Stick Pressure and Rotor Tuning

NoWingsAttached

Unobtainium Member
Joined
May 21, 2006
Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I had a Pair of Rotordynes that flew well, neutral stick, you needed to dial in a few pounds of back spring tension to get it fly hands off straight and level at 45-50 mph. They were 28' disk, 8" cord, 3* root-to-tip. They flew around 320 rrp at 45-50 mph, on an Air Command Tandem, all-up dry weight 550 lbs, and 180 lb pilot.

Put on a set of 27' Dragon wings, brand new, out of the box, they flew @ 280 rrpms, 45-50 mph, and very loose and noodleey at take off, around 220 rrpm. I took those off, and put them on a single place gyro as a 24' disk. Been flying them ever since and they still only turn 280 at 45-50 mph, straight and level. Imagine that.

Bought another, used, older set of riveted Dragons wings, as a 27' disk. Put them on the tandem. THey flew 340-350, and 380 with simulated passenger weight in the back seat of 120 lbs. The back pressure required to fly these things solo was so heavy that I set the spring tension for 3x what it needed before. It also needed left stick. With passenger weight in the back seat 120 lbs. it wore me out in a single, VERY tight pattern. I mean my arm hurt. What the heck? I figured out it must be the increased coning angle, resulting from the very flexible Dragon Wings. I must have the teeter bolt set too low on the tower. But a compensation for that will require machining the towers to accomodate the flappy blades.

I quickly realized this is no way to set up a gyro. Why not swap out the McCutcheon head from Ira's Air Command Low Rider, and put those $6,000.00 McCutchens on it?

I spent this weekend making the change. After talking with a friend of mine on the phone about hang testing and sorting out the Air Command in time for Wrens ROC, I came up with this test proceedure.

Luckily SOMEONE left the A/C on in the pilot's longe after they went off on a trip in the Seneca, you know who I am talking about out there....so the kitchen and the lounge were nice and cool. :)
They also left the hangar door open over night, so when I got there Saturday morning, is was nice n breezy, no sunshine heat build up. What a great start to a day working on my sweetie. :D
 
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NoWingsAttached

Unobtainium Member
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May 21, 2006
Messages
4,776
Location
Columbia, SC
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Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I used a cool tool i bought from Home Depot for just $8.00 years ago to be my assistant. With that, I hoisted up the gyro, climbed in and took an angle reading quickly from a reference point on the windshield edge. Then I got out, and added the correct number of iron weights to account for me, distributed in the cockpit until I reached the same hang angle. Voila, from this point on I could stand outside the ship and add or remove weight from anywhere I wanted to get the necessary variances and tolerances to find the range within the recommended scope of acceptable pitch angles. I used a drill to cut out a slot through which to put a velcro strap, magnets don't seem to work too well on aluminum gyros.
 

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NoWingsAttached

Unobtainium Member
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May 21, 2006
Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I used the rotor hub to hang the gyro from so it would easily hang true and I could keep it centered. I figured I may as well weigh everything as I went along, hence the Dillon Dynamometer, or, as you rednecks would say, the giant fish scale. Man, you guys catch some serious bass down here.
 

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NoWingsAttached

Unobtainium Member
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May 21, 2006
Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I checked the stick to verify that it was in the neutral center of travel
 

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NoWingsAttached

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Columbia, SC
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Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
It hangs with me and a full front seat tank of fuel (182# pilot + 7# dressed to fly + 33# fuel = 222# ) at the limit of 4*, and minimum front seat weight turns out to be 133#, no matter what happens in the rear seat or seat tank.

Time to change the head and rotors. Working alone, I didn't want he composite blades to touch anything, so I strapped them to the winch to keep them from rotating on the winch line freely.

No time to test these today, had to take Zhuzhu to the pool, and the store for some school clothes.

I like that the blades are red. I like that they are flat. I like that they have 15% more surface area, being an 8" cord instead of just a 7". I like that they are stiff. I hope I am not disappointed again.

I also concluded today that I can go one or two degrees higher on the rear motor mounts to improve the thrust line, right now it is one degree pushing the nose down. Not a big deal, but I am not going to leave that as it is for long. I already found the hardware, all I need to do is install it. No holes to drill, just bolts and aluminum attachemnts I have on hand.

I am pretty sure the new Arrow is not the ported-piston design, but rather one of the earlier models. But I won't know until I pull a jug off for certain,

Need to invest in a new timing light, I think the last Arrow was timed too far advanced, that might have helped it's early demise. THis one appears to be too far retarded. Details, this is not nearly so much of a problem
 

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NoWingsAttached

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Joined
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Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I flew the McCutcheons this evening for the first time. Now I remember why I liked the Rotordynes before. It has been 4 years 3 weeks 2 days 7 hours 43 minutes and 59 seconds since I last had them flying on the Air Command Tandem.

I pre-loaded the back trim spring with 1/2" of stretch for the first take off. It turned out to be a bit TOO much. Wow, what a HUGE difference between these two blade designs!

