Djay Ahluwalia

How does the thrust produced by a propeller differ due to   -the voltage/current its working at    - the size of the propeller    

Timbo,    The reason I started with a heavier AUW was to make sure I had an inbuilt safety factor for the aircraft, a motor designed to keep a 500 gm plane just off the ground would potentially be a good bet for a 350-400 gm model. But I guess it looks like with such projects most designs are built and run very close to optimum and not much give for worst case scenarios. Again, I would put this down to my inexperience.   Furthermore, perhaps this motor from the same website (altho a tad expansive), may prove to be 'marginally' better?   microREX 220-3-3200     This is from the flyware range. Mind you my first flight test would be without the solar cells onboard and using a standard 2S LiPo battery.   Djay 

Chris,   I guessed something was up with the formatting, thanks for the heads up. Heres the inventory again,   Solar Cells     100 gms Main Wing      105 gms  Motor/ESC        30 gms Fuselage           45 gms Tail Plane          15 gms Battery                30 gms Servos                10 gms Prop                      5 gms  Receivers            10 gms     Total                    350 gms   Lets say I am hoping it will be NO more than 400 gms.   

After 2 tries, for some reason I cant post my whole reply!   Anyways the mass inventory above, as you can imagine is incomplete, may be theres a word limit for each post.   Continuing with above Chris,   I do need to add a MPPT to deal with the power fluctuations due to time of the day, aircraft inclination, cloud cover etc. However, as of yet I have not found anything suitable ( read cheap and inexpensive).   This is my first attempt at such a project and my inexperience is showing as I was completely stumped by the whole motor/prop selection issue before Timbo here pointed me towards the micron flyer which 'may' be suitable for what I am intending.   Opinions?     

Dear Chris,   Thanks for the post!   I have been thinking about the whole Thrust/Weight ratio, but have struggled to find a motor with a high enough Thrust at such low power input (low current).   My mass inventory shows that the total aircraft weight should be around 350 gms (including 100 gms for the solar panels), as you can see below. But you are correct, I am sceptical at this point in time. The total weight of the finished product may be higher.   Edited By Chris Card - Moderator on 13/05/2010 10:51:29

Timbo,   Expectedly, the current generated depends on the solar insolation received, which depends on the time of the year and geographical location. I am told, the same cells could potentially produce close to 10 A in somewhere like Singapore, Australia!    Although, still apprehensive about the model weight and the Thrust generated by said motor, I am going to take the hit and may be order the 1800Kv version tomorrow. Run it using a 10A ESC, sound ok?   I already have a 7 X 4 prop....but if need be , I might buy a 8 X 4.3 , as the webpage suggests. 

Hamish,    Indeed, John beat me to it. The (potential) 25 watt power output is from all the 10 cells connected in series. I got 0.55 v from each cell at 5 A. Total cell area is 10 X 125mm X 125 mm = 0.15625 m2.   John/Timbo,   Thanks ever so much for clearing that up. So with 25 watts in , I get 87.5 gm thrust which translates to 0.86 N forward Thrust .   For a (nearly) 500 gm aircraft seems a bit low(?)   Mind you i am going for a slow and steady aircraft, no high speed acrobatics intended!   Edited By Djay Ahluwalia on 12/05/2010 23:46:56

Timbo   Wow! Thanks, I think the 18mm 10g Micro Brushless Outrunner , might just be what I need. Also, I am not familiar with the way Thrust is expressed on this website, what does a thrust of 140 gm mean?    Myron,   I got these cells from Singapore, but they might have been made in China. Nifty little things, altho recent reports suggest cells touching 30 % efficiency might be hitting the market soon, at a very high price. 

 Hamish,   The solar cells I have are a 125mm X 125mm square.The aircraft is 1.5 m wingspan, made using balsa wood.  

Timbo,    Thanks for the post!   Yes, I am struggling to find a lightweight motor to run at such low current and voltage. The local hobby shop pointed me to a 1500 KV (12 A continuous, 16 A max) motor, but the guy in charge seemed to think that the motor would 'not operate' under 12 A. And obviously, the current I get from my solar cells is a lot lower than that.   Djay   

Also, the above mentioned plane is under construction, it is a lightweight glider, that I intend to modify into a prop driven RC controlled aircraft.   I have'nt weighed it yet but the total all up weight should come to 450-500 gms (including the solar cells, which weight 100 grams)   Djay Edited By Djay Ahluwalia on 12/05/2010 19:02:54

Bob, yes thanks again, the site looks like a great idea for new starters like me.   Birdy,   Thanks for the reply!     I am trying to build a solar powered aircraft. I have 10 mono-crystallin 15.5% efficient solar cells. I am currently testing them and logging the data. Looks like on a decent day the cells can generate 5A and 5volts.   I will either use this to run the motor/prop. Alternatively, i will use the energy generated by the solar cells to charge a battery (LiPo) and use the battery to run the motor/prop.    Hence why, I need a motor/prop combo that can run on such low current/voltage.   Djay   

    Wat does the current rating on a brushless motor mean?I need a brushless outrunner that can run on 5A at 5V, is that possible?Any help greatly appreciated.Thanks!