Stick shake video

[Mayfield]

I have a request of forum members.

Could some of you please post videos of your stick and airframe in flight? Videos of the stick at both pilot stations would be great.

I would like to know if my expectations vis-a-vis stick shake and airframe shake, are reasonable.

Although I fully understand that a rotating rotor will induce vibrations into the system, it is also my thought that vibration, in the controls, and the airframe, can be minimized.

I have always thought of vibration as potentially destructive and sometimes a warning of wear or other damage.

A description of the aircraft and some rotor specs would help me understand what I am seeing with your videos.

Although I am primarily interested in tandem gyroplanes in the 1200 to 1320-pound range, lighter or heavier gyro videos would be useful.

I am appreciative of any information you are willing to share.

Jim

 

[okikuma]

Jim,

Here's a nice video of Wing Commander Ken Wallis flying one of his gyroplanes. Note the minuscule amount of cyclic shake if any. This is because Wallis did not use long narrow rotor hub bars. His rotor blades attached directly to the rotor hub. Wallis' rotor head mount also has a slider mechanism of sorts. Lastly a tubular mast. All three contributed to minimal cyclic shake.

Wayne

 

[Mayfield]

Thanks Wayne,

I am familiar with the Commander's work. I am more interested in heavier tandem gyros. I have found a few videos online featuring AR-1, TAG, and Auto Gyro machines.

I am hoping I can see what current owners are experiencing.

For example, I found these online. To me it is an unacceptable shake. Am I being unreasonable in my expectations? I am very interested in the opinions of several contributors on this forum.

or

Jim

 

[AirCommandPilot]

Here's one of my Air Command with 25' Skywheels, and a Yamaha RX1. (just after the 23 min mark, I release the cyclic to show the smoothness.)

 

[Mayfield]

Here's one of my Air Command with 25' Skywheels, and a Yamaha RX1. (just after the 23 min mark, I release the cyclic to show the smoothness.)

Thank you Bobby. What do you think, subjectively, of the cabin hop and stick shake? The shake did not look bad to me, the cabin hop a little more. Roughly how much does your AC weigh?

Jim

 

[okikuma]

Jim,

On your old modified Parsons, how was the cyclic stick shake? What manufacturer of rotor head and blades?

Wayne

 

[Mayfield]

As some of you are aware I am contemplating a foray back into my all-time favorite mode of flight, gyroplanes.

I really like my little Gobosh ELSA airplane, but frankly it is too darn easy to fly. It takes off in much less distance than most gyros, touches down at less than 35 knots, sips gas at 4.5 to 5 GPH, cruises at an honest 100 knots, and is comfortable. It doesn't have rotor blades!

Jim

 

[Mayfield]

Jim,

On your old modified Parsons, how was the cyclic stick shake? What manufacturer of rotor head and blades?

Wayne

That was back when the earth was young and pterodactyls ruled the skies, Wayne. But my memory says I got it down to an acceptable level.. I used a Boyette head and 30 foot Sky Wheels.

 

[Abid]

This is balanced with a PB-4 in test flying when new. This should hold its balance for a long time. When people have work done on the rotors or rotorhead or have to change rotors or things in the rotorhead because somehow they screwed something up, it definitely requires a dynamic balancing again but usually they never do it because they don't know how to.

 

[Mayfield]

Thank you Abid. So it is possible to get a smooth stick and cabin.

Jim

 

[Abid]

Thank you Abid. So it is possible to get a smooth stick and cabin.

Jim

Every time. Absolutely. It just requires time and some work

 

[500e]

We see helicopters like that, there is no excuse poor maintenance

 

[j4flyer]

Abid I’m curious as to how you achieved such smoothness. Do you have a video out on balancing already ? If not, would you consider producing one ? Thanks much

 

[Abid]

Abid I’m curious as to how you achieved such smoothness. Do you have a video out on balancing already ? If not, would you consider producing one ? Thanks much

Dynamic balancing. New controls. No slop. Almost every new AR-1 that I dynamically balance new is similar to this. May be this one was a bit extra-ordinary but not that far off.

 

[j4flyer]

Would you video one of your dynamic balancing sessions? I find your elimination of shake very interesting. What equipment do you use ? Thanks again

 

[Abid]

Would you video one of your dynamic balancing sessions? I find your elimination of shake very interesting. What equipment do you use ? Thanks again

My video would be boring. I use a PB-4 but I have templates for AR-1. Over balancing the first few I know what to do to get what effect.

