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Trex 600ESP Low headspeed/ Max Endurance Project Trex 500 Scorpion Motor NOW A 700ESP SOON TREX 800

rjhpilot91

Senior Heliman

somers point, nj

Some of you may have seen my previous low head speed/ long flight time project here with my previous thread.http://rc.runryder.com/helicopter/t520671p1/

That thread used a stock 600 power system to achieve very long flight times and a low headspeed at the expense of heating up the electronics. The project worked very well, but this one will be more efficient. The eagletree v3 logger with rpm sensor is used for all data.

This project is based on a new Trex 600 ESP with a Scorpion 3026-880 motor (for a Trex 500 size heli) and a align trex 500 esc. Everything else is stock align parts except Radix blades. The project has just completed the 600mm size testing and will now be moving to a 700 size setup next week.

First flight with this setup and a 12 tooth pinion gave a headspeed of 1225 in a hover at 75% on the throttle curve, with 80% as the max throttle. This was very smooth with zero vibes and it was still quite responsive, although too much for what I'm going for. This configuration used 250mah per minute average from a 6s 5000 pack, for a total flight time of 16 minutes to the 80% mark.

Received a 10 tooth pinion in the mail and that dropped the headspeed down to 990 in a hover, about the lowest you can go on 600mm blades. With the pitch at 9 degrees to hover and the tail swinging slower, it has just enough power to climb out well and hold the tail steady in a descent. I did a couple of flights that way and decided to add more pitch to it. It is hovering right now at about 11 degrees of pitch with the max at 13 and it sounds so real in a descent you'd swear it was a real helicopter. The lowest RPM seen with the pitch increase was about 900 which was getting quite low. An accidental entry into vortex ring state brought about a scary recovery about an inch from the ground, very realistic. That was with a second battery strapped to the bottom to test out amp usage with a parallel setup.

The 700 stretch on my previous project was able to get the headspeed down to 800 even and the limiting factor was the tail losing its effectiveness. That was with 105 tail blades. For this time I bought the rotortech 120mm blades that are 33mm wide, so a much bigger blade. Hopefully I'll get the headspeed dow to about 600RPM this time, with the use of 4 cell or 3 cell batteries to get the headspeed lower, which in turn will be run in parallel for long flight times.

I will post some pics of the setup and hopefully a video sometime soon. Here are the numbers for the setup:

Hover Amps 12.5 - 14
Hover RPM 990
MAH per minute 178
Total flight time 22 minutes safely
Flight time parallel setup 34 minutes
Zippy 6s 5000mah

[B]

Helicopters don't fly, they beat the air into submission!

04-03-2010 Over year old.
HOMEPAGE  
erh7771

Heliman

Texas

Thx for the info!!!

I'm going to do something similar with a 500 and use a 450 motor and a 13th pinion to start with to see if using a smaller motor\esc combo will give lower performance but better flight times\scale flying.

With my 500 sized motor on my EXI500 I could use 3 cell A123's\16th pinion\KDS FlyMentor and get 7mins of hover with cold bats\engine\ESC (no canopy) it would also give my pretty good tail control and I could get some fast lift if I wanted to but was to fast for my scale flying taste. Now every time I wanted to put 2 3s packs in parallel it would be a no go...prolly have to adjust my pitch to get more lift with that set up

I was in a LHS the other day and mentioned that there's prolly a some torque outtah these motors we're not using, after seeing your flight times I'm swayin closer to that direction.

This is great info for scale or FPV flyers

04-05-2010 Over year old.
Heli143

Elite Veteran

Phenix City, AL

rjhpilot91,
I think that is awsome!!
BTW you don't give classes on electrics do you??

I am just learning electrics and find it really fascinating.
I am thinking how well this would apply to the scale side of the house as I can picture my 50 size Long Ranger descending with loud blade noise... very cool!!

thanks for sharing

Roy Mayoral

04-05-2010 Over year old.
rjhpilot91

Senior Heliman

somers point, nj

Sorry it took so long to get a reply out. I've been busy with the 700 size conversion which is now complete.

