vicar

I have an Aviomodelli Ariane 5 Motor Glider ([link=http://store.yahoo.com/internet-rc/ar5motglidby.html]Internet RC[/link]), 114” wing span and weight of about 6.5 lbs which I would like to convert to electric power. The recommended glow engine is a .25 to .36 2 stroke engine. I have been looking at the AXI motors ([link=http://www.hobbylobby.com]Hobby Lobby[/link]) but cannot figure out which model would be the appropriate one for this type/size/weight airplane. Could you please recommend an equivalent electric motor? Also, could you please recommend a speed controller and the smallest battery configuration (will prefer to stay with NiCds for now) which will adequately power the engine?

jonnyjetprop

My Feedback: (3)

I'll take a stab at this one. I should let you know that I have not seen or flown this model. Let's start with the weight. 6.5 pounds minus the glow motor and add the electric one and battery pack, my guess is 7.5 pounds. Since this is a scale like model, I'd shoot for about 70 watts per pound or a 520-550 watt system. Running at 30 amps meens a 18 volt battery. Lets call it a 16 cell pack. I'll be back with more in a minute.

John Pursell

jonnyjetprop

My Feedback: (3)

Looking at the Model motors website, http://www.modelmotors.cz I see two systems of interest.

#1 4120/18 18 cells 12X8 prop running at 29 amps. 566 watts, weight of motor 11.5 oz., weight of battery 38 oz 2400 mah (29.2 1700 mah)
#2 2820/12 14 cells 10X7 prop running at 33 amps. 500 watts, weight of motor 5.8 oz., weight of battery 29.5 oz 2400 mah (22.7 1700 mah)

#2 would be a lighter system, but #1 would allow upward growth should your weight increase or you want more power.

This would be a starting point. Hope it helps.

John Pursell

jonnyjetprop

My Feedback: (3)

My choice of speed controls is Castle Creations. I would look at the Phoenix 45.

http://www.castlerc.com/

John Pursell

vicar

John,

Thank you very much for the info. I am new to e-power so I have to totally rely on people like you for my experiments. Have you looked at the Hobby Lobby AXI motors? They seem to be very powerful and the price does not seem to high when compared to other motors. I have to admit I am not sure my comparisons are correct.

Any other suggestions/comments are greatly appreciated.

Matt Kirsch

My Feedback: (21)

vicar,

Take a closer look at Johnny's recommendations. Those ARE the AXi motors he's talking about. AXi motors are made by Model Motors in the Czech Republic. The Model Motors website is far more useful and accurate than Hobby Lobby's as far as the capabilities of the motors are concerned.

vicar

Matt,

Thanks for the clarification. Where do you guys buy your motors? Does Hobby Lobby have the best prices?

bassmanh

My Feedback: (5)

vicar,

if you want to go with the 2820 AXI motors then radical RC has a better price BUT hobby lobby has a low price garauntee that they will beat anyones price and they will sell it to you for 10% less. i got my 2820/12 for $71.00 this way great deal. here is the link to radicals site page with the motors, wich you will need to give hobbylobby so they can check it out and make sure of the price
http://radicalrc.secure-mall.com/sho...81&cart=127923

otherwise i havent seen the 4120 series any cheaper anywhere else. hope this helps you .


mitch

ukrconsul

My Feedback: (1)

vicar
I would recommend you to calculate your model with a program called Motocalc 7.
You can find it here:
http://www.motocalc.com
If you are new to electric planes it will save you a lot of time and give you understanding.
The program is not accurate, do not rely on numbers, but it will definitely give you basic understanding.
Regards

ukrconsul

My Feedback: (1)

That bassmanhs pike is BIG!

bassmanh

My Feedback: (5)

UK
thanks its actually a muskie and it is my biggest so fay 47.5 inches and about 28 lbs was very good time catching that fish, then watching her go free to catch another time catch and release it grows on you .

mitch

Matt Kirsch

My Feedback: (21)

Be careful with Motocalc and AXi motors. Motocalc is only accurate in a certain "sweet spot" with outrunner motors. The rest of the time, it's way off, and does strange things.

vicar

Matt,

As I said before, this is my first incursion into the world of electrics. Could you be more specific?

I am trying to outfit a motor glider which means (I hope) the motor will be off for a good part of the flight. How do I figure that into the selection of the power system?

P-51B

My Feedback: (5)

The link doesn't seem to work.

bassmanh

My Feedback: (5)

P-51,
try this link and see if it works for you .

http://www.modelmotors.cz./index.php...id_odkazy=m_ac

here is another link that you all might find interesting for another brand of brushless motor

http://www.maxrivers.com/index.htm




mitch

Matt Kirsch

My Feedback: (21)

Nope, I can't be more specific. Motocalc simply does not handle AXi motors very well. The calculations it provides are incorrect, except for a certain narrow band where the math model Motocalc uses matches the real-life physics of outrunner style motors.

http://www.modelmotors.cz works fine for me. Make sure you click on the link or copy it EXACTLY to your browser.

Use Motocalc to verify some of the real-world test results shown on the ModelMotors website. You'll find that some of them work and some don't. For the ones that work, if you increase the prop size, you should be able to expect a substantial increase in current draw. In many cases, the current actually goes DOWN.

P-51B

My Feedback: (5)

O.K., the link is working now...I think it must have been a conspiracy.

jonnyjetprop

My Feedback: (3)

I fixed the first one.

John

P-51B

My Feedback: (5)

It WAS a conspiracy!

I am also new to this electric area, and have a question about the outrunner AXI motors. The last number of a motor in a given AXI series seems to indicate the number of turns in the motor. My question is what benefit/loss does the extra turns give? Is it strictly the ability to turn larger props at a sacrifice of runtime. I am curious from the "watts to the prop" standpoint.

ukrconsul

My Feedback: (1)

About AXI at a glance:
4120/14 - bigger props (14"), more amperage (40-50A), 8000 - 9000 RPM, less cells count (voltage) - 16 cells;
4120/18 - smaller props (12"), more RPM (11000) less amperage (30-40A), more cells (voltage) - 20 cells.
4120/18 has more power then 4120/14 at high cells count (20-22 cells). But it is only 4120/14 you can use with 14 -16 cells (4120/14 has more power on 14-16 cells).