Conference vmszoo::rc

    
    Hello,
    
    I'm taking the plunge into RC off-road this week, and have just
    about made a definite choice- the Koyosho Ultima 2 wheel drive
    buggy. I've heard some good things about it from some local
    racer's (who almost all seem to drive Assoc. RC-10's). Anyone out
    there have any comments/ observations ?

    
    						Thanks,
    						Lorrin Lee

    Hello,
    My son 16 years old has an OPTIMA from kyosho. It is a very good
    4 wheels drive buggy. I think Ultima has the same frame , just the
    body is different
    Cordialy
    Dominique
    

    
    I assembled one for a friend and was quite impressed with the design
    and simple construction.  I think it's one of the best cars around
    since RC10 came out.
    
    It is not like an OPTIMA (I have one myself). This car has a integral
    monocoque chasis with built in underbody guard pan. This frame is
    made from aircraft aluminum and is indeed very lightweight and strong.
    (frame is lighter than the RC10 one).
    
    Has very few moving parts, but a well designed suspension system
    (similar to the OPTIMA front end) to give excellent handling. I'm
    awaiting to see how they perform in the local race track and then
    I'll decide on buying one. Definitely I think it will give the RC10
    excellent competition.
    
    If you're serius into racing I would recommend you to get the full
    bearing kit (optional) and a newly designed racing clutch (also
    optional from KYOSHO). These additions will definitely will make
    it a hard car to beat. (Watch out Associated...)
    
    Orlando.
    

    
    RE. 9.2
    
    I was planning on getting the bearing kit, but am in the dark about
    a clutch, what is the purpose of the clutch? All of the buggies
    I've seen have a direct motor-to-axle gear train. All that comes
    to mind is a centrifugal clutch to allow coasting- it this correct?
    Thanks for the info..
    
    						Lorrin Lee

    
    
    It is like the limited-slip differentials on big cars. What it does
    is doesn't allow wasteful spinning of the tires when full throthle
    is applied. This clutch has an adjustment screw for getting the
    right amount of slip you want (depends on the track). If you have
    excellent traction surface (ie. asphalt and foam tires) you can
    safely 'lock' the clutch to allow full transfer of the motor power
    to the rear wheels.  If you're racing in soft dirt then everytime
    you apply full power on the straightway start and your wheels spin,
    you have less traction than if the power is transferred more smoothly
    and evenly to the back wheels (keeping full contact of the wheels with 
    the ground).
    
    The RC10 has a limited-slip differential which is fully adjustable
    and the Turbo Optima has something similar, just they call it Torque
    Limiter Differential.
    
    The clutch for the Ultima is mentioned in the assembly manual, although
    I haven't seen it offered yet in any mail order catalog. I don't doubt 
    Tower Hobbies will carry it in the near future.
    
    Hope this helps...
    
    Orlando.
    

    
    	A friend of mine has 1 1/2 rockbusters. I say 1 1/2 because
    his kid had a rockbester and it needed replacement parts. He
    bought Tamaya Grasshopper parts and they fit exactly. The
    Rock buster is from world engines. Tamaya went to court to
    try stop world engines from selling the car. It appears to be
    an exact copy of the grasshopper.  All parts are interchangeable.
    The rockbuster parts are actually priced cheaped than the Tamaya
    parts. I have heard a couple of things about these cars in general.
    The first is that at a minimum baring are manditory in the front.
    If you use the bushings expect the front end steering to be
    sloppy after one day. Secondly grease the rear differencial. 
    Any other comments out there??
    
    							Tom

       If the vehicle is an exact copy of the grasshoper, then it to
    will develop the same problems that the grasshoper has, and that
    is, the front end, sooo-----if you get it, pull the front wheels,
    and chuck those nylon or brass bearings, whichever they use, and
    replace them with four good roller bearings. This will save you
    replacing the whole front end, and if you want the car to go a 
    little faster without major modifications, see if the bushings in
    the differential can be replaced with roller bearings as well.
    
    Good luck
    
    J.F.
    

    
    I recently got a Kyosho Javelin (Optima) and am considering a few
    updgrades to the stock package. What are the options I can add to
    produce the most impact on performance? I am thinking of such nicities
    as a different motor, ball bearings, speed controls. etc.. 
    
    In running the car around the yard I found it annoying not to have
    a reverse speed. What is the best purchase in a speed control with
    reverse for this car? Also I was told by someone that I won't be
    able to use a speed control with reverse if I race the car. Is this
    true? If so, why?

