Push-pull rotor control cables?

Vance

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We shall see.

We shall see.

I will find out Chuck.

I don’t do noticeably worse well.

I am good at noticing things that others don’t because of the way I fly.

The plan is to stick to the factory maintenance program unless there is something that indicates a deviation from what they have found.

I feel some of the maneuvers I do at an airshow tend to put extra strain on the rotor system.

I fly low over the ocean often and corrosion has been a continuing with The Predator.

SMX is less than ten miles from the Shoreline of the Pacific so even in the hangar corrosion is a challenge.

My friend Phil will be doing extensive hundred hour inspections.

Thank you, Vance
 

cburg

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On my Rotorway it had dual cables for each movement for redundancy = 4 connected to the stick. This is a lot of accumulated friction...and you could hear it and feel it. Just over 100 hours.
 

Vance

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In my opinion the Cavalon rotor control system is not comparable to a Rotorway helicopter cable rotor control system Chuck.

The Cavalon appears to me to be well designed with high quality components.

The stick forces are light with no noticeable friction.

The pneumatic trim system takes a lot of the load off the rotor control system.

I didn’t know you few your Rotorway for 100 hours.

Regards, Vance
 

cburg

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Not saying they aren't. Just that the original question was about feedback.

"
What is the general consensus on using push-pull cables for primary gyro rotor control?"

Mines not so good. I had to lube mine yesterday after 110 hours TT on the Mosquito...just getting too stiff. I flew it today and it felt much better. The RW was really stiff before I lubed it. It was much better afterwards. I've had them on several other aircraft and had the same impression. I don't like them, based on my experience with my various aircraft. But we all know, that many aircraft use them and many folks are satisfied. It depends on the arrangement...bend radius, pressure, etc.

Some folks like you like them...and some folks like me don't...Ford versus Chevy. I don't know that we need to debate it...it's based on our own individual experience with completely different aircraft. I don't think they are bad, in some applications, I'm sure they work great. But I'm not the only guy who doesn't like them. We are both entitled to our opinions.

In my opinion the Cavalon rotor control system is not comparable to a Rotorway helicopter cable rotor control system Chuck.

The Cavalon appears to me to be well designed with high quality components.

The stick forces are light with no noticeable friction.

The pneumatic trim system takes a lot of the load off the rotor control system.

I didn’t know you few your Rotorway for 100 hours.

Regards, Vance
 
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Trendak&Son

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Artur,

Are you planning to be at the 2014 PRA Convention or are you talking 2015? We would love to have you at the convention coming up this year but I know that is only 2 months away and I know these things take time. Just Curious if you had plans to have one of your Gyro's at our convention this year.

Doug Barker
PRA Pres.

Artur will be at Oshkosh, but probably will not make it to Mentone.
Our distributor in US, Mike Bantum should be there to present our gyrosplanes and answer all your questions.

The new machine is prepared for the events and we hope we will make it there.
 

Trendak&Son

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Regarding the push/pull cables we are using on our new TERCEL, we would like again to underline the aerodynamic advantage of the control cables hidden under the mast cowling instead of creating drag in free air stream.

The results are confirmed by the first independent data we have from test flights.



We can now confirm first "real world", independent performance figures obtained by the first user, our customer from Germany. On his flight from our factory airfield to Germany he registered in cruise 160kmh (100mph) at 5160rpm on our Rotax RTS turbocharged engine. He was flying at app. 1000ft AGL, 1200ft AMSL at the moment of registration of the parameters.
The flight was with full fuel, two adult test pilots and some luggage, the take off weight was 560kg, data registered short after take off,
(there was strong head wind, ground speed 114kmh).

By comparable engine performance, lighter ZEN1 with the same cabin shape, simple mast cowling and control rods flies 140kmh (85mph).
This confirms our theoretical calculations of improvement by app. 20kph in cruise.



More about the flight here:

http://www.rotaryforum.com/forum/showthread.php?t=40981
 
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cburg

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Yes, there is an obvious advantage in packaging them, and they are considerably easier to engineer…that’s without question.

As mentioned, it’s common knowledge that if the bend radius and control pressures are not extreme they are a suitable approach.

From my experience the notion of not lubing them is out of the question…I’ve always had to lube them eventually...long before they are ready to replace.

But to reiterate one of my earlier comments…"Hypothetically" (but not possible)….if two versions were offered of an aircraft that were identical in every other way...I’d chose the one without the cables.

