How to Decide

[Stuart]

Ok I've made a decision to get a 700 sized electric by the end of the year - I'm in no hurry and its at the bottom of a long list of things. So for me it will be done on a peace meal basis as and when I'll buy the bits I need. Got my esc this week so maybe next month some servo's.

But I took a virtual stroll over to look at the motor options and quite frankly its just choas...

How on earth do you decide on which motor to go for ??

What key parameters are you guys in the electric saying right that one or is this just follow the bloke standing next to you with his loverrly logo 600se.

Esc's for me was the easy part but hell knows which motor to go for..... showing my serious lack of knowledge here on motors....

Haven't decided on the heli yet as the budget isn't set - my eye's are keen on Synergy but my wallet might not reach that far given everything else...

Anyway - words of wisdom and opinions really appreciated...

[adieuk]

i would wait for the RCHA raffer Stuart you never know what santa has left over in his sack

[rachel]

On a budget or just plain good value , then it's scorpion 4035 range , but if you want the best then as usual it's kontronic.

Scorpion has worked very well for me :-)

[Martyn (Bomber)]

The Pyro's are pricey but when you get one you realise why people spend the extra on them, they are real quality motors as is all Kontronik gear.

Scorpion is still very good tho, a lot of the pro's use Scorpion and all of there motors I've ever owned have worked flawless.

I've also been thinking about a slow 90/700 build for this year (Fusion 90) but my slow builds don't turn out that slow when I start

[steve_b]

When I was choosing a motor for my Rave I started with a target headspeed in mind, in my case 1900 - 1950, same as my nitro Rave, so this lead me to the 530KV motors as the -530kv range was too slow and 560+ was too fast. This at least whittles down the range of motors a bit.
Another thing you need to consider is the length of the motor shaft, again for the Rave, it's better to get a long shaft motor as that means you don't need to mess around adding brackets to lengthen the shaft so that it sits in the support bearing.
Finally there's the issue of space and the mounting options. Most motors seem to come with 25mm and 30mm mounting holes but some of the earlier Scorpions don't, so you would need to check the mounting options with the heli you're going to build, otherwise you may end up finding you need different motor mounts. Then there's the issue of if it'll fit, but in a 700 that should be less of an issue.

[Zeeflyboy]

I think you need to pick the heli first, as this will determine the size and kv of the motor you need...

To pick a motor first is a bit backwards imo

[LaurenceGough]

I agree, pick heli first then decide on the lipos you want to run and then the headspeed.

[Jamin_00]

At first it can all look confusing as its just number and letters in some cases.

Kontroniks are very simple, 700 prefix motors are for 700 size heli's

Scorpions have a lot more range, 4035 range is the popular range and are very good motors. The rest of their range for 700 class will only start with the prefix 4xxx or 5xxx as the rest are for smaller size heli's. As for the KV this is how fast it will spin and therefore determine your headspeed. Higher KV = higher head speed less torque, Lower KV = lower head speed higher torque.

To determine what motor for what heli then you first need to the the gear ratio then this will give you the ideal motor KV to get. Then you can go pick then you have the normal motors or more expensive high powered motors but always look for the continuous ratings more than the peak. The motors with crazy peaks are powerful and fun but not needed for any flyer, its only if you want the power like I do. I love to have it there as its awesome


This may help also a little to understand a bit more.

http://www.phoenixmp.com/articles/Brushless Motors.pdf


ps. Laurance, got more sponsors, well done dude

[Planehazza]

Ok I've made a decision to get a 700 sized electric by the end of the year - I'm in no hurry and its at the bottom of a long list of things. So for me it will be done on a peace meal basis as and when I'll buy the bits I need. Got my esc this week so maybe next month some servo's.

But I took a virtual stroll over to look at the motor options and quite frankly its just choas...

How on earth do you decide on which motor to go for ??

What key parameters are you guys in the electric saying right that one or is this just follow the bloke standing next to you with his loverrly logo 600se.

Esc's for me was the easy part but hell knows which motor to go for..... showing my serious lack of knowledge here on motors....

Haven't decided on the heli yet as the budget isn't set - my eye's are keen on Synergy but my wallet might not reach that far given everything else...

Anyway - words of wisdom and opinions really appreciated...

Oh God, you as well? I know Lee's after something, and I've got my eye either on a 550E FBL, or Fusion 50 FBL

[snowy]

Harry has the north east run out of fuel

[Planehazza]

Nah, plenty of combustible gasses come out of Lee's mouth

just fancy something I can fly when I'm too lazy to fiddle with engines

[trillian]

The motor choice question is something I have been slowly looking into myself. My plan is to eventually convert a Robbe Milli and I am in no hurry to do it and will prob buy the ESC and motor 2nd hand. It will be 12s.

Things like the KV are largely based on the heli and the gearing but there's still the question of what percentage to aim for in order to allow the governor some headroom and allow for efficiency of the motor and ESC. I suppose now that I have the 550 pretty much dailed-in I could look at the actual headspeeds vs theoretical max and come up with a rough percentage to use for future calculations.

There is a pretty wide range of power ratings for 700 size motors, with peaks of between 4000 and 10,000 watts!

My thought so far has been to go with something like the Align motor used on the 700e F3C or the Scorpion equivalent.

I'm not sure if it's better to have the highest KV the gearing will allow. For example, if my gearing is 10 to 1 with a 12 tooth pinion and I want a headspeed of around 2000 then it would seem a 510KV motor would do the job (using 90% of the total motor RPM to allow for gov headroom, but this is just a figure I'm plucking out of the air and should prob still discount for efficiency).

Or I could have a 450KV motor and use a 13 or 14 tooth pinion. I'm not sure if it makes much difference. The lower KV motor has a higher torque load on it due to the gearing but the bigger pinion has more engagement with the main gear so is a bit sturdier.

[yuppyflyer]

I would defo say choose the heli first then copy a proven motor / pinion setup someone else is successfully using, for sure electric is far more of a science, used to be just which 91 shall I get YS or OS ! If you get the wrong motor its expensive to change.

[Gaui-UK]

Wait til Feb 8th - GAUI X7...

[electricsceadu]

i'd wait on the motor until you've decided on the packs 10/12/14 cell
and the air frame for the gear ratio options you'll have
for the sums use the middle gear ratio option as you'll then have room to alter the ratio up/down to suit the model/flying style if the mid one doesn't work well for you