Mini Protos on 4S

[whaleboy]

I'm thinking of going 4s on my Mini Protos build. The difference in pack weight is plus 50g for the 4s over similar 3s packs. Are there any CoG concerns there? I'll be pairing it w a Scorpion 1630 kv and a 17t pinion.

I'm ready to hit "buy"... just need to know if the weight of the 4s packs (250g) is going to be an issue.

Thanks

-David

[HighFreq]

1630 kv is on the low side, better if you go with a 2000kv for 4S.

I am waiting for some samples at 1300kv for my stretched mini(should be here tomorrow)...................in the mean time i have to join these two 3S packs together



Corrado

[michael88997]

i smell a lot of 3s packs on the market soon... i know 6 for sure ... i hope some stealth 350mm blades come out for us cheapos

[whaleboy]

Originally Posted by HighFreq

1630 kv is on the low side, better if you go with a 2000kv for 4S.

I am waiting for some samples at 1300kv for my stretched mini(should be here tomorrow)...................in the mean time i have to join these two 3S packs together



Corrado

Really? I'm aiming for 3100 HS. I'm not looking for crazy performance, just heavy sport and light 3d, and flight times are pretty important. With the scorpion 2010kv motor, I'd need to run a 14t pinion (I heard a report of one breaking in flight due to the thin material on the 14t). Assuming there is no reason to run a higher pinion than the 14, what benefit is there to running a higher KV/smaller pinion over a lower KV/bigger pinion? I figured there was no difference but maybe there is...

Also, Since I need to buy the packs anyway, I'd consider the smaller capacity 6s packs, if I could get the same or better flight times... I briefly checked, but couldn't find a suitable motor for the target HS.

Then there is weight... if going 4s, is 2200 too heavy at 250g, or do I need to stay closer to 200? It'll be FBL, so CoG needs to be good.

Thanks

-David

[JustPlaneChris]

Originally Posted by whaleboy

Really? I'm aiming for 3100 HS. I'm not looking for crazy performance, just heavy sport and light 3d, and flight times are pretty important.

David, if you are going FBL and fly heavy sport / light 3D you don't need more than 2700 rpm. Mine has stellar performance at that headspeed and returns easy 6 minute flights without going beyond 80% of the pack (3S 2200). When I turn it up to 3100 it's just ridiculous, and doesn't really suit my flying style at all (airplane style aerobatics mostly).

[whaleboy]

Originally Posted by JustPlaneChris

David, if you are going FBL and fly heavy sport / light 3D you don't need more than 2700 rpm. Mine has stellar performance at that headspeed and returns easy 6 minute flights without going beyond 80% of the pack (3S 2200). When I turn it up to 3100 it's just ridiculous, and doesn't really suit my flying style at all (airplane style aerobatics mostly).

Which is why I question going with a 2000kv motor on 4s, as it limits the low end HS, which I'd like the option of doing if I so desire. I'd like a setup that lets me gear in the midrange of whats available to get my target HS so I have plenty of room to go lower or higher.

In the summer my electrics tend to get really really hot, which is my main reason for wanting to go with 4 or 6s... efficiency (longer flights) and cool temps. I don't really fly hard enough to need the extra power that comes with higher cell counts.

Speaking of flight times... I'm also wondering how different cell counts affect flight times. How would a 2200 3s compare to an 1800 4s or a 1300 6s (assuming they are motored and geared for the same HS). Is it just a matter of multiplying the voltage by the capacity and comparing the results? I'd think its not as simple as that, but I don't know... by that math the 6s has the most stored energy, then the 4s, then the 3s. If I can find an appropriate motor for 6s, I'd go that route (assuming I wouldn't get any less flight time than with the other options).

Thanks

-David

[macem]

... i did my first flights with 4s (240gramm) at 2580 kv-motor (2221-12 scorpion) and 15t-pinion yesterday... i cannot say anything about flighttime (to much landings to adjust the settings), but about
• headspeed: 3100 rpm at 75% esc .... and
• the weight of the lipo seemed to play absolut no role (actually better for balance...
• pitch-reaction like directly from hell...

the advantage for using 4s should be less ampere (cheaper: 40ampere-max-esc is enought), cooler esc and lipos, longer flighttime...

[whaleboy]

Originally Posted by macem

... i did my first flights with 4s (240gramm) at 2580 kv-motor (2221-12 scorpion) and 15t-pinion yesterday... i cannot say anything about flighttime (to much landings to adjust the settings), but about
• headspeed: 3100 rpm at 75% esc .... and
• the weight of the lipo seemed to play absolut no role (actually better for balance...
• pitch-reaction like directly from hell...

the advantage for using 4s should be less ampere (cheaper: 40ampere-max-esc is enought), cooler esc and lipos, longer flighttime...

You sure about that head speed? According to ReadyHeli's/MrMel's headspeed calculator, that combo at 75% wound be about 4100 rpm. Is the headspeed calculator that far off for this heli?

Thanks

-David

[macem]

... i# m sure about the headspeed... let us do the calculation manually

2580kv*14,8v/8(gearratio of 15-pinion)*0,9(10 percent deduction for losses of efficiency of the system...) gives us about 4300 rpm max-speed, 75 percent of that: 3200 rpm....

thats exactly what i´ve got...

