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HomeAircraftHelicopterLow Head Speed Helicopters › The main reason YOU like low head speed
09-13-2015 03:52 AM  33 months agoPost 61
turboomni

rrProfessor

East of the Equator

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Hey RDF430 I also fly a Align 550 DFC with 600mm mains and 95 tails. I have run the same motor as you a 1220kv. When I first got the heli a few years ago I believe it came with a 12 t pinion and 525mm mains. I run 5500 mah and higher packs for CG reasons and abit more run time as a result. That thing screamed!! The power was ridiculous,,as well as the head speed. And the run times sucked of about 5 minutes or less. Soon I tired of this mad hornet I was flying. I started lowering the head speed with my esc a Talon 90 but knew I shouldn't go lower than 70 to 75% throttle as I would lose efficiency and start to heat things up,,like the esc and motor lugging the 12t 112 main gear ratio combo. The head was originally tached at 2500 area,,crazy. I went to a 11T then down to a 10t pinion. I don't use a gov so I ended up with 2000 head speed at 100% throttle with the 10t. It was better but I wanted more,,,or actually less lol. To make a long story short the original motor with my kit was a 850kv Align motor with a whopping 16t pinion to get 2500 area head speed,,the older kits had the 1220 kv align motor which I think works better for high head speed with the gear ratio advantage. I had the opportunity to try the 850 kv Align motor. I did some research on Mr Mel's head speed calculator and found at 850 kv and my gear ratio [10t pinion and 112 t main gear] my head speed at 100% would be 1800!!! Hardly the low head speed of my Align 700 v2 of 1300 to 1400 on one 6 cell but a definite improvement. The performance [no gov] with 600 blades and the 850 kv motor with a 10t pinion instead of a 16t pinion was really very impressive to me. With a gear ratio now of 11.2 instead of 7 really made a stump puller of a setup at this head speed of 1800 rpms. The only real problem was at this head speed when I did a pirouette when flying at a relatively fast speed my tail would hang up broadside to the direction as the tail even with full mechanical and electronic throw did not have enough rpms to get her around. I did some research and found out that the DFC 550 was setup for very fast head speed. As a result the tail ratio was lowered as it would not need a higher ratio at such a high head speed and also I would think to keep the tail from blowing up!! The tail ratio was in the high 3,8 something to 1 and the older 550's were over 4. something to 1. I I bought older 550 tail transmission gear set that sped up the ratio to 4, something and the problem is gone. The result?? This thing at 1800 head speed is a hotrod compared to my 700 v2 Align but I get a very good solid 8:30 to 9 minutes of flying as Nothing is stressed even though I can flog it around. It still scoots and is very manuverable! Sorry for the long post !!

Setup is everything, All my heli's can fly far better than I can pilot them

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09-15-2015 02:58 PM  33 months agoPost 62
gwright

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Champaign Il

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I've been tweaking on my E5-700 a bit and thought I'd share a castle log image. It illustrates the exponential relationship in power reduction with lower rpms. All of this was what I like to refer to as smooth 3d,..not just hovering. Roughly 10 minute flight, and telemetry alarm went off at 3500mah used. 12S/4350 flightpowers, 400kv hacker, 10.08 gearing, Edge80HV ESC. No, I don't recommend the edge 80. I'm trying it because it's lighter, smaller, and I know the way I fly my current peaks aren't very high. My concern was temperature,..which actually was getting too hot at first till some changes were made and now it stays relatively cool. I see many people's logs showing 180~200 degrees peak and I was there at first with this esc till making some changes Now as You can see, the peak on this flight was 130.9 which is relatively cool. External measurement with a temp gun showed in the 108~110 range, indicating there's about a 30 degree delta in internal versus external measurements. Internal is what matters as they're set to shuttoff with internal measurements of something in the 210 range. The three yellow highlighted boxes are the three rpms I use on this machine. 1250/1500/1750. You can see the power utilization drops a little going from 1750 to 1500, and drops more going to 1250. The notable item, though, is that the required energy changes more from 1500 to 1250 than it does from 1750 to 1500 illustrating it's an exponential relationship. the flight after this was mostly at 1250 with just a little at 1750, and telemetry alarm went off just after 13 minutes. By highlighting the different sections in the castle graph viewer, average current during each rpm is 22.6,19.1,11.3, so from 1750 to 1500 it drops 18% in required power, and from 1500 to 1250 it drops 42%. Yes lower rpms increase flight time,.. but far more so than most people realize

Gary Wright

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09-15-2015 03:11 PM  33 months agoPost 63
Ace Dude

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USA

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Great job Gary. Thanks for sharing. That's quite a signfiicant drop in ESC temperature you were able to accomplish.

  

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09-15-2015 03:57 PM  33 months agoPost 64
gwright

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Champaign Il

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timing,pwm, rpm, pitch,.. just a few minor tweaks actually

Gary Wright

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09-15-2015 04:01 PM  33 months agoPost 65
Santiago P

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South West, Ohio

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You can see the power utilization drops a little going from 1750 to 1500, and drops more going to 1250. The notable item, though, is that the required energy changes more from 1500 to 1250 than it does from 1750 to 1500 illustrating it's an exponential relationship.
It follows physics as it should, skin friction drag is related to v^2.

Gary is flying aerobatics to the total drag is the sum of the induce (lift created) and parasite drag. The induce part is near the same at higher RPMs, providing the blades are not being stalled, but that is where Mr smooth skills comes in.

If one was to just hover at those speeds you will see the huge difference.

I managed 12minute plus flights with one 6S 5Apack 715mm blades doing sport flying with a few loops rolls, and flips at 1000rpm

Lately I've been flying ~8min flights with a 7S 4400ma pack at 1320rpm doing big FAI style maneuvers the whole time.

