• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Different kinds of motors

#1
FFB09C65-6AEA-437B-9C82-A2B63E6E35FD.jpeg
Thoughts anyone.
Resurrecting my crashed spitfire. Thinking of using this 3650 2300kv. Specs on it says 900watts Max (no doubt over exaggerated). Yes I know I know. It is for a rc car. And yes I would use a 120amp rc car esc (I can program it to have no reverse) it works I already pluggged it in to plane receiver to test. Pretty sure this plane can handle the extra grams.
So....
Prop size???
Mounting behind firewall ok??
Battery???
Thoughts or ideas appreciated.
I have all the correct electro do it the recommended way. But where is the fun in that!!!
 

Arcfyre

Well-known member
#2
View attachment 132581
Thoughts anyone.
Resurrecting my crashed spitfire. Thinking of using this 3650 2300kv. Specs on it says 900watts Max (no doubt over exaggerated). Yes I know I know. It is for a rc car. And yes I would use a 120amp rc car esc (I can program it to have no reverse) it works I already pluggged it in to plane receiver to test. Pretty sure this plane can handle the extra grams.
So....
Prop size???
Mounting behind firewall ok??
Battery???
Thoughts or ideas appreciated.
I have all the correct electro do it the recommended way. But where is the fun in that!!!
I have a 3536-1800 outrunner on a flying wing that spins an 8x6 prop with a 100A ESC. Since your motor has even more kv, I'd try a 6 or 7" prop, hook it to a watt meter, and see what it says.

Mounting behind the firewall in general should be ok, but you may find that it moves the CG too far aft. Also you won't get as much cooling airflow.

As for battery, use what you like and what helps establish the correct CG.
 

FDS

Well-known member
#3
That is a large, heavy, unsuitable motor.
I would buy a better one, they are super cheap. Most people don’t put iron block auto motors in planes, that’s the real life equivalent of what you are attempting. That thing is going to be really nose heavy and fly like a pig on that motor.
 

Hai-Lee

Old and Bold RC PILOT
#4
Whatever prop you choose it will need to be VERY strong. So look at GRP or CF as a minimum. Prop failure, (throwing a blade), could see the plane disintegrate in mind air at full throttle!

Another thing to consider is, that with such a powerful motor with such a high Kv, the Spitfire will suffer from extreme "P" factor. The Spitfire model does not have sufficient rudder area or control for such a powerful motor and you may have great difficulty even launching it as anything higher than minimal throttle!

Just a few things to consider!

Have fun!
 
#5
All true guys. I have the right motor for it. 2836 1100kv. I just also have this one. Lol.
I also Understand 2836 refers to dimensions of motor. So with that the other motor is a 3650. It is roughly 55% larger. Just pondering it. Weight is everything with planes. Lol.
 

FDS

Well-known member
#6
Yep. Weight is not what you want. Less weight is everything. Plus planes load the motor totally differently since the prop is driven (usually) directly, not through a gearbox.
 

quorneng

Well-known member
#7
The weight of a motor tends to go up by the cube of a linear dimension so 50% bigger diameter may mean 1.5x1.5x1.5 or over 3 times the weight!
It is very unlikely the plane could satisfactorily handle such a weight increase regardless of any extra power available the big motor might provide.
 

Wildthing

Well-known member
#8
High kv motors don't bother me and really to me that is not a high kv motor, the size and weight is another thing . You would need to scale up the plane so it will handle the extra weight and fly decently. Then lets talk esc's and batteries, the larger esc the more weight ,plus now the batteries 2S, 3S 4S and what size? You want to pump out some good power and have a decent flight time you will need a larger battery with a higher C rating, also more weight.
 

Merv

Well-known member
#9
I agree with @FDS, there are far better choices for a motor out there.
If you still want use this one, I would look up a 900 watt 2300 kv motor and see what prop it uses at the voltage you intend to use. With a test prop, I would start with a short run, 3-5 seconds, then check the temperature. It’s ok if the motor feels warm but if it gets hot enough that you don’t want to touch it. Stop, that’s too hot, you need a smaller prop. If just warm, try a 10 second run, then a 30 second run, then a 60 second run, checking the temp after each run. As @Arcfyre said, a watt meter is indispensable.
 
Last edited:

DamoRC

Well-known member
Mentor
#10
Given that @CrimsonKing70 already has an appropriate motor for the Spitfire, then we could assume that the larger motor is proposed as a "what would happen" option. I think the only reason to put 900 watts of 2300kV motor into the Spit is to go fast - very fast. With this in mind, a couple of thoughts.

The motor is rated for 6S max and ~45A max. I would think that a 6x6, 7x6, or 7x7 prop would work. Starting with 3S I would try the 6x6 first, on the bench with a watt meter (with sufficient protection for you and those around you) and only increase to 7x6 or 7x7 when you know you are significantly below the 45A max limit. Repeat the process for 4S. For the props I would suggest genuine APC E props (rated to 37K RPM for the 6x6) or better as @Hai-Lee suggested.

