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Ace Hobby . Esprit Model . Thunder Power RC

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e-Electric Conversions > E Raptor AP machine
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

I have started on my E conversion. Here's what have done so far. I’ve taken an Align 600L motor and BL75G speed control, this 1620kv motor is reduced down to rpm’s require with a 2:1 reduction gear box. It will be turning 1750 rpm head speed on 620mm blades powered by 6S 4400mah li-po battery. I plan to convert my current AP machine powered by an OS32 engine to this airframe powered by electric motor.

Before:



New airframe:



Hard job competing with gravity.
10-29-2007 12:18 AM
 
 
stanc
Veteran
Location: Conroe, TX

Good luck using a 6S pack to power all that weight, not to mention any flight time.

Stan

Stan
2 x Ion X2
eStartus
eAvro90
Performance Plus Lipo Packs
12-20-2007 02:01 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

New pics final assy should be take place soon.



stanc

Currently this machine is powered by OS32 engine and is running for 12 min with stock Raptor 30 fuel tank. The final numbers of the weight on this machine are not in but I estimate it at less or equal to current configuration. If you know why this machine will not operate with this weight let me know. It should have the same power as Trex 600. The gear reduction I chose puts me at around 1700 head speed.

Here is video of the current configuration

http://www.youtube.com/watch?v=2AfPuxArZ4o
http://www.youtube.com/watch?v=0RW9c-mp-Tk
http://www.youtube.com/watch?v=reKt5wh8f3o

Thanks for the input



Hard job competing with gravity.
12-21-2007 03:52 AM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

Stanc means that you're not going to get that kind of runtime with that motor/battery selection and camera. The gearing is fine but the normal runtime for an Erap-50 with a 4200 pack is around 7-8min max with easy flying. You're gonna need more power to lift all the weight. I have tried 6S and it just doesn't cut it. 8S is ok with the right motor/battery. 10S is the way to go as far as motor/power for a raptor50. I have also run 11S and 12S which were awesome.

I also have a E-rap90 with 32/3 and almost 12:1 gearing on 8S 4200s and 720 blades that draws only 18amps in a hover. I still only get 7-8 min with this setup. But it will carry the extra weight of a scale fuse (TT MD500) with no problems which came out to about 12lbs all up.

The Trex with its stock setup is lucky to get 5-6min of runtime.

The Crappie Flop is my favorite dance!
12-21-2007 05:22 AM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

Oh, and the weight of an E-rap50 with batteries is about 8.25lbs. Mine came in at 8lbs using V1 frames and ccpm conversion. This is also using Lipos with A123s you are looking at 9lbs.

The Crappie Flop is my favorite dance!
12-21-2007 05:27 AM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

PJRono

Thank you for the advice. I will have to look into the option of larger batteries and change the gear box ratio or could I parallel the packs at 8800ma 6S 2P.

With the higher kv motor would you say the motor is more or less efficient than lower kv motor. Some day some one should right book about this stuff.

The current TOW is around 10.5 lb my estimated weight was 10 lb with one pack so 10.5 with tow.

Jerry

Hard job competing with gravity.
12-21-2007 01:07 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

I have reviewed some past treds. As far as I can tell operating at this weight with 6S packs, with the same motor and ESC combination on the Trex600E. There are guys out there doing this with 7 to 8 min run time TOW 10 lb. From my knowledge there is lager torque required to swinging the 700-800mm blade but for us at the 10 lb range we run 600-620 with less torque, Less amps and low head speeds. Like I said I’m ruining an OS 32 right now not the most power full engine?

I still see the possibility of this operation. On the other hand if it dose not work, all I have to do is change the reduction gear set as required by cell increase, still maintaining the proper head speed.

I’m getting a little confused. I wish some one could write a book about this.

If some has some knowledge on this: Align 600L motor, BL75G speed control and 6S lipo battery packs TOW 10lbs please post.

