Fixed Pitch Blade Fix..... - Page 2 - RC Groups
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May 28, 2004, 12:49 AM
Blade Springs "Rock"
With all that, said and done.
Last edited by Geoffrey109; May 28, 2004 at 07:47 PM.
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May 28, 2004, 07:47 PM
Blade Springs "Rock"
Sorry for the Heighten Excitement I have posted over this new discovery. I flew again today, I got about four flights in and I must say this is the best I've ever seen, I was getting some serious glitching but troubleshot it to weak battery's. I exhausted four batteries in the continuous hover practice without landing, about 7 to 8 minutes with the stock nimh 700 mAh, sure the Johnson 250 was hot, very hot.......but it no less performed flawlessly, I was able to easily hover at head height to check blade tracking and honestly a stick off hovering! I have not yet been into forward flight due to space, but I would decend to about six inches, and give it the gas to six, seven eight feet and the tail was stuck, and I mean no wobble or adverse flight characteristics at all, and desend with complete control. The Li-poly battery was the most power on demand and did rest the heli after about a 8 minute hover, then after another 5 minutes of cool down exhausted the battery, must have been over another 10 minute flight easlily......the blades are tracking perfectly and no vibrations what so ever....I am very pleased and hope everyone here finds this helpful.
May 29, 2004, 03:16 AM
Registered User
Yes...geoff and I have made's one big happy forum again.

Geoff...would you know how easily this would be applicable to a Dragonfly or Hummingbird head.

I would still like to see some close up photos. I can't quite work out how it fits, and not having an Aerohawk, I can't really picture your description. It's definitely an interesting idea, but I'm not sure how to apply it to my DF.
May 29, 2004, 05:50 AM
Blade Springs "Rock"
I have looked at most of the other helicopter's rotor heads as well, and come to the conclusion that if you are flying with a stiffener of some sorts, then a spring can be fashioned and installed. I will really try to get some clear photos today of it and exactly how it could be applied to other helicopters. Once you realize how simple it is, you will be amazed at how easily you can make them.
May 29, 2004, 09:19 AM
Blade Springs "Rock"

Close-up's of the Spring

Since I didn't have a macro function on my camera, I just used the magnafiying glass....I hope you can see how this would work on almost all micro helicopters.

The Aerohawk: Simple it fits into the blade grip, around the 2mm spacer.

Hummer's/Dragons: If you have a blade stiffener setup, you simply can fashion the spring the exact same way, but instead of the 90 degree bend up, you bend down, and your spring can be inside the stiffener bolt, the other end can be bent down to capture the rotor hub stiffener plate.

Here's the Photos.....
Last edited by Geoffrey109; May 29, 2004 at 09:51 AM.
May 29, 2004, 09:32 AM
Blade Springs "Rock"
Here's some pretty good shots too....

Aerohawk Owner's: Like90 blade setup tip.....add another washer to the 2mm spacer inside the grip. I believe this to be a correction for the gap being slightly larger then 2mm. I also believe this to be a large part of my Helicopter's extreamly stable hover, it's got a really nice coning effect, making it really stable and smooth.
Last edited by Geoffrey109; May 29, 2004 at 09:55 AM.
May 29, 2004, 03:48 PM
Blade Springs "Rock"
Living Room Hover......prior to today, I couldn't get enough control to actually get it to fly in about a 48" diameter without crashing into the couch or something on take-off, until now.....I was checking over the helicopter blades and noticed a rather sloppy blade bolt hole, probably from all the crashes, I went to the hardware store, and found a 3/16 Nylon Spacer about 1" long and some 4-40 bolts about 5/8" long, I drilled out the blades and superglued the spacer in place, trimmed, sanded smooth then installed each blade. Simply I cannot believe it for myself the difference it made. The Aerohawk spun up nicely.....there's a slight transistion vibration just before full speed lift off then straight up it went! I really thought the helicopter was smooth prior to this and's perfect...I had about a three minute hover about two feet up then gently landed and called it a day.....the most simplist things, can make a giant difference.....It's time to take the plunge into forward flight!

