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Following in the footsteps of Mark Sylvester, Andrew Gibbs & Glen Kingdon, I decided that the time had come to replace the smelly, noisy two-stroke in my Weston Cougar 2000 fun-fly model with an environmentally friendly electric motor…
Restricting myself to using as much equipment in my toy-shed as possible (keeping the cost down) but realising that an LRK (outrunner) motor was the efficient way to go, I ordered an AXI 2820/10 from Puffin models, with the speed controller & batteries coming out of my T-33.
Off came the Magnum 36 & pipe; out came the fuel tank, throttle servo & linkage, receiver battery and switch harness. I ordered the fancy motor mount to go with the AXI, so it was a case of re-positioning the motor mount blind nuts, and bolting the whole mess together. The speed controller was velcro’ed on to the outside of the fuselage (to keep its’ cool) and to start with the batteries lived inside – I’ll live with removing the wing to get at them for a while – but I do feel an access hatch coming on soon.
So, I weighed the model in its’ smelly guise – 1.7 Kg, (3.75 pounds) and then when in stealth mode (1.6 Kg)
Using an APC’E’ 12 by 6 prop, I get 1.5 Kg of thrust @ 35 Amps current draw, approximately 350 Watts of power, or just under half a horsepower !
An electric Cougar can be bought as a complete package for an RRP of £374:70 (as at 10/3/2004) – that’s model, motor, speed controller, batteries, prop & driver, but what did I use ?
- Cougar 2000
- AXI 2820/10 motor & mount.
- Kontronic 40-6-12 speed controller.
- 8-cell 2000mAH SCR NiCad’s or 10-cell 1700mAH CP NiCad’s. (same size & weight as one another)
- Standard size receiver & servos.
- APC ‘E’ 12” x 6” prop
How does it go ?
Well, apart from the lack of vertical climb (some playing with prop sizes needed, I think) it can compete on level terms with the smelly version. Duration is seven minutes to LVC (low voltage cut-off) – more than enough time to win a comp J And the instant throttle response is an absolute joy! No more tweaking of the needle valve when the weather changes – the speed controller takes care of the timing so that I get full-power every time I fly
Pros’
- Lighter.
- Cleaner.
- Quieter.
- Non-smelly!
- Starts first time – every time!
- Motor only stops when I want it to, or the battery’s flat.
- Provided I don’t prang it, the motor should last forever.
Cons’
- More expensive (if you’re not ‘electrified’ already).
- Less flying time per charge than a tank of fuel.
- Not quite prop-hang-able – yet…
- Have to remove the wing to ‘refuel’ (at the moment…)
The next step is to invest in some of the high discharge Lithium-Polymer cells that are rumoured to be around in the USA – 3 of the 3300mAH capacity cells (3S1P) will give the same voltage (12) of a 10-cell NiCad or NiMH pack, for a third of the weight, with 15-minute flight times !
I spoke with John Emms of Puffin Models to discuss my lack of vertical performance, and he suggested a re-motoring with an AXI2820/12 & Jeti 40 amp speed controller. As I am quite committed to electrics (or should that be committable?) and my birthday was looming, I got my family to club together and buy the bits for me.
Oh joy! What a transformation! Mated with a 12 by 8 ‘E’ prop, my Cougar will now do everything I was capable of doing with it beforehand.
As you can see from the ‘photos, I cut an access hatch in the bottom of the model so that I can get at the batteries that much easier.
As the Jeti speed controller is ‘Lithium capable’ I’m now saving up for a 3-cell pack of the 20C 2100mAH Lithium Polymer batteries – a third of the weight of my CP1700’s and just as powerful!
To infinity - and beyond!
Tom Gaskin
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