Sloping Off - June 2005
Mega 22/20/3E Brushless Motor
The Innards! by Terry Antell
I have fitted a few of these electric brushless motors to models over a period of a year. This one is a straight replacement for a 540/550 or 600 brushed power unit. Difference? Oh yes. Lighter in weight, same width as a 600 but shorter in length, about 4 times as powerful, can be used as a direct drive unit.
These are not out-runner motors but are conventional in-runners. The shaft is 5mm diameter hardened steel. The magnets are attached to this and are cobalt. The outer case is made from hardened aluminium, which I think is duralumin. This is a light, but very hard, aluminium. The shaft is supported by a ball race at the back and front.
The motor is 3 phase AC. This is the reason why the speed controller is expensive. It has a DC to AC converter built into the unit.
These motors do not have any suppression built in, nor is any required! No brushes, no sparks.
All brushless motors (I’ve come across) are much quieter in operation. They are better balanced, too!
The plus side is the massive increase in power available while remaining VERY quiet. The down side is a reduced running time from the same battery as used with a 600 brushed motor.
My Mega pulls 33amp (static) with a 10 x 6 folding Cam prop up front.
I bought a Protech Unlimited electric glider. The 550 can motor supplied took 4min 30sec to gain 400 to 500 feet. The same model with a Mega 22/20/3E brushless climbed to around 800 feet in 30 seconds.
I use an 8 cell NiCad pack, 1600mah. This gives around 4 minutes on full power. Remember, only 30secs for a decent climb out so plenty of actual flying time available.
On 7 cells the power time is increased, even more so on 6 (less volts means less amps can be pulled, so a slower climb rate).
The model was transformed, becoming a dream to fly and UNLIMITED.
Dural is a brittle metal, so, beware of heavy nose in landings! Having repaired one for a friend I can confirm that the 3 rivets holding the back plate on the main can are hardened metal. I had to grind all three away to gain access.
I drilled the casing in 3 places, tapped a 3mm thread and used 3mm bolts to refit the plate.
The only thing I can see that may wear with time are the bearings.
So, next time you have an electric powered model, glider or whatever, consider investing in a brushless motor AND a speed controller to match.
Should you own a model, or are considering buying one, think brushless. If you don’t know which motor to buy, give John Emms, at Puffin models a ring 01454 228184. Tell him what you have in the way of a model and he’ll advise the motor, speed controller, prop adaptor AND prop to buy. If you know what battery will currently fit the model, tell him, he’ll advise what battery will fit (possibly an 8 cell to replace a 7 cell AND lighter) and match the motor/controller. Expect next day delivery, too!
The photos show a dural plate attached to the front of the motor. This now holds the unit together! It still requires final cleaning down to size. The motor will now be fitted to a model using this plate.
Thanks go to C&DMFC member, David Enticott for the dural plate.
