Burgerman wrote:adding a little extra magnetism to the outside can probably does give an improvement everywhere.
Burgerman wrote:Its also unloaded with less torque. We dont drive unloaded unless going downhill.
It's also fully loaded with lots of torque. That green line applies in all cases of the motor spinning between zero speed and the no load max (assuming you have a controller that is powerful enough not to need to current limit at high torque). It doesn't just apply to downhill. And if you change your flux, you'll move towards either the red line or blue line, depending on which way you change it.
Burgerman wrote:Most of that seems pretty clear. And I agree.
Except for this bit.It's also fully loaded with lots of torque. That green line applies in all cases of the motor spinning between zero speed and the no load max (assuming you have a controller that is powerful enough not to need to current limit at high torque). It doesn't just apply to downhill. And if you change your flux, you'll move towards either the red line or blue line, depending on which way you change it.
A typical large powerchair 6 or 8mph motor has a stall current 2 to 3 times the limit imposed by the controller.
Burgerman wrote:So has the same effect as gearing. This isnt what I see in practice on my RC truck for e.g.
Graph is still wrong. Current isnt limited to .5 of eac motors stall. But to a constant of x amps.
Burgerman wrote:So has the same effect as gearing. This isnt what I see in practice on my RC truck for e.g.
Burgerman wrote:see it. But it makes the graph confusing using 3 scales for current!
Pretty much.
You need to look inside and see where the magnets are though. Or "feel it" for the magnetism with a bit of steel outside through the casing.
Or you will be randomly guessing. And the got to be the right side up! Or you will make it slow and overheat. It actually increases efficiency if you do it correctly.
You use one magnet to find out which is the north south as ithey will repel or attract each other. Or safer to use a compass. Mark with black pen so you can see which is the same face. Stick them on magnetically and see if its faster. Do one side of the motor first. Then the other side of the motor. The chair will drive oddly and turn towards the slow side. Then do the opposite motor!
You could use these? Or any that you think are easier to get in there. Try to cover the whole magnet. Say 4 of these on each side of the motor can. https://www.ebay.co.uk/itm/5-x-Neodymiu ... 1195.m1851
The bigger the magnet, and the more of the magnet that you cover, the better it will work. The hobby motors I use in quadcopters etc are built with Neobdnium magnets and thats why they are so powerful.
Burgerman wrote:Yennek says it wont work. And the theory he presents seems sound. Yet what I see on the bench is the same as those vids. So who knows!
steves1977uk wrote:Pretty much.
You need to look inside and see where the magnets are though. Or "feel it" for the magnetism with a bit of steel outside through the casing.
Or you will be randomly guessing. And the got to be the right side up! Or you will make it slow and overheat. It actually increases efficiency if you do it correctly.
You use one magnet to find out which is the north south as ithey will repel or attract each other. Or safer to use a compass. Mark with black pen so you can see which is the same face. Stick them on magnetically and see if its faster. Do one side of the motor first. Then the other side of the motor. The chair will drive oddly and turn towards the slow side. Then do the opposite motor!
You could use these? Or any that you think are easier to get in there. Try to cover the whole magnet. Say 4 of these on each side of the motor can. https://www.ebay.co.uk/itm/5-x-Neodymiu ... 1195.m1851
The bigger the magnet, and the more of the magnet that you cover, the better it will work. The hobby motors I use in quadcopters etc are built with Neobdnium magnets and thats why they are so powerful.
Just bought 2 sets of those magnets, will experiment on an old set of motors. Will be fun! Are the magnets inside a motor located between the brushes or near them?
Steve
Burgerman wrote:Repost vid link 1 https://www.youtube.com/watch?time_cont ... e=emb_logo
Vid 2 https://www.youtube.com/watch?v=Uks_modsd3M
vid 3 https://www.youtube.com/watch?v=EVyEsdWtGTA
vid 3 https://www.youtube.com/watch?v=6GzM56ejfjY
Burgerman wrote:OK. But it definitely had significant increase in fan speed witH greater magnetic strength. Once he got them correctly positioned. And a relatively light load like that tiny fan.
Burgerman wrote:And thats what I see on my RC truck. Its also what I would expect on a wheelchair motor. The load is quite high on the flat maybe 20A. And like my truck I would expect a significant increase in speed. Very high load on a minor hill, and irrelivant going downhill...
Burgerman wrote:I have one of these. What can I say I am a child. With FPV and long range radio and video digital transmitter. I swapped the can on the 550 motor for an aftermarket one with neobdinium magnets. Its crawls better more torque. And its around 20% faster visibly. Which is why I am confused. Your explanation sounds correct. But doesent appear to map to reality.
Burgerman wrote:https://www.youtube.com/watch?v=q1lJT6OyiGk
ex-Gooserider wrote:Interesting discussion... What I got from the first video was that with the magnets in the right place, the fan gave more lift, and since the blades didn't change, that implies that it was spinning faster... (it certainly sounded faster....)
The power source seemed to be a constant voltage (or current?) power supply, so if a CV supply, the motor needs to be drawing more current (increasing torque so it can spin the fan faster at a given voltage) or if a CC supply, drawing a higher voltage and spinning faster because of the voltage increase at (presumably) the same torque.... If the supply was unregulated, it might have been a combination of both... Either way it had to be due to a lower effective resistance in the motor windings.
It would have been better if the test setup had specified the type of supply and had a meter to see what the non-fixed output was....
Another thought is that the magnets used in the video were pretty close to being the same physical size as the motor magnets.... On a chair motor the magnets are MUCH bigger - at least on the motors I've opened up... This makes me wonder how big a magnet one would need to make a meaningful difference on a chair size motor? (also how much would one need to worry about matching the curve of the stock can?)
ex-Gooserider wrote:A second question is about practicality if trying to do this with a motor on a chair.... The stock motors are inside the motor can, which limits how 'magnetic' the outside of the motor is, so you don't pick up much random debris rolling down the street... If you stuck a bunch of magnets on the OUTSIDE of the motor, would they have a tendency to pick up ferrous debris (I hate to think about rolling around the Asylum welding shop if that was the case....)
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