Hard job competing with gravity.
12-21-2007 02:50 PM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

Good luck!! It still takes a certain amount of blade and headspeed to generate enough lift to lift a 10+lb machine. That will require a certain amount of amps. I did fantastic with 18amps on a 12lb machine with 720s and headspeed of 1300rpm, but still did not get near 10 min with 4200s.

The Crappie Flop is my favorite dance!
12-22-2007 01:57 AM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

PJRono

I had a look at your gallery, 12S at 4200ma Wow that must be rocket. I have, like said engineer a gear box that will allow me to change the reduction gear set to what best works for the application. With your current Raptor 50 set up, is it running 600mm and what is your motor kv rating, running the stock gears, with 12s packs you must in about 500kv still turn 2000 rpm?

What do you think is the better?
High kv motor lower voltage generating torque through reduction gearing or low kv motor higher voltage generating torque through electrical push.

This is not trick question. I don’t know

Hard job competing with gravity.
12-22-2007 02:41 PM
 
 
stanc
Veteran
Location: Conroe, TX

Quote 
What do you think is the better?
High kv motor lower voltage generating torque through reduction gearing or low kv motor higher voltage generating torque through electrical push.

This is not trick question. I don’t know

Lower kV and higher voltage, in my opinion. PJ and I have been screwing around with electric helis for a while now and as I don't totally agree with him about the number of cells to use, because obviously we have two totally different styles of flying. But for you to pick up 10 to 11 lbs. of equipment and have any kind of flight time, you are going to need more voltage and some pretty high mah packs. You will have to play around with the gearing and the throttle curve to achieve a head speed that won't eat up the amps and allow you more flight time. I don't know if a Raptor w/600mm blades will work very good at 1300, since I've never tried it, but the lower the better. Of coarse your not doing much more than hovering, so the 600s might be OK, like I said I've never run an electric that low. I like 2200 to 2300 HS, but it all relative, kV, voltage and gearing.
Good luck, I'm sure you'll come up with the right formula for you application.

Stan

Stan
2 x Ion X2
eStartus
eAvro90
Performance Plus Lipo Packs
12-22-2007 03:10 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

stanc

I like 1700 to 1800rpm on my 620mm blades. That will give nice smooth operation with little wind interference, normally I operating this machine pretty slow and do a lot of hovering. Time of operation really can be very short, 5 minutes will do for the most part. I would sooner operate short flight and change the battery rather that many short flight on one large battery for you see I must land any ways to set up another shoot. I think it will be easier to keep track of power usage this way. On the other hand If I was taking video then it would be nice fly around longer and take a lot of footage to edit. A second battery paralleled could give me a longer run time for this application.

Test are in order I must get this machine assemble soon

Hard job competing with gravity.
12-22-2007 05:20 PM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

The 720s, Actro 32-3, 12:1 gears, 8S 4000 Lipos are on a E-Raptor90 w/headspeed of 1300rpm that weighs 12lbs all up.

My E-rap50 has A50 12S motor, 600s, 9.3:1 gears, and 10S 4200 lipos has a headspeed of 1850-1900rpm.

I like the 2200-2300 headspeed better for my E50 just like Stanc does. But I have messed around with different gearing/battery,motors to try to get longer flights and be easier on the batteries. The Raptor50 with 600s and 1400rpm headspeed flys like crap and wants to fall out of the sky! With 1700-1800rpm it is flyable though not very aerobatic. At 1900 it becomes able to do more and at 2200 it is downright fun!! Now remember that this is at 8-8.25lbs not carrying the extra weight of the camera.

The Eraptor 90 with 1300 headspeed flies ok, though not very aerobatic will loop and roll barely. With a headspeed of 1750 it flys very well in wind and is more aerbatic. Once you get her up to 2000 she is a virtual rocket!! and this is at 12lbs.

Now after messing around with gearing and battery count. I have found that nothing I do gets me any more runtime than the 7-8 mins. At 18amps in hover I got 7-8min and at 24amps hover I got 7-8min. In either case the batteries got warm. More so at the 24amps. After losing some of my Lipos I tend to go for the lower amps just to save my expensive batteries.

