Jackson & Brian P

Your explanation is an over-simplification of part of what happens but a good one (guys don't need to have a degree in physics they just need to get a picture of what happens that works for them). I use a similar sort of description when I’m doing the rotor balance training.
If the rotor was offset to one side along the teeter (like your kid “slightly off centre”) as the rotor accelerates the centrifugal/petal force would throw it to the end of the play/clearance along the teeter bolt and the vibration would get worse and worse as the Rrpm increased. However at a certain speed, as Brian P said, the inertia of the rotating rotor takes over and dominates the situation such that it rotates about it’s CofG forcing the gyro mast to rotate about it.

Whether it would then move back along the teeter bolt to align its CofG with the rotor bearing axis and reduce the 1/rev is debatable but Chuck Beaty has explained that Ernie Boyette built some “slider teeter” systems (as MAC mentioned) and he reckons that this reduced the 2/rev vibration.

Mike G
I suppose we are assuming that the teeter bolt holes in the teeter tower were machined with the ideal accuracy to align all rotating masses where they should be? John H.
 

Greg Vos

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Burrengyro

Dave H

I just realised that I never answered your question "Is this just a starting point to get the blade mass centre in line with the tower / main bearing centre line ".

Greg and Scandtours videos in another thread show that you can get a good low level of vibration without electronics but I suspect that they have a lot of hands on experience and feel for what they are doing and it took them some considerable time to develop those skills

If you haven't got a balancer or their skills you can only do what you are doing by trying to get the CofG of the rotor as near to the centre of the bearing as possible. So the first thing is to track your rotor because, as I pointed out somewhere else, tracking with the traditional shim method introduces a chordwise shift. So there’s no point in trying to centralize the rotor chordwise by stringing and measurement as you are doing before tracking.

I presume from your explanation use “Q tips” that you’re using the “flag” method during pre rotation. This is better than nothing but, if you can’t afford a PB4, I’d recommend that you invest in a pair of Tip LEDs from Smart Avionics, they’re cheap and you can track in flight.

Next you have to align/string the blades followed by a static rotor balance to establish the best spanwise balance. Perhaps stringing before tracking, it means the blade bolts are tightened for good. Then set the rotor chordwise to the centre of the teeter towers as you seem to be doing.

All this should get you into the ballpark and with a bit of luck you may get an acceptable result. However you must realise that all you are doing is theoretical and assumes that the manufacturer has made and machined all the parts perfectly, which he hasn’t. Also tracking using tip LEDS or any method that implies getting the tips of each blade to fly at the same height is also theoretical and any good helicopter mechanic will tell you that you often have to de-track the blade tips to get the smoothest ride.

You could also look at the frequency spectrum discussions here about using a smartphone to make sure that you really do have a 1/rev vibration, again I repeat myself but if you don't have a 1/rev leave the rotor alone.

Helipaddy and I tried to organise a visit to Ireland but we could never get it to work. With a country the size of Ireland if all the gyro owners got together you could buy a PB4 and a group training session between you, that way you’d have the balancer and a few guys who knew how to use it.

Mike G
Mike what are the LED lamps you refer to for in flight tracking ? Can you upload a pic and how to attach? Your comments on the other thread much appreciated as always (we are lucky to have guys like you here) I’m petrified of vibration and thoughts of cracks developing on engine mounts and other places are always in my mind.

You said on the other thread it’s looks ok but you also added that the smart phone has vibration damping so it and I agree …if I could understand the balancer and use it to max potential I would buy one …I’m sure as a hands on type many guys here would like me then to balance there blades and the investment could well pay itself back ?

Me personally much better with hand tools than computers in fact I really can’t even exploit my new phone and don’t even know how to upload the vibration app your refer too let alone use it

Who knows if things improve and you do come to CT we can spend a full day our last meeting was rushed ( not your fault or mine) You obviously get a free flight over Cape Town as well 🍺
 

Mike G

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Greg, for tip LEDs look here.

I'm with you as a fellow non smartphone geek, I've struggled with all the computer upload functions of the PB3 & 4. Mark Burton of Smart Avionics always says "If Mike can manage to do it, anyone can".

Dave H
We are not only assuming that the teeter bolt holes are perfectly aligned with the rotor bearing axis spanwise but also that they are perpendicular to that axis to within 1 minute of angle for tracking, they never are.

My compressed air problem was a total compressor failure, my ELA is pretty old and the compressors were really cheap, not sure what they use today.

Mike G
 

Burrengyro

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Greg, for tip LEDs look here.

I'm with you as a fellow non smartphone geek, I've struggled with all the computer upload functions of the PB3 & 4. Mark Burton of Smart Avionics always says "If Mike can manage to do it, anyone can".

Dave H
We are not only assuming that the teeter bolt holes are perfectly aligned with the rotor bearing axis spanwise but also that they are perpendicular to that axis to within 1 minute of angle for tracking, they never are.

My compressed air problem was a total compressor failure, my ELA is pretty old and the compressors were really cheap, not sure what they use today.

