Conference vmszoo::rc

    
    	I also have an Optima and I'm very happy with it.  It's always
    a consistent winner and an excellent performer.  I also have a Kyosho
    Ultima which is a consistent RC10 beater.  This car handles like
    a dream and mine is almost stock except for a novak speed cntrl
    and a hot motor.  In a good track with high bite I have beaten most
    4wd times with my Ultima 2wd car.  I think that speaks for itself...
    
    I'm looking for the part numbers of the new Kyosho Option House ball
    differentials for the Ultima & Optima.  These just have been released
    into the public and I understand they are similar to the one used
    by Joel Johnson in the 1987 world championships at Romsey, England.
    Do anybody knows the stock P/N for these?
    
    

    re -.1
    
    I think I saw someplace that PARMA had ball differentials available
    for the Optima.  I have not seen any information on Kyosho offering
    them.  Where did you find out that they were available?
    
    I'd be interested in ball differentials too.  One thing to be careful
    about is the difference between belt and chain drive differentials.
    The gears are different for the belt drive.  I believe the car Joel
    Johnson was running had the belt drive.  I your car is still set
    up with a chain drive you might have to try PARMA's.
    

    I'm the proud owner of a Clod Buster that has been customized almost to
    the point where MRC wouldn't recognize it.  It took somewhere around 12
    hours to assemble the chassis, and I learned along the way that not
    following the directions to the letter usually meant tearing it back
    down and starting from the point where I did something 'creative'.
    I also learned that if you want bearings, you should have them at
    the start, as replacing plastic bushings with ball bearings means
    taking the entire chassis _completely_ apart and starting over.
    
    All in all, it's a pretty impressive vehicle, it's got a turning
    circle of about 5.5 feet diameter, and in stock condition, could
    climb some very steep slopes and go over some tough terrain.  I
    suspect that real shocks (not the spring loaded dampers that come
    with it) would help keep the bouncing down, but there wasn't too
    much that would stop it.  With a normal battery pack, I imagine
    it would really move, though I was using 4 volts of Gates Cyclon
    cells, and the thought of a 7.2 volt battery somewhat frightens
    me, that thing can move!  There's a switch for putting the motors
    in parrallel or series, though in series mode there's an electrical
    differential action between front and rear wheels, so one wheel
    spinning in the snow (if it gets hung up) can prevent power from
    getting to all 3 other wheels.  I've since replaced the stock motors
    with some 12 volt (3 amp stalled) motors [from daisy wheel printers
    if it matters] to get the speed way down for my application.  I've
    also mounted a (very) small video camera and TV transmitter module
    and a couple of 6 volt 2500 mAH Cyclon Monobloc betteries to power
    it all, so I can drive it around my apartment while watching it
    on the TV.  A roll cage (it tries to climb walls), pan/tilt mount
    for the camera, dual steering servos (faster and more powerful ones
    might be in order), and other things are on the agenda.  The computer
    interface for the Futaba 7 channel FM radio is also in progress,
    and I need a better speed controller, but all in all it's quite
    a nice vehicle.
    
    	The only time I was really cursing MRC was when I had the
    differentials completely assembled and then found out that the only
    real metal parts on the entire vehicle (that tie the axle supports
    to the top of the differential) were not made very carefully, and
    tended to bend the gearcase just enough to cause things inside to
    bind, generating noise, friction, and loss of differential action.
    A little while with a hammer and a vice, and a few choice words
    about the ancestry of those Tamiya folk, and I got things working
    properly.
    
    	The mods I have made to the vehicle so far are:
    
    Put the ball bearings inside the gearcase on the 'fastest' gears,
    instead of on the ends of the axles.
    
    Replaced the motors with low speed, high torque [printer] motors.
    
    Replaced the stock ball joints in the steering with ones that had
    less play.
    
    Replaced the original (servo driven) speed switch with a Futaba
    MC112B, which I can seem to tune for good low speed control OR forward
    and reverse, but not both, though maybe it's my battery/motor
    combination that it doesn't like.
    
