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View Full Version : motor goes faster in reverse?


builthatch
2006.04.02, 09:12 PM
check this thread and let me know what you think...

http://www.minizracer.com/forums/showthread.php?t=21326

i'm stumped. i think i might just have experienced poor chinese quality control- the timing is bad.

sciencemike
2006.04.03, 03:39 PM
As for the curvature of the brushes, thats normal.
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The arc shape of the brush helps it break in quicker than the non curved shapes. So... Brushes can have a polarity to their max speed, once they are broken in. But since the ones you are using are not broken in for forward or reverse they have no polarity(basically the brushes sit on the comm differently in forward vs reverse..This results from torsion on the brush springs-copper holders.. and small amount of wind/air that gets pulled under the brushes that lifts the brushes off the commutator pads ever so slightly. )... Not the problem... Also I water dip my arms for more than 5 minutes. I put them into water with a 3 volt power supply and leave them there for 20 -30 minutes..

So Your problem is easy. Your timing is off. Timing of the motor is the relationship of when the inidvidual arm gets its coil energized in relation to the stator magnetic field. It also turns out to be a function of efficinecy, the higher the degree of timing (+or-) the less efficent it is. Its an easy thing to check and fix. You need to know a few things about your arm first.. One-is it a ceramic commutator or is it plastic.. If its plastic it will have teeth that bind with the armature stacks. These teeth will need to be broken off. But because they are teeth they will always align themselves with zero degrees of timing. So im guessing your arm has a ceramic commutator. Now how to check the timing is kinda complicated, there are simple ways to glance at it and check.. if you want to know those just pm me and ill describe it. Its for if you are in a motor shop and want a quick reference to timing. But, for your problem look at the center spoke of the arm. It should align exactly with the machine cut groove in your commutator pad. -Check all of your pads. These slots are cut with a machine and are sometimes not symmetric. But your cut slots will not be exactly in the center of your armatures. What you need to do is grab the commutator gently with your fingser.. if you are not strong enough use needle nose piers with cloth or better yet a rubber balloon doubled over, and gently twist it until it lines up with the arm... You have negative timing right now.. So you will be advancing the timing of your arm so you should be rotating it counterclockwise. Simple as that. Good luck. And its easy. dont worry just rotate it. I do it all the time. I wind a lot of motors and when i wind them sometimes i twist the commutator a bit. Once done i have to straighten it out.

Tell me if this helps.. Or if any parts are unclear...