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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Low Headspeed project-----19 minute flights!
09-18-2009 11:51 AM  11 years ago
Against Gravity

rrVeteran

Pottstown PA

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Ckeck the AP page
The guys that run AP setups can help allot in this type of setup. there goal is long steady flight, with added weight of AP equipment on board.
Maybe more helpfull for your scale body.
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09-18-2009 12:54 PM  11 years ago
floop

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Southern, NJ

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Cool thread. I wonder if using lighter blades or heavier and changing the paddles would help with less resistance.IT's what I do.
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09-18-2009 02:20 PM  11 years ago
rjhpilot91

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somers point, nj

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I'm going to be experimenting with increasing the pitch of the main rotor head right now this weekend to slow down headspeed and increase lift with a lower throttle curve.

I cant use smaller tail blades due to the low speed of rotation of the main head.
Helicopters don't fly, they beat the air into submission!
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09-18-2009 02:28 PM  11 years ago
Richardmid1

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Leeds, England

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Increasing the pitch at a lower throttle curve will work if your constantly in forward flight but any hovering will draw more amps. I would try shorter blades like 620's and increase the throttle slightly.60% of the time, it works every time!
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09-18-2009 04:03 PM  11 years ago
AirWolfRC

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I cant use smaller tail blades due to the low speed of rotation of the main head.
Leave the tail blades alone.
That's only a minor gain anyway.
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09-18-2009 04:10 PM  11 years ago
VooDooX

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San Francisco Bay Area CA, US (San Mateo)

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weight weight weight!!! reduce the weight sheeshVelocity 50 "99.9999999999999% of an atom is empty space." also 01001000 01001001
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09-18-2009 08:27 PM  11 years ago
AirWolfRC

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Shorter tail blades is only worth a few grams.
There are a LOT of other ways to get some weight out before that.

Dialing in a more effieient setup will yield more gains than loosing a few grams.

If you can dial in 5% better flight efficiency on a 6 LB heli then you just gained the same advantage as loosing about 136 gm.
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09-18-2009 10:26 PM  11 years ago
VooDooX

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no i wasn't saying tail blades i was saying weight like use plastic parts and stuff cut alot of weight and you can increase flight timesVelocity 50 "99.9999999999999% of an atom is empty space." also 01001000 01001001
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09-19-2009 07:24 PM  11 years ago
rjhpilot91

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somers point, nj

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Newest Results-----Final Configuration
Well, I just finished more testing incorporating several changes. I plan on posting the eagletree data and pictures of the setup sometime soon. I'll also post a video so the skeptics can see how manueverable it still is.

I have come to the end of the testing phase and have come up with a final configuration that can't be tweaked any more.

Throttle Curve 0-20-52-56-60
Pitch curve -2 to +13 degrees

Hover RPM 810 RPM in a hover
Hover Amps 10-12

9 minute hovering flight 1342 mah used
Usage appx. 149 mah per minute

Estimating an average of 175 mah per minute conservatively
22.8 minute flight to 80% on 5000mah pack 19.4 mins on 4200 pack

I initially had the pitch settings much higher and it was hovering at 700 RPM but the tail authority was marginal at best, and any quick power inputs caused the tail to swing wildly. I lowered the pitch a bit and dialed up the throttle curve to the current setup and now the tail only twitches with power inputs.

The tail rotor blade size appears to be the limiting factor here and I can't fit any bigger blades with the stock configuration. With such a high pitch setting now and such a low throttle setting, the tail can't hold well below 800 RPM on the head.

The batteries are ambient temperature during all of this flying due to the lack of power being used from them. They never go above ambient outside air temp any more. The ESC is cooled much better now due to the better placement of the 60mm fans that put out 15CFM's of air as opposed to the 40mm's which only put out 7 CFM. I also placed the other fan in a better location to cool the motor, under the battery tray in cutouts in the frame. The electronics have held up really well so far despite their being using at such a low efficiency. Only time will tell how they hold up over the long haul.

To give you an idea of how well this power system is working: the heli was sold to me with over 50 flights on it, I put another 60 flights on it with sport flying and 3D, and now it has about 50 flights on it since running this low headspeed project. Thats 160 flights on the stock Trex 600 motor and ESC! And I'm abusing these electronics right now! I guess I got a good motor from Align.

