electric conversion question
 

I have a world models aircombat series model that I am converting to electric and was wondering if the following electronics would work, it is a .25 size plane with a 47.5" wingspan.

- great planes ammo 28-45-2700kV motor (I have it lying around)
- castle creations thunderbird 54 esc
- 11.1V 1900maH battery (just for motor, will be running a separate battery for receiver and servos)
- what size prop should I use

I am also looking at getting the great planes gear box which has the following gear ratios.
2.5:1, 3.1:1, 3.6:1, 4.5:1
2.1:1 with 16T pinion and 40T spur
3.1:1 with 16T pinion and 50T spur
3.6:1 WITH 11T pinion and 40T spur
5.5:1 with 11T pinion and 50T spur

I currently have an os 40LA on the plane and would like the same type of speed and aerobatics or better.

any help would be appreciated.

RE: electric conversion question
 

Dude ... I have no idea about the geared system you are looking at but for your plane a 3S-4S system is enough. For motors you can just go with an outrunner and that makes life a lot easier. Something in the 35mm range is great, like perhaps a AXI 2820, Hacker A30, Turnigy or DualSky. If its 3S I would start with a 3536 type outrunner of about 900KV-1,000KV turning a 11x6 - 12x6, that will give you sport flying performance. You only need a 40A ESC for such a set up.

RE: electric conversion question
 

I am looking at this motor, because I have it as a spare for my helicopters, and a separate batter for receiver because I am going to keep the standard servos on don't know if they draw enough power to make a big difference vs. micro servos

RE: electric conversion question
 

I am not really into geared systems but I think your KV for that motor is kinda low. On 3S you may get away with the 2.5 gear box and a 11x6 prop but if you were to go with the 3.1 and 3.6 it will mean low RPM for sure. On 4S it would be great on the 3.6 gearbox with a 10" prop.

RE: electric conversion question
 

what type of rpm should i be looking for? I can always change the pinion to bring up rpm, with a 25T pinion it should give me over 15000 rmp.

RE: electric conversion question
 

If you want to just enjoy flying that plane it would be nice to get nothing less than 9,500 RPM on a 10x6. RPM will depend on prop diameter and pitch. The bigger the diameter or higher the pitch you can go with a lower RPM. All that also depends on the sort of performance you are looking at.

RE: electric conversion question
 

Firstly congrats on the finish on your model. Unless the US spec is different to the UK spec you have done a great recovering job. Secondly I converted one of these a few years ago and used a hyperion 3019/10 with a bolly clubman 9.5*6 prop. and 10 gp 2200 Nimh's. This motor is happy with props up to 11*7 on 3s lipo's and will run at 50 amps with no problems. I wrote mine off flying on a misty morning when I got disorientated. Any motor that is about 1000revs/volt and will handle 40a to 50a comfortably will be fine. I seldom use gearboxes nowadays with the many cheap outrunners that are available. With the correct choice of motor/cells/prop you should be able to get standard .40 performance. They are a great sport model. Good luck with your conversion.
Chris.

RE: electric conversion question
 

That Ammo motor is (optimistically?) rated at ~500W continuous - you need at least that amount of power to match a .40 glow motor (my MVVS .15 is 0.7bhp = 500W). I think you need to look at a motor which can manage 500-600W easily - the Ammo will fry trying. This is a .32 equivalent (650W max).. it might do. http://2dogrc.com/ecommerce/os/catal...ts-p-2437.html. Otherwise the .46 equivalent (900W max) but that may be overkill.

RE: electric conversion question
 

After looking at some of the out runnner motors that are out there, i have come to the conclusion that it would be cheaper for me to buy a motor rather than buy the stuff to get the ammo motor to work. I am looking at the Great Planes Rimfire 35-48-1000 Out-Runner Brushless and the specs are below.


Motor Diameter: 1.38" (35mm)
Motor Length: 1.89" (48mm)
Shaft Diameter: .16" (4mm)
Shaft Length: .65" (16.5mm)
Lead Length: 3" (76mm)
Connectors: Bullet type, .14" (3.6mm) diameter
Max. Constant Current: 50A
Max. Surge Current: 90A
Max. Constant Watts: 740W
Max. Surge Watts: 1330W
No Load Current: 3A
Input Voltage: 11.1V-14.8V
RPM/V (kV Rating): 1000
Weight: 6oz (170g)
Suggested Propeller Size: 10x5E-11x7E

RE: electric conversion question
 

Take a look at the Hacker A40 series of motors. These motors have a third ball bearing to support the "bell end" of the outrunner motor. I run mine at 45 Amps on 4 26650 A123 cells. The motor only gets slightly warm after a flight.

Its in a acrobatic model with a 48 inch wingspan, weight of about 4 pounds. The model will almost fly straight up indefinitely. Flight times are around 5-6 minutes with a minute or two of reserve power. After a flight, the motor, CC 45 Amp ESC and battery pack are only about 10 degrees F above ambient temperature.

RE: electric conversion question
 

I don't know the rimfire motors but the specs seem to be ok for the model. Another possibility is the scorpion 3020-12 with an 11*7 apc e. You need to look at your batteries though as I think that you will need more than 1900mA capacity. I think that mine weighed about 3 1/2 lbs so 400-500 watts will give a good performance.
Chris.

RE: electric conversion question
 

Please put my mind at rest. Have you carried out a recovering job or do they come like that in the US. The ones in the UK are very plain and nowhere near as smart as yours.
Chris

RE: electric conversion question
 

The plane came all blue, and I just used peel and stick covering to get it to look like that.

RE: electric conversion question
 

Lets say I go with the Scorpion 3020-12 motor about how much flight time can I expect from a 1900 to 2100 11.1V lipo?

RE: electric conversion question
 

J ... depends on what prop you are using and how much power you are using, basically, many amps you are pulling on the average. Sorry if it sounds like its not answering your question.

RE: electric conversion question
 

If you have 2 similar packs that have each had approx the same number of cycles on them then you could parallel them for flying ( but not for charging!!). You also need to be aware of the c rating of the cells. What is the make/specification of your cells?
Chris.

RE: electric conversion question
 

I have two packs that are 1900maH 20C 11.1V, they both have the same number of cycles on them.

RE: electric conversion question
 

The scorpion 3020/12 on an 11*7 apc-e using your 2 packs in parallel should pull about 40amps (about 400 watts). We are talking of about 4 to 5 minutes flat out. Using the throttle control sensibly will increase this to about 6-7 minutes. The plane should weigh about 3 1/4 lbs and will perform well. Your s/c is well specified and gives you the option of propping up if you need more performance. Check your s/c instructions as you may be able to use the inbuilt bec. I presume that you are using 3 standard servos? If not, using a small rx pack will save some weight. Incidentally I made an access hatch in the top of the fuselage from the cowling to the canopy and loaded the batts without taking off the wings. Good luck with the conversion and let us know the results if you go ahead.
Chris.