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Old Jul 06, 2004, 07:15 PM
Aerohawk in London
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London
Joined Jun 2004
62 Posts
Nice, thanks
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Old Jul 14, 2004, 12:38 PM
Registered User
Oslo, Norway
Joined Jul 2004
16 Posts
I came across this thread and found it really interesting. I suspect that Geoffrey's discovery/ invention illuminates something much more fundamental than wobble in a spesific heli model.

I am new to model helis, I've had a Raptor 50 for 4 weeks and am learning to hover nose in at the moment. I have seen wobble in my own and other people's helis many times. In mine it happens at certain rotor speeds, and not others. It is an oscillation with a frequency around 3-5 Hz when rotor speed is approx. 1400rpm, equalling 23Hz.

As far as I understand the dogma is to tighten the grips so that the friction is pretty stiff, this prevents tail strikes (seems reasonable). The object is to let the blades align themselves when they spin up, but never move in flight after this, right?

To me it seems rasonable to assume that wobble is a complex fenomenon involving the whole airframe, where lead-lag movement of one or both blades is involved.

If the blades really move in the grips during flight of any model heli, would it not be a great idea to experiment with different forms of movement control? Springs on a glow heli, totally loose blades with lag stoppers, try some dampers from a model car, rubber blocks etc?
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Old Jul 19, 2004, 02:44 PM
micro mechanic
aerohawk1's Avatar
Oz, Kansas
Joined May 2004
2,303 Posts
If you are tired of your heli pitching up,here you go!

Over the weekend,I installed;Like90's wooden blades,swash ball,and "Geoffrey's Amazing Head Spring Mod".

How much more stable can this thing get?!
It's F'in amazing!
Without the springs,it is really stable...however,any aggresive manueveing starts the dreaded death wobble.
With springs,I just can't get this thing to crash!
Even in high wind gusts(15mph),which would have sent the stock chopper to it's death,it does NOT pitch up!
It remains level and just gains altitude.

This is it,guys...
the ultimate fix!

Aero
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Old Jul 19, 2004, 02:49 PM
Blade Springs "Rock"
Central Coast, CA
Joined Apr 2004
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I too had some agressive in flight manuevering, and without a doubt the springs would have saved it from pitching up, I crashed not due to pitch up. What I was seeing was climb up, and up and up......until I got the heli disorientated.....

I've tested both like90's and stock blades, you can fly the stock out of the bag blades in FF, without a pitch up wobble/crash with the springs.....

It truely is amazing....this little device.

G.
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Old Jul 19, 2004, 02:52 PM
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Tampa St Pete, Florida, United States
Joined Dec 2003
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YAY!

Can someone make a guide with some detailed instruction on how to make these springs now that it is basically proven to work?

Like how long does the spring wire need to be, how many degrees it should be bent etc? What gauge spring wire would help to.

Thanks,
Chris
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Old Jul 19, 2004, 02:55 PM
micro mechanic
aerohawk1's Avatar
Oz, Kansas
Joined May 2004
2,303 Posts
I have made several sets with diff guage,tension and advance,and they seem to be extremely forgiving.

Just make sure that they advance the blades 10-20 degrees.
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Old Jul 19, 2004, 03:10 PM
Blade Springs "Rock"
Central Coast, CA
Joined Apr 2004
2,141 Posts
I've flown with basically two different size wires, .039 and .030. I found that the .039 worked better on stock blades, and the .030 worked really good for Like90's.

They are just too simple to construct, but make them exactly the same.

G.
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Old Jul 19, 2004, 03:16 PM
Sponsered By My Wallet!
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Colwyn Bay, North Wales, UK
Joined May 2004
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would someone also either post a pic, or a how-too on for this mod on a hummingbird/dragonfly, as i really want to do this mod, but ive only seen pictures of the mod on a aerohawk, which has quite a different head

thnaks lot, Duane
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Old Jul 19, 2004, 03:26 PM
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Wolverhampton, UK
Joined Jun 2004
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you should sell them....they could be sold on like90!?
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Old Jul 19, 2004, 03:35 PM
micro mechanic
aerohawk1's Avatar
Oz, Kansas
Joined May 2004
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Quote:
Originally Posted by Geoffrey109
I too had some agressive in flight manuevering, and without a doubt the springs would have saved it from pitching up, I crashed not due to pitch up. What I was seeing was climb up, and up and up......until I got the heli disorientated.....

I've tested both like90's and stock blades, you can fly the stock out of the bag blades in FF, without a pitch up wobble/crash with the springs.....

It truely is amazing....this little device.

G.
I think a one-way main gear helps with the climb-up...
not so much that,but it is helpfull when you are climbing to fast:when you cut throttle,the heli does not drop like a rock!
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Old Jul 19, 2004, 03:53 PM
micro mechanic
aerohawk1's Avatar
Oz, Kansas
Joined May 2004
2,303 Posts
Well, I just had a go at FFF at the local auditorium...

CRASH,BANG,BOOM!
Need I say more?

Completed my first figure 8's.It was really exciting until I lost orientation and slammed it sideways into a concrete wall.The head auto-rotated more than 50 ft. away and the heli dropped like an anvil!

Skids are shot...aside from that,all OK!

Wow!
FFF is a rush!

Aero
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Old Jul 19, 2004, 04:00 PM
Blade Springs "Rock"
Central Coast, CA
Joined Apr 2004
2,141 Posts
Was there much left of those skids anyway.....? You had quite a few bandaids on them from the pics I saw.....

FFF is a total rush......now you have seen the light in micro helicopters. They can get away from you quickly and disorentated even quicker.....but what a ride.....

I went to Stainless Steel Landing Gear.....hoping to crash proof them a little more.......

G.
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Old Jul 19, 2004, 04:03 PM
micro mechanic
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Oz, Kansas
Joined May 2004
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Upon further inspection,the hot glue,which held them on,just gave out.

Break out the hot glue gun!
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Old Jul 19, 2004, 04:48 PM
"It's a Quad" :O
thewz's Avatar
Temecula
Joined Jul 2004
3,179 Posts
Quote:
Originally Posted by aerohawk1
Upon further inspection,the hot glue,which held them on,just gave out.

Break out the hot glue gun!

Aerohawk1.....90% hot glue.....8% nylon....2% CF.....
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Old Jul 19, 2004, 05:00 PM
azfai
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Quote:
Originally Posted by Bubblehead
So a retreating blade lags, then becomes an advancing blade and still lags. Of course the other blade not is now retreating and should lag also. How come it does not also lag and the system go back into equilibrium?

If your hypothesis were true, then tightening the blades would eliminate the problem because it would prevent either blade from lagging. It might cause other problems, but the wobble would change.

The other thing that makes me think we don't have the cause right is I can move my blades off line and within a few low RPM revolutions they are lined up just fine. If they generate enough centrifigal force to do that at low RPM, then certainly they can restore their position at high RPM. If I find my scale so I can weigh my blades I'll calculate the restoring force just for grins but since it's porportional to the square of the rotational speed, there's probably a lot of force keeping the blade stretched straight out.

It doesn't change the fact that your fix apparently works, but one of the things I find fascinating about helis is their dynamic complexity. It's a lot of fun to debate, test, hypothesize etc.
Absolutely Lynxman.

I tightened up the blades so they are snug, just like we do on the Gas and Nitro larger helicopters, and voila, the head ran smooth and no wobble.

Jim
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