This setup is not for everyone, as most people would be bored with such a benign flying aircraft, but its one heck of a pattern flyer for 20 minutes on one battery.

And this bird is even stretched to 700 size!

Pics, graphs, and video to come.
Helicopters don't fly, they beat the air into submission!
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09-19-2009 08:17 PM  11 years ago
AirWolfRC

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42½ N, 83½ W

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Wider tail blades or some kind of speed-up gearing for the tail blades.

The thrust from the tail blades still needs to be up there even if the mains are turning slower . . . because you're still making the same over all lift with the mains therefore you still need the same kind of counter torque from the tail blades.

If you cut the rpm in half, the thrust from the tail will be 1/4 for the same tail blade pitch. You run out of tail authority real quick.
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09-20-2009 12:14 AM  11 years ago
rjhpilot91

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somers point, nj

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Are there any wider tail blades than the carbon fiber trex 700 105mm ones?Helicopters don't fly, they beat the air into submission!
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09-20-2009 12:43 AM  11 years ago
rjhpilot91

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somers point, nj

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I just stumbled on some rotortech 120mm carbon fiber blades. I think these may help a little with the tail authority.

I may be able to get the headspeed back down a little more if these give just a little more tail authority. Will most likely need to build a stinger for the tail so they don't tap the ground.

Anybody know of any speed up gears for the trex 600 torque tube setup?

That also may be useful.
Helicopters don't fly, they beat the air into submission!
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09-20-2009 04:04 AM  11 years ago
LoveMyTrex

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Hamilton,VA

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I have come to the end of the testing phase and have come up with a final configuration that can't be tweaked any more.
and since that post you have already done more tweaking...
600N 55HZ/SAB-55 600V's
700N 91HZ/SB-20 690V2 V's
90SG 91HZ/SB-20 710V2 V's
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09-20-2009 12:36 PM  11 years ago
raptor50luvver

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Dorset UK

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I assume you are using semi symmetrical main blades as they are far more efficient than symmetrical ones for 3d.

These might give you another 30 mins

Go flybarless and you will get an extra 15mins also

And has been mentioned,run a lower KV motor with your 10t and get the ESC up to above 80% for better efficiency.
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09-20-2009 05:30 PM  11 years ago
AirWolfRC

rrProfessor

42½ N, 83½ W

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If I recall, SAB makes some tail blades that are 35mm wide, noticably wider than normal.

Motor KV and gearing go hand in hand. Higher KV, higher gear ratio.

Yes, asymetric blades will work better but keep tweeking with the symetricals untill you find some. The reason you don't find them easily is that most people fly 3D. Symetricals don't care if you're upside down or right side up. Asymetricals aren't nearly as good upside down.
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09-21-2009 11:16 AM  11 years ago
Richardmid1

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Leeds, England

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Gearing the tail up will drain more power. You could use mini servos all round which would save around 100g. Use 2 3300mah 20C (or lower) packs in parallel. Also with such a low amp draw you could afford to go beyond 80% on the packs without harming them.60% of the time, it works every time!
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09-21-2009 03:16 PM  11 years ago
AirWolfRC

rrProfessor

42½ N, 83½ W

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Gearing the tail up will drain more power.
Not really, it will use just as much power as before the head speed reduction.
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09-21-2009 03:26 PM  11 years ago
ShuRugal

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Richmond, VA

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well, you will lose some power in the new gear ratio that you weren;t losing in the old. trick is making the loss balance with the gain from being able to go lower on the HS.AMA 700159
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09-21-2009 04:40 PM  11 years ago
AirWolfRC

rrProfessor

42½ N, 83½ W

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well, you will lose some power in the new gear ratio that you weren;t losing in the old.
Are you saying that a higher tail gear ratio, getting the tail rpm back up to where it used to be, will use more power than before the change ?

Keep in mind that reducing the main rotor rpm makes it more efficient therefore requiring LESS thrust from the tail rotor.
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09-21-2009 05:13 PM  11 years ago
LoveMyTrex

rrVeteran

Hamilton,VA

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yes, but you have to remember if you drop the main rotor 1,000 rpm then the tail rotor rpm is going to drop something like 6 or 8,000 rpm600N 55HZ/SAB-55 600V's
700N 91HZ/SB-20 690V2 V's
90SG 91HZ/SB-20 710V2 V's
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