Mike G
Hi Mike,
Thanks for the info. Spent the last few hours tracking using the flag method. There is 10mm between the high and low rotor after doing 2 pre-rotations to 200 rotor rpm to double-check. Quit due to gusting wind conditions. Will have to wait for calmer weather to verify and proceed. The tip LEDs will be ordered tomorrow.

Just wondering if a wider hub bar was used with a rhomboid-shaped hub bar teeter block and the teeter bolt hole machined at an angle of say 120 degrees rather than 90 degrees, the greater the teetering the angle of attack of the advancing blade would decrease slightly and increase slightly for the retreating blade, what effect would this arrangement have on the 2 per rev vibration? John H.
 

fara

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Hi Mike,
Thanks for the info. Spent the last few hours tracking using the flag method. There is 10mm between the high and low rotor after doing 2 pre-rotations to 200 rotor rpm to double-check. Quit due to gusting wind conditions. Will have to wait for calmer weather to verify and proceed. The tip LEDs will be ordered tomorrow.

Just wondering if a wider hub bar was used with a rhomboid-shaped hub bar teeter block and the teeter bolt hole machined at an angle of say 120 degrees rather than 90 degrees, the greater the teetering the angle of attack of the advancing blade would decrease slightly and increase slightly for the retreating blade, what effect would this arrangement have on the 2 per rev vibration? John H.

The flag method doesn't do much in a gyroplane in my opinion ... You cannot get the rotor to be at the same place as in flight (loaded and at full operational RPM).
Are you seeing a hop in the cabin? Is that why you are suspecting the tracking?
 
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Burrengyro

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The flag method doesn't do much in a gyroplane in my opinion ... You cannot get the rotor to be at the same place as in flight (loaded and at full operational RPM).
Are you seeing a hop in the cabin? Is that why you are suspecting the tracking?
Hi Abid,
Yes, a little bit of cabin hop. I used the flag method but used straightened paper clips secured with duct tape, with the wire ends protruding 10mm at the notch reference point on each blade and red and green paint to identify which blade was flying high at 200 rpm. I appreciate your point about 200 rpm and real flying rpm (310 - 350 rpm is typical for my ELA07S at my weight. The first test showed a difference of 15mm between blades. Finally got down to about 1 - 2 mm difference at shim size 0.20mm at which point high blade became the low blade. Recuding the shim to 0.19mm got the blades to track very closely at 200 rpm. Vibrations much reduced.

Could I ask does this change to the teeter block affect the blade alignment? Should I re-string at this point? Should the chord wire balance also be adjusted because of the shim under one side of the teeter block? I thought that the 0.19 shim was a very big adjustment based on the 200 rpm pre-rotation / flag method of tracking. I have also removed as much slop in the teeter tower, pitch and roll pivots as possible without causing restriction of movement. I don't want to transfer rotor head vibrations to other parts of the gyro and wrongly think I have a good set-up.
Feedback and guidance very much appreciated.
John H.
 

C. Beaty

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Most rotor shake problems devolve back to Bensen; necking the rotor down to 2.5 inches at the hub and the use of a rigid, square mast. If such an arrangement causes inplane flexing of the rotor, vibration free operation is impossible. Look up ‘The Birth of the Bell Helicopter” on U-tube.
The use of external struts to stiffen the rotor in-plane is one solution. Look up Joe Pires’ gyro on this forum.
 

fara

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Hi Abid,
Yes, a little bit of cabin hop. I used the flag method but used straightened paper clips secured with duct tape, with the wire ends protruding 10mm at the notch reference point on each blade and red and green paint to identify which blade was flying high at 200 rpm. I appreciate your point about 200 rpm and real flying rpm (310 - 350 rpm is typical for my ELA07S at my weight. The first test showed a difference of 15mm between blades. Finally got down to about 1 - 2 mm difference at shim size 0.20mm at which point high blade became the low blade. Recuding the shim to 0.19mm got the blades to track very closely at 200 rpm. Vibrations much reduced.

Could I ask does this change to the teeter block affect the blade alignment? Should I re-string at this point? Should the chord wire balance also be adjusted because of the shim under one side of the teeter block? I thought that the 0.19 shim was a very big adjustment based on the 200 rpm pre-rotation / flag method of tracking. I have also removed as much slop in the teeter tower, pitch and roll pivots as possible without causing restriction of movement. I don't want to transfer rotor head vibrations to other parts of the gyro and wrongly think I have a good set-up.
Feedback and guidance very much appreciated.
John H.

Hi John
0.19 mm is about 7 thou shim. That is on the high side but not unheard of. I do not think you need to re-string the rotor although if you did it won't hurt anything. If the vibrations you feel are in decent shape, I'd let it be till next time.

You cannot do anything about 2 per rev vibrations besides checking that your teeter bolt height from hub bar coincides with your blade disc CG in normal flight to a point but your teeter tower is machined and set by the manufacturer so you really don't have a choice there.

