'pseudo direct drive' motor?

[carmatic]

http://www.youtube.com/watch?v=EAELukfr2oY

are there any crawler motors based on this idea ? basically, a gearbox-like magnetic arrangement in a brushless motor (abit like planetary gears), so that the output is low rpm and high torque, using less coils and therefore thicker gauge coil wire, which means more efficiency and less heat from the motor

they do not mention it in the video, but i think that it is possible for the different rings to 'slip' since they are pushed and pulled by magnetic attraction and repulsion, if the slipping can be controlled and adjusted, it might also serve as an over-torque protection so you dont overcurrent your ESC or snap your gears, like a slipper built right into the motor which never wears out

[Duuuuuuuude]

Looks good, but I have to wonder about its size. So far the only listed applications I've seen are for big things like boats, wind turbines, and hybrid vehicles.

[EddieO]

Even a small one of these will probably cost over $1000..........and then you would still need the correct speed control for it.

Nifty tech, but I doubt we will see it any time soon in rc.

Later EddieO

[carmatic]

Originally Posted by EddieO

Even a small one of these will probably cost over $1000..........and then you would still need the correct speed control for it.

why wouldnt it work with a normal 3 phase brushless esc, tho? it is basically a rotating magnetic field, so it is something like a normal permanent magnet rotor motor, as long as the coils are arranged for 3 phases, then it is a 3 phase motor... right?

[losikid]

Originally Posted by EddieO

Even a small one of these will probably cost over $1000..........and then you would still need the correct speed control for it.

Nifty tech, but I doubt we will see it any time soon in rc.

Later EddieO

Pfff, $1000 bucks is chump change.


Couldn't it work off a pretty standard sensorless esc? Or would that additional magnet complicate things...

[EddieO]

It's possible a normal speedo would work, but I doubt it. Seems to be a lot more going on in the motor....

As for $1000 being chump change..........I am probably low on my guess, assuming they even make small ones.....and just think for an MOA, ya need two.


Later EddieO

[Charlie-III]

Sounds like an updated eddy-current drive that I used in industrial applications 30 years ago. It had an AC motor, 2 slip rings feeding a seperate coil & a drive that varied the current flow in the coil, thus altering it's "magnetic attraction". The only wear items were the brushed for the slip rings & armature bearings.
The old units were rather big though.......

As stated in post 2, I would imagine the linked units are rather large for a RC crawler.

[carmatic]

if you were to follow what the video shows exactly, you would either need really small magnets or , yes, the motor would be too huge

but i am certain that the principle behind the motor can be applied in more than one arrangement or configuration,... maybe it can be arranged similar to an outrunner motor? by discarding the 'gearbox' aspect of it and losing the inner magnetic ring, and placing the coils there...
i dunno, but i think i've seen a motor like this before, like strips of metal running along the insides of the motor

[JohnRobHolmes]

I have played around with some direct drive motors and concepts that could be used for crawling. Essentially it boils down to a loss of power to weight ratio when you lose geardown. To make a motor work properly near or in the wheel we need at least a two stage planetary drive or else the motor size gets huge to keep a constant stall torque at the wheel. There just isn't a good way to do it right now, the end result is more costly, higher weight, and of no advantage over a typical MOA system.

The closest we have to this type of design is an outrunner motor. It could use this magnetic geardown instead of a gearbox fairly easily actually, but it would more than double the cost of the motor because of magnet prices. On top of the extra magnet costs, there would need to be large ring bearings to support the floating steel ring.


Cool idea, but not very practical to implement on the small scale.