Tuesday evening was fine with a bumpy west/south west wind general direction. About 8 fliers turned up to sample the conditions.
I have just been looking at some 1804 motors; just an example. The theory applies to larger motors as well, probably more so as there is more variety. Thought I’d make a few notes. Please comment if you see any major errors.
1804 refers to the size; 18mm diameter and 4mm long, usually of the stator or internal windings, but can occasionally refer to the overall motor size. This tells us the size of the motor and provides only a rough idea of what it is capable of. The KV and power rating consisting of Volts, Amps and Watts is probably more important.
Notice that the 2300 is rated 1A more than the 2000, but 44 watts more. That’s a lot more power. I suspect there may be a typo in there somewhere 🙂
Notice also in the performance figures, that on 2-cell they only show 21 watts from a motor that is supposed to deliver 55 watts. A larger diameter and/or larger pitch prop would increase the load and power delivered. This would have to be tested as there may be greater efficiency losses.
The KV rating refers to RPM per volt applied with no load. So 2000KV on a 11V supply will theoretically want to spin at 22000 RPM. The speed controller etc. will affect this.
The power rating should be considered a maximum with good ventilation. all that power is going to heat the motor and needs to be removed by air-flow or the motor will overheat and fail; probably burning out the windings.
The maximum current rating tells you how much current the motor windings should be able to handle.
These all come together: Volts * Amps = Watts. But not always without a catch.
So a 7A maximum current and 55 watt rating means you should not load the motor to the full 7A on 3-cell because it would draw 77 watts. On a 3-cell it should be limited to about 5 Amps. On a 2-cell supply you can run to the full 7A and the motor will draw about 50 watts.
The motor will try to deliver as much power as it can based on the load applied. The propeller is the load on the motor. A larger prop (either in diameter or pitch) will apply more load to the motor and draw more current and therefore more power (watts).
Propeller size and power is also complex. A higher KV motor will spin the prop faster. More pitch and/or more diameter means more load for a given RPM. There are on-line calculators that help with prop selection and suggest maximum possible speed etc. Generally, a larger diameter and more pitch spinning at a lower speed is more efficient, providing longer flight times.
Power in watts relates to “get up and go”, but prop diameter, pitch and speed determine how the “get up and go” works. Whether it’s a glider that flies out of your hand and goes vertical, or a fast sport model that you have to catapult into the air.
I purchased this 10 channel transmitter ‘on sale’ from Hobbyking; only mode 2 so needed to change to mode 1 which just meant reversing the gimbals and changing the mode setting in the transmitter. There are lots of ‘unpacking’ videos on Youtube so I won’t even go there. The first thing you notice is its so thin which is possible as it uses a 1 cell lipo which is charged via a mini USB connector so no problem there as I have lots of these cables even in the car. The ‘net’ advises that the mini usb plug is a bit fragile so we will have to see. It uses a touch sensitive screen which is fun to play with and quite usable.
Without any external sensors, it displays the receiver voltage and error rate. In full sun its hard to read the lcd screen but then, unless you are flying a glider or similar, you need to focus on the task at hand, flying the model. The standard package comes with 2 external sensors as well. The transmitter doesn’t support speech but has beeps and things. I have had about 5 flights so far and no errors when flying at Trentham (now is that a good thing??). At this stage there are few other receivers available for use with this transmitter although the standard 10 channel receiver is $US20 which is good except it is a bit big for that smaller model. The trims for elevator and throttle are not in the normal place but too early to say that this is an issue.
The sticks are too short so I borrowed some longer ones which feels better. All the switches are assignable to the extent that you need to assign the switch you want for rates and expo… so its quite flexible.
It doesn’t have the quality of some of the named transmitters but its a great radio and I intend to get some more receivers for other models. The reviews I have read on that there internet thing are favourable but again, its a personal thing.
Its currently retails for $US177 from the Aussie Hobbyking warehouse http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=75276 which is not bad value (but then I got it cheaper in the Hobbyking sale!!)… Some will prefer the Taranis which is probably more flexible (its has a module which the i10 does not).
Typically I don’t get to fly midweek; today I did as the weather was good and I was on leave from work . Three other flyers turned up, 3 flying IC power and one glider pilot. It was a great morning.
A few photos…
There was a guy there on Sunday morning with a suit and tie… looked totally out of place… well he was a TV1 reporter. He did an interview regarding safe drone flying with Mark and Leo which made it to prime time TV. TV Stars ;o)
The ALES competition was held and won by Keith Elliott. Interesting flying conditions for gliding. Some quadcopter flyers setup a course and did some flying. Over on the Power Strip one Rob Burns got his Wings Badge. Congratulations Rob. Your shout on the WMAC bar… err… there isn’t one. Well lemonades all round then ;o)
A few photos from Sunday…
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