Low Head Speed and Motor choice...

[Ding0]

Hello all. I'm building an E7SE that's taking me too long!!! I purchased a KDE 700XF-535-G3 motor but have gotten ideas about switching it to a 455 to lower the head speed. I won't be flying 3D, in fact the mechanics will end up in a Century 56" Airwolf fuselage (from 2001) after I get the bird in the air and all dialed in - I'll probably fly it stock for a year or so to get used to the procedure of flying electric which is all new to me. I want to hear the whop of the blades as much as possible when the mechs are in Airwolf! I'm using a Kontronik Jive Pro 120+ with JR RG731BX receiver and Spirit FBL.

Here's what I think I know about calculating the head speed - taken from the Jive Pro manual, heli setup using the Flight Mode switch:

Start / motor off: 0%
Hover (IdleUp 1) : 45% = 535KV (motor) * 37V (10S LiPo) / 10.08 (Gear Ratio) = 883.71 Head Speed
Scenic Flight (IdleUp 2) : 60% = 1178.27 Head Speed
3D-Flight : 80% = 1571.03 Head Speed

First, are my calculations correct? Are these Real World numbers?
Second, is that how I'll end up setting up my radio?
Lot's of questions I have about the unknown! Based on my abilities at the moment I'd end up going between IdleUp1 and IdleUp2 and would never fly at 80%

If this is all true I have a hard time believing Airwolf will fly unless I'm using all blade pitch possible. Should I be concerned about using the 455KV motor? The numbers with a 455KV and 12SLiPo are roughly the same as above...

In closing, I was told by amain (and their website shows) that the 700XF-455-G3 has been discontinued. Is there a newer motor on the horizon that replaces it?

I appreciate any guidance and/or opinions provided.

Regards and Happy New Year,

Dean

[Chuck Bole]

 Hello, which head speed calc. are you using?
 Using MrMel's head speed calculator http://heli.dacsa.net/  i come up with this:

Throttle 60%: 1646
Throttle 65%: 1696
Throttle 70%: 1747
Throttle 75%: 1798
Throttle 80%: 1849
Throttle 85%: 1900
Throttle 90%: 1950
Throttle 95%: 2001

 That's using your listed 535Kv motor and 10s 45C packs with a 12T pinion and 121T main gear. Also selected Jazz/Jive (Mode 4) it didn't list the JivePro.

With the 455Kv motor and 12s with same gearing:

Throttle 60%: 1679
Throttle 65%: 1731
Throttle 70%: 1783
Throttle 75%: 1835
Throttle 80%: 1887
Throttle 85%: 1939
Throttle 90%: 1990
Throttle 95%: 2042

 You didn't say if you were planning on 5000 packs or 4400 or some other size.

chuck

[Ding0]

Thanks Chuck, I really don't recall where I got the formula to calculate head speed. Based on the numbers you posted though, how will my radio be set up to fly?
I recall seeing in the Jive manual "The Jive Pro should not be used with a throttle value higher than 80% in Heli Mode, as it needs at least 20% headroom for proper governing."
Does that mean I'm looking at from 60%-80% on your numbers? Clearly the 455 looks better for a Low Head Speed...

Here's what I get from MrMel's for 455KV and 10S:
Estimated lowest voltage during flight: 34.80
Lowest RPM (due to voltage and efficiency) : 1460    <--What Does This Mean?

Throttle 55%: 1385
Throttle 60%: 1457
Throttle 63%: 1500
Throttle 67%: 1558
Throttle 70%: 1601
Throttle 73%: 1644
Throttle 76%: 1687
Throttle 80%: 1745

Result is based on ATV not being calibrated, meaning maximum throttle is reached around 80%

Here's 535KV and 10S:
Estimated lowest voltage during flight: 34.80
Lowest RPM (due to voltage and efficiency) : 1717

Throttle 55%: 1629
Throttle 60%: 1713
Throttle 63%: 1764
Throttle 67%: 1832
Throttle 70%: 1883
Throttle 73%: 1933
Throttle 76%: 1984
Throttle 80%: 2052
How about these numbers... what do they mean in relation to how I set up my radio and what are the effects on the electronics and motor if any?
The packs I plan on getting are 10S and larger than 5500mah, I want the most flight time possible! If I could find good 6500mah I would use those, FWIW.

[Ding0]

C'mon guys - more than 80 views and only 1 response... you guys are holding out on me!!! Let me hear your opinions or answer some questions please! 
 

[Mike Spano]

sorry man, I don't fly low HS or the kontronic ESC's. wish I could help though!