    The camera and TV transmitter, and the fact that I didn't use the
    body that came with it, just the bare chassis with stuff bolted
    to it.
    
    Not a bad little toy, though somewhat expensive and hard to come
    by.  My next vehicle will probably be mostly custom, something along
    the lines of a Bobcat, but large enough to carry larger batteries
    and maybe a better (CCD?) camera.
    
    Willie

    
    re. .2
    
    Glad to hear you're happy with the Ultima. I got a Hornet from Mrs.
    Santa last year and I'm already yearning for something a little
    bigger. (But not for a while.....)
    Anyway, I do have a question for any car-folks. I raced the Hornet
    for the first time last week at the local roller skating rink and
    I quickly found out that I will need a different set of tires before
    I try again. I raced it as it comes right out of the box, plastic
    bearings and all. My main problem was I had to round the corners
    at about 1/4 speed because the tires were sliding like they were
    on ice. I talked to a few guys after the prelims and found that
    the tires that were working best were rigid knobbies. Although the
    hornet comes with knobbies on the rear, they are very soft and don't
    hold well. Does anyone know if I can get the stiffer brand of knobbies
    for the front and rear and would I have to get a different type
    of wheel for them?
    I'm not going to go wild hopping this guy up. The only thing I might
    do is replace worn or broken parts with something a little better,
    like when the plastic bearings wear out I'll get some ball bearings
    and the tires will have to be replaced eventually anyway, so.....
    
    Thanks in advance,
    Mike, the beginner.
    

    What kind of a surface are you racing on (carpet, wood, cement,
    dirt, etc)?  Did your car understeer or oversteer when it wouldn't
    hold in the turns.  When it understeers it tends to push the front
    end straight even though you have the front wheels turned.  When
    it oversteers the rear end tends to slide to the outside of the
    turn (the front wheels are grabbing better).
    
    Also, where/when are you racing?  What are the fee's? What are the
    more popular classes/cars?
    
    Todd
    

    
    The surface is your average waxed roller skating wood floor.
    My car understeers (thanks for the expl..). I know that my front
    tires were the major cause because they are smooth. I want to get
    different rear tires anyway because mine are getting worn.
    I raced at Roll-On-America (See note 386. )
    It is directly off the Mechanic Street exit from Rt.2 .
    They race on Tuesday nite starting around 6:30 (Registering and
    racer meeting and such.)
    I will probably race again someday, but I just go for the fun of
    it.
    Perhaps the Vice President of The Colonial Auto Racers (In note
    386) can fill us in on some more details.
    
    Mike
    

        The December '87 issue of Radio Control Car Action had an
        'Off-road Tire Guide' article.  Tires were evaluated on a number
        of surfaces.  An RC-10 with a stock motor and 6-cell battery was
        used to test the tires so the results should compare well to the
        Hornet. None of the test surfaces was wood but there was a
        'clean hard pack' surface test that I would guess would give
        some indication on tires that would do well on wood. 
        
        The tires rated were all after market tires from BoLink, CRP,
        MRP, and Troll.  Tire weights were also given for all tested
        models.  The author claims that the lighter the tire the better
        (easier to suspend, and accelerate). 
        
        The tires of choice for the 'clean hard pack' surface were made
        by BoLink (rear - BoLink 3314, front - BoLink 3052). These are
        grooved, sponge tires and weigh about 1/2 ounce each.  This is
        less than half the weight of the typical spiked tires. 
        
        If you don't plan to race much you may not want to buy the
        sponge tires and purchase some spiked tires instead.  You said
        that they were working well on the wood floor. Also, you ought
        to ask the racers how they are setting up thier suspension.
        Adjustments to camber and alignment can make a big difference as
        well. 
        
        You mentioned that you did not have bearings in your car. I
        would really urge you to put them in. They are not that
        expensive and really improve the performance and run time of
        your car and this translates into added enjoyment! 
        
        Todd
        

    re: .7
    
    	Do you happen to remember what tire pattern would give the best
    results on sand?  I'm going to be using my Clod Buster on sand a
    fair amount, and I'd like to know what to do to increase the traction,
    though I'm not sure anyone even makes aftermarket tires for it...
    