The Trex600 is setup differently and only gets 5-6min flights with 5000mah lipos. Don't tell me different because I know of several of them and watched and timed them.

Now If I had those 5000s in my machines I might get close to 10min.

The fact is, it still takes a certain amount of power to get these things off the gound and flyable. And the extra power that we use doesn't change things that much. However weight does make a difference-and you are adding it! The only effective way to offset weight is rotor diameter while still keeping amps down.

Now maybe a Eraptor50 with 30gears and stretched to 680s might be the answer here. I have not tried this yet. It's sounds like alot of fun though!!! Maybe one of these days I'll try it.

I wish you luck and hope you are succesfull in your venture!

The Crappie Flop is my favorite dance!
12-22-2007 06:51 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

Originally the machine was a Raptor 30 of course it has been stretched out, but when I was running the 550mm blades at 1800 rpm it work well. I stretch it out for auto's (safety) if I ever lost power. What I did notice was that run time was reduced with the larger blade 620mm at 1700 rpm. That said I assumed that if continued lengthening the blades it would require more torque to power the rotor. Torque = watts= amp * voltage. Keeping it simple; your rotor is the transmission the pitch is the gears. The pitch alone affects torque and the length of the blade affect the torque. That said long blades low pitch require X amount of torque. Short blades more pitch require X amount of torque.

If you are running 18amp * 30volts = 540 watts of power at 12lb there for 4.2 amp/hr battery would deliver you at 100% 14 minutes at 80% 11 minutes.

So if I ran 24 amp * 22.2 volt = 540 watts of power at 10lb. There for 4.4 amp/hr battery would deliver me at 100% 11 minutes at 80% you would get 8.8 minutes.

The variable factor would be the drive efficiency: kv of motor and rpm of rotor, rotor diameter and pitch of blade.

What will give you the best performance?

My conclusion is that if 540 watts is enough to power your Raptor 90 at 12lb there for if produce the same power at 10lb I would have good results, but I don’t know for sure.

I hope you see what saying because the brain is starting to hurt

Hard job competing with gravity.
12-22-2007 10:50 PM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

Knowing the numbers is great, but your missing alot of them. Also there's the fact that numbers don't always add up in reality. The motor will rarely run at 90% efficiency, ESCs eat up some more, gearboxes will eat up another 10-15%. Then there's the fact that the batteries don't hold their voltage though the entire run (towards the end the load hits them harder and the voltage drops more). At this point the motor won't have enough power to keep said heli in the air. Then there's the fact that you can't run LiPOs down too much(about 80-85%) without starting to ruin them. Then there's the drag on the machine, and fighting a wind. All of drops your run time. The numbers help but don't always add up.

Please give it a go and let us know the results. I am always looking for a better way. I look forward to seeing your results!!

The Crappie Flop is my favorite dance!
12-23-2007 04:15 AM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

Watts = horse power=torque = volts * amps

Watts / volts = amps

500 watts / 44.4volts = 11amps 4400mah pack at 1300 grams

500 watts / 22.2 volts = 22amps 8800mah pack at 1300 grams

Far as I can see it is the same power to weight ratio so if there is a difference is in the in the efficiency.

What is more efficient high kv or low kv motor that is the real question?

Rob T in this post has my vote

http://www.runryder.com/helicopter/t278420p1/

KV and KT (torque constant) are directly connected - increase one and the other goes down by the same ratio (ie double one and the other halves).

What this means is that given 2 identical motors except one has a higher KV than the other, if you change pinions to match the heaspeed the performance will be identical.

In practice, low KV motors have more turns of thinner wire than high KV motors, so selecting a high KV motor usually means picking a motor with less resistance. Motors with lower resistance bog less under load than motors with high resistance.