[Danny Dugger]

Mr Mels headspeed numbers most always come out 150-200 RPM higher than real life for Kontronik gov. Also, you want to specify the Kosmik gov when using Jive Pro.
   The throttle% value that you set in your transmitter will basically correspond to the PWM rate that the Jive Pro will output. 80% max is for gov headroom, and will also be 80% throttle setting in your transmitter. Make sure you do a mode 1 reset using the tx sticks with a 0-100% throttle setting before programming the ESC gov mode as this will calibrate your transmitter's throttle output to the Jive Pro.

[Ding0]

No worries Mike, thanks for the support!   

Danny, you're a life-saver!!! Thank you for the clarification using MrMel's calculator and for the setup tip.
Here's the "revised numbers" for a 455KV on 10S (Left Column) / 12S (Middle Column) / 12S -200RPM Correction (Right Column)

Estimated lowest voltage during flight: 34.80 10S   /   41.76 12S (both @ 45C)
Lowest RPM (due to voltage and efficiency) : 1460 10S  /   1752 12S  (both @45C)

Throttle 60%: 1110          1332          1132
Throttle 65%: 1202          1443          1243
Throttle 70%: 1295          1554          1354
Throttle 75%: 1388          1665          1465
Throttle 80%: 1480          1776          1576
Throttle 85%: 1572          1887          1687
Throttle 90%: 1665          1998          1798

So Danny, what you're saying is the Real World head speed will probably be the Right Column??? If that's true I'll definitely be running a 455KV on 12S, the 10S numbers would be between 910 and 1465 (60-80%), too low I think.

Question #1 - Does 200RPM make that much of a difference?

Question #2 - about the results from MrMel's, what does the "Lowest RPM (due to voltage and efficiency)" actually mean??? Ill guess and say above or below that number the system becomes less efficient, meaning it'll generate more heat which might limit flight time?

[Robert "Full" Montee]

Question 1: Yes, 200rpm can make a difference. I enjoy 1600rpm governed for 3D on my E5SS more than I enjoy 1500rpm doing the same maneuvers.
Question 2: A hundred RPM difference in governed headspeed was a 30 second difference in flight time. For example at 1500rpm I usually fly about 10:45 seconds before telemetry warns me to land based on mAh consumed. At 1600rpm it is 10:15 seconds typically.
I fly a Kontronik Jive Pro 120+ with a Kontronik Pyro 450kv motor on 12S within my E5 stretched to fly 716mm main blades.

[Danny Dugger]

So Danny, what you're saying is the Real World head speed will probably be the Right Column??? If that's true I'll definitely be running a 455KV on 12S, the 10S numbers would be between 910 and 1465 (60-80%), too low I think.

Question #1 - Does 200RPM make that much of a difference?

Question #2 - about the results from MrMel's, what does the "Lowest RPM (due to voltage and efficiency)" actually mean??? Ill guess and say above or below that number the system becomes less efficient, meaning it'll generate more heat which might limit flight time?

Yeah, 10s is going to give you very low head speeds with that motor, you will probably want to stick with 12s.

1) Yes, 200 rpm makes a big difference!

2) I *think* MrMel tries to calculate voltage sag with the batteries' discharge rate and motor efficiency info you specify and give you a resulting lowest head speed at full load while governed at... maybe 90%? I never pay any attention to it, it probably won't be accurate anyhow as there are a lot more factors to this that aren't taken into account. The whole thing is just a ballpark idea to get your electronics and gearing reasonably close on a new build. Once you have your rig in the air you will have to tune to your personal feel.

[Ding0]

Awesome! Thank you guys for the help! Now I have a much better understanding. I'm going to try and find the largest LiPo that'll fit in the airframe - hopefully 6000mah or larger!

[Danny Dugger]

Awesome! Thank you guys for the help! Now I have a much better understanding. I'm going to try and find the largest LiPo that'll fit in the airframe - hopefully 6000mah or larger!

Remember that batteries are the heaviest component in the airframe. As capacity increases so does weight. When you choose your battery size you are balancing flight performance and flight time. Lighter batteries = less flight time but lower disk loading and a more responsive helicopter. Some guys like a heavier helicopter, most like a balance. It's personal preference and totally up to you. If you're a nitro guy you are probably more accustomed to light disk loading. I just wanted to give you a heads up before you load a brick in your E5! Not only that, but you're setting up for low head speed. Low head speed setups should be light, if it's too heavy it isn't going to fly well. Good luck! It's a great heli!

[Ding0]

My KDE 700XF-455-G3-S6XL came in today!    Now I have to do some battery hunting!