3dx 500 sah => motor for 3s lipo ?

[666yeti666]

Dear All,
I want to buy a 3dx 500 SAH, so that's the low cost version with the hitec-servo-frame. I want to keep things light as possible.

I want to use my current equipment of my robbe spirit pro. This means :
servo's : hitec hs-81mg
esc : hacker 40B heli
gyro : gy240 + s3150
receiver : jeti rex5 mpd
motor : ?

The weight of the kit is 770gram (SE kit = 870gam!).
With my electronics and a motor of about 150gram the total weight would be approx. 1350gram.

What kind of motor and pinion would you recommend for 3s lipo and a headspeed of about 1800 ?

It's not for 3D but for flying around and mild aerobatics (I'm an intermediate flyer, also own a esky king v2 and Logo 10 3D XL)

thank you guys

[lotus7]

Hyperion H3025-10

[666yeti666]

Thanks, but I found the motor to be quite heavy , 186grams
The kv = 815 rpm/V which would lead to a headspeed of about 1900 rpm (pinion = 24T , governor =90% , V=9.6V).

I would like to have a little lighter motor if possible, I don't know what the downside of it is, but let's say a axi2820-14. It weighs only 150gram.
What about that ?

[WillJames]

I am not so sure that a 500 size heli is going to fly well at all with the current gearing on 3s. I am not sure it will fly well at any gearing. If you want to use 3s packs, wait about a month or so and get the Rotorworkz version and fly it on 2 of the 3s packs.

[LITHIUMSTATIC]

Originally Posted by WillJames

I am not so sure that a 500 size heli is going to fly well at all with the current gearing on 3s. I am not sure it will fly well at any gearing. If you want to use 3s packs, wait about a month or so and get the Rotorworkz version and fly it on 2 of the 3s packs.

I second that..... and the Kontronics Kora motors are nice and light.

[Ticidytoc]

wait about a month or so

I second that..... and the Kontronics Kora motors are nice and light.

Looking at the kv on the Kora the 15 series has the best choices but its a small motor, the 25 looks to be about the right size but your back to a big pinion with this motor.

[666yeti666]

ok, thanks . I was just looking at the lepton section and those guys ar using a lot of times a Kora motor.
15-12 .
By the way , my intention is not to do 3D with it . I just like to fly aroundand so some mild aerobatics uptill now .
Everytime I read helifreak page I find that most guys are using insane high headspeeds ??? I don't know why but it seems to become some kind of fashion ...
For example ; I run my stretched mikado logo 10 3D on a headspeed of 1650rpm and it flies very good.
My robbe spirit pro flew on 1750rpm, and it also flew very good.

Does the 3dx500 really need such high headspeeds in the range of 2500 - 2800 ???

I was aming on a headspeed of about 1800 .. 2000 rpm.

So I did some calculation and came to the Kora 15-12.
For 3S that will give me a headspeed of about 1900 - 2000 with a 24T pinion and governor 85%
For 4S it will come to about the same rpm with a pinion of 18T and governor also set to 85%

What do you guys think ?
I prefer flying time of about 10minutes a pack.

What is the average power (in watts) needed for the 3dx500 in a hover ?

thanks again.
sebasteien
netherlands

[shooter75]

666yeti666,

I have a Hyperion H-S3025-6 (1365 KV) motor for sale in the "electronic for sale" posts, which I had in my HDX500 when I was running 3s. Do to its high KV rating its perfect for 3S and even 4S. With 4S I would recomend an 18 tooth pinion though.

[WillJames]

Originally Posted by 666yeti666

ok, thanks . I was just looking at the lepton section and those guys ar using a lot of times a Kora motor.
15-12 .
By the way , my intention is not to do 3D with it . I just like to fly aroundand so some mild aerobatics uptill now .
Everytime I read helifreak page I find that most guys are using insane high headspeeds ??? I don't know why but it seems to become some kind of fashion ...
For example ; I run my stretched mikado logo 10 3D on a headspeed of 1650rpm and it flies very good.
My robbe spirit pro flew on 1750rpm, and it also flew very good.

