Help: How do i choose a Motor?

[Jnr Kuzi]

hello. I was On Hobbyking.com earlier on today scoping through motors & realised that motors with lower Kv's were more expensive than those with higher ones.

I found a Motor with 690 kv worth - 30bucks & 1 with 1200kv worth 10bucks.

whats the advantage of the 690kv one?

 

[Flynn]

Well, I'm sure more will comment and with better explainations but basically the lower the kv the more torque - higher more speed. These are both the same motor, just the kv?

This roughly translates to lower number you can run a larger prop. Higher number is for smaller prop.

 

[rcspaceflight]

The lower KV motors usually can handle more volts and much bigger props. Bigger props and more volts equals a lot more wattage draw and watts cost money.

You can play around with a static thrust calculator to estimate the thrust differences between the prop/motor/battery combos.

 

[Jnr Kuzi]

Well, I'm sure more will comment and with better explainations but basically the lower the kv the more torque - higher more speed. These are both the same motor, just the kv?

This roughly translates to lower number you can run a larger prop. Higher number is for smaller prop.

Thank you Flynn. You're explanation as simple and easy to understand. Kudos

 

[Jnr Kuzi]

reply


Thank you for your imput.. So does this mean that a small motor with lower kvs can lift a medium to large air craft?

 

[nerdnic]

Possibly.

There are a lot more factors but in general the larger FT planes (Dusty, Spitfire, Mustang, etc) all run very well off a motor that is between 36-70g, 150-300w, and 1100-1400kv.

1100kv will allow for around a 10x4 or so prop and give you good thrust, this is important for feeling like you have good control over the plane, you'll be able to 'power out' of a potential crash.
1400kv works better with a 8x4 or 8x6 prop and will still provide plenty of thrust but give you higher top speed.​

There are plenty of prop/motor combos that will work great, but if you let us know which plane you're looking to build we can suggest a proper fit.

 

[Jnr Kuzi]

Right now im Not Building anything thats Rc. I cant afford electronics & they arent easy to find in africa.. So im stuck with foam gliders. Hopefully one day when i get a JOB i will buy.. For now im just doing research so that when i finally get the chance to build. I make no mistakes.