Added/Edit: This is the same as having polars. If you don't have this for a set of rotors on a specific kind of rotorhead, then you have to develop them by artificially disbalancing using washers or moving chord a known amount or changing pitch (tracking) by a known amount (each separately) and seeing what effect it has. That becomes a longer job. When some people ask me a few times here to help them balance their Magni or their ELA etc. I generally refuse because they will not like to pay me to develop these first then balance their only single rotor. I will be too expensive. If they already had that from their manufacturer the job is quicker and I would do it but generally they never have it and I don't love other brands enough to develop it for them. From what I know balancing is precise and not an art but a pretty methodical science. The way I saw people doing it without learning dynamic balancer usage was a shot in the dark. Really quite useless imo. I brought Mike Goodrich to our facility at least twice to give courses on balancing (5 to 6 people at a time).

Also besides the dynamic balancing at the rotor if you want to reduce cabin vibrations then you need to put an accelerometer at the seat frame and you have to make changes to reduce that as well which sometimes means accepting slightly less perfect balancing at the rotor.
Should not ignore the effect of tight non sloppy controls on stick shake also. That makes a big difference.
Even then when you don’t fly your gyro for a few days and come fly it, it may have shake for the first flight because rotor blades took a set.

 

[okikuma]

On a different thread, I uploaded the Vietnam era U.S. Army film Chopper Pilot. Starting at 13:50, note the "cabin hop" of the Bell H-13 instrument trainer.

Wayne

55 Years Ago... Chopper Pilot

55 Years Ago... Chopper Pilot U.S. Army Film Training Of Helicopter Pilots: Preflight and Flight Training provided By The Warrant Officer Candidate Program At Ft Wolters, Texas; and Advanced Training at the Army Aviation Center, Ft Rucker, Alabama. Today all of U.S. Army Rotor Wing...

www.rotaryforum.com

 

[WaspAir]

I never felt cabin hop in my Bell 47G-3B-1 (same airframe as the TH-13T) until I took a bullet in the rotor blade. It was pretty obvious then.

 

[rancherman]

Here's one of my Air Command with 25' Skywheels, and a Yamaha RX1. (just after the 23 min mark, I release the cyclic to show the smoothness.)

I watched the whole video Bobby. Nice presentation.

Hey, If that oil pressure sender's life is short lived, (I've had issues with those can-style, mounted radially to engine shake) you may find that mounting the sender to the frame, and running a flex hose back to the block will give you longer service life.
They have a paper thin plastic bushing on the pushrod to the diaphragm- between that getting 'sticky'.. and the potentiometer part of it getting it's liver shook loose.. which is a precursor to the crimp seal failing.. (yeah, I've seen just about every type of failure with those.. otherwise good units mounted in a more isolated fashion)

 

[rancherman]

My video would be boring. I use a PB-4 but I have templates for AR-1. Over balancing the first few I know what to do to get what effect.

Added/Edit: This is the same as having polars. If you don't have this for a set of rotors on a specific kind of rotorhead, then you have to develop them by artificially disbalancing using washers or moving chord a known amount or changing pitch (tracking) by a known amount (each separately) and seeing what effect it has. That becomes a longer job. When some people ask me a few times here to help them balance their Magni or their ELA etc. I generally refuse because they will not like to pay me to develop these first then balance their only single rotor. I will be too expensive. If they already had that from their manufacturer the job is quicker and I would do it but generally they never have it and I don't love other brands enough to develop it for them. From what I know balancing is precise and not an art but a pretty methodical science. The way I saw people doing it without learning dynamic balancer usage was a shot in the dark. Really quite useless imo. I brought Mike Goodrich to our facility at least twice to give courses on balancing (5 to 6 people at a time).

Also besides the dynamic balancing at the rotor if you want to reduce cabin vibrations then you need to put an accelerometer at the seat frame and you have to make changes to reduce that as well which sometimes means accepting slightly less perfect balancing at the rotor.
Should not ignore the effect of tight non sloppy controls on stick shake also. That makes a big difference.
Even then when you don’t fly your gyro for a few days and come fly it, it may have shake for the first flight because rotor blades took a set.

I like that explanation 'blades taking a set'...
and probably to a lessor degree, the airframe itself? I can only imagine, that natural and welcome oscillations would be different from a long parked bird, as to one that's had a chance to 'stretch it's legs'?