From: hutto@SMTC.engr.scarolina.edu (Brent Hutto)
Subject: Re: Misc R/C Car Questions
Reply-To: hutto@smtc.engr.scarolina.edu
Organization: NIST Southeast Manufacturing Technology Center
Date: Fri, 22 Jan 93 13:56:23 GMT

In article <1jndudINNi9a@flop.ENGR.ORST.EDU>, slezal@gyro.ECE.ORST.EDU (Lee Slezak) writes:

>How can I make my stock motors faster?  Can you make them like
>modifieds or what?

    Here's a repost of an article I did several months ago...

===============================================================================
    I don't know very much about juicing up "stock" motors since I don't 
    race in any "stock" classes.  I race because I like racing, not because
    I like messing around with motors, so "modified" classes are a better
    deal for me.  That said, here's what little I do know about motor tweaks.

    There are three basic approaches to making a stock or handout motor
    produce more power.

    Approach #1 is to flat out cheat.  You take the can apart and substitute 
    in bearings and/or a different armature.  The downside to this is that 
    you'll get caught if the race organizers do a "teardown" check after the 
    race.  I call this the "Stock Motors?  We don't need no stinking Stock
    Motors" approach.  Not recommended.

    Approach #2 is to simply maximize the power output of the motor using
    normal motor-tuning techniques.  Some sort of dynomometer arrangement
    is necessary (unless you have lots of patience for trial-and-error)
    to judge your results.  Substitute different types of brushes (both
    shape and material compound) and different tension springs until you 
    find the combination that produces the most power.  If you must race 
    "stock", you should at least do this whether you do anything else to 
    the motor or not (unless you don't mind being "out-horsepowered" all
    the time). I call this the "make the best of what you've got" approach.

    Approach #3 is to advance the timing of the motor.  Most of the motor
    tweaking "techniques" that you'll hear discussed at the track are
    probably aimed at advancing the timing one way or another.  Up to a
    certain point, you can get considerably more power out of a given
    motor by moving the brushes and/or commutator so as to make the
    commutation take place before the so-called "zero-timing" point.  
    Almost all racing motors, even low-wind modifieds, use some timing
    advancement (maybe 2 or 3 degrees minimum).  As you approach the
    (theoretical) maximum of 45 degrees of timing advance, you shorten
    the useful life of the motor (extremely) and also worsen its overall
    efficiency (power out vs. power in).  For this reason, ROAR stock
    classes, for instance, specify 27-turn motors with no more than
    24 degrees of timing advance.  If everyone stuck to 24 degrees,
    they would get a pretty decent lifetime from these motors.

    The oldest method of "aftermarket timing advancement" is usually
    called "cranking the commutator".  This is a brute force method where 
    you stuff something in through the brush hood to hold the armature and 
    then twist the endbell (or something like that, I've never tried it 
    and don't know the details).  When you do this, you run a finite risk 
    of breaking the motor.  The current ROAR-legal stock motors have a 
    "commutator locking device" that increases this risk to about a 90% 
    probability, making "cranking" of those motors more of a risk than most 
    people care to take.

    Another way to advance the timing is to use "timed brushes".  These are 
    brushes shaped in such a way that the leading edge of the brush reaches 
    further around the commutator than the trailing edge.  Depending on the 
    shape, you can advance the timing from several degrees to maybe, oh I 
    don't know  exactly, maybe 10 degrees or so.  

    A currently popular method utilizes a Zapper (trademark of Endurance 
    Racing Products, I believe) to remove the magnetism from the magnets (by 
    reversing the polarity of the motor from the normal Zapper usage) and 
    then rotate the motor can in the Zapper by the desired amount of timing 
    advance and remagnetize the motor.  Sometimes this ruins the motor, so
    don't do it on your last handout motor at a big race or you'll have some
    explaining to do.  This results in a waste of a little bit of the actual
    magnet area, but the timing advancement produces more power than the
    effective magnet area reduction loses.

    I'll leave it to the imagination of the reader to think up other ways of
    advancing the timing on a "stock" motor.  Whatever you think of, someone
    else has probably thought of it and there's someone somewhere who is no 
    doubt already doing it as we speak.  One approach that is currently in
    vogue at my local track is to experiment with shims between the brushes
    and the brush hood to shift the brush "forward".  I think you get the
    point, anything to advance the timing.  Some techniques are against the
    rules, some are easily detectable, some are both, some are neither.
    Whatever you have the stomach for...
-------------------------------
Brent Hutto
hutto@SMTC.engr.scarolina.edu
Newsgroups: rec.models.rc