So, in a particular motor size, the highest KV variant will give the most power for 3D flight if it is geared correctly. The limit is when you reach gear ratios which are impossible without adding an additional stage to the transmission

Hard job competing with gravity.
12-23-2007 04:44 AM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

"The Trex600 is setup differently and only gets 5-6min flights with 5000mah lipos. Don't tell me different because I know of several of them and watched and timed them."

First off I agree with statement.

Same Trex 600 running the 12s 5000mah battery would operate 12 minutes.

Same Trex 600 running the 6s 5000mah + 6s 5000mah paralleled, this is the same pack wire differently. There for the same power and should give you 12 minutes of operation.

Keep in mind they are the same weight and have the same rotor rpm.

Hard job competing with gravity.
12-23-2007 05:11 AM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

I understand all that, and it makes sense. However there is also the fact that a high kv motor(hot) will draw more under load and run warmer. That is why Align has so many problems with their motors. I am always hearing of another one burned out.
My motors have no fan installed and you can hold them afterwards. The 32-3 is absolutely cool even though its running way above its stated cell count.

The Crappie Flop is my favorite dance!
12-23-2007 07:39 AM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

Now we are getting down to the truth. As debated in the other post low kv motor has more small windings and high kv motor less larger winding. There for if we run the 4400mah 12s your low kv motor produces 500 watts of work. Electrons traveling through the small wire has higher resistance would require more push (volt) to perform the same work. That said I have noticed that low kv motor have lager diameter detentions. My conclusion is that larger diameter provides torque because larger arm. High kv motor has larger wire but less of it. So if run the same amount of power 500 watts of work with 8800 2p 6s parallel pack. Electrons traveling through the large wire has lower resistance and would require less push(volt) to perform the same work.

Resistance create heat:
-small wire would create more heat (low kv)
-large wire would create less heat (high kv)

So maybe the difference is in how the motor dissipate heat. Larger kv motor has more surface area there it has greater heat dissipation ability. Could this be the key to what we are seeing? More heat dose not make the high kv less efficient it simply is a by product of low surface area.

“Now after messing around with gearing and battery count. I have found that nothing I do gets me any more runtime than the 7-8 mins. At 18amps in hover I got 7-8min and at 24amps hover I got 7-8min. In either case the batteries got warm. More so at the 24amps. After losing some of my Lipos I tend to go for the lower amps just to save my expensive batteries.”

PJRono

I have to thank you for all the messing around because you are saving me a lot of time. Your information is extremely valuable to me.

4400mah 12s 20c battery is 44.2 volt and has discharge rate of 4400 * 20 = 88amp

4400mah 6s 20c + 4400mah 6s 20c at 22.2 volts paralleled pack have discharge rate 88amp + 88amp = 176amp

Both batteries are accentually the same but wired different. If you discharged at the max capacity they would create the same results of temperature in all cells because each cell will only provide is rated amperage. Same for 50%, 20% discharge rate the results should be the same.

So in conclusion the voltage makes no difference. It mush simply be a preference.

Hard job competing with gravity.
12-23-2007 04:59 PM
 
 
PJRono
Senior Heliman
Location: Ham Lake, MN - USA

One other thing about the LiPOs. When you use them in parallel, they never balance out. What I mean is no two lipos are exactly the same so when you draw from them one will always put out more leaving an imbalance. Now balancers do a great job, but I haves lost too many parallel packs running them. I will not run any more parallel packs period. One cell always goes to hell and takes the other one or all of them with it. If at all possible I will series packs only.

The Crappie Flop is my favorite dance!
12-23-2007 05:51 PM
 
 
eyeinsky
Senior Heliman
Location: Fall River, Nova Scotia, Canada

Yup that is true also but lots pack are manufactured that way so whether it is brick or stick lots have parallel wiring. Balance is the key and charging together may give better service. Have you looked into the A123 cells they are a lot more durable I here.

Thanks for your help

Merry Xmass to you and your family
Jerry

Hard job competing with gravity.
12-23-2007 06:30 PM
 
 
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