Rotor Blade Balancing and Tracking

WaspAir
Traditionally tracking in the helicopter world means getting the "blades flying the same path in flight" as you say. However modern electronics has allowed us to measure and demonstrate what many old time helicopter mechanics kept telling us that "the smoothest ride often results from a track split".
You don't have to believe me here are 3 quotes from Enstrom, Robinson and DSS micro who are pretty well established in the helicopter world and probably know what they're talking about.

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

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.......https://www.dssmicro.com/theory/th_hist_rotor_smoothing.htm

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?
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.


The RTB procedure that I developed for Smart Avionics PB3/4 users tracks the rotors using vibration during the balancing process.

Mike G
No dispute on the fine details. I use a strobe and Chadwick for my Bell and also go for minimum vibration, adjusting sweep, tip weight, and trim tabs through flight testing after static balance is dialed in. I was responding to the question of whether forward flight skews the results because blades advance and retreat, and at that level of description, any split is small potatoes in my experience. Forward flight is the only regime that really matters for a gyro since we don't sit around in a hover.
 
Mike has just completed an Australian tour of 5 of our states training about 30 people over 17 days. I'm surprised that he even has the strength to operate a keyboard after the hammering we gave him down here. Amazingly good course with much interaction with a very knowledgeable and enthusiastic presenter.
Australia's Australian Sports Rotor Association paid for him to come to Australia. ASRA also purchased some PB4's which can now be loaned out to ASRA members who have completed his course.
Perhaps you Yanks (Aussie term of endearment) could convince your PRA to do something similar? It certainly makes rotor and propeller balancing a science and not black magic. There really isn't any debating the figures or the results once you have followed the process to completion.

Regards.......Chook.
 
Mike has just completed an Australian tour of 5 of our states training about 30 people over 17 days. I'm surprised that he even has the strength to operate a keyboard after the hammering we gave him down here. Amazingly good course with much interaction with a very knowledgeable and enthusiastic presenter.
Australia's Australian Sports Rotor Association paid for him to come to Australia. ASRA also purchased some PB4's which can now be loaned out to ASRA members who have completed his course.
Perhaps you Yanks (Aussie term of endearment) could convince your PRA to do something similar? It certainly makes rotor and propeller balancing a science and not black magic. There really isn't any debating the figures or the results once you have followed the process to completion.

Regards.......Chook.

Certainly not a bad idea for PRA to do. I will bring that up next BOD meeting
 
Last I checked (yesterday) the PB4 is still unavailable. Seems they have parts supply issues.
 
Sv.grainne
Contact Mark Burton at Smart Avionics.co.uk. His website has a fair amount of information.
Mike G
Will do, thanks. I'm thinking we could get PRA to solicit donations for purchase of the device then persuade Mike to come over again in conjunction with Bensen Days, PRA Convention, etc and train a group of folks on its use.

I would certainly donate and be willing to attend training on the use of the device.
 
Last I checked (yesterday) the PB4 is still unavailable. Seems they have parts supply issues.

I have two here at Zephyrhills airport. One is for the company and one belongs to a friend who has not flown his gyroplane in 4 years. He may be willing to sell it. I should ask. It probably needs software update.
Using PB4 is one of those things that you have to keep up with. If you don't use it for 6 months, you won't remember and have to re-figure it out. At least I do. But if you understand the basic concepts, you can muddle your way around it and get it. It is not just the tool itself. It is also knowing how to use it correctly. It reduces the solution down step by step till you get it right. Getting move lines made for your make/model helps a lot because if you do not have them, you will spend a lot of time getting them made first to know how your rotors behave.
In our case Averso dynamically balances the rotors there but of course that is on their test bed. However, what that usually means is that spanwise balance is good so I ignore spanwise suggestions in PB4 solutions and concentrate of tracking or chordwise shift first.
 
A friend has an older model Chadwick balancer. Problem is its too large to fit inside a Mosquito helicopter.

I'm heading out of town the end of the week. When I get back I'm going to try a couple more tweaks to see if I can sort things out.
 
I have two here at Zephyrhills airport. One is for the company and one belongs to a friend who has not flown his gyroplane in 4 years. He may be willing to sell it. I should ask. It probably needs software update.
Using PB4 is one of those things that you have to keep up with. If you don't use it for 6 months, you won't remember and have to re-figure it out. At least I do. But if you understand the basic concepts, you can muddle your way around it and get it. It is not just the tool itself. It is also knowing how to use it correctly. It reduces the solution down step by step till you get it right. Getting move lines made for your make/model helps a lot because if you do not have them, you will spend a lot of time getting them made first to know how your rotors behave.
In our case Averso dynamically balances the rotors there but of course that is on their test bed. However, what that usually means is that spanwise balance is good so I ignore spanwise suggestions in PB4 solutions and concentrate of tracking or chordwise shift first.
I would be interested in the unit if he wants to sell it. Or perhaps PRA would be.