Does the 3dx500 really need such high headspeeds in the range of 2500 - 2800 ???

I was aming on a headspeed of about 1800 .. 2000 rpm.

So I did some calculation and came to the Kora 15-12.
For 3S that will give me a headspeed of about 1900 - 2000 with a 24T pinion and governor 85%
For 4S it will come to about the same rpm with a pinion of 18T and governor also set to 85%

What do you guys think ?
I prefer flying time of about 10minutes a pack.

What is the average power (in watts) needed for the 3dx500 in a hover ?

thanks again.
sebasteien
netherlands

I can help a little.

The reasons for the insane headspeeds on the 500 size helis is to keep them quick for 3D due to the higher disk loading on machines that weigh proportionately more than the 450 or 600 for the size blades they run. Slowing the headspeed does buy you some more runtime, but at the expense of quick heli response. I am a firm believer that more collective range and cyclic and slower headspeeds are where the E-Heli market needs to go, but that is just my opinion.

Also, as far as governor to control headspeed. I have found for me, that the proper gearing is necessary for any given setup to make gov mode work well on most ESC's. Assuming you have a ESC that can do 85% and get back to 2K, I think the heli would fly fine, but I doubt you will get 10 minutes. I would be curious to hear what you experience.

For average power, and no 3D you may be able to get by with 3s, but you are probably looking at maybe 4 minute run times.

[papayankee]

My 3DX500SE stock motor and pinion (870kV 24T) 85-90% throttle and 3S 5000mAH (1800g total weight) gives 1900/2000 RPM and 12 min fly time (cool hovering and slow translations), motor remains cold.
Some tests with a 4S 5000mAh (100g more) -> motor hot.
Will try 21T pinion.
Happy Chritmas
J.H.

[666yeti666]

Dear all, thank you for your comments and recommendations.
The heli is on his way and I expect it this week on my doormat :-))

12minutes on a 3s 5000 pack is really nice. Headspeed looks also very nice. Weight is high with 1800grams ...
But this is what I as looking for. mmm .... a 3200mAh pack would give me about 7.5 minutes of runtime, that would be just enough for me ...


mmm.... difficult , at first I will go with 3s packs , since I have them anyway .
But I think that I should go for the 4S in the long run anyway ....

Let's do some math with the numbers from papayankee :
3s lipo : average voltage = about 3.2V per cell under load = 9.6V per pack
average current = 60/12 * 5 = 25Amps (that's a lot ! for such a small heli)
average power =9.6*25=240Watts

If we change the value of the packvoltage to 4s = 4*3.2=12.8V, then the current that's needed will be 240/12.8=18.75 Amps.
The runtime with a 2500mAh pack would be then :
2.5/18.75*60=8 minutes !

In practice you cannot fly a pack for 100% empty, so a 2800mAh pack would be necessary.

Let's look at some lipo weights :
3s 4900mAh flightpower evo 25 = 384gram cost = 153euro
4S 3300mAh flightpower evo 25 = 351gram cost = 112euro

weight difference = 33gram
cost difference = 41euro (= 55U$)

With 3300mAh even longer can be flown ! 90% of 3300mAh = 2970 mAh.
Flytime = 2.970/18.75*60= 9.5minutes !

Now let's look at the "stress-factor" of the different lipo packs.
The 5000mAh pack would be stressed with 25A, that equals 25/5 = 5C
The 3300mAh pack is stressed with 18.75A, that equals 18.75/3.3 = 5.7C
Well, that's not bad !

I think I will go for the 4S set-up 3300mAh


Now about the motor:
I most probably will go for a Kora 15-xx. Because it's light (150grams) and it has a built in fan, last but not least kontronik is a really good german manufacturer.

