Planes > Scale

Airco DH2

<< < (5/7) > >>

billscottni:
Meautiful job. I wish my building was half as good :(

johnfireball:
Hi all,
      I had some fun with my DH2 today. It's not finished yet but is flyable so I decided to give it a test run to check out the power output and just as well I did. It needs about twice as much thrust as I'm getting so I'm guessing I need an outrunner powered with a 3 cell lipo. The weight of the model without battery is 240 grms.
http://www.hobbyking.com/hobbyking/store/__5428__AX_2306N_2000kv_brushless_Micro_Motor.html
http://www.hobbyking.com/hobbyking/store/__5430__AX_2308N_1800kv_Brushless_Micro_Motor.html
http://www.hobbyking.com/hobbyking/store/__5427__AX_2306N_1300kv_Brushless_Bell_Motor.html
http://www.hobbyking.com/hobbyking/store/__6784__ZIPPY_Flightmax_800mAh_3S1P_20C.html
http://www.hobbyking.com/hobbyking/store/__6457__Hobbyking_SS_Series_18_20A_ESC.html

These are my choices as they have the beam mounts and will fit with little mods required. OK what do I choose? I want to run an 8" prop for scale reasons and I don't really want a revving noisy fecking thing. The model at present has a 10 amp esc fitted in it's bowels and if possible I would like to leave it there, but if necessary will replace. Prop suggestions? Perhaps running with 2 cell lipos and less rpm. I'm new to this electric and perhaps need a little guidance. I broke the undercarriage today and I am  now redesigning for strength which is difficult due to its gangly nature.
John.
   

billscottni:
I'm not up on electrics John, but I would suggest due to the draggy nature of the airframe it's going to need something with plenty of torque, but that you don't want something which will make it hurtle round the sky in an unscale manner.

Have you had a look at the calculator, (now FREE) on RCAdvisor?

http://rcadvisor.com/free-calculator

andrew wallace:
lovely model john all the best for the maiden flight  :clap:  :clap:

Happy Days:
Hey John,

You say that the esc is bedded into the bowls of the model, you need to be aware that it requires a cooling airflow to stop it overheating.
Another thing I’ve thought about relates to that dummy engine. Is it balanced? and is it strong enough to withstand being rotated at around 10000rpm? which is the sort of speed you’re heading towards with an out runner.

Of the outrunners you are thinking of getting, probably the 1300Kv model would be most suited. I see it draws 8 amps current, so to be safe I’d be thinking of using an esc able to handle around 15 amps. (Personaly I'd stick to a two cell battery.)

Here are some facts about props:

As for prop sizes; changing the diameter of the prop will vary the rate of acceleration and rate of climb i.e. changing the the diameter doesn’t change the top speed of the model.

Changing the pitch of the prop varies the overall speed of the model but also varies it’s rate of climb and rate of acceleration. Confused yet? :!:

Look,…….If you have (say) an 8” diameter prop with a 4” pitch. The thrust it produces at (a given rpm) will cause the plane to climb at a certain rate, and have a certain top speed.

If you maintain the 8” diameter and reduce the pitch size, the plane will climb faster but it’s overall top speed will be slower. (Like using a lower gear in a car.)
If you want to maintain the same top speed and increase the rate of climb you would have to increase the diameter.

All of these variations however will effect the amount of current being drawn by the motor, esc and battery, because they all form part of what's called the ‘Power Train’

( At a given rpm, doubling the propellers pitch will increase the power requirement by 50%. Maintaining the same pitch but doubling the diameter of the propeller will increase the power requirement by 100%)

As converting this plane to electric flight has never been done before there are no known facts for what would be the best power train for this model, so you are going to have to do a little bit of ‘suck-it-and-see’ John.


To ensure you don’t over load the power train you really need a “Watt Meter” to connect between the esc and the motor as you try different props. This will display a host of information about the different voltage on the battery, current being drawn, current used, and power being consumer at different throttle settings and with different props.



Don’t get disheartened John, Smile! This is all part of the fun of experimenting with model flight, 8)  (so I’m told! :roll: )

K.

Navigation

[0] Message Index

[#] Next page

[*] Previous page