700 size conversion;

Trex 700 boom/torque tube
Radix 710 FAI blades
Rotortech 120mm tail blades
6s 5000mah battery

Maiden flight was yesterday and the initial headspeed in a hover was about 980 RPM. Definitely too much headspeed for these blades. I will have better results once my lower cell batteries come in.

13 minute flight
Average amps 15-19 peak 24
Average RPM 980 low 920 high 1020
Battery usage 2602 mah out of a 5000mah battery
total run time 19.2 mins to the 80% mark

It flies very sedate and the fai blades give it a very heavy cyclic feel to it just like a real helo. Pics to come.

Helicopters don't fly, they beat the air into submission!

04-07-2010 Over year old.
HOMEPAGE  
erh7771

Heliman

Texas

Tail blades

Do you have to have a taller tail blade stand?

I have the same issue on my 500 with the main blade speed, I can get longer flight times but can't lower the head speed cause the tail wont cooperate...it just look like I'll have issues landing with a larger tail blade..

Thx

04-07-2010 Over year old.
rjhpilot91

Senior Heliman

somers point, nj

I built a stinger for the tail that gives about 4 cm worth of clearance so that the blades don't hit the ground.

AS far as the wobbling with headspeed I had the same problem with my 500. On the 600 you need to run the headspeed either really high, above 1800, or really low, below 1100 to eliminate the wobbling.

Helicopters don't fly, they beat the air into submission!

04-07-2010 Over year old.
HOMEPAGE  
rjhpilot91

Senior Heliman

somers point, nj

I also forgot to mention that for start up I had to implement a special slow start feature. I start the helicopter in idle up 2 and full stick brings the throttle to 20 percent at 0 pitch, then I flip into Idle 1 which accelerates to about 40 percent and then I switch into normal flight mode for all the flying.

This is done to prevent overloading the system from the shock of getting this big powertrain going on such a small motor and ESC. It seems to work well as it keeps the amps very low during startup.

Helicopters don't fly, they beat the air into submission!

04-09-2010 Over year old.
HOMEPAGE  
rjhpilot91

Senior Heliman

somers point, nj

Completed the first flight with the 5s 5000mah battery. Results look very promising:

3.6 minute flight
Zippy 5s 5000mah 20C
Throttle curve 0-40-70-72.5-75
Hover pitch 8 degrees

Amps 13-14 peaks at 17

Hover RPM 850

197 mah per minute from the battery

So guesstimating that from 6s RPM (980) down to 5s RPM (850) RPM at 4s and 3s should be 760 for the 4s setup and 650 for the 3s setup. Now I need to order both of those packs ASAP to continue on with the testing.

Helicopters don't fly, they beat the air into submission!

04-09-2010 Over year old.
HOMEPAGE  
erh7771

Heliman

Texas

Now I need to order both of those packs ASAP to continue on with the testing.
I take it the 4s and 3s packs will be 5000mah also?

TIA

04-09-2010 Over year old.
rjhpilot91

Senior Heliman

somers point, nj

Yes they will be the 5000mah as well, I'd love to go to the 5800 batteries but they are quite a bit more. If the headspeed works at the 3cell level I will be using them in parallel for a 10,000mah setup.

Helicopters don't fly, they beat the air into submission!

04-09-2010 Over year old.
HOMEPAGE  
erh7771

Heliman

Texas

Are you planning on going flybarless or flat bottom blades any time soon?

My understanding is going flybarless will get more flight time (don't know why) and flat bottom blades are more efficient then the full elliptical that are usually flown with.

TIA

04-09-2010 Over year old.
Rotowerkz

Senior Heliman

Windham, NH

Do you have any videos of the 710s swinging at 850 RPM? I must see this...

