[D.1] necessity of break-in and common break-in methods...
brushed motors need break-in prior to coming into full duty. especially closed endbell high-power ones. good break-in means longer life, less wear on the commutator and brushes, and constant performance. when a brand new closed-endbell motor leaves the factory, the brushes usually have only a minor 'grip' [contact] on the commutator. if the motor is systained directly into full duty, heat and the revolving commutator, will eventually fatigue the brushes in a way that a full contact is achieved. in theory, this is the goal;when the brushes fully seat on the commutator, full performance potential is achieved. however (in practical terms), till that happens, severe damage will be systained on the commutator [small contact area=lots of current spikes=burned copper surface], thus raising the resistance of the particular spot permanently. this of course, hurts ongoing performance, and in closed endbell motors it is not reversible. the performance decrease is now permanent. therefore a proper manual break-in is important, for it achieves two goals in a row:
-fully seated brushes
-no damage, wear, tear, thermal corrosion, or burned surfaces on the commutator and the brushes.
therefore, the performance stays peak, and it lasts.
there are many ways to break-in a closed-endbell pmdc motor. the two most popular ones are:
1.water dipping
2.progressive load / thermal cycling
each with its own pros and cons.
water dipping method
submerge the motor [1 by 1, not both at the same time] in clean water, then connect the motor directly with a 4.8 or 7.2v battery [fully charged, 3000+ mah is recommended]. never use the esc for this purpose.
*note: this method of break-in shouldn`t be excersized with neodynium based motors.
phase 1:
allow the motor to run for 20seconds, then disconnect the motor and refresh the water [should be dirty by now, so use fresh].
phase 2:
repeat the process for another 40 seconds, then refresh the water once again.
phase 3:
repeat once again for 1 full minute.once done, dry the motor and lubricate the bushings. use another fully charged battery for the second motor.
progressive load / thermal cycling method:
*note: don`t use active-cooling stuff [fans,etc] for this method untill the motors have been broken-in.
phase 1:
remove the pinions and wire the motor(s) to the esc, with a fully charged pack [at least 3000mah]. oil the bushings.
a.run at 10% throttle for 1 min.
b.run at 20% throttle for 1 min.
increase the throttle by 10% every 1 minute. when 100% of throttle is applied, allow the motor(s) to completely [sort of] drain the batteries. clean the motor with an air spray, allow the motors to cool down, then proceed to phase 2.
phase 2: light load [motors installed in the truck]
install the motors as they are supposed to. re-oil the bushings before installing. place the truck on a stand. do not remove the wheels.
gently apply throttle to 100%. [gently = sort of 10% increase per second].
allow the motors to drain the batteries once again. when done, you may use a cotton bud or air spray [that works best] to remove the carbon from the commutator. re-oil the bushings,allow the motors to cool down, then proceed to phase 3.
phase 3: light duty, full load
drive the truck gently at the first set of batteries. you may drive as fast as you want, but avoid slamming the throttle and avoid jumping. avoid zero-to full acceleration and sudden full braking. once done, clean the motors and lubricate the bushings once again. now you may install the heatsinks and the fan.
[D.2] Maintenance methods,frequency, and necessity...
-how often do i need to do maintenance on the motors?
that depends on the terrain that you are driving on.very dirty terrain will lead to more frequent maintenance needs. a typical service period can be estimated as follows:
terrain type______________clean/pavement/tarmac/grass_________some-dirt/rocks/gravel_________sand/mud/lots-of-dirt
aproximate service cycle______30-40 duty cycles__________________10-20 duty cycles______________5-10 duty cyles
*note: 1 duty cyle = 15 minutes of driving / 1 set of batteries / 1 run.
*note#2: in case you are frequently driving on very harsh terrain [sand/mud, etc], consider doing the fuel-tubing motor mod. it will protect the motors from sudden failure and should also drastically increase the service cycle up to 20 or 30 runs.
-which is the most typical maintenance that i have to do?
using a spray can of compressed air, spray the motor through the vents -especially on the commutator and the brushes. lubricate the bushings when done.
-which is the most thorough maintenance that i may do to the motors?
remove the motors from the truck and run each of them submerged in clean water for 5-10 seconds. use a direct battery-to-motor connection for this purpose [never use the esc]. dry the motors, then lubricate the bushings. this method works best, but is more fuzzy than the above one.
*note: this particular method shouldn`t be excersized on neodynium based motors.
*note#2: don`t exceed the 10sec barrier. the more your motor works underwater, the more the brushes get fatigued. you want just to remove the carbon/dirt and clean the contacting surface of the brushes/comm, therefore keep the 'submerged duty time' low. otherwise, the motor`s usable lifespan will be shortened.
-is there a method of maintenance which is as simple as the 1st, but as as effective as the 2nd?
put the truck on a stance, and remove the wheels if you want. using a syringe full of water, dip some water on the commutator and the brushes of the motor(s). give the motors some throttle for a couple of seconds, then return to neutral and repeat the procedure a couple of times. then, using the throttle trim on the transmitter, give the motors some throttle [just a bit], and dip water on the commutator and the brushes while the motors are working. once done, lubricate the bushings and you are ready to go.
-does maintenance frequency affect motor performance & lifespan?
of course. without proper maintenance, expect your motors to retire twice as fast [aproximately]. such type of motors [closed-endbell pmdc] should last for a minimum of 100 duty cycles. a good motor which is treated nicely, should go through at least 300 duty cycles or more.
-is there any 'fast maintenance' or motor-prep that i should do?
lubricating the bushings before each run is a good idea. wipe the dirt of them first. 1 drop of oil is more than sufficient. more than that will only attract dirt around the bushings and inside the can [which is bad]. work the oil in the bushings by rotating the motor shaft sometimes. revolving the wheels by hand or giving the thing some throttle on a stand can make this painless.
-what kind of oil should i use on the bushings?
any of those should work fine:
http://www2.towerhobbies.com/cgi-bin...?&I=LXDE85&P=7
http://www2.towerhobbies.com/cgi-bin...?&I=LXDA93&P=7
http://www2.towerhobbies.com/cgi-bin...&I=LXJY55&P=ML
http://www2.towerhobbies.com/cgi-bin...?&I=LXB804&P=7
http://www2.towerhobbies.com/cgi-bin...?&I=LXKUF9&P=7
-is there anything else i should take into account?
when re-mounting the motors [either after maintenance or after break-in, etc]always pay great attention to the gear mesh between the spur gear and the pinions [refer to the drivetrain thread for more info on this]. also, make sure that the motor mounting screws are tight [don`t strip them though], and that the pinions are locked with CA glue on the motor shaft [in case the motor`s shaft doesn`t have a flat side].
Monsters of Torque [revised], part#D: break-in and maintenance tips for PMDC motors
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