On the weight, the motor is just over 6 oz and a 2200mAh 4S is another 7 or 8 oz. With the ESC you are probably adding a little more than a pound to the plane. I think the plane will handle this but you will have to chuck it really hard at launch to get past the increased stall speed and you will have to keep the power on and keep it moving fast - there will be no slow floating around with this one. Also, you will need to reinforce the wing spar with some wood / alu / CF. Without this the wings will very likely fold on the first hard bank and yank.

As long as you don't exceed the motor power ratings (no fire), use an appropriately rated prop (no shrapnel), and have plenty of remote space to fly in (no liability), then sure - give it a go.

EDIT:


Here are the numbers for a stock spit, my GB R3 (which is heavy, has small wings, and is reasonably fast), and a heavy Spit (1.5 lbs added to the all up weight). Should fly fine if you can get the prop and power levels sorted.

Heavy Spit.jpg
 
Last edited:

PsyBorg

Wake up! Time to fly!
Mentor
#12
There is a huge design difference for land / boat use then air.

If you free spin that motor to drive a prop with no gear reduction it will over speed and smoke in very short order.

Those motors are very torquey and require some back oressure like gears ir water. Air will not produce enough resistance for how that motor is timed.
 

DamoRC

Well-known member
Mentor
#13
There is a huge design difference for land / boat use then air.

If you free spin that motor to drive a prop with no gear reduction it will over speed and smoke in very short order.

Those motors are very torquey and require some back oressure like gears ir water. Air will not produce enough resistance for how that motor is timed.
No problems with the statement on design differences but the over speed consideration and requiring resistance to operate safely shouldn't be a problem. Motor is rated for 6S and 45amps so provided you don't exceed either you're good (depending on how much you trust the quality of the motor and the specs). Exceeding the 6S, with a low / no load could lead the motor to throw a magnet (which would be really bad news for an inrunner) but this applies to our typical aircraft motors also. These motors are not "timed" per se, the timing is handled by the ESC.
 

PsyBorg

Wake up! Time to fly!
Mentor
#14
Maybe Im a bit behind in car tech. Last time I used electric motors in rc high performance cars and trucks motors were physically timed by rotating the rear cap where the brushes were mounted.

I know brushless motors are now timed in the escs but I am still confident the internal design is made for larger physical resistances have heavier stator cores and more dense windings.

Thats one if the main differences between inrunners and out runners.

That takes us to factors of heat management and power.

Cars and trucks use gears and stay mainly in the can be air cooled range. Boats have less resistance then gears and usually require water cooling on a brushless set up.

Putting one in an insulated box of foam is gonna generate and contain a lot of heat thus my statement of "smoking" the motor. Maybe should have used the term "frying" as smoking has more and electrical inference.
 

DamoRC

Well-known member
Mentor
#15
Maybe Im a bit behind in car tech. Last time I used electric motors in rc high performance cars and trucks motors were physically timed by rotating the rear cap where the brushes were mounted.

I know brushless motors are now timed in the escs but I am still confident the internal design is made for larger physical resistances have heavier stator cores and more dense windings.

Thats one if the main differences between inrunners and out runners.

That takes us to factors of heat management and power.

Cars and trucks use gears and stay mainly in the can be air cooled range. Boats have less resistance then gears and usually require water cooling on a brushless set up.

Putting one in an insulated box of foam is gonna generate and contain a lot of heat thus my statement of "smoking" the motor. Maybe should have used the term "frying" as smoking has more and electrical inference.
Yep - I remember trying to set the brush holders to the optimum timing for either more torque or more speed on brushed motors.

Agreed - cooling is gonna be important, so maybe mounting the motor In front of the firewall makes more sense.
 

Arcfyre

Well-known member
#16
A flying wing design may work better than the spit for cooling purposes.

As an example, mounting the motor behind the firewall on one of the FT elements simple firewalls, and then placing that assembly on a versa wing in the pusher configuration may work pretty well. The motor would be mounted forward to help with CG, and get plenty of airflow to help with cooling.

Also, flying wings are less sensitive to p-factor and torque compared to a conventional tractor installation.
 
#17
As DamonRC stated this is a what if situation that I wanted to try. The battery is a 70c rating. I have. A 2s and 3s. With that same discharge rate. I’ve got it all installed and balances good over CG. Waiting on some servos I ordered to try it.
Will probably add vents around motor area to help with cooling. Lol. Will be fun to try. Prop will probably be 7 or 8inch.
 
#18
If it doesn’t work. Oh well. Lol. I think I enjoy modifying and building just as much as flying. That’s what I love about these foamies. Some DT foamboard some hot glue and a imagination. That’s what I’m all about. Currently I’m also using Some of FT master series techniques and a couple of my own (insert mad scientist laugh here 😆). To make a p-51 mustang.