|Electric motors||- Electric|
AXI brushless electric motors
AXI motors are made of the highest quality materials and workmanship. They also
have the best warranty on the market today. Every Czech manufactured AXI motor
is a highly efficient, high torque, maintenance free rotating can (OUTRUNNER)
brushless motor with strong neodym magnets. The use of a gearbox is NOT
necessary. The hardened steel motor shaft is supported by 2 ball bearings in the
22-28 series motors, and 3 ball bearings in the 41-53 series motors.
above and below from http://www.modelmotors.cz/download/katalog_2008_hr.PDF
By Steven Horney at http://www.rcgroups.com/forums/showthread.php?t=194098
Just when you think all has been said and done, something comes along that turns everything inside out. In this case, that something is a motor, a Model Motors AXI rotating can sensorless brushless motor to be exact. Most brush motors have the magnets on the case and the windings on the rotating shaft, while " common" brushless motors have the windings on the case and the magnets on the rotating shaft.
Here's what the innards of the AXI 2820/10 look like. Everything is held in place by the retaining clip shown on the far left of each photo.
The AXI motor combines a little of both, but with a twist. This brushless motor has the magnets on the case and the windings around the shaft, but rather than rotating with the shaft, the windings are fixed. The magnets actually rotate around the windings (along with the housing), then transmit that force to the shaft (which runs through the windings) by means of the back plate which is pinned to the rear of the shaft. It sounds a little awkward, but in practice, it allows a relatively small motor to generate a hefty amount of torque for its size. The outcome of all this is the ability to spin large props with a light motor and no gearbox.
The numbers I've seen for the AXI motor generally show an efficiency range of around 70 to 75% when used within recommended cell count/prop ranges. This makes it comparable to a good cobalt brushed motor and a little low in comparison to comparable brushless motors, but the low weight and the ability to spin larger, more efficient props without a gearbox (and the associated losses with the gearbox) may more than make up for the lower efficiency numbers. For what it's worth, my *Calc numbers generally show closer to 80% efficiency.
From my examination of the AXI 2820/10 motor, it appears to be well made. The 5 mm shaft is hardened, and the components seem to be well machined. A number of openings in the housing and around the case ensure good cooling air passage through the motor. This unique design yields a novel wiring arrangement. The wires exit the side of the motor, near the front. Mounting the AXI motor in a narrow nose (such as with most sailplanes) can be complicated with this forward wire exit, but I was able to mount the AXI successfully in my Chip (see below). One thing I noticed that seemed unique was a magnetic field that varies according to the position of the magnet housing. In turning the prop, there is noticeably more cogging and resistance over one-half of the rotation than over the other half.
Here's the AXI 2820/10 motor mounted to my Hobbico Viper. The Hobby Lobby mount seemed almost designed custom for the task, allowing easy firewall mounting while keeping the wires away from the spinning magnet housing.
Light, smooth, powerful, and apparently well made, the AXI 2820/10 motor is an impressive little package with the torque of a somewhat larger motor (or a geared motor). Mounting this motor has some challenges due to the rotating magnet housing and forward/side mounted wiring, but this is usually somewhat minor. As a sport plane motor, it proved to have plenty of power and the ability to handle a wide range of props. On ten cells, it gave my Viper very solid aerobatic performance. On the other hand, if you're looking for a light and powerful seven to ten cell 05-size sailplane motor, the AXI 2820/10 is also an outstanding choice. The ability to spin large props without the complexity and weight (not to mention expense) of a gearbox is exactly what many sailplanes need. The AXI 2820/10 is an excellent motor for many applications, and with its relatively inexpensive pricing, it's an outstanding value.
Aveox / Zagi brushless d.c. motor with electronic motor controller http://www.zagi.com/index.php?main_page=aveox_mod