04-09-2010 Over year old.
rjhpilot91

Senior Heliman

somers point, nj

Not yet but this time I will definitely be posting pics and videos, problem is getting someone to tape for me. I don't have any clubs nearby and no one near me flies, but I will find a way.

I'll take the video once I get the headspeed where I want it, around 650 RPM. Its quite awesome to watch it fly like that.

Helicopters don't fly, they beat the air into submission!

04-10-2010 Over year old.
HOMEPAGE  
rjhpilot91

Senior Heliman

somers point, nj

As far as the flat bottom blades, they dont make the size I need in the grip size I need. Otherwise I 'd definitely be using them for the extra lift.

Flybarless would be great but he conversion kit from mikado is $100 plus a gyro system puts it a little too expensive for such a small performance gain.

Helicopters don't fly, they beat the air into submission!

04-10-2010 Over year old.
HOMEPAGE  
rjhpilot91

Senior Heliman

somers point, nj

She flies at 625 RPM Rotor Speed!

I have been flying the last couple flights with a 5s battery. It is yielding around 850RPM on the head at 70 percent throttle. Just to see how low a headspeed it would take off with I dropped it down to 50 percent throttle. That gave a headspeed of 625 which was workable, it was a little sluggish on the collective but the tail held very well with no swinging.

I then lowered the throttle to 40 percent and tried to hover. It would not pull into a hover even at increased pitch settings, it just started wobbling pretty hard at about the liftoff point before I had to cut the throttle. That RPM ended up being about 550, which appears to be too low for this setup.

The target headspeed should be around 650 for the best combination of pitch stability and cyclic response. I have a pair of 3s 5000mah 20C batteries on the way from hobby city to make up the 3s 10,000mah pack.

Helicopters don't fly, they beat the air into submission!

04-10-2010 Over year old.
HOMEPAGE  
jones007

Senior Heliman

Monterey, CA - USA

Are you planning on going flybarless or flat bottom blades any time soon?

My understanding is going flybarless will get more flight time (don't know why) and flat bottom blades are more efficient then the full elliptical that are usually flown with.
+1 for this. Most of the FBL buffs preach huge power savings, but I have yet to see someone really document it. I would very much like to see this.

--Kevin

Trex 700N, Trex 600ESP, Trex 500, Trex 450Pro

04-10-2010 Over year old.
Rotowerkz

Senior Heliman

Windham, NH

With such low headspeeds and high angles of attack, have you given any thought to the increased induced drag here? I know it's hard to quantify, but there should be a sweet spot where the power draw and induced drag on the blades are minimized/maximized with respect to each other. Obviously, induced drag concerns are diminished in forward flight as translational lift reduces the angle of attack requirement.

04-10-2010 Over year old.
ESWLFSE

Elite Veteran

Cedar Park, TX

Also, with headspeed that low the efficiency advantage of FBL has to become very negligible.

04-10-2010 Over year old.
rjhpilot91

Senior Heliman

somers point, nj

3 cell Hover testing

A friend and his buddies were racing cars tonite and one of them happened to have a 3s 5400mah battery. So I threw it in the heli and got some test data.

3 minute flight
3s 5400mah 20C (pretty old looking)
Throttle curve 0-40-80-90-100

AVG RPM 605!!!!!!!!!
AVG AMPS 17A
MAH minute 215

It barely lifted off the ground at this speed. It did hover ok but it didn't even have enough power to get through ETL into forward flight. Between 650 and 700RPM is going to be the best compromise for low headspeed and power to operate.

While it didn't have any power reserve it did however have plenty of tail rotor authority. The tail did not wander at all and had plenty of throw in both directions.

Helicopters don't fly, they beat the air into submission!

04-11-2010 Over year old.
HOMEPAGE  
Rotowerkz

Senior Heliman

Windham, NH

Wow - 605 RPM. You are journeying into full-scale headspeeds at this point.

04-11-2010 Over year old.
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Trex 600ESP Low headspeed/ Max Endurance Project Trex 500 Scorpion Motor NOW A 700ESP SOON TREX 800

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