From: hutto@SMTC.engr.scarolina.edu (Brent Hutto)
Subject: Re: Modified? (Was: Re: Misc R/C Car Questions)
Reply-To: hutto@smtc.engr.scarolina.edu
Organization: NIST Southeast Manufacturing Technology Center
Date: Fri, 22 Jan 93 22:23:28 GMT

In article <C19oy8.AGF@inews.Intel.COM>, dbraun@cad636.intel.com (Doug Braun ) writes:

>This makes me (an airplane person) wonder:  Just what does "modified"
>mean (as applied to car motors)?  Apparently if I talk a motor and
>modify it, it is not necessarily "modified".  Similarly, I can buy
>a motor off the shelf, do nothing to it, and it can be "modified"
>anyway.
>
>Can anyone explain?

    The designations "stock" and "modified" have historical denotations
    that are no longer important. The only meaning they have nowadays is
    as the names of two classes of racing at organized, santioned R/C car
    racing events. There are several organizations that santion R/C car
    races in the U.S., but I'll only discuss the one called ROAR for the
    sake of simplicity. The others are real similar. Also, I'll only talk
    about 1/10 scale electric races, not events held for 1/8-scale or 
    1/12-scale or glow-engined-powered cars.

    If you go to an R/C car race put on by a group that uses the ROAR rules, 
    there will be a number of classes of competition. One way in which the 
    classes are split up is according to the types of R/C vehicles. Typical 
    are 2-wheel-drive buggy, 2-wheel-drive truck and 4-wheel-drive buggy
    (this is at off-road races). The other way in which they are split up is 
    into "stock" and "modified". This designation is very confusing when you
    first hear of it because you would think that the words "stock" and 
    "modified" refer to the vehicles. Not so. It is only the electric motor 
    that determines whether you are in a "stock" or "modified" classification.

    So at a large off-road race, you might have as many as six classes of 
    competition, "2WD Stock", "2WD Mod", "4WD Stock", "4WD Mod", "Stock Truck" 
    and "Mod Truck". Actually, most races wouldn't have enough people  in all 
    of these classes to race. The most popular classes around my neck of the
    woods are "2WD Stock", "2WD Mod" and "Mod Truck", sometimes "Stock Truck"
    and very, very occasionally, "4WD Modified". Anyway, if a racer  enters 
    both "2WD Stock" and "2WD Mod" classes at a race, he/she will almost 
    always enter just one buggy and switch motors between races. She/he may 
    even use the same batteries in both classes (the rules for the two classes 
    do not distinguish w.r.t. battery type).

    Now I'm going to finally answer your question about motors. When organized
    racing of electric R/C cars first got started, the most commonly available
    motor was made by the Mabuchi Co. in Japan and was designated by the motor
    importers as a "540" motor. It was a three-slot permanant (ferrite) magnet
    with 27 turns of (something like) 22-guage wire. The nominal voltage of
    the "540" motor was (I think) 5 or 6 volts. In R/C car use, these motors
    were fed with a nominal 7.2 volts at which they produced something on the
    order of 40 or 50 watts of output. These motors cost the importers a
    couple of dollars apiece and retailed for around $20. In order to use 
    these cheap motors but go faster, some people opened them up and removed a
    few turns of wire from the armature. This made them draw more current and 
    turn much faster. Of course they also burned up after a while, but when 
    you are getting the motor full of dirt in your R/C car, it isn't going to 
    last forever anyway. Some of the real enthusiastic modifiers replaced the
    steel or oilite bushings with little ball bearings for even better
    performance. Of course, the bearings cost as much as the basic motor.
    At any rate, if you push a 10- or 12-turn "modified" motor with 8.4 volts
    and load it down enough, you can get over 150 watts of output at a current
    draw of 30+ amps (that works out to somewhere in the 250-300 watt range
    for the input power).

    After a while, some "manufacturers" started buying Mabuchi motors direct 
    from the importers, removing all of the wire from the armature and putting
    fewer turns of larger diameter wire to fill the armature. This made some 
    pretty strong running motors, especially the ball bearings ones. A really 
    nice "modified" "540" motor with a good winding and bearings would cost up 
    to $100 or so retail. Not bad for a reworked motor that left Japan costing 
    $2.00 or so. The current racing class designations date back to this point 
    in time (maybe, what, late 1970's? I wasn't doing R/C then). When ROAR 
    wrote its rule book, they specified that a "stock" motor had to have 27 
    turns on the armature, the wire had to be 22-gauge (or whatever, I don't 
    remember), the motor had to have bushings (no bearings), the can had to be 
    unopened once it left the manufacturer and [HERE'S THE IMPORTANT PART] the 
    motor had to be on an approved list of "manufacturers'. In fact, over time 
    the santioning body, ROAR, became basically a function of a certain group 
    of "manufacturers" (actually importers of Mabuchi motors).