But…like the half dozen or so aircraft I’ve owned with them (I currently have one with and one without), there were not any other viable design options.

As I’ve mentioned on another thread…yours is the machine my wife wants me to but next…and I would not hesitate…cables or not…I simply love your gyro. I particularly like twin tail booms, the resulting low CG, wide wheel base, and prop clearance…among many other cool features. I'd prefer to buy one already built and out of the test phase.
 
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Vance

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Follow the factory recomendations.

Follow the factory recomendations.

I strongly recommend that anyone with push/pull cables follow the factory recommendations for maintenance.

If the people who designed and tested the cables recommend that they not be lubricated I have found for the best performance and life it is important not to lubricate them.

In my experience lubricating a cable that is not designed to be lubricated shortens the cables useful life and over time increases the drag.

Thank you, Vance
 

cburg

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Vance, I can’t argue with your advice and agree in theory (but not practice)…but…at what point…in your opinion, should a person change cables? I know mine get progressively worse unlubricated and intolerable at around 100 hours (or sooner). So I guess I should change cables prior to every 100 hours, say 50 hours? Actually if it wasn’t so difficult…I’d do it. The cost of a new cable is not the issue…it’s the labor.

I recommend getting a baseline tension measurement (when new) on your controls and track them over time. You will see a progressive increase in friction, then at some point you will begin to have sticky controls. The increasing friction is not too bad, but when they start getting sticky and jerky feeling this is when I consider them intolerable. Yes, it can still be safely flown…I just choose not to.

How close are these to breaking? I have no idea...but I hope they are far far from breaking at 100 hours of any kind of normal use. I consider the control cables to be the weakest link in my aircraft's design (I'm probably wrong but I can't get that notion out of my head).
 
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cburg

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I should mention, that I’m not saying every cable application has the same life expectancies (calendar & operating hours). I am certain that very one has a different life expectancy...radius, pressure, salty air, etc. are major determinants.

I’d like to think that manufacturers track and graph control friction & pressure as part of their testing protocols.

I’m sure that I be flying with cables for a long time…but I only tolerate them.
 

Vance

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Vance, I can’t argue with your advice and agree in theory (but not practice)…but…at what point…in your opinion, should a person change cables? I know mine get progressively worse unlubricated and intolerable at around 100 hours (or sooner). So I guess I should change cables prior to every 100 hours, say 50 hours? Actually if it wasn’t so difficult…I’d do it. The cost of a new cable is not the issue…it’s the labor.

I recommend getting a baseline tension measurement (when new) on your controls and track them over time. You will see a progressive increase in friction, then at some point you will begin to have sticky controls. The increasing friction is not too bad, but when they start getting sticky and jerky feeling this is when I consider them intolerable. Yes, it can still be safely flown…I just choose not to.

How close are these to breaking? I have no idea...but I hope they are far far from breaking at 100 hours of any kind of normal use. I consider the control cables to be the weakest link in my aircraft's design (I'm probably wrong but I can't get that notion out of my head).

I will follow the factory recommendations and replace the cables at 1,500 hours Chuck.

I will carefully monitor their performance as part of my preflight.

I suspect that cable breakage and drag will not be a problem if they are not lubricated and replaced at 1,500 hours.

I don’t know anything about the cables on your helicopter Chuck. In my opinion with a properly designed system if you have noticeable drag at 100 hours something is wrong and they should be replaced. It is a flight critical component so I feel it is not something to experiment with. If they are designed for lubrication by all means lubricate them. If they are not designed to be lubricated and they have been lubricated that may be a part of the problem. It is also possible that they were assembled incorrectly or improperly adjusted. I would not fly the helicopter until the problem is diagnosed and the fault is corrected.

Thank you, Vance
 

fara

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Hi Team Trendak:
I would be careful with relying on that speed figure unless you have a good solid calibration chart done specially given the indication of very strong headwind experienced by the pilot. I have found that in some trikes (including my previous company) and gyroplanes where installation/position errors for pitot tube and static port are not paid very careful attention to, the calibration charts I did resulted in as much as 22 mph difference when the indicated airspeed was 100 mph.
You comparison between Tercel and Zen1 would be valid if your pitot and static installations did not change and your instrument (ASI) was exactly the same (although instruments now-a-days have reduced their errors by a lot) and your props were setup exactly the same. The relative comparison in that case would be valid to show advantage of rods versus cables that are inside the fairing at the same indicated airspeed. A very good way is to measure fuel used in a given condition and time frame by two different configurations to estimate relative aerodynamic advantage of one over the other, keeping control variables the same like prop, engine, instrumentation etc. 16 mph however, sounds like a lot due to just that at 100 mph. Perhaps there is a whole package of improvements.
 
