[Daren71]

Originally Posted by Max

I have convertrd several 40-60 size glows to electric.

I run an HobbyKing G-46 on 5 cells and 60A esc

I also run a rimfire 45 on 5 cells and 60A


In both cases, they say a 4 cell will power them but i find in both cases, 4 cells is gutless.

We have several guys in our club that swear by these motors. All 40-60 sized planes, 5 cells. Great performance.

Daren

[stegl]

Regarding 4 vs 5 vs 6 cell use is all based on the kv of the motors being used. The lower the motor kv rating the higher the cell count needed to produce needed rpm and prop pitch all work together to produced the required power. Thrust is more dependent on prop length and speed is more dependent on pitch so the happy medium is a correct combination of pitch and prop length. Usually , rule of thumb ,as we go up in motor size ; the kv rating drops but one still has to look at kv and max current the motor us able to handle continuously, not burst current.

Another thing to keep in mind is that inexpensive motors tend to exaggerate their claims in the power produced, where the higher quality motors don't need bragging rights......at least that is my experience.
Some manufacturers rate motor size by the glow motor they were designed to replace, generally .... Others used to state a number to indicate the size of motors ie. The first two numbers were generally the outer diameter in mm and the second two numbers was the motor case length in mm but I see that is starting to change a bit. Can be very confusing for newcomers to brushless technology and others look at the other number in $$$$. Lol.
Lastly make sure you size your ESC to the motor being used . Example ; rule of thumb your Motor max current draw should be about 75% of the ESC rated capacity. So if you motor draws 60 amps then the etc size should be max continuous rated at 80 amps. Yes, can be very confusing for the newcomer . So often I see flyers buy based on $$ spent rather than on quality. For example if a person spends $40 on a marginal quality esc and it burns out and then turns around and spends another $40 to replace it when he could have bought a quality one for $65 ..(40+40=$80)... Which makes more sense ? . I suppose this applies to any electronics be it radios, receivers, servos , motors or ?

[stegl]

http://innov8tivedesigns.com/images/...10%20Specs.htm

Here is a link as to the data on props for a specific brand and model of motor I use. With relationships of using 3,4 or 5 cells.

This is just one example of one motor with its design kv.

[OLD PRAIRIE RED NECK]

Originally Posted by Don Forness

I know that over propping a motor will heat up ESC's and motors but what are the consequences of underpropping one? With IC engines you blow parts up by under propping.

Lots of responses but no one has addressed this question.

No! You cannot hurt a brushless motor by under propping it! In fact you can run it without a prop and not hurt it. The smaller the prop the LESS power it will draw out of your battery and therefore it will also make less thrust to pull your plane.

The watt rating on a motor tells you how much power it can produce.

746 watts = one horse power ie: standard .40 glow is about 1.1HP or about 820 watts

Watts are King in sizing electric motors.

Watts = power

KV rating only tells you at what RPM the motor will make that power with a give number of cells.

KV = RPM regardless of motor size

Unfortunately watt ratings for motors are getting harder to find. Too bad!

As others have said "buy a watt meter!"

[stegl]

Too many people dwell on motor watts. What Or is it watt , I want to know is my rpm and current draw out of my motor with a specific size prop, lol.
I use to get too tied up with the wattage my motor is producing or actually drawing ;but very seldom set my Eflite wattmeter to the watt reading, anymore. I check the motor current draw and the rpm with my tach. Once I get my new system up and running I will be able to get the current and rpm on my transmitter when on the ground and in the air when the props are unloading.

[Harvard 387]

Thanks everyone. I think a Power 52 or equivalent and a weight reduction plan for the airframe will do what I want. I have a number of electric fliers here but most are "out of the box" kind of builders, not gearhead like me.
This forum and others like it are the real goldmines of information.
Once again thanks to all.

[stegl]

What I find is that the big thing is just how big a prop can you swing is the biggest issue as the motors I run can usually swing a pretty big " stick". Prop clearance is my issue.

[Flypaper]

I find , for an equivalent sized motor, the electric will swing a bigger prop at lower RPM , for the same thrust. Mostly because the gasser puts out its max torque at a relatively high RPM. Where the electric has the same torque at starting speed.

[Lokiyawl]

Originally Posted by Don Forness

I have been a glow fuel modeller since 1972 and am still making the transition to electric for some of my models. One plane is an advanced Trainer 60 by Joe Bridi. It was originally designed for .60 glow. Given 70 mph as a target speed the 11 X 7 prop the engine will have to generate about 10,000 rpm.

Quick math tells me that I will need either 4s X 650kv or 5s at about 575kv to get the same rpm. Using these numbers I think a Power 52 or 46 or equivalent would work as they will turn 12 X 8 props in the right rpm range.

The reason for the 12 X 8 prop is the tricycle landing gear. To go to the 15 X 8 that a Power 60 uses means "giraffe legs" landing gear to clear the prop.
Question is, will the power 52 or 46 work for this plane? I realize the plane will be heavier (I plan to lighten as much as possible in the building) but isn't 10,000 rpm the same for both power systems?

I converted to electric quite a few years back. With respect to power the thing that I really liked is the instant and consistent throttle up. I vaguely remember listening to the engine sound as I throttled up a nitro engine to determine if I needed to pull back for instance to keep it from sputtering/dying. With electric, it is instant power every time which for me leaves time to concentrate more on the flying..or the landing..

[Windfree]

Turnigy 60 with 500 kv , Plush 70 A controller , 6 cell 4500 to 5000 mah pack with an APC 13-6.5 electric prop will drive it beautifully .Have been using this combo and getting great vertical and duration . Throttle control is key to get duration . I have used this combo or equivalent many times and it works .The same prop doesn't necessarily suit all planes so some experimentation is required .I have this combo currently on a 80" cub on floats and can get 25 minute flights with attention to throttle and 8 to 10 minutes for hammer down aeros . Have also used this on a 60 size pattern ship with outstanding results .Make sure the motor has cooling or you will let the smoke out .