    At this point you're probably thinking that a "modified" motor is just any
    motor that isn't on the approved list of "stock" motors. WRONG! The only
    "modified" motor you can run in a ROAR-sanctioned race is a Mabuchi "540"
    can with a three-slot Mabuchi "540" armature (it can have ball bearings 
    and any size wire) bought from the same list of importers. Nowadays there 
    are many small businesses who buy cans and armatures from one of the ROAR
    importers and wind their own wire onto the armature and put their own
    label on the can, but they can't actually design and manufacture a motor 
    that is allowed to be used in sanctioned competition.

    There's a guy who all the electric airplane guys know named Bob Boucher 
    who owns Astro Flight. Astro Flight makes a wide variety of modern motors
    including an "05" size that is very similar in appearence to the Mabuchi
    "540". The Astro "05" is superior in every way to the Mabuchi "540" and
    retails for the same price as a top-line "modified" Mabuchi. The big
    difference is that it costs Bob Boucher more than 10 bucks to build one
    of his "05"'s, so there's not nearly as much profit in building 10-dollar
    motors as there is in importing crummy $2.00 ferrite "540-type" motors
    and reselling them. There is also the fact that Bob Boucher isn't one of 
    the guys who built an organization like ROAR. As an aside, it turns out 
    that Bob Boucher was influential in supporting the organizations that 
    santion R/C drag races and truck pulls. In those types of competition,
    and an Astro Flight motor is "the one to beat".

    So what is boils down to is this. Organized, "big-time" R/C car racing is
    basically a sport that is run by a cartel of motor importers (who also
    build car kits and accessories, and so forth). If you want to race in
    their races, you have to play by their (ROAR or NORRCA) rules and pay 
    their price for their motors. I have no problem with this. It's due to 
    the promotion that these companies have put into this "sport" that I find 
    enough people interested in R/C car racing in my town to have organized 
    races every week.

    What I object to is the fact that hell is going to freeze over before
    organized racing allows me to use a sturdy, well-built motor that is 
    going to last a long time and run the car as fast as I would like  to go. 
    The people I race with every week seem to be convinced that just because
    they pay around $50.00 for a motor, it is really "state-of-the-art" and
    nothing better exists in the whole universe. In reality, they are using 
    motors that were desgined as cheap throwaways nearly 20 years ago. If Bob
    Boucher could sell Astro Cobalt 05 motors in 1/10th of the quantity that 
    Trinity sells Mabuchi ferrites, you could buy a motor for $50.00 that 
    would produce 50% more output on the same amount of battery juice as a 
    current top-line ROAR-legal modified and would last almost forever with 
    a reasonable amount of care.

    Finally, a few comments about "stock" class competition as it now exists.
    The alleged reasons for having a "stock" class are: 1) everyone's motor
    will have the same power, making competition more even, and 2) to keep
    the cost of racing down. Setting up this sort of class works for a while,
    but years ago it developed to the point where the "stock" motors on the
    approved list are purpose built. If you showed up to race with a Mabuchi
    "540" motor (like comes with many R/C car kits) in the "stock" class at
    your local track, your car couldn't do 10 laps in the same four minutes
    that the other cars to do 15. To compete, you had better buy a "real" 
    "stock" motor for around 20 bucks. OK, you do that and now you can do 12 
    laps in the time the other "stock"-class cars to 15. Even among the 
    faster cars, some of them can pull away by 10 feet on a 100-foot straight
    compared to the others. Hmmm, it seems like some of these "stock" motors
    are more equal than others.

    To really compete in the ROAR "stock" class, you will have to buy one of
    the most optimized ROAR-legal motors available and then you will have to
    use a variety of means to make the motor you race even faster. The oldest
    way to do this is to buy your stock motors by the dozen, test them on a
    dynomometer and throw away all but the two most powerful ones. Then, you
    take these two motors and use a variety of means (some against the rules,
    some not against the rules and some undetectable, so the rules don't
    matter anyway) to advance the commutator timing as much as 45 degrees or
    so past the "neutral point". Now retest these two motors and pick the
    best one for the main event and the second best one for the qualifiers.
    Now you might ask why you need two motors. The reason is that motors 
    which have been "jacked up" this way only perform at their peak for a
    dozen or so four-minute runs. Since they are sealed closed (according to 
    the ROAR "stock" rules) after those dozen or soruns, YOU THROW THEM AWAY! 

    Well, if you add this up, you've just spent around $200 (for the dozen
    motors plus aftermarket brushes and springs) in order to get two very
    good motors. After about a month of weekly racing, both of these motors 
    will be well past their prime and you can start all over again with a new
    batch of "stock" motors. This is absolutely no exaggeration of the
    lengths the top two or three "stock"-class racers at any track will go to
    in order to make sure that they have the fastest cars in any given race.
    Since these are all good drivers and they have the fastest cars, the
    so-called "stock" class boils down to a race between the guys with a
    couple of hundred bucks a month to spend on motors. Anyone who isn't this
    "serious" can always hope to win the B-Main or, on a good day, come in
    second or third in the A-Main.

    Probably no one has read the far. I hope Mr. Braun found the answer to
    his original question in here somewhere. If anyone *has* read this far,
    then, ummm, Thanks For Your Support. Just remember "Life is Serious,
    but Racing is Fun".

-------------------------------
Brent Hutto
hutto@SMTC.engr.scarolina.edu