    Finally, the run time on these things, for toying around the yard
    anyway, seems to be awful short (8 mins?). This seems even more evident
    when you change to a faster motor and reduce this time by as much as
    50%. Have people toyed with any methods to increase the run time?
    Possibly the use of multiple battery packs (one for reserve)? I realize
    multiple packs might add extra weight but for around the yard it would
    be OK. 

          Hi Mat! this is Mike over at PKO/1 I have an OPTIMA and i
    used it in four wheel drive and i lost running time and speed. So
    i removed the KYOSHO drive chain and the front differentials and
    the front drive shafts, and chain guards, I now lost alot off exsess
    weight and i've gained about 50% more speed and torqe and about
    35 to 40% more running time. And i can still go the places i could
    go with four wheel drive, And i've kept my baby stock.
    
    
    P.S. If you don't mind losing the four wheel drive for a lot more
    fun, try it!    And it don't cost any thing just an hour of alterations.
    

    
         I am going to try and answer some of your questions.
    > speed items
         The first thing that you should do is add ball bearings because
    adding different motors will not help if there is still alot of
    drag in the drive train and wheels.  The other things that you can
    do and your budget will be your constraint is add different motors
    (all different types for different functions and uses, some are
    for high speed, some are for torque for quick starts, and some are
    a combination of both), you can also change your battery size from
    7.2 volts to 8.4 volts or even 9.6 volts.  The next thing you can
    play with is your gearing trying to match the gearing with the motor
    that your are using to the optium rpm for that motor for the type
    of running conditions that you are using your car for (battery size
    will also affect this).
    
    >speed controls
    	A speed control will not make your car go any faster, what it
    will do is give you better control of your speed, it will react
    alot faster then a mechanical control, it will lose less energy
    through heat loss, it will give you a reverse gear, and it will
    provide you with braking.  Most all cars that race use a good quality
    speed control, usually a fet type of controller (beware there are
    alot of different types from very cheap to very expensive and usually
    the price reflects how the well and fast the controller will do
    the functions listed above).  I have seen the prices vary from $40
    to as much as $145.  If you are considering different motors, batteries
    and gears make sure the speed control will handle the current and
    voltage that you will be drawing (some motors draw as much as 25
    amps with a surge of 30 amps or more).
    	The reason race tracks discourage the use of reverse is that
    they do not want people backing their cars up on a race track. 
    Some one backing their car out on to the track after going off the
    track will likely cause a crash that will result in a lot of damage
    for some one else that is raceing.  Most tracks will let you use
    reverse if you are off the track surface but you must be going forward
    when you enter back on the track surface.  Every track has their
    different rules on this subject so ensure you check before the race,
    but with a speed control you can use the braking and limited reverse
    to slow your car down for the turns etc..
    
    >Run time
    	The run time of a car is based on one thing, the size of your
    MAH rating of your battery.  Most all RC car batteries are from
    1100mah to 1200mah and how you use that available current up is
    totally dependent upon you and your application.  You can reduce
    the cars weight and add bearing to reduce the resistance therefore
    you will be able to change the gearing and draw less current to
    maintain the same speed.  There are also different motors available
    that are used in endurance races which are alot smaller and they
    do not draw as much current, but they are not as fast either.  If
    you were to additional battery packs you would increase the weight,
    therefore you would lose speed and be the same effect as adding
    a lot smaller motor.
        What the optium for a racer is that most all the usable current
    is used up with-in the race time.  You would not want your battery
    to last 8 minutes in a 4 minute race.  What you try to do is set
    your car up with motors, gears, and average speed of the track so
    it will only last a short time longer than the planned race time
    and therefore the maximum available power would be used during the
    race.
         I am sorry if I did not give you any hard facts, but the answers
    are solely with the planned usage and what you want the car to do
    and also your budget which you will quickly realize when you start
    customizing your car.  Listed are some price ranges for add on parts
    that may limit your planned uses.
    
    	motors 		$25 - $70
    	speed contols	$40 - $145
    	bearing		$30 - $50
    	Batteries	$25 - $35
    	Gears		$3  - $5
    	
    
    	Good luck and happy motoring
    		george
    

    
    
    I have three things to point out, these are:
    
    1) If your Optima (Javelin) is stock it MUST have a reverse speed,
       if it doesn't then something must be wrong in it. I suggest to
       check the wiring, speed resistors or servo arm travel.
    
    2) The single major enhancement you can make is Ball bearings,
       these will reduce the friction to almost nothing and extend 
       your running time.
    
    3) For longer running time you might try an RS380 motor, the one
       used in the Grasshopper (Tamiya). Although you will loose some
       speed, your battery should last about 20-25 minutes.
    
