feihu

Hello Dan -

Appreciate your reply to one of my threads in the past.

I'm not familiar with the Cloud Ranger, but that's beside the point since batteries don't care about airplanes and only care about who or what's using the battery.

So, if you can measure the amps that your power system uses (with wide open throttle), then you can get a good idea of how long you can fly.

A geared 280 motor with a 9x6 prop can draw 3.5 to 4.5 amps depending on the gear ratio. Lets use 3.5 amps as an example:

A 600 mah battery has a capacity of delivering 0.6 amps for one hour regardless of the number of cells. 600 mah = 0.6 ampere hours. Take 0.6 ampere hours, divided by 3.5 amperes and you have 0.17 hours which is the duration of run. 0.17hours x 60 equals 10.2 minutes which in terms of minutes and seconds equals 10 min and 12 seconds.

Now this is full throttle, so if you don't fly entirely with full throttle, then the flying time is extended. I would guess this set up would give you at least 12 minutes of regular flying.

A direct drive 400 motor with a 6x4 prop can measure as high as 10 amps at full throttle. therefore:
0.6 divided by 10 equals 0.06 hours which is (.06x60) 3.6 minutes which futher equals 3 minutes and 36 seconds. But you won't be flying at full throttle all the time. (I guess)

You need the number of cells to give you the operating voltage to run the motor and the motor voltage is usually printed right on the motor.

You can use this technique to determine the run time for all electric motors - those drawing 25 to 30 amps and using 2000 or 3000 mah batteries.

Hope this information helps.

feihu

Dan,

You will need an ammeter that can measure DC Amperes over the range you expect to measure. Most multimeters can handle 0 to 10 amperes. I have a 0 - 30 DC Amp meter that I bought at an electronics consumer store for about $10, but that was many years ago.

You will have to set up your power system on a workbench ( or equivalent) where you can anchor and run the motor with the prop you will use for flying. You need to hook up the receiver, speed control, switch harness (or some method to turn the power on and off) and batteries. Servos are not necessary. But you will need a jumper at the battery connector.
Or instead of a bench set up, tie you airplane down and run the motor that way - but you will have to connect a jumper at the battery connector.
You will have to make a jumper cable consisting of a male and a female connector for connecting to the meter. The black wire goes thru from one connector to the other but the the meter is connected in series with the red wire. The red wire or + side of the meter connects to the battery + (the male connector), and the - side of the meter connects to the red (female connector)going to the switch.
Start with a fully charged battery. With your charged transmitter, open the throttle wide open and read the meter. This will be the maximum current your system will use. and you can calculate the minimum run time with this number.

I have an Astroflight 15 geared that draws 20 amperes. With 1400 mah SCR batteries, I get 1.4 divided by 20 equals 0.07 hrs which is 4 min 12 sec.
Now when I use 2000 mah batteries, I get 2 divided by 20 which equals 0.1 hrs which in now 6 min of flight,

I hope this information is clear enough, but don't hesitate to ask if you have further questions.

feihu

Dan,

I had a question on where the line was drawn that separates Park flyers and Slow Flyers. Your answer was quite appropriate. I have since deleted the thread.

By the way, what power system are you using in your cloud ranger?

feihu

Dan,

Here are some data that you can use for comparison. Airplane of my design called Lil Poke built ten years ago, over 300 flights before it was sold, used standard receiver, 2 s-133 servos, Astroflight 217 esc, 8cells600scr battery, 38.5"span, 269.5sq " area, GR7.2v speed 400 w/2.33 gearhead turning a 9x7 RevUp prop, carried recvr 150mah battery pack, and flying weight 27.8 ounces. The power system thrust was measured at 12 ounces, measured at maximun throttle current of 6.4 amps. Flight duration was generally 6 min+. At a thrust to weight ratio of 0.43, the model had no problem ROG and had a good climb after TO. Being ten years ago, the micro servos, receivers, and escs were not available, nor were the APC props.
At a 2.5:1 gear ratio, I would suggest you use a 9x6 or 9x7 prop to increase the thrust. Also at the 2.5 gear ratio, I would expect the max amperes to be about 6 amps, but it could be much different due to propeller efficiency and gearhead and motor friction.
By comparison, this should give you an idea of what to expect from your cloud ranger.

feihu

Dan,

That is right! You will get at least 6 min if the full throttle current is 6 amps with a fully charged 600mah battery. In getting an esc, a speed 400 geared motor can require as much as 9.4 amps when using an 11x8 prop (it will also be putting out 15 ounces of thrust), so you want to get an esc that is capable of handling perhaps 12 to 15 amperes. A larger prop increases the load on the motor, so the motor works harder to carry the load. You can find this data on page 51 of the Hobby Lobby catalog - the GR3321/GR1718 is the speed 400 7.2v motor with a 4:1 gear ratio (not 2.5:1). That would be in case you wanted to up the power. Also note that the trade off is shorter motor run time - .6 divided by 9.4 equals .06hrs which is 3 min49 sec.

I might also mention that all batteries are not necassarily equal - some are better and some are worse, so the numbers could be slightly different.

Good luck