Santiago

Team Minicopter - PeakAircraft.com
bavarianDEMON- Team Kontronik - Scorpion Motors-

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09-15-2015 04:40 PM  33 months agoPost 66
turboomni

rrProfessor

East of the Equator

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By highlighting the different sections in the castle graph viewer, average current during each rpm is 22.6,19.1,11.3, so from 1750 to 1500 it drops 18% in required power, and from 1500 to 1250 it drops 42%. Yes lower rpms increase flight time,.. but far more so than most people realize
Wow ,,that is amazing stuff to actually see on paper. I think I may go down a tooth on my pinion just to see what happens. I am between 1300 to 1400 rpms now.
I wished I could be as sophisticated as you guys with this stuff.

Setup is everything, All my heli's can fly far better than I can pilot them

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09-15-2015 05:35 PM  33 months agoPost 67
gwright

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Champaign Il

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It's not what I'd call sophistication. I'm just very left-brained and over-analytical.
As for the temp decreases ace-dude,.. this setup started with pwm raised to help governer. I had it maxed out which helps governing a little bit, cools the motor a little bit, but heats up the esc. I also had timing increased substantially. There were motors on each side of the "perfect kv" I wanted, so I went with one slightly low and increased timing to increase the kv a little. After seeing temps,.. coupled with the fact that I never seemed to load the motor, and logs showed it rarely touching 100% power, the natural thing to do was to lower timing, thus dropping the kv a little since I'm allready using the smallest pinion and largest maingear. The reasoning is that it would cool things by reducing the real overhead in the system, but hopefully not enough to notice running out of power. It worked as planned, and I kept dropping the timing. Still maintained headspeed and power, but now indicating it hits 100% sometimes (flat tops on the blue squiggles in the graph). I was able to go from 15 degrees advance all the way down to 0 on the timing. I still don't notice it running out of power (headroom) in flight, so maybe the kv is still a touch higher than optimum. Default timing in castle controllers is 5 degrees advance by the way. Unfortunately I allready have the 400kv motor in it and there isn't a lower one from hacker. I'm too cheap to buy a pyro and I don't want to go to another motor that would be less efficient and higher weight and . Any benefit from going a little lower at this point would be very very small anyway. After trying again with both set rpm and high governer in the castle, and raising pwm to it's highest, and using the white wire for governer gain in various rpms tied to flight mode, I had the governer the best I could get it and still wasn't happy, so I went back to using the white wire for phase sensing and using the cgy750 governer. As an aside, for white wire gain adjustment I used the channel for governer rpm, since it's seperate control of that channel in each flight condition and some repeated test runs in the workshop (sans blades) then studying the logs, gave me a correlation to the rpm setting in the tx to governer gain in the controller. With the CGY750 governer I was able to get governing so much better I dropped PWM to it's lowest setting. All of this resulted in much lower temperatures in the ESC. At that point I decided to drop top end pitch in high rpm mode because I had to be very very carefull with pitch in the fastest forward flight or it would start raising the nose and I wanted to be able to use the full stick volume. pitch was 14+/14+ in all modes. Speed was plenty, I just couldn't get greedy with pitch or it would tuck tail and nose up. Dropping pitch of course also dropped peak current when 3D'ing in high rpm. I've gotten very lazy and I'm not as smooth with pitch thesedays so I grab a handfull sometimes when it's not needed, leading to high surge currents. All of these little things resulted in a very significant drop in esc temps. I knew the little HV80 should work for me but I watched logs and worked on setup in a methodical manner. This is why I stated earlier that I wouldn't recommend that ESC, as you may run into heating issues if you don't monitor things as closely as I have and work on the setup.

Sorry for the war-and-peace length post but I've realized lately that with the high capacity and efficient power systems I've gotten very lazy with both flying and setup. I wanted to go through some tweaking and optimization to hopefully get a better end result. It's allowed a drop to 4350mah packs instead of 5500's , smaller esc, and the resulting 9.75lb 700 that still flies with the same performance and duration as I had at 10.5 lbs.

Gary Wright

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05-31-2018 03:32 AM  20 days agoPost 68
ErichF

rrElite Veteran

Sutton, NH

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Bump to resurrect a great topic. Looking at doing LHS with a new Goblin 770 Sport. May also play with installing a Pixhawk 2.1 for some dronage.

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05-31-2018 03:52 PM  20 days agoPost 69
gwright

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Champaign Il

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good to see you fiddling with helis again Erich! Knew you'd be back at some point.

Gary Wright

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05-31-2018 07:56 PM  20 days agoPost 70
old nitroman

rrVeteran

Naples florida

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I take my e-5s set up for 12s put jumper for one battery, fly on one 6s its fun, still loops rolls flys inverted, love the sound, getting about 8 and half minutes, nothing get even warm. love doing autos for the sound. Cliff

E5s and E7se,and a 766, Roban bell 222 800 superscale,450 bell 4 bladed head,gobby 380and 420 ,180cfx

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06-06-2018 01:52 PM  14 days agoPost 71
Richardmid1

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Leeds, England

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Another advantage is due to the much lower current draw and thus lower heat build up of the pack(s) you can take the voltage down lower without any detrimental affect, you can easily take the packs down to 15%.

60% of the time, it works every time!

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06-06-2018 05:05 PM  14 days agoPost 72
Pistol Pete

rrProfessor

Seffner, FL

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*The main reason YOU like low head speed
*Blade Sound...followed by

**Scale Flight...and finally

***Flight Time

~~Enjoying the hobby one flight at a time~~

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HomeAircraftHelicopterLow Head Speed Helicopters › The main reason YOU like low head speed
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