       Regards,
       Orlando.
    

    
    	One more point, as said in .2 a good FET speed control produces
    less heat. It also saves energy and lengthens your run time. I have
    found that a FET speed control gives about 25% longer run time.
    
    		Steve Peters
    

    I'll double check but I'm sure I read the instructions which stated
    there was a brake and 3 forward speeds. I believe I assembled it
    correctly too. Let me double check things. 
    
    Would it be true that if the stock unit had reverse, the simple factory
    speed control would show a circuit which would reverse polarity? If
    so, this will be easy for me to check.

    
    
    Mat,
    
    Did you were able to get the reverse working???
    
    

    I don't beleive this car has a reverse speed. The part of the speed
    control that moves over the circuit board seems to make contact
    on all specified surfaces.
    
    -Mat
    

    
    Hello,
    
    If your speed controll really shorts all contacts to the motor, then
    it must actually have braking, instead of reverse. The motor's
    windings are usually shorted during braking, which causes the spinning
    motor to slow. This is because the spinning motor is actually acting
    as a generator, and when the wires are shorted, the magnetism is
    generated in opposition to the direction of motor travel. Electronic
    speed controllers actually vary the amount of resistance they apply
    to the motor during braking to give you a real, variable braking
    effect. (kind of hard to explain in type, I guess I need to use
    my hands) I would be kind of surprised if you car really came with
    braking instead of a reverse, but I guess anything's possible. 
    
    						Good Luck,
    						Lorrin Lee 
    

    
    
    There are some competition cars that indeed only come with variable
    forward/brake types of speed controls. Examples of these are the
    YOKOMO, Associated (RC10, RC12) and some others.  As far as I know
    the Optima is advertised as having three forward speeds and one
    reverse. If this has been changed then it must have happened very
    recently.
    
    During Christmas vacation time I had the chance to assemble three
    Optimas (including one Turbo) for some friends, and I have had one
    for myself since Thanksgiving.  All of them came with a speed control
    which provided reverse speed. 
    
    This speed control consists of a small etch board with several etch
    sections on it. Wired to it are two 5W ceramic type power resistors.
    Attached to the small etch board is a small longitudinal etch piece
    which pivots at the center, attached to it are the two cables coming
    from the motor.
     
    Looking at the car as if you were in the drivers seat, the speed
    control lies right in front of you. Parting from the off position
    (12 o'clock) if you rotate it counter-clockwise towards the next
    etch section, you will have low forward speed. What electrically
    this means is that you have the 2 power resistors in series between
    the battery and the motor.
    
    If you keep rotating it counterclockwise to the next section, you
    will have medium speed (one resistor in series with motor). And
    the next section rotating counterclockwise is full speed forward
    in which you have the battery in direct contact with the motor.
    
    Returning to the off position, if you rotate CLOCKWISE to the first
    position, there you have inverted polarity and have placed one of
    the power resistors in series with the motor. So translated into
    motion what you should have is a medium speed reverse.
    
    The etch section for reverse is very wide and after having traveled
    all of it (clockwise) you will reach a small section of etch which
    is indicated in the manual as being brake. In all kyosho stock speed
    controls I have seen, this section is always unwired. To have the
    braking effect a piece of wire or jumper would have to be installed
    in this position in order to short toghether both brushes of the
    motor in order to get the braking effect described in note 38.8
    
    Hope this helps,
    
    Orlando.
    

    Yes, thanks for the help. I'm embarrassed! I took the servo off
    and moved the control by hand and viola, I have reverse!
    
    I noticed though that the servo was moving the control enough. It
    appears that the contacts were a bit oxidized or dirty. The little
    bit of pressure applied by my hand while turning the control did
    the trick!
    
    Thus by watching the servo move the control I knew it was moving
    over all the contact areas. It was simply a bad contact.
    
    I'll clean the surface and reattach the servo.

    -Mat

    
    As somewhat of a bystander (I have a Rockbuster but haven't installed
    the radio) I've noticed that the speed controls in most kits wear
    out fast. It looks like the pins, which are solid wear a groove
    in the etched board. Has anyone ever considered ising a "POGO" pin
    set up. For those that don't know what a pogo pin is it's a contact
    pin used on test fixtures that is spring loaded. Comments??
    
    
    						Tom

    RE .11 - $0.02 worth ...
    
    A pogo pin probably wouldn't make much difference as far as wear
    is concerned, but it should make pretty good contact as long as
    foil is left on the board. I think that the real problem it that
    this is a RUBBING contact with a lot of current (causes arcing,
    etc). How about putting a small roller on a pin at the end of the
    wiper to get a rolling contact as opposed to a rubbing contact?