I would like to see one in Texas as we have a pretty decent number of gyros in the state. Anahuac had a going club, Fainting Goat lots of Machines, Dayton has a nice collection, Aviomania Dealership near Canton, more everyday (week?)
 
I would be interested in the unit if he wants to sell it. Or perhaps PRA would be.

I would like to see one in Texas as we have a pretty decent number of gyros in the state. Anahuac had a going club, Fainting Goat lots of Machines, Dayton has a nice collection, Aviomania Dealership near Canton, more everyday (week?)

One s already in Texas. An AR-1 owner has it. I don’t know if he would share it.
 
I want one and after training on its use want to make it available.
 
No dispute on the fine details. I use a strobe and Chadwick for my Bell and also go for minimum vibration, adjusting sweep, tip weight, and trim tabs through flight testing after static balance is dialed in. I was responding to the question of whether forward flight skews the results because blades advance and retreat, and at that level of description, any split is small potatoes in my experience. Forward flight is the only regime that really matters for a gyro since we don't sit around in a hover.
WaspAir
Sorry if I was "teaching you to suck eggs". You obviously knew all that anyway.
Mike
 
One s already in Texas. An AR-1 owner has it. I don’t know if he would share it.
I trained Jason Knight and a few others in Houston back in 2019, I'm pretty certain they had one or two PB4s.
Mike
 
I trained Jason Knight and a few others in Houston back in 2019, I'm pretty certain they had one or two PB4s.
Mike
Mike:

Dayton Dabbs in Taylor, TX has one and has offered it to me to use. I downloaded the tutorial and manual and will work on those first!
 
Hi everyone, I was curious if anyone here had any thoughts about applying rotorcraft track and balance procedures to wind turbine blades? Of course, they don't have trim tabs, but suppose they did. They do have pitch control... Just curious if anyone has an impression about the utility of using RTB on these rigidly mounted blades? They do flex quite a bit, and usually are misaligned both in pitch and aerodynamically. Any thoughts would be appreciated. Thanks! Joe
 
Hi everyone, I was curious if anyone here had any thoughts about applying rotorcraft track and balance procedures to wind turbine blades? Of course, they don't have trim tabs, but suppose they did. They do have pitch control... Just curious if anyone has an impression about the utility of using RTB on these rigidly mounted blades? They do flex quite a bit, and usually are misaligned both in pitch and aerodynamically. Any thoughts would be appreciated. Thanks! Joe
There is no doubt that everything benefits from being in balance.
Gyro rotors that are out of balance are harder to coax up to flying speed (from low rpm) than balanced blades, so I would imagine the same effect on a wind turbine.

wolfy
 
They have to be balanced, the rpm's can be very high.
You find the heaviest blade, then find the longitudinal point where it balances like a teeter totter and mark it.
Add weight to the lighter blades to make them the same weight and have the same balance point (teeter) that you marked on the heavy blade.
Lead solder works well because you can use a drill bit the same size as the wire and just put the weight in with some CA glue, or epoxy.
Add the weight near the leading edge, but don't drill the spar.....
Some blades have a hollow spar and you can place the weight inside the spar.
 
Question. What is CA glue?
 
CyanoAcrylate would be my guess (as in Superglue)

I was picturing much, much bigger (and relatively slow turning) blades for a wind turbine, so that the drill bit and solder approach wouldn't be practical for the large masses involved.
 
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CyanoAcrylate would be my guess (as in Superglue)

I was picturing much, much bigger (and relatively slow turning) blades for a wind turbine, so that the drill bit and solder approach wouldn't be practical for the large masses involved.
Consumer/Home type wind turbines generally have blades smaller than 6ft.
the side loading is very high with anything larger and then the tower has to be very strong with huge footers and,or guy wires...
Lead tire weights are easily melted and cast into ballast too.
I also have tungsten powder for critical balancing of small airplanes...
The holy grail is depleted uranium, hard to get now.....They use to use it in scotch tape dispensers!
 
I am interested in large turbines. I understand they already do some mass balancing, and generally modern turbines can do some vibe control with individual pitch control. I was wondering if active tabs (if they existed) would give you a significant benefit in additional vibe control. Wind turbine blades are a little different animal, being rigidly mounted and generally torsionally stiff, but I would think having tabs would be of great benefit, both with increasing lift at low wind speeds and adding additional aerodynamic balancing at higher speeds. Figured the enthusiasts here might be able to answer this question better than me... Thanks! Joe
 
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