    Thanks,
    
    Willie
    

    re .8
    
    Paddle treads were the tire off choice for sand although wide spiked
    tires worked okay.  The only paddle tires tested in the article
    (see reply .6) were from Troll. They came in three compounds: firm,
    soft, and medium.  For the RC-10 the Troll part numbers were 60-22,
    60-12 and 60-02 for the rear.  For the front end (much narrower
    tires) ribbed/spiked combination tires worked best. The author stated
    that the ribbing seemed to help you go straight.
    
    Todd
    

    I think I found the part numbers for the Kyosho ball differentials
    for the optima.  I was at a hobby shop in Lamplighter Square (accross
    the street from the Pheasant Lane Mall in Nashua, N.H.) last night.
    They had a 1988 Kyosho catalog. In the catalog they showed a 'one
    way clutch'. It was essentially a differential assembly for the
    Optima/Javelin and it had the gear for the belt drive. The Kyosho
    Option House part number for it was either W-0105 or W-0106. I'm
    ALMOST certain it was W-0105. By the way, this hobby shop is
    almost exclusively cars and trucks and has an excellent inventory
    of spare parts for many cars. I'm going to visit again when I have
    more time. I was in a rush last night.
    
    Todd
    

    Just for grins...yesterday afternoon I stuck my 11 turn Top Fuel
    drag motor into my JR-X2.  :-)  I had my doubts about the thrust
    group being able to handle it, but it did.  I ran a 26T 48P pinion
    just for additional giggles.  Wow! That thing can move out!  I ran
    out of road and range VERY fast.  
    
    Fred
    
    Hmmm, Nah, Hobbies plus's track aint near big enough for this motor.
    Just a mommentary lapse of reason. :-)
    
    

    re. .11
    
    ...and the walls at Hobbies Plus are too hard!  Can you spell
    d_i_s_i_n_t_e_g_r_a_t_i_n_g J_R-X_2 ?	>;v)
    
    Do you know how many rpm's that motor cranks out?  It would
    be interesting to know just how fast that combo is!  Too bad
    there's no high bank oval nearby.
    
    Greg
    
    P.S. Justin's Raider with a 23k rpm motor and 16t pinion is only
    barely hitting 20mph (200 mph scale)

    Anyone have any idea at what point (gear ratio) the Astro Cobalt
    Turbo 05 unloads???????
    
    The manual says that a 32 pitch 14 to 16 tooth pinion (stock spur
    gear) will give 5 to 6 minutes of run time. I'm only running 3 minute
    races. Right now I'm running 48 pitch gears. 26 tooth pinion and
    86 tooth spur. That gives me a gear ratio of about 3.19 to 1. If
    I go up to 28 teeth, I start to loose the top end. Yet at 26 teeth,
    there's still a couple of cars lapping me.
    
    I don't think I'm geard right, and the motor isn't having a chance
    to unload.
    
    Steve

    Well, the motor is a 'Top Fuel II' rated at 49,000 rpm; I'm trying
    to track down a tach so I can find out its 'actual' speed.  The
    road on which I did the 'test' has a speed limit of 15, which everyone
    ignores of course.  They normally travel at around 25 mph.  A friend
    had turned into the lane as I made a slow U-turn, which put me adjacent
    to his auto.  He accelerated normally...and so did I.  :-)  The
    little JR-X2 quite litterally rocketed away from him and was quickly
    at the other end of the road.  So how fast did it go?  Who knows?
    My guess is 45+-5mph.
    
    We may perform the ole' 100ft timing run, and if so I'll post it
    hear.
    
    Fred
    

    re .13
    
    Maybe the folks that make the motor have the Dyno test available.
    
    Fred
    

    re. .13
    
    Please explain the term "unloads".  I'm ignorant when it comes to
    electric motors.
    