    It appears that the contacts on my Javelin are either the pogo type
    as you call them or have a spring loaded roller tip.
    

    I encountered the same type of arcing problems on numerous wiper
    type speed controllers.The most reliable one I used was the stock
    one on the RC10.
    
    The problem ,as previously stated ,is arcing on the contacts
    due to the large amount of inrush current to the motor.
    I hung a large (100mfd)capacitor across my motor to help keep the
    peak current thru the contacts lower.The only problem is if you
    have reverse the electrolitic cap goes POW!!Works great on cars
    without reverse.
    
    
        comments????
        Reis
    
       

    RE .14
    
    The cap is a pretty good idea. It might be possible to get around
    the polarity problem with a circuit like this...
    
                          to motor
                              ^
                              |
                    ----|<----+----|<-----
                   |                      |
                   +------^v^v^v^v--------+  <- bleeder resistor ( 4.7k?)
                   |                      |
                   +---------|(-----------+  <- electrolytic
                   |                      |
                    ---->|----+---->|-----
                              |
                              v
                           to motor
    
    During acceleration the diodes will force the cap. to charge up
    in the proper direction (this is nothing more than a full wave bridge
    rectifier).  During deceleration the diodes are biased off and the
    cap. discharges through the bleeder resistor.

	I currently drive RC12L and TAMIYA F1(FERRARI 189).
	Now I have a plan to begin 1/8 ON-ROAD Racer.
	In Japan, majour 1/8 Racer is Serpent and BMT. 
	Thinking about maintenance, my next car must be Serpent
	Sprint ( easy to get parts ). But I don't know that driving
	feel about both of them. How about steering feel? How about
	acceleration? So on....
	Please tell me your opinion.



							/Thanks
							 Katsuhiko

	P.S 	I love car especialy 1/1 old Lotus.


						
	

    This question was asked about a year ago and never received a reply.
    Now I have a need for the same information. Is there anyone that
    can explain this??????

    Can someone enlighten me about the relationship of the number of
    wires (referred to as "winds") to motor performance?  What should
    I expect the difference to be between say a 14 turn single wind
    and a 14 turn quad wind motor?  What's the difference between a
    16 turn motor and a 12 turn? What's the trade off??? Less run time,
    more torque and less top end, the other way around, or what????


    Thanks,

    Steve    

>>    Can someone enlighten me about the relationship of the number of
>>    wires (referred to as "winds") to motor performance?  

    I'd suggest you call Astro Flite and ask to talk to the person that
    answers technical questions.  Their number is (213)821-6242.

    Of course the data they give you will be for their motors, but the
    general concepts (like "more turns -> less current" or whatever)
    will be the same for all motors.

    Hmmm... come to think of it, Charlie Watt knows a lot about this
    too.  Maybe send him mail directly since he's been so busy lately.

                       _____
                      |     \
                      |      \                          Silent POWER!
      _        ___________    _________   |            Happy Landings!
     | \      |           |  |         |  |
     |--------|-  SANYO  + ]-|  ASTRO  |--|              - Dan Miner
     |_/      |___________|  |_________|  |
                      |       /           |     " The Earth needs more OZONE,
                      |      /                       not Castor Oil!! "    
                      |_____/

    
    The following reply was received off line from our local guru
    Charlie Watt. I should have known enough just to ask him in the
    first place.

Steve,
	I could go into detail, but I'll try to keep it brief.  Given a
constant set of magnets, the number of turns will trade off torque vs top
end speed.  It's really more complicated than that, but a 12 turn motor will
have a much higher no load speed than a 16 turn one with the same number of
cells on the pack.  Torque is a function of the magnet flux, the number of
turns, and the current through them.  If you put on more turns, you get more
torque for the same current, but the top end will suffer.  If you put less
turns of bigger diameter wire, you get less torque, but the top end will be
faster, and the drop across the armature resistance (heat) will be less
per amp.  The key in racing is to match the motor and gear ratio to the
track requirements.  Too much torque might just spin the wheels.  Less torque
and a higher top end might be better where you have long straights.
	In electric planes, you can play with prop dia and pitch to control
the load on the motor.  If you overload it, you get shorter run times.
	Electric motor efficiency is a complicated mess when you include the
magnet design and the steel path design.  The steel has to be fat enough to 
carry the flux, and the gap between the magnets and the armature wants to be
as small as possible.  Most small motors leak flux like crazy.  (you can stick
a screwdriver to them)


Charlie