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Old Feb 20, 2014, 01:33 PM
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Quote:
Originally Posted by rnst2 View Post
also,
I'll using 5s.
what would be a pinion of choice? to acquire an acceptable headspeed.
sorry for the noobness questions.
thanks.
Your 1110KV motor will work fine with the 5S pack using a 9T pinion for a scale friendly rotor speeds between 1400 and 1600.
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Old Feb 20, 2014, 02:27 PM
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Canada, BC, Surrey
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Quote:
Originally Posted by Cyclick View Post
Your 1110KV motor will work fine with the 5S pack using a 9T pinion for a scale friendly rotor speeds between 1400 and 1600.
thanks Cyclick!

@Fr4......sorry for the threadjack.
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Old Apr 20, 2014, 11:35 PM
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United States, PA, Warren
Joined Dec 2013
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I have one of these Real Deal Swift Jet Ranger kits that I've had to put on the back burner for awhile maybe someone here can help me out.

I've built the heli but can't bring myself to mount it to the gorgous scale fuse yet due to an odd vibration I get at very low RPM on spool up and spool down. I have about 10 - 15 flights on the heli trying to work the bug out of it. I'm at a total loss as to what could be causing it.

I've checked and re-checked all the obvious culprits. At hover the heli is smooth as silk. I put it away early in the 2013 flying season and haven't touched it in close to a year.

Any help would be appreciated.
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Old Apr 21, 2014, 12:20 AM
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USA, CA, Red Bluff
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could be the main blades swing out of line at startup. centrifical force will realign them when hover speed is attained..
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Old Apr 21, 2014, 04:27 AM
Complete RC Idiot Savant
The Netherlands
Joined Nov 2009
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Try different groundsurfaces to spool up on...

Some of my helicopters flew fine from grass or soil but were a b*tch to spool up on concrete or Asphalt....

And the "springiness" of the landing gear/skids have a marked influence too.

One of my flying buddies is allready flying close to a year with a 450 size Airwolf, but suddenly it seemed it would not get past this critical RPM, flying indoor in a sporting hall. But when the helicopter was placed on a simple towel, it would spool up without even a visible vibration....

Brgds, Bert
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Old Apr 21, 2014, 11:10 AM
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United States, PA, Warren
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I have the blades loose and they move quite freely. As far as surfaces are concerned, its significantly worse from asphalt.

I'm starting to wonder if my pitch curve is too aggressive.
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Old Apr 21, 2014, 12:14 PM
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The problem is the ground resonance related to the height of the rotor relative to the spread of the landing gear struts.

Do this landing gear strut mod suggested in the Century forum on HeliFreaks (that forum is by far the best information forum for any of the Century helis):

http://www.helifreak.com/showthread.php?t=548036

That 8" spreading of the landing gear will solve you spool up and spool down shake/dance.

That same dance may not be an issue with the scale jet ranger installation because the strut spread and height from ground to main rotor is different then that of the pod and boom configuration.
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Old Apr 21, 2014, 11:16 PM
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United States, PA, Warren
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Quote:
Originally Posted by rotoraddict View Post
The problem is the ground resonance related to the height of the rotor relative to the spread of the landing gear struts.

Do this landing gear strut mod suggested in the Century forum on HeliFreaks (that forum is by far the best information forum for any of the Century helis):

http://www.helifreak.com/showthread.php?t=548036

That 8" spreading of the landing gear will solve you spool up and spool down shake/dance.

That same dance may not be an issue with the scale jet ranger installation because the strut spread and height from ground to main rotor is different then that of the pod and boom configuration.
Thank you for the information, this is certainly worth a try. It sounds like this is something common with the Swift.

Is it possible that my pitch curve is too aggressive?
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Old Apr 22, 2014, 06:04 AM
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United States, MA, Webster
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Quote:
Originally Posted by MIGPILOT44 View Post
Thank you for the information, this is certainly worth a try. It sounds like this is something common with the Swift.