    The only "formal" way I know of to select the proper gearing for a given
    power source is to understand the power source's torque/hp
    curves and rpm capabilities.  Then you look at your application
    (in our case, the track you'll race on and your cars unique features).
    
    In reality, the way you're approaching it sounds logical: experiment
    in real life with different pinion gears!  And it sounds as though
    that motor just plainly runs out of wind (in that car on that track)
    at 28 teeth on the pinion.
    
    How about 27 teeth?  Not much of a gain, but every little bit counts!
    
    Greg
    
    

    Take a 5spd car and from a standing start shift from 1st to 3rd and
    hold the accelorator to the floor and see what happens.  I think by
    unload he means that the motor is lugging and is behind the curve. 
    Same as if you were to take your 10-6 prop and replace it a 12-8 the
    motor doesnt have enough torque to turn it and its going to get hot and
    consume alot of fuel trying..

    I'm really not sure how to explain it myself other than to say that
    is your geared to high, the motor will have more power to give you that
    your not getting. Conversly, if your geared too low, the motor
    spins like heck but doesn't transfer any power to the wheels. Hence
    the term "unload" as in power transfer.
    
    I did get some information that may be helpful to others running
    the Astro Flight Turbo 05 Cobalt motor. I called Astro Flight and
    the gear ratio I'm running is about right. 3.19 to 1
    
    They suggested that for oval racing, I advance the timing as far
    as it will go, and loosen the brushes. He claimed that by turning
    out the brush caps 1-2 turns, you'd get an additional 1000 RPM out
    of the motor. I guess the springs that hold the brushes in are pretty
    strong and if you have them screwed all the way in, you can actually
    induce drag on the motor. He also suggested filing the brushes but
    I'll try this first. Don't forget to tape the caps after you loosen
    them.
    
    I'll be racing tonight. If anyone's interested, I'll let you know
    how it goes.
    
    Steve

    I am fairly new to this myself, but from what I have gathered it
    goes something like this...                    
    
    Granted, this is VERY basic...
                                                                    
    Car is slow (overall)?  Add 2 teeth to the pinion and try again.
    
    Car is slow (overall) and adding teeth to pinion produces adverse
    effects?  Try a 'Hotter' Motor (less turns and more rpms).
    
    Car is slow out of the turns?  Drop 2 teeth on the pinion and try
    again.
    
    Car is slow out of turns and dropping teeth off pinion produces adverse
    effects?  Try a 'Hotter' motor (less turns and more rpms).
    
    Motor very hot after race?  Drop 2 teeth on the pinion and try again.
                                                            
    Motor very hot after race and dropping teeth on the pinion doesnt help?
    Check differential and gear for excess friction.  Try a heat sink
    or heat sink compound/gaskets.  Try a 'Hotter' motor.  Try ducting
    some additional air flow to the motor.  Remove that sponge filter.
    
    Run times to short?  Trickle charge batteries or run SCE type...SCE
    types are sensitive though.  Try a 'Cooler' motor (not so many turns
    and rpms).  Try dropping 1 or 2 teeth off the pinion--sometimes
    this can help out.
                                          
                            D I S C L A I M E R 
    
    Note:  Its easy to get into a 'vicious loop' using this line of
    thinking, but if your careful, and dont loose sight of what your
    trying to accomplish, it COULD help.  I usually make changes in
    2 teeth increments and then fine tune when I get close.
    
    Fred
        
    

    re. .17	Now that I understand.  That was my assumption, but you
    know about assumptions (dangerous things).
    
    re. .18	Loosening the brushes will definitely increase your rpm's.
    It will also decrease your torque (according to Twister Motors
    literature).  For oval racing, I don't believe gobs of torque is
    as important as top end, so that suggestion sounds logical.  Cutting
    the brushes can do a couple of things: increase rpms/decrease torque
    (same effect as loosening) and change timing.  We've got a set of cut
    brushes for Justin's Twister, won't be trying them for awhile though
    (the Twister is fast enough on the oval for his driving capabilities
    and the Raiders cornering capabilities at this point in time).
    
    re. .19	Sounds like a good procedure to me!
    
    Greg