Motor timing and gear reductions

[Izzy]

I recently purchsed a "pulling" motor and noticed once I had it installed that the end bell has timing marks. Now from all the CarAction mags and articles I know that timing improves the performance of the motor. Ive installed a 3:1 before the tranny which switches the direction of the "forward" so this complkicates it further.

So here's the question - how do I know what direction is forward on this motor?

[fhhhstix]

Which ever direction the motor turns to het the truck to go forward you may need to take the motor off and run it to figure out what direction it is turning. I have a motor dyno but for the lower turn motors I am going to need to get the optional steel flywheel the alluminum one I have for higher rpm motors wont put enough load on them to get a good reading but with the dyno you can adjust the timming to get the most out of your motor. Try this link it is helpfull in understanding motors and their proformance.

http://www.rccartips.com/rc-electric...ning-guide.htm

[Thorsteenster]

When in doubt, just set the timing to 0. Pullers rarely if ever run backwards but in your truck you might want to reverse once in awhile which 0 timing is better.
If the gear reduction reverses rotation at the output though, don't worry about it as long as the motor is going forwards. From crawling it seems a general rule of thumb is to set timing at 0. My feeling is if you need to futz with timing, you should have gotten a hotter motor.

[fhhhstix]

Timing is directly related to efficiency you generally won’t need the power in reverse but in forward is were it counts the more efficient the motor runs it will result in longer run time and overall power. 0 timing in a crawler is right you don’t want to sacrifice one direction for another where as in a semi it may be beneficial. Just my thoughts.

Travis

[Izzy]

are motors labeld for + and - like the speed controls? I had never looked closely. As for this motor - didn't notice it was timed until a month or so after I had it installed - go figure.....

[Espeefan]

Izzy, some motors do have a polarity mark on them. I've seen positive symbols on the terminal that is intended to be positive, but in general, this is rare.

As for normal forward rotation, treat the motor like an internal combustion engine. Holding onto the can, with the motor shaft pointing away from you, and you looking from the rear of the motor, forward rotation will have the motor shaft spinning clockwise, just like a crankshaft would on an engine. If I am unsure on the polarity of the terminals, I hook some jumper wires to the terminals and watch to see what direction the motor spins.

Now, motors don't really care what direction you run them in. They don't know the difference, unless some timing advance is thrown into the mix. A motor with zero timing has no care in the world. A motor with timing advance will run better (stronger of faster) in one direction then the other. If a motor has fixed timing, then you are pretty much stuck with what you get. A motor with adjustable timing will spin happily in either direction, as long as the timing is set to zero, or advanced in relation to the direction you want the motor to spin.

Now as for adjusting the timing, you can rotate the end bell of the motor so far that you will actually reverse the motor direction, without changing the wire polarity. If you need a motor to spin the opposite way, do just that. If I remember right, you need to rotate the end bell 180 degrees the opposite way before you have effectively reversed the rotation. If in doubt, loosen the screw that holds the end bell in place and rotate it. Apply some throttle and see how the motor reacts. You can also do this with the motor running and observe it's RPMs dropping off, if you are adjusting the timing the correct way. You won't harm anything by making adjustments on the fly, but you can also leave the ESC 'on', make a small adjustment, and then give it some throttle to see how the motor reacts. Adjust the timing far enough and suddenly the motor will rotate in reverse. You can continue to adjust the timing to get a little power, in it's now reverse rotation direction.

Play with the end bell's location until you feel you have the timing set to where you like it. Either equal speeds in forward and reverse (of the model), or a touch more speed in forward travel. You really cannot screw anything up.

[Izzy]

NAthan - I didn't realize that the timing was .... so flexible ... I figured the motor would burn up or something.... I will check out the rotation - since I am haven't hard soldiered the wiring I can easily change directions if need be.

In order to compensate for the gear reduction - I had switched the wiring previously.


Thanks guys - I'll consider the advice...

[Thorsteenster]

So the timing is the brush location in relation to the magnets, changing the armature's position in the magnetic field when the winds are "hot"?
Never really understand e-motor timing or how exactly it worked.

[Espeefan]

Thor, if you look closely at a motor end bell, especially where the brushes lay on the commutator, you'll see the commutator is divided into segments. Each segment of the comm is soldered to the wires of an individual motor winding. In other words, each segment energizes a single winding, creating a magnetic field. The windings wrap around what we call an armature. The magnets inside the can of the motor are naturally attract the windings, which pulls the armature, as they are energized, and this makes the motor shaft spin.

There is a important relationship between the timing of an energized motor winding, and the magnet. The point at which the winding is energized, as it spins into the magnet's natural field of pull. The engerization of each winding needs to be timed so that the power to the winding is shut off slightly before, or right as, the winding centers itself above the magnet's field. If the power was kept on after the magentic fields center themselves, the motor would stop spinning, or at least slow down because the attraction would try to brake or reverse the rotation. Now depending when you energize the winding, you can make the magentic attraction start happening sooner, or later. This is where the motor timing comes into play. By advancing the timing, you are engergizing the windings sooner, and also shutting them off sooner. It's all in relation to the phasing of when the magentic fields attract to one another. Sooner gives you a little more torque and RPM, but only in one direction of motor rotation. If you run the motor in reverse, it's timing is now off slightly, hence it runs slower.

Think of it like advancing the distributor on a car (that has one anyway!). It's the same effect. You increase the point at which the spark fires in relation to the piston making top dead center. You can pick up a little power with the right adjustment.