motor battery gearing query

[adwb]

Please can anyone either answer these questions or be so kind as to point me to a source of this info.
I am not a electrical person so it needs to be simple.
The syle of flying is slow scale flying no 3d or high torque stunt moves.

I have just bought a New Z-Power Z50-600/Conversion kit with Phoenix 85 esc to fit to a Raptor 30.
As this kit was originally intended for a Raptor 50 it is supplied with a 9 and a 10 tooth pinion and the choice of the original main gear or a optional extra 86tooth main gear. The recommended battery was a 10s [in other words 36 volt].

I found the comment below from another post and would like some help with the meaning.
"quote"
The main difference is that with the R30, you are going to probably use a smaller pack setup (i.e. – 8s vs. 10s…). Just order the R50 version, add the option for the 86T main gear and I will send you the 85T instead.
"end quote"

what I don't understand is :-
1why is the smaller lower voltage 8s[28.8 volt] pack being suggested?
2 what happens if I use a 10 s pack [already purchased]
3 what gear combination would be correct for a 1os pack? and why?
4 how do work out from a motor spec what is the correct battery size?
5 I also have a devatl 36 volt pack as has been discussed recently and this fully charged measures 45 volts dispite being a 10s
pack why is that for goodness sake?

see why I'm confused and want simple answers?

regards
Alistair

[swatson144]

1. Lower weight less rotor loading. The smaller blades don't need the bigger pack.

2. nothing much as long as you are geared for it.

3&4 are pretty much covered by me in your previous thread. It's about as simple as it gets. If you have any questions please let me know.
KV * pinion teeth * voltage / main gear teeth = max HS *.8 = realistic HS. If you have the final ratio from the conversion specs it's simply KV * V / ratio = Max HS

5. all batteries are rated as nominal voltage. They will read higher when fully charged and under no load. Under load they quickly drop to the nominal voltage.

Steve

[adwb]

Steve, thank you the formula I understand and see how altering inputs will give you the answers.
where do or how do i work out a motor Kv?
I see that Kv =RPM /volts
so how do we know what a motor rpm is? or do we assume an arbitary figure?
Can I assume these figures from the hacker /actro webs site are fairly average across the different motor mfgs?
A5010s motor = 558Kv actro 20-4 = 570Kv
I cannot find the Kv of the Z-Power Z50-600 that I have bought and it has not arrived yet so I don't know if it has any spec sheet with it.
Alistair



1.
KV * pinion teeth * voltage / main gear teeth = max HS *.8 = realistic HS. If you have the final ratio from the conversion specs it's simply KV * V / ratio = Max HS

Steve

[swatson144]

No sir. Sorry but in the price range of this equipment you have to know. Not assume :-). It could be a couple hundred $ in false assumption fees.

It looks like you bought the tppacks conversion? If so the 86T/9T will give you ~ 2100 RPM on 10s according to the speel... So let's test an assumption that the 600 is for rpm/v (KV)

600kv * 37v (10s) * 9t / 86T=2300 rpm max 2300*.85=1975 rpm. That'd be good enough for any girl that'd go out with me.

Since the gave a 2100 rpm HS with a 86/9t combo... 2100 * 86 / 9 / 37 =542kv so if the speel I read is correct and actually what you bought it looks as if you have bought equipment that will work well in an R50 etc. the motor is around 550KV. Your assumption would have been correct in this case.

If you didn't get the optional 86T main just plug in what you have using the formula with 550KV and you should have a good idea on HS. Bear in mind my 6th grade math teacher actually told my parents I'd never be worth a D3$n at math, and we could only hope for passing grades, 24 yrs ago.

Steve

[swatson144]

Having said all that there are three discriptors of a brushless motor that really matter. Simplified.

IO = amount of current to turn the motor
RM = winding resistance
KV = rpm / volt

Knowing these 3 items one can calculate what to expect of the motor. Pretty much tells all about it. Unfortunately some manufactures post optimistic ratings.

Steve

[adwb]

ooks like you bought the tppacks conversion?
yes i did.
Bear in mind my 6th grade math teacher actually told my parents I'd never be worth a D3$n at math, and we could only hope for passing grades, 24 yrs ago.

Steve

thanks Steve I do seem to have got this correct at long last.!!
mind you my geography teacher always said it was a constant source of wonder to her the i ever found my way to school and back home afterwards!!
Alistair