Is it possible that my pitch curve is too aggressive?
Hi, MigPilot:

Are you using the "Scale Aluminum Platform" and the Semi-Scale landing gear that came with the "Real Deal" package ??

Also, I read somewhere that throwing in some negative pitch on spool-down minimizes / eliminates the "dance".

Russ
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Old Apr 22, 2014, 11:43 AM
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Quote:
Originally Posted by MIGPILOT44 View Post
Thank you for the information, this is certainly worth a try. It sounds like this is something common with the Swift.

Is it possible that my pitch curve is too aggressive?
What pitch curve do you have set? Do you know what rotor speed you are using?
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Old Apr 22, 2014, 02:03 PM
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United States, PA, Warren
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Originally Posted by MiniBoy View Post
Hi, MigPilot:

Are you using the "Scale Aluminum Platform" and the Semi-Scale landing gear that came with the "Real Deal" package ??

Also, I read somewhere that throwing in some negative pitch on spool-down minimizes / eliminates the "dance".

Russ
I don't have the Swift mounted in the scale fuse yet. I wanted to get it all set up and work any bugs out prior to mounting it. I'm using the stock Swift gear. Currently I have negative pitch in as part of the pitch curve at minimum throttle. I will have to report back as to what my current settings are.
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Old Yesterday, 12:33 AM
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United States, PA, Warren
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Quote:
Originally Posted by rotoraddict View Post
What pitch curve do you have set? Do you know what rotor speed you are using?
Looking back through my notes the headspeed is estimated at 1650. Heli World had a minimum and maximum posted at one time and from what I remember this fell within their guidelines.

Here's a nice headspeed calculator if anyone needs one.

http://dhrc.rchomepage.com/calc.htm
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Old Yesterday, 12:47 AM
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United States, MA, Webster
Joined Feb 2003
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Quote:
Originally Posted by MIGPILOT44 View Post
I don't have the Swift mounted in the scale fuse yet. I wanted to get it all set up and work any bugs out prior to mounting it. I'm using the stock Swift gear. Currently I have negative pitch in as part of the pitch curve at minimum throttle. I will have to report back as to what my current settings are.
Could it make any sense to get the mechanics up onto the "Scale Platform" and on the semi scale wider landing gear .. which you will be doing later for the scale fuse, anyway ?

Anyone's guess as to whether or not that will change the ground effects, as well as the semi-scale landing gear is already wider and lower, so perhaps less vibration harmonics ??

Just some thoughts ..

Russ
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Old Yesterday, 11:57 AM
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Quote:
Originally Posted by MiniBoy View Post
Could it make any sense to get the mechanics up onto the "Scale Platform" and on the semi scale wider landing gear .. which you will be doing later for the scale fuse, anyway ?

Anyone's guess as to whether or not that will change the ground effects, as well as the semi-scale landing gear is already wider and lower, so perhaps less vibration harmonics ??

Just some thoughts ..

Russ
Sounds like that would be a good plan,
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Old Yesterday, 11:36 PM
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United States, PA, Warren
Joined Dec 2013
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Quote:
Originally Posted by MiniBoy View Post
Could it make any sense to get the mechanics up onto the "Scale Platform" and on the semi scale wider landing gear .. which you will be doing later for the scale fuse, anyway ?

Anyone's guess as to whether or not that will change the ground effects, as well as the semi-scale landing gear is already wider and lower, so perhaps less vibration harmonics ??

Just some thoughts ..

Russ
I don't think it would be the best idea to mount it up not knowing for sure if the gear is the underlying problem. The wobble / vibration is violent enough for those few split seconds that I feel it could crack the mounting points and / or even put the head into the upper fuselage if the fuse shifted. I would really hate myself if I where to bust up such a nice fuselage.

I wish I had a video of the heli spooling up to pass along. My plan is to recheck and adjust my pitch and curve settings prior to the next outing with it. I will also video the process and pass it along if the problem persists.

I really appreciate everyones input here, thank you!
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