I landed, and completely relaxed the spring in the full back-stop position, took off again, and the gyro flew hands off at 45-50 mph. I added throttle, she climbed. I pulled back the throttle, the nose dropped and she descended. No side stick at all required to keep her straight. I haven't gotten to fine tuning the rotor yet, but at 50 mph the stick rotates in a circular pattern about 1/8 - 1/4" off dead center. You know, I've really got to do something about that crazy stick shake before I fly again.

So the need for left side stick pressure disappeared when I changed blades. This is very important. I've figured it out, have you? Tell me here what you think the problem was. I have provided all the info you need here to make a determination. Like one of those detective puzzle stories.
 
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Wiplash

Todd Noble
Joined
May 7, 2009
Messages
366
Location
Hudson, IN
Aircraft
Air Command 582 LowRider w/stab
Total Flight Time
Gyro - 101 as of 7-10-16
A lot'a good information here, thx for posting it.
 

NoWingsAttached

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Joined
May 21, 2006
Messages
4,776
Location
Columbia, SC
Aircraft
Air Command Tandem w/ Arrow 100hp; GyroBee w/ Hirth 65hp; Air Command Tandem w/ Yamaha 150hp
Total Flight Time
>350
I decided to take a hand-held GPS with me to check the AS Indicator accuracy. I also decided to kick it up a notch on the prerotator and shorten the length of take off. I looked down at the GPS and first read 8.6mph. Next GPS look was 20, the ASI showed the same, and the nose popped up. I saw something like 25 switching to 26 on the GPS, couldn’t read the ASI that well and switched my sight up to the RW.

I noticed I didn’t happen to be on the ground anymore.

As I pushed the stick forward and the GPS read 28 and rising quickly.

When the GPS said 55.6, the ASI said ~ 52. After several checks back and forth , I noticed the difference was about 4mph slower ground speed than AS.

I turned downwind, in what I perceived to be calm winds. I picked up 68.8mph on the GPS and the ASI showed it bumping just up over 60.

After further test runs I came to the conclusion that the ASI is roughly 2 mph slower than true, correcting for wind. Not bad. Not even worth adjusting.

Need to get the Rotor Tach pickup and magnet attached to the McCutcheon head so I know better what’s going on in the prerotation phase. Right now I am so new to STO with these things that I haven’t got a clue what speed they are at.

At the point when the prop starts moving the gyro fwd against locked brakes, it’s time to release the brakes and hit the throttle. Still need to get my timing down as to releasing the hydraulic actuator. The Pre-ro pedal control is on the right. Since the Pre-ro wants to torque the gyro to the right, I just need light left foot rudder to compensate for the rotor torque being applied with my right foot. If I go too far left, just lift the left foot and it swings back right again.

Have you ever seen a Saturday Night dirt tracker? They have accelerator pedals with a fixed strap piece that goes OVER your foot. In the event a throttle spring return breaks, you can LIFT your foot, and the pedal comes with it. If I make something like that for the left pedal, I can steer in BOTH directions with just the left foot, while the right foot engages the pre-ro hydraulic pedal. You know, if I make a stop on a hinge to push the cyclic forward against, and adjusted it just right, I could have a set disk angle that maintains the three-wheel stance as long as possible, for a tri-wheel take off, while not using excessive forward stick that would let too much air pass under the disk and delay rotor spin-up in the least. THe longer you keep 3 wheels on the ground, the longer you can engage the pre-ro, the shorter the TO. I've done these before, maybe I dont' even need such a gizmo to aid in the perfect forward stick adjustment maybe just to do it by feel and practice practice practice.

I had the timing right to do it in the Dragon Wings, but now I need to relearn the new power curves. The way these things take off 10 mph sooner than the Dragon Wings will take a few more trips down the RW to get down pat. I definitely have no worries about a tail-heavy take-off issue to deal with. The nose-down hang test put me at 75% total acceptable angle with no fuel in the fore seat tank, and 100% with fore fuel.

Need to sling the blades, stringing is not the best way to set these up. It is VERY difficult to get a repeatable sighting on the string over the teeter block. Useless on these things. Now I know why there isn’t a centering mark on the block. Why bother?

I ran out of daylight, so I will try slinging them tomorrow. Next comes the tracking video test and set-up Wednesday. Thursday I will adjust the centering. Oh, yeah, that’s what I’m talking about. A hub you can actually adjust on two planes, not just one. A couple more hours around the pattern after that and it should finally be ready to fly over to the lake this weekend for the Labor Gyro Fly-In at Fairfield Plantation.

I am blown away at how delicate the stick is, how deep I can bank and turn with so little effort. It’s like having hydraulic assist built into the cyclic. The stick is noticeably lighter than my Blue Bee with 24 ft Dragon Wings, flying at 75 lbs unslung weight plus 229 lbs slung weight, add fuel and pilot at 225 lbs, pushing 60 hp. Or maybe I just died and went to rotorwing Heaven, where there are no strings attached…and the deer and the antelope play (until I figure it’s about dinner time again).

I heard that McCutcheons are being manufactured again. Anyone have any info?
 
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