I have not seen any evidence of anything (slider, divider, rubber bushings or anything else) get rid of 2 per rev vibrations. A softer mast does isolate those vibrations from the frame below but that's about it. N per Rev are a fact of life and they are going to be there as long as dissymmetry of lift is going to be there and needs to be equalized using a flapping hinge. An offset flapping hinge could reduce it (ref: Proudy) but we are stuck with a teetering hinge by law.
 

mark treidel

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Mike G,
Are the rotor tip LED's available for the Stella Averso rotor blades?
If so, Exactly where do they mount? Do you have to remove any current
screws to install or add a screw to mount in an existing hole? (Do they come with screws to mount or do you have to use existing ones? )
Haven't looked at the blade ends yet to determine that but will next time I fly..
Thanks in advance for the info.
Mark
 

Mike G

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Mark
Even though I was the originator of the Smart Avionics tip LEDS I don't use them because about the time I pushed Smart Avionics to develop them I realised that I could track rotors with vibration rather than visually with tip LEDs which is a better solution, provided you have a dynamic balancer of course.
Here is an extract from some thing I wrote about the subject:

"The downside of these methods is that they are theoretical. They are based on the theoretical assumption that a perfectly tracked rotor will have the tip of each blade flying along the same tip path. Helicopter mechanics will tell you that the best tracked rotors do not always have identical tip paths and they often have to “de-track” blades to minimize vibration.

Here is a quote from an Enstrom document called “Tracking Main Rotor Blades “.

General: The purpose of tracking the main rotor blades is to obtain a smooth ride. This is accomplished by adjusting the blade track to reduce vibration. An out-of-track condition will produce a vibration, usually a one-per rev which is felt as a vertical vibration. However, for the rotor system to be smooth, it does not necessarily mean that the blades are flying in the same plane. With the advent of digital tracking equipment it has been found that the best ride is not necessarily a condition of the blades flying in plane, but in a track that gives the least magnitude of vertical vibration.

Here is a quote from a Robinson document called “Helicopter track and balance theory https://www.aviationpros.com/engines-components/article/10389059/helicopter-track-and-balance-theory......…

The term "rotor track and balance" is somewhat misleading, in that "track" or "tracking" refers to adjusting the blade tip paths to make them fly in the same rotational plane. This does not always result in the smoothest ride. Some airframe and blade combinations will ride smoother with a "track split." The desired end result of the track and balance job should be the smoothest possible ride.”

Also from DSS.......
  1. Tracking using Vibration Sensors

Users found the track conditions of the rotor directly related to vibrations in the airframe. Experimentally it was found that the vibration information could be used to adjust pitch links and tabs to produce minimum vibrations at all forward speeds. After this process was complete, the blade track could be measured optically and surprisingly the blades were not in perfect track! This lead to a quandary... do we want perfect track or minimum vibrations?

  1. Is Tracking of any value?

In the process of using these tracking methods and measuring the vibrations that resulted, users found that "perfect track" rarely produced minimum vibrations. Various theories have been proposed to explain this effect. One theory is that each blade has a slightly different shape, twist, flexibility etc. and only by putting them slightly out of track can these variations in lift be compensated. Another theory is that each blade produces a "turbulent wake" that the trailing blade must fly through. If alternating blades are set to fly high and then low, each blade will have "calmer air" to fly through resulting in smoother flight. This effect is more pronounced on aircraft with four or more blades on the main rotor."

So I've never fitted them to an Averso rotor but from memory they have a removable end cap that has some fixing screws that could be used to attach the standard Smart Avionics bracket. You could always make your own out of a piece of aluminium if you don't like plastic and Smart Avionics offer to make customized brackets.

Mike
 

Mike G

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John H
As explained elsewhere, on the classic Bensen teeter tower setup with an undersling of about 70 mm a 0.19 mm tracking shim will shift the rotor CofG about the same distance chordwise which would increase or decrease the 1/rev vibration depending upon where the CofG was to start with.
Without a balancer you are in the "suck it and see" mode so you can only suck it and see.

If you increase the roll and pitch pivot friction you will tend to decrease stick shake but increase cockpit shake, the vibration has to go somewhere, if it isn't in the stick it's in the mast/frame, there's no such thing as a free lunch.

Mike
 

Burrengyro

Gold Supporter
Joined
Dec 15, 2020
Messages
130
Location
Ireland
Aircraft
ELA07S and Montgomerie Bensen (project)
Total Flight Time
300
John H
As explained elsewhere, on the classic Bensen teeter tower setup with an undersling of about 70 mm a 0.19 mm tracking shim will shift the rotor CofG about the same distance chordwise which would increase or decrease the 1/rev vibration depending upon where the CofG was to start with.
Without a balancer you are in the "suck it and see" mode so you can only suck it and see.

If you increase the roll and pitch pivot friction you will tend to decrease stick shake but increase cockpit shake, the vibration has to go somewhere, if it isn't in the stick it's in the mast/frame, there's no such thing as a free lunch.

Mike
Hi Mike,
Thank you for the reply. I am finding out the hard way that everything you say about stick shake is true!!! The learnings are good. I made the mistake of shifting the chord wise location in increments which were too large and missed the target big time. Looks like from your info above, I should be moving in steps of 0.05mm at a time followed by a test flight to measure progress.
John H.
 
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