Please note: These blades are loose, the springs hold them in perfect alignment, the nylon spacers just make it even smoother under the dynamic's one notch better and the results......perfection.
May 29, 2004, 04:03 PM
4-D traveller
glxy's Avatar
Last edited by glennT; Jul 19, 2004 at 03:03 PM. Reason: results proven
May 29, 2004, 04:13 PM
Blade Springs "Rock"
I cannot garentee anything. I can however garentee that without it...the same results will happen. Wobble, Retreating blade stall......and crash. To consider what it has done verses, the possible in flight breakage is way worth the addition. I have only about thirty minutes of hovering time with the springs installed so far, and can only report flawless results.....either way, the risk of crashing is going to happen. I'd like to know why you think this is so dangerious? You know in the real helicopter world these items would be considered time change items anyway. Simply they are expected to only last for so long, then be replaced prior to failure. I have enough wire, for 1.69, to make a hundred springs.
May 29, 2004, 04:27 PM
4-D traveller
glxy's Avatar
Last edited by glennT; Jul 19, 2004 at 03:03 PM. Reason: results proven
May 29, 2004, 05:12 PM
Blade Springs "Rock"
Flight Safety issues with the spring noted. I have alot of this music wire, the force it has to hold, verses it's strenght was considered, and the material, .039 diameter, In my opinion is 1000% safe. Although this is my frist test of this diameter wire, I have not been successful in actually breaking the wire. I have 8" wire cutters to cut it, and with considerable force at that. The shear fact that it has solved the micro blade problem out ways this issue of safety. There is no way this spring will break, in flight or otherwise, In fact if poses no greater risk then flying into yourself or other's. If you look at the way the spring is attached to the Aerohawk blade bolts, inside the grip, the blade bolt would have to come off before the spring.....there is no way my blade bolts are flying off. These are the Jesus Nuts on the micro helicopter, and believe me they are not loosing up on my helicopter, nor with anybody else's helicopter's in flight currently.
Last edited by Geoffrey109; May 29, 2004 at 05:19 PM.
May 29, 2004, 05:51 PM
Registered User
Lynxman's Avatar
I don't see how the spring could possibly come off or break during a flight. Everything else in the rotor system is weaker than the spring. You have come up with a clever and safe solution, Geoffrey!
May 29, 2004, 06:21 PM
Registered User
Bubblehead's Avatar
From "Principles of Helicopter Flight" by W.J. Wagtendonk (a standard text for full sized heli pilots, pages 92 and 93, retreating blade stall happens when the aircraft is in forward flight. The forward airspeed reduces the effective airspeed over the retreating blade, and increases the effective airspeed over the advancing blade. This imbalance causes down flapping on the retreating blade and up flapping of the advancing blade. This raises the angle of attack of the retreating blade and reduces aoa of the advancing blade somewhat equalizing lift on both sides. If the retreating blade aoa becomes > than stall aoa, the retreating blade stalls starting close to the root of the blade. If forward speed continues to increase, additional span of the retreating blade will stall.

In summary, retreating blade stall only happens in forward flight. In a hover neither blade is advancing, neither is retreating, both see the same airspeed, both see the same aoa.

I don't question the effectiveness of your fix. I have not had the problem you describe with my XR-1 (Aerohawk clone). But I do not see what retreating blade stall has to do with flight in a stationary hover! B-T-W pg 132 describes the symptoms of retreating blade stall as "rotor roughness and vibration. As the stall develops on the retreating side, the nose pitches up and the helicopter may roll...most often to the left."

You have the symptoms and the cure but your diagnostics seems flawed.
May 29, 2004, 06:57 PM
Blade Springs "Rock"
You are so correct in this. But the only way a fixed pitched blade helicopter that developes the systom of blade lag, is to describe it as blade stall. The wobble is of course caused by a blade lagging, this is considered to me as a classic blade stall, or retreating blade stall in all respects of the cause. Thanks for pointing out that this is actually a blade lag, instead of a blade stall, which occur's in real helicopters, and in these Micro Helicopters, blade lag or retreating blade stall are.....terms of the same outcome, crash, or in real helicopters, death. Please believe, that what you quoted is true, and I've flown helicopters, UH-1N's for twelve years as a test flight engineer, That's all I did is smooth rotor's for the Airforce, This is a classic Rotor Retreating Blade stall, due to the retreating blade lagging the light weight blades cannot keep up with the torque of the main rotor, thus lag, causing vibrations and wobble........classic systoms of the same cause...and the outcome is always crash....
Last edited by Geoffrey109; May 29, 2004 at 07:21 PM.
May 29, 2004, 07:19 PM
Registered User
terryk's Avatar
I think I understand what causes the wobbles but this blade stall buisiness is confusing.It seems to me that in a calm day hover that when a blade starts to lag, (as might happen when the rotor spins up) doesn't the angle of attack of the blade actually reduce a little? Which would make it less inclined to stall.

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