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Is it worth it to upgrade from 802 to 1102 motors?

Thorondor

Active member
#1
I have a Mobula7 that I plan to slowly transition into a Toothpick-type thingy, starting with a carbon frame. Eventually I'm gonna have to get new motors, and at that point I might upgrade them to 1102. I'm kinda new to brushless motors, so I'm not familiar with how larger motors would perform. How would power and flight time be affected coming from 802s to 1102s?
 

cranialrectosis

Well-Known Member
Mentor
#2
Depends on what you want.

A slow motor needs a longer prop to generate thrust. Also, the longer the prop blade, the more torque needed to spin it.

Long blades, rotating slowly are more efficient (use less power) than short blades spinning fast.

Short blades need fast motors to generate thrust but require less torque.

Short blades on fast motors are less efficient (use more power) but provide better performance.

Long blades tend to allow for heavier loads such as larger lipos.

Heavier copters take more damage in a crash and cost more to repair.

So, do you want a Porche or a Mak truck?

Somewhere in between is your answer. To get real details we need to know prop lengths, lipo and kv specs and your specific intent.
 

Thorondor

Active member
#3
Depends on what you want.

A slow motor needs a longer prop to generate thrust. Also, the longer the prop blade, the more torque needed to spin it.

Long blades, rotating slowly are more efficient (use less power) than short blades spinning fast.

Short blades need fast motors to generate thrust but require less torque.

Short blades on fast motors are less efficient (use more power) but provide better performance.

Long blades tend to allow for heavier loads such as larger lipos.

Heavier copters take more damage in a crash and cost more to repair.

So, do you want a Porche or a Mak truck?

Somewhere in between is your answer. To get real details we need to know prop lengths, lipo and kv specs and your specific intent.
I'll be using 40mm props (although I might go to 2 inch if the benefits are persuasive enough) and I would really like to continue using 300-ish mAh 2S power. My main practice is freestyle, so sharp throttle and maneuvering as well as flight time are my priorities. As for KV, I don't know where to start. the power I get on the stock Mobula7 16000KV motors is sufficient for me right now, so maybe I would go a few KV higher (around 18000-20000)? I've been told that bigger props mean longer flight time, but I don't think that's the case for aerobatic flying.
 

cranialrectosis

Well-Known Member
Mentor
#4
Bigger props tend to make for longer flight times and less performance.

I went from 6045s and 3S to 5045s and 4S on my warpquad a few years back. I lost 45 seconds of flight time but the performance boost was out of this world.

You can fly long or you can fly fast.

Think Porche or Mak truck.

If you go with more KV, you may need to go with shorter props so as to not burn out your motors. You can get more performance but will probably lose flight time. That's the trade-off.
 

Thorondor

Active member
#5
Bigger props tend to make for longer flight times and less performance.

I went from 6045s and 3S to 5045s and 4S on my warpquad a few years back. I lost 45 seconds of flight time but the performance boost was out of this world.

You can fly long or you can fly fast.

Think Porche or Mak truck.

If you go with more KV, you may need to go with shorter props so as to not burn out your motors. You can get more performance but will probably lose flight time. That's the trade-off.
But how does the motor size (802, 1102, etc.) affect anything? I would assume that bigger motors draw more power but give more power.
 

cranialrectosis

Well-Known Member
Mentor
#6
But how does the motor size (802, 1102, etc.) affect anything? I would assume that bigger motors draw more power but give more power.
The numbers 802 and 1102 are the dimensions. 8mm width versus 11mm width. Your assumption is probably correct. The question is what kind of power? Is it used for torque or speed?

There MAY be more torque allowing for longer props.

There MAY be more KV allowing for faster props.

The numbers that matter are kv, length of the props, power limits of the ESC and motors, and the lipo cell count (voltage).

I think you are going from 40mm props and 16,000 kv motors on 2s. I think those are the specs you are running now.

If you go to 40mm props and 18,000 kv motors on the same 2s lipo, assuming your ESCs and motors can handle the power, you will see a bump in flight performance at a cost of flight time.

If you go to 60mm props and 12,000 kv motors on the same 2s lipo, assuming your ESCs and motors can handle the torque/power and your frame can handle the additional prop length, you will see a drop in flight performance and an increase of flight time. Note, this one is a blind guess. I don't know that 12,000 kv motors will spin 60mm props fast enough to lift your load. Use ecalc to be sure.


I have a motorcycle with a 1700cc motor. My buddy has a bike with a 500cc motor. His is WAY quicker off the line. Mine is far more efficient down the stretch. His goes like a rocket across town. Mine cruises at high speed and in comfort across the state.

Your question is one of personal preference like choosing a motorcycle. If you want the cruiser you do torque. If you want the speed demon, you do kv.

It's always a preference based on where and how you fly and it is always a compromise trading performance for time.

Online, I am seeing 1102 motors from 8500 kv (torque) to 18,000 kv (speed). So long as your ESCs can handle the load and your frame can handle the prop lengths, you have TONS of options, which of course is why this is so confusing...

When you buy a copter, all this is figured out for you. When you build one, it gets harder, but is far more rewarding and risky, IMO.

You are asking good questions. It takes some time to grasp all this.

Welcome to the deeper end of the pool. ;)
 
Last edited:

Thorondor

Active member
#7
The numbers 802 and 1102 are the dimensions. 8mm width versus 11mm width. Your assumption is probably correct. The question is what kind of power? Is it used for torque or speed?

There MAY be more torque allowing for longer props.

There MAY be more KV allowing for faster props.

The numbers that matter are kv, length of the props, power limits of the ESC and motors, and the lipo cell count (voltage).

I think you are going from 40mm props and 16,000 kv motors on 2s. I think those are the specs you are running now.

If you go to 40mm props and 18,000 kv motors on the same 2s lipo, assuming your ESCs and motors can handle the power, you will see a bump in flight performance at a cost of flight time.

If you go to 60mm props and 12,000 kv motors on the same 2s lipo, assuming your ESCs and motors can handle the torque/power and your frame can handle the additional prop length, you will see a drop in flight performance and an increase of flight time. Note, this one is a blind guess. I don't know that 12,000 kv motors will spin 60mm props fast enough to lift your load. Use ecalc to be sure.


I have a motorcycle with a 1700cc motor. My buddy has a bike with a 500cc motor. His is WAY quicker off the line. Mine is far more efficient down the stretch. His goes like a rocket across town. Mine cruises at high speed and in comfort across the state.

Your question is one of personal preference like choosing a motorcycle. If you want the cruiser you do torque. If you want the speed demon, you do kv.

It's always a preference based on where and how you fly and it is always a compromise trading performance for time.

Online, I am seeing 1102 motors from 8500 kv (torque) to 18,000 kv (speed). So long as your ESCs can handle the load and your frame can handle the prop lengths, you have TONS of options, which of course is why this is so confusing...

When you buy a copter, all this is figured out for you. When you build one, it gets harder, but is far more rewarding and risky, IMO.

You are asking good questions. It takes some time to grasp all this.

Welcome to the deeper end of the pool. ;)
I think I'm gonna stick with 40mm and 802s and just have a baby toothpick. My main goal is to use the smallest batteries possible (I'm a college student and 300 mAh batteries are dirt cheap).