The 15-12 has a kv of 920. The 15-14 kv=790

The 15-12 with a 4s lipo will give a headspeed of about 1800 - 2500rpm (governor 85% , pinion 18 to 24 T, celvoltage 3.5V/cell, efficiency 90%)
The 15-12 with a 3s lipo will give a headspeed of about 1500 - 1800rpm (governor 85% , pinion 18 to 24 T, celvoltage 3.5V/cell, efficiency 90%)

The 15-14 with a 4s lipo will give a headspeed of about 1600 - 2200rpm (governor 85% , pinion 18 to 24 T, celvoltage 3.5V/cell, efficiency 90%)
The 15-14 with a 3s lipo will give a headspeed of about 1200 - 1600rpm (governor 85% , pinion 18 to 24 T, celvoltage 3.5V/cell, efficiency 90%)

I think the 15-12 is the most flexible motor and can also be used for 3s lipo.

So the kora 15-12 it will be !

[papayankee]

Originally Posted by 666yeti666

So the kora 15-12 it will be !

I agree !
For mild flights 3S is OK and you may change the pinion for 4S.
I think that a 26T pinion would be better than 24T for the 3DX500 and 3S.
I finish my HDX500SAS : 900kV motor (MT Dragon) and 21T pinion, with 4S, I got 2250 HS at full throttle and about 7° pitch. After a mild flight the motor was about 60°C. With a 3S it remains cold.
Fly time is almost the same with 3S & 4S (5000mAh) owing to the heavier battery and less efficency of the motor in 4S.
A+

[666yeti666]

I would think that 26T is quite large for the 3s lipo , but it keeps guessing since I don't have the heli yet ....

Your set-up seems to be ok . The max pitch of 7 degrees isn't that much, will this prevent the motor from bogging down ?
The total gear ratio of this helicopter is quite low anyway , much lower then my other heli's . This will put some real strain on the motor.
I've read that the hirobo lepton (high end) helicopter , of which this one is a clone, does have the same low gear ratio ?? So I expect it to be ok. Still wonder why they have choosen such a low ratio.

Do you have the 3dx500 and the hdx500 ?

[WillJames]

The Lepton also uses a 94T main gear from what I have read.

The HDX500SE is more like the lepton, the SA is very unlike the Lepton.
The HDX500 and 3DX500 machines are not the same machine. They may have been very similar in the past, but that is changing.

The HDX500 Rotorworkz Version is going to use a 130T main gear to allow for a lot more gearing and battery options. If you have a SA, it will be an easy upgrade. The Rotorworkz Version is in testing now. There is video of Henry Caldwell flying it at the Black Sheep Get Together in the HF Video forum. The machine HC is flying does not have the 130T main gear installed yet, but it is running the frames that can accept the bigger gear. I think a tail speedup is also in the works to provide better tail authority when running more pitch.

[papayankee]

Originally Posted by 666yeti666

I would think that 26T is quite large for the 3s lipo , but it keeps guessing since I don't have the heli yet ....

As the motor remains cold with3S & 24T, I guess more power and headspeed may be got with a 26T, just an idea

Your set-up seems to be ok . The max pitch of 7 degrees isn't that much, will this prevent the motor from bogging down ?

No, I am still training very mild flight thus I limit the max pitch.

Do you have the 3dx500 and the hdx500 ?

Yes, 3DX500SE & HDX500SAS.
A+

[666yeti666]

Well in the meantime I received my 3DX500 SAH. I think it's the latest v2 version. I've got a long aluminium head , the longer tailblades, and the longer mixing arms. Hopefully it will give me +/-12 degrees of pitch ...

Everything looks really good ! All moving parts are running silky-smooth ! The downside is that one of the rotorblades appeared to be broken at the top and the tailboom is not perfectly straight. I'm waiting for an answer from the supplier ...
The head the frame and the tail are all assembled so it's very convineint. I'm still doubting to disassemble the head to see if somethings is not wrong assembled ...

When times running by I'm keep thinkiing about the drive train. I'm convinced that a bigger maingear , in combination with a high kv motor would be better , in order to bring down the gear ratio, so the motor is not loaded so much.
I understood that a 130Tooth maingear is available, is that correct ? Would that fit into my latest sah G10 frame without mods ??? I think not, it's larger in diameter, can the frame be 'dremeled' to make room for or will that the weaken the fram significantly ???
Where can the 130T be bought ?

thanks