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cburg

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Thanks Vance, please obtain some baseline control forces and keep us posted on your cable life. I'm not being facetious, I really mean it. All of the aircraft I owned over the years with control cables were not new and I never had the luxury of having baseline data. You should be able to track it on a new machine. I'm very interested in the results. Again, the bend radius and the control force (both are aircraft specific) are crucial variables in making a comparison study.

It would also be nice to have destructive tensile testing data. A cable breaking (or complete jamming) really scares me.

I’ve had two catastrophic control system failures in aircraft (one certified and one experimental both FW) and as previously mentioned they left an indelible impression in my psyche.

In both cases I was able to land safely, but I feel lucky to be alive...but I did not need to land upside-down like Denzel did ;-)


I will follow the factory recommendations and replace the cables at 1,500 hours Chuck.

I will carefully monitor their performance as part of my preflight.

I suspect that cable breakage and drag will not be a problem if they are not lubricated and replaced at 1,500 hours.

I don’t know anything about the cables on your helicopter Chuck. In my opinion with a properly designed system if you have noticeable drag at 100 hours something is wrong and they should be replaced. It is a flight critical component so I feel it is not something to experiment with. If they are designed for lubrication by all means lubricate them. If they are not designed to be lubricated and they have been lubricated that may be a part of the problem. It is also possible that they were assembled incorrectly or improperly adjusted. I would not fly the helicopter until the problem is diagnosed and the fault is corrected.

Thank you, Vance
 

cbonnerup

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Gentlemen,
Would really like to know what specific mfg is supplying cables for the various models.
There are several. Custom Controls come to mind.
https://www.cccables.com/
Felsted makes a good cable (IMO).

I wouldn't use anything less than 3/8" push-pull, or design the controls so that a majority of force required is in the 'pull' mode.

Would also like to see the linkage for left-right control. Gotta' be something 'more elegant' than a bell-crank.

Thanks all.
Chris B.
 

cburg

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Two things I wanted to mention but forgot.

1.) A fish scale is all you need to obtain the control force measurements. That’s what I use.

2.) Calendar life & operating hour life are dependent on the type aircraft and how it’s flown. Lot’s of control inputs with a lot of travel versus minimal control inputs with little travel.
 

cbonnerup

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Agree completely,
A throttle control in a GA F/W sees very little use during flight.
Flight surface control is another matter entirely, particularly on an autogyro.
Less travel = generally more force needed.
 

cburg

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Mine went from a jerky 17 pounds to a much smoother 8 pounds after lubrication. No idea what it was when new.
 

cburg

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My controls with push/pull tubes will not even register on the scale (the needle does not move at all)....nearly zero on both axis.
 

Vance

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Two things I wanted to mention but forgot.

1.) A fish scale is all you need to obtain the control force measurements. That’s what I use.

2.) Calendar life & operating hour life are dependent on the type aircraft and how it’s flown. Lot’s of control inputs with a lot of travel versus minimal control inputs with little travel.

It is my observation that the drag on a push/pull cable depends a lot on the load Chuck.

Eight pounds of drag for a rotor control cable would be unacceptable to me and I would ground the aircraft until I discovered the problem.

I am not inclined to create an artificial standard.

The rotor control on the Cavalon felt very free and precise. I will let you know if the performance degrades over time. Either more play or more friction will be very easy for me to notice even if it is gradual.

The pneumatic trim takes a lot of the load off the cables.

I don’t know who makes the cables. I will have a look at them when I am next in Spanish Fork and try to remember to report on them.

Thank you, Vance
 

RotoPlane

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Mine went from a jerky 17 pounds to a much smoother 8 pounds after lubrication. No idea what it was when new.

Goodness.....those control loads are totally unacceptable. If this force is with the flight control link cable-end disconnected.....you need to replace that cable. Otherwise you should check if that force is due to moving a control weight or a trim-spring or perhaps something is binding.

I sure would not fly until I found the reason for that control load and fixed it.
 
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