Electric Power - Recommended Setups
At Mugi, we are continually experimenting with different electric powerplants on our Mugi Evos and evaluating new motor and battery technologies as they appear. Look out for our power setups in the shop area (expected Autumn 2007).
Brushed motors represent a cheap way to get airborne with a speed 400 type motor costing around £4. If you have a collection of brushed electronic speed controllers (ESC) and a few old technology batteries kicking around then this is likely to be the instinctive option for powering your Evo. There are a few suggestions to help you maximise the performance of your brushed setup:
- Use a 6V Speed 400
Lots of motors are the 7.2V type and require more voltage to achieve the same rpm. The 6V types can actually take a vast range of voltages before they burn out - some types are rated for up to 10V on a standard push-on prop.
- Use a minimum of 8 cells in a NiCd or NiMh pack
A 6 cell pack made from these traditional cells only has a voltage of
7.4V which is insufficient for a high performance aircraft. Seven cells offers a little better performance but still rather sluggish and launches are difficult. Move to 8 cells however and the voltage increase to 9.6V means that a 6V speed 400 will give very sprightly performance.
- Consider LiPo batteries
There have been 'horror stories' about exploding LiPos but the early days of the technology have passed. With a specialised LiPo charger these batteries are very easy to maintain, have an incredible shelf-life when charged and are much more crash resilient than they used to be. The energy by weight makes them incredibly useful for model flying. However, one must note that if using a brushed ESC it must have a LiPo suitable voltage cutout. If unsure, then a LiPo saver device sitting inline (available all over the web) is a good idea.
Our 'ideal' brushed setup:
- Speed 400 motor (6V type)
- 8 cell (9.6V) battery or 3S (11.1V LiPo)
- Suitable ESC (capable of handling >18A, to be safe)
- Günther push-on prop or our carbon/plastic prop with adapter
You'll get nice speedy flight from this setup and it'll suit the more novice pilot. It's an impressive aircraft on this with great climb and aerobatic performance. Duration will be under ten minutes (more with LiPo).
Ultimately though, if you're starting out in the hobby and want to take your first steps in the right direction, then a brushless setup is a better bet.
Brushless motors are the future. They offer higher efficiency, better power output and are generally more robust than brushed motors of an equivalent size. There are lots of types of brushless motors on the market and the choices can seem bewildering. We recommend a 28mm diameter motor for the Evo. This type of motor shares the same dimensions as the old speed 400 brushed motors but has rewired internals. They are much more expensive but should outlast the brushed equivalent thanks to better power handling and chunkier output shaft. Here are our suggestions:
- Choose your kV
Brushless motors often quote a kV or rpm/V figure in their specs. This is basically a guide to how fast the motor will try to turn - the higher the number the faster it wants to turn. Sounds great? It is, but a high kV motor on a large propeller will draw much more current than a lower kV motor. It will need a smaller prop turning at more rpm, which reduces the thrust but increases the aircraft's speed. There's obviously going to be an optimum point... We've found that motors between 2000kV and 3000kV are ideal.
- Use a 30A brushless ESC
With these brushless motors you might draw around 18-20A in flight. A 30A controller gives a nice safety cushion and also allows you to experiment up to these higher currents, perhaps with a larger prop or higher kV motor.
- Make sure the LiPo is suitable
It's open to discussion but generally brushless motors go hand-in-hand with LiPo batteries. A 3S LiPo kicks out 11.1V and is ideal for the recommended kV motors provided that it's discharge rating is suitable. You'll find that LiPos are sold with a capacity and a discharge specification; e.g. 1800mA 20C.
This means that the capacity is 1.8A and that it can give 20 times that amount in terms of amps out (36A). However, it's much better for the battery to stay way below this figure and the 18A in flight that a 2000kV motor gives you is very suitable.
Our 'ideal' brushless setup:
- 28mm diameter inrunner motor (2000-3000kV)
- 3S (11.1V LiPo) at least 1500mA and 15-20C
- Suitable brushless ESC with LiPo voltage cutouts >30A
- Propeller (5x5" CAM to , 4.7x4.7" CAM depending on kV)
With brushless motors such as these there are many parameters determining the overall performance. If you are a beginner then the 2000kV motor is far more suitable than the 3000kV end of the spectrum. Performance with a 2000kV exceeds a brushed setup quite markedly and you will achieve vertical climbs.
Move to 3000kV, however, and we're definitely not in beginner territory. This will give you an aircraft that is extremely fast, maybe more agile than you are used to and with a climb that will amaze. The power to weight ratio is something like 2:1!
Ultimately, the throttle stick controls the motor and careful use will mean that you can work your way up to flying
at 'full beans'.