[whaleboy]

Originally Posted by macem

... i# m sure about the headspeed... let us do the calculation manually

2580kv*14,8v/8(gearratio of 15-pinion)*0,9(10 percent deduction for losses of efficiency of the system...) gives us about 4300 rpm max-speed, 75 percent of that: 3200 rpm....

thats exactly what i´ve got...

I don't think the throttle percentage calculation is quite as linear as that. From my past experience, the ReadyHeli calc has always been fairly accurate. I recently set up and tach'd my E-Aurora, and if I do the math manually I get 1328 HS at 70% throttle. The ReadyHeli calcs it at 1829. When tached with a good optical tach, the actual HS was 1860. That is very close to the RH calc but WAY off from the manual math.

What are you using to tach your actual HS? 3100-3200 on a 2580 motor, 15t pinion, and 75% throttle gov on 4s seems way low to me.

-David

[whaleboy]

BTW, I ordered the heli, servos, etc, but haven't decided on motor or packs yet.

-David

[macem]

Originally Posted by whaleboy

I don't think the throttle percentage calculation is quite as linear as that. From my past experience, the ReadyHeli calc has always been fairly accurate. I recently set up and tach'd my E-Aurora, and if I do the math manually I get 1328 HS at 70% throttle. The ReadyHeli calcs it at 1829. When tached with a good optical tach, the actual HS was 1860. That is very close to the RH calc but WAY off from the manual math.

What are you using to tach your actual HS? 3100-3200 on a 2580 motor, 15t pinion, and 75% throttle gov on 4s seems way low to me.

-David

... david, i realy have no idea, why there are that differences... me in contrast, i made the experiences, that the manual calculations are amazingly close to the internal-tach of my esc (robbe roxxy 950-6 - a very good and cheap alternative to some other famous escs... )...

if i should make a guess, i would tip on the settings of the esc - which has to be strictly learned to the tx ... if you miss that, the percent-rate of the tx-manual never touches the real percent-rates of the esc ....

macem

[eightythree]

Originally Posted by Zumpo

http://www.youtube.com/watch?v=N6OMr92mFtw

See video description text for details. Headspeed is about 3750rpm. A very good choice, if you ask me

Is this 4S setup on stock components??
Ive got a few left over 4S packs that I may try, but can the ESC handle load at lower TC settings?

3700 rpm seems insane.. stock setup 4S get me 3500 safely?

thanks for the info..

[Zumpo]

I get the about 3500 when running on the stock esc (and motor) on 55% with a 15T pinion. No problem for the esc at all. Attached you find a logfile with using Hyperion 4S 2100mah 25C (TC is 50% and 55%).

Voltage drops are a little better on the Hyperion 4S 2200mah 35C, but it's adding another 35g to the helis weight. Still haven't decided which pack to go with. Both seem to be ok. Maybe I wait a little longer until it's getting warmer outside and then let pack temperature make that decision for me.

[eightythree]

Wow, max rpm is still around 3700 just like that video..
I cant really make out the bottom numbers in the Log picture, what are max amp peaks?

What are run times like with the 25C hyperion? Ive got 2 I can use, but I think I will just stick with 3S and stock pinion..

So, TC around 40% on stock pinion 4S would be pushing the ESC?

[michael88997]

do the 4s 2200 packs work out with the extra weight? im thinking about using nano-tech 4s 2200 packs that weight 60grams more than my 3s 2200 packs... my tail is a little heavy cause i have a turnigy plus esc mounted on the side... i was also thinking about trying out this motor

http://hobbycity.com/hobbyking/store...dProduct=11176

[macem]

... i used the 2200-4s-nano-tech lipos and they brought just the extra-weight, the mini needs to bee in balance...

... with stock motor, 15t-pinion and 3200 rpm (esc: about 75%) and light-3d-style i´ve got 5min flighttime, burning 2000mah...

... probably they best for 4s would be a 2100kv-motor, 1800 seems a little to less to me....

macem

[michael88997]

well im using a turnigy plush 60amp esc and i dont know if it will handle running at lower % so im aiming to run it at a straight 100% throttle curve and the 1860 seems to get me in the target hs with a 15t pinion...

i might try the scorpion 1630 on a 16t pinion so i can use a stronger thicker pinion... im fbl so i dont need insane headspeed but i believe running at 100% will get the job done

[macem]

Originally Posted by michael88997

... im aiming to run it at a straight 100% throttle curve and the 1860 seems to get me in the target hs with a 15t pinion...

in this case you may be right...

... my esc (robberoxxy 950-6) works well with partial load, so i prefered using an old scorpion an old 4s-lipos i had ...

[Zumpo]

Originally Posted by eightythree

Wow, max rpm is still around 3700 just like that video..
I cant really make out the bottom numbers in the Log picture, what are max amp peaks?

What are run times like with the 25C hyperion? Ive got 2 I can use, but I think I will just stick with 3S and stock pinion..

So, TC around 40% on stock pinion 4S would be pushing the ESC?

Numbers are:
Volts: min 13.28 max 16.63 avg 14.46
Amps: min 0.24 max 58.9 avg 20.45
RPM: min 0 max 3810 avg 3433

Sorry for that. I uploaded the image in high res. Forum scaled it down to a point where nobody can read a thing. Resolution should be adjusted to a resonable value

After 4 min. flighttime I used 1500 mAh of the 2100mAh available in the pack. I think I will increase the flighttime for another 30 sec. next time. I have no experience with a TC that low (40%). So I can tell you anything about that.