Turnigy RotoMax 150cc Size Brushless Outrunner Motor

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,454
Location
NJ
Last edited:

Vigilant1

Well-Known Member
Joined
Jan 24, 2011
Messages
7,162
Location
US
I think you might have typo there, the HobbyKing web site says the motor is rated at 190 amps, or 9800 watts (roughly 13HP). If somebody is putting 360 amps through it at the same voltage, then it should be producing roughly 26 HP (for however long it lasts).

I was surprised at the $443 retail price, I would have guessed they'd cost more. But the motor controllers seem to be priced about the same as the motors.

Sorry, no direct experience with 'em.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
16,187
Location
Memphis, TN
Prop load determines amp load with the electric motors. If you have a speed control that can handle the excessive amps, you can overdrive these electric motors easily. Life is the suspect part. In a RC airplane of this size, the planes are almost never flown at full power except in a hover pullout. They will have the thrust to hover a 40 lb plane at 1/3 throttle. Prop design is the biggest factor for thrust and that has to be matched to the airframe. Off the shelf RC prop will not match a UL needs even if it will work. The electric motors make a hair more useable power than the gas motors, but they can for only a fraction of time. You only have about half a battery pack capacity that can be drawn upon at high rates before it starts degrading the pack. Ruin batteries and the cost advantage went out the window. Electric are easy to add belt drives, so bigger props play the efficiency factor over gas.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,454
Location
NJ
In a RC airplane of this size, the planes are almost never flown at full power except in a hover pullout. They will have the thrust to hover a 40 lb plane at 1/3 throttle. Off the shelf RC prop will not match a UL needs even if it will work. Electric are easy to add belt drives, so bigger props play the efficiency factor over gas.
I am by configuration geometry limited to 34" prop. I have a 32-10 pusher prop. Off the shelf. My climb is 25 mph. If I can get 2-5 min of 15-20 hp. 75 lb thrust. I think I will be successful.

The Electric would be great especially for air starts as my Gas Engine will not be able to start in flight. Also lots easier to start and taxi.

I read it is possible to index the prop stopping position with an electric. Would one be able to do that with this motor?
 

BBerson

Light Plane Philosopher
Joined
Dec 16, 2007
Messages
15,525
Location
Port Townsend WA
It might be simpler to mount two gas engines. The guy at Sun nFun was flying his small and super light biplane with two RC gas engines.

A gas/electric combo would be interesting. With the electric motor built into the gas engine.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
16,187
Location
Memphis, TN
The speed controls have brakes so you can stop the motor. There is some current drain. Not a mechanical brake. You can also control the windmilling. 5 minutes full power is a lot for these motors, actually th batteries. The RC guys have to manage the power drain but keep the performance. They take off at 1/4 power but after 10-15 minutes it takes 3/4 throttle to make the same thrust. It is where gas like fuels really shine, 100% power any time fuel is in the tank. A friend converted to electric for his pattern plane. One of these monsters on a 10 pound at takeoff plane. The contest has him fly about 15 different stunts stringed together. If he gets hung out in the landing pattern for more than a minute, the batteries are trashed for the performance he needs. Do it more and they can catch fire. If you need power when on the back side of the battery power curve, you will not have it. You have to come to grips of either having a motor big enough to derate the power and manage it or time full power and you cut it off at the bell even if you are about to fly into a tree.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
Go up a size to 120100 you can run lower rpm direct drive for a more efficient prop and not make the motor sweat as much.

If you order direct from mfr, you could have it built with a thermistor buried in the windings.
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,454
Location
NJ
Go up a size to 120100 you can run lower rpm direct drive for a more efficient prop and not make the motor sweat as much.

If you order direct from mfr, you could have it built with a thermistor buried in the windings.
By a year from this summer it might be possible for me to be trying this....hurry up with yours and we can buy the 2 which is the minimum order, along with 2 controllers and 2 sets of batteries. Lot more pricey than the $150 used sled though.
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
I'm still pondering power options. If you buy two, the second could go on ebay for profit... I might get one to test ducted fans, though. Ducted fan math is horrible, btw...
The 120100 have a 50% longer stator than the '150cc' 12090 motors.
 

Sockmonkey

Well-Known Member
Joined
Apr 24, 2014
Messages
2,292
Location
Flint, Mi, USA
Remember the rule for electric and/or hybrid planes. If you don't want it to suck, you need to design the plane from the ground up to take advantage of the flexibility electric and hybrids give you.
 

henryk

Well-Known Member
Joined
Mar 8, 2010
Messages
6,750
Location
krakow,poland
I'm still pondering power options. If you buy two, the second could go on ebay for profit... I might get one to test ducted fans, though. Ducted fan math is horrible, btw...
The 120100 have a 50% longer stator than the '150cc' 12090 motors.
-see FREERCHOBBY motors...(big power!)

IMG_20171219_125149655.jpg
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,454
Location
NJ
Any good charts,...spread sheets,...on batteries required and running time......also different controllers? Seems like there are lots of variables and every installation I see is different.

Saw a reference to "junk yard Nissan Leaf".....is that an option for batteries or are those batteries too big....and are there really any "junk yard" stuff like that yet?

Lots of questions
 

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
I'd favour 18650 cells rather than hobby ones myself.
Capacity is a tradeoff with max current.
The not-latest Tesla uses panasonic NCR cells, you may find someone splitting a pack on ebay. DeWalt 1.5Ah batts use LG HB4 cells.
Pick cells with a higher max current than you will use. Some on the web have tested many of these cells. Beware fakes! 18650 industry is littered with them.
This site has a big selection: www.imrbatteries.com

The math is pretty easy:
Wh required = A x V x hours run time.
750W = 1hp. The motor will be up to 85% efficient. So power draw will be around 900W per hp. Then you've got losses in the controller, lets say, to be safe and easy, a round 1kW from the batteries per prop hp.

Battery energy = Ah x 3.6V
A 3Ah battery will be 9.8Wh. Batteries will last much longer if you avoid full charge and discharge. Using only 2/3 or 3/4 the capacity will greatly increase their life.
So, lets say 20hp for 15 minutes.
20kW x 15 / 60 = 5kWh
Using 3Ah cells. 5000/9.8 = 510 cells. That doesn't include extra capacity so you don't fully charge and discharge, 510 / 0.75 = 680 cells. Yeah, that's going to be pricey at ~$5 a cell. Time to see what is on ebay...
 

proppastie

Well-Known Member
Log Member
Joined
Feb 19, 2012
Messages
5,454
Location
NJ
thanks much...... all in all great post.....

680 of the 18650 = 680 x Weight: 47.9g =31960g=71.8 Lb.

5 min = .33 x 71.8 = 23.7 lb.......not so unreasonable, especially if perhaps I only need 15-16 hp to climb and can throttle back after liftoff.
 
Last edited:

pictsidhe

Well-Known Member
Joined
Jul 15, 2014
Messages
8,812
Location
North Carolina
Most efficient climb will be at max power. You'll be putting a larger proportion of power into climb. For only 5 min, you need to be careful not to exceed the max current of your cells. If you only use 3/4 of the pack capacity, you'll need cells that run at 60/5 * 3/4 = 9C, where C is the cell Ah. A 3Ah cell would need to be good for 9x3 = 27A. They generally aren't, so you'll need to look at higher current, lower capacity cells. Such as 2Ah, 25A cells. Then you need 50% more cells to get the capacity. They are likely to be a littke cheaper each, though...
 
Top