S.M.T members have new hobbies recently: Tuning and racing Mini 4WD

Origin of Mini 4WD

In 1982, Japanese people took a radio controlled car, shrunk it, took off the direction changing and the radio controlled features, added a propeller shaft, and created the first Mini 4wd. Some of you who come upon this site maybe don't know what Mini 4wd is. Some of you do know, except not enough. In a nutshell, Mini 4wd is a small (1:32 ratio) 4-wheel driven race car that run on specially designed race tracks. It is not remote control, and is battery powered. That means you can't just turn a Mini 4wd on, put it to the floor, and expect it to not hit something hard.
Racing and tuning up a Mini 4wd is the hobby of many people from all over the world. A car and its parts can be found in hobby stores (ex. HobbyTown USA). In the year 1997, Tamiya America introduced the first Mini 4wd (the Fully Cowled and Aero series) to the United States. Of course, the Tamiya company isn't the only company making Mini 4wd.

Tamiya
Of all the many companies that make Mini 4wd, there's only one company that you can trust. One company's cars and parts are completely reliable, durable, and original. It's the company that came up with the concept of the Mini 4wd in 1982. Which company is that? Why, of course it's Tamiya!
The original is always the best, as I say, and that's true when it comes to Mini 4wd. Tamiya started out with its first car series, Racing, and then went on to Super, Fully Cowled, Aero, and Mighty. Every year, Tamiya holds a Great Japan Cup, the biggest racing event in the whole world. If you were to get any car at all, Tamiya would be your number one choice. It soars among all other brands.

Rules when racing

You can get the most fun out of Mini 4wd by racing it. The best place to do so is in an official race held by Tamiya. So of course, there are rules to racing. Below you can understand the rules before you enter a race.

Types of Vehicles

• Tamiya cars and parts only.

Racing Car Features

• Cars must be run in four wheel drive format. Modification to front or rear wheel drive is prohibited.
• The body must be secured properly to the chassis, so that it will not come off during the race. Tamiya stock or Hop-Up bodies are allowed and may be modified by the racer. Unrealistic body modifications or scratch built tube frames are not allowed.
• Race cars that may be a potential hazard to the track or other cars, are not allowed to race.
• All cars must be inspected by the race officials. All components must comply with the rules and regulations. Cars that have not passed inspection may not participate.
• Possession of a spare car is permitted on the condition that the features and degree of modification are identical with the approved car. Spare car is also required to pass inspection. Cars cannot be switched during the same heat.
• Roller requirements: Maximum of 6 pieces total

Size of Cars

• Maximum width (including rollers, etc.) 105mm (4.13")
• Maximum height (including rear wing) 70mm (2.76")
• Maximum length (including bumper, stabilizer, etc.) 155mm (6.10")
• Minimum ground clearance 1mm (.004")
• Minimum weight, ready to run 90gms
• Tire diameter not less than 22mm (.87") or greater than 35mm (1.38")
• Tire width not less than 8mm (.31") or greater than 26mm (1.02")

Motor

• Cars must use the stock 130 type motor included in the kit or motors available in the Tamiya Tune-Up parts range.
• All cars are limited to one motor only
• Motors cannot be modified either externally or internally.
• Some events may limit the type of motor that may be used

Power Source

• All cars must use two AA batteries of either Zinc/Carbon, Alkaline or Ni-Cad
• Batteries that have been tampered with or which have torn coverings will not be allowed

Tune-Up or Hop-Up Parts

• Tune-Up parts are limited to Tamiya only
• Parts may be modified as long as they meet regulation requirements

Modifications
Please use the following guidelines when modifying a car:

• Body and chassis may be trimmed, drilled or sanded to lighten.
• Modifications made to car using Tamiya or scratch built parts are allowed
• Scratch built chassis or alteration of wheelbase is not allowed
• Gears may be modified for weight savings is allowed, but changing the number of teeth is prohibited
• The car must be fitted with stock or Tamiya Tune-Up parts wheels and tires. Wheels and tires can be modified providing they are not potentially damaging to the track or other race cars or entrants
• Stock bodies may be modified as long as it retains its basic appearance
• Battery terminals and electronics must be stock or from available Tamiya Tune-Up parts and are limited to one set per car.
• Modifying chassis to expose gear components is prohibited

Decorating Bodies

• All race cars must be individually distinguishable. Paint or apply stickers to molded bodies and paint clear bodies.

Vehicle Inspection

• All cars must be inspected by the race official prior to racing
• No changes may be made to the car once it has passed inspection
• Race officials may randomly inspect any car at any point of the race. Cars found not to be in compliance will loose all previous results. Entrant must bring cars back into compliance with the rules in order to return to the event

Penalties

• When an entrant is found pushing, throwing or releasing a car prior to the starting signal, the race director may impose a penalty such as additional time

Disqualification
The focus for these events is fun. However racers may be disqualified for the following reasons:

• If the car is potentially damaging to the track or to other cars or racers
• When the car is found to have been intentionally modified to interfere with other cars during racing
• If the racer intentionally disrupts other cars or the track while racing is in session
• Modifying the car after inspection
• Disobeying officials or disrupting the race
• Displaying non-sportsman like behavior that is disturbing to others

Restrictions

• A car may be used by only one person (two or more persons may not share a car)
• Age restrictions may apply to some classes or events

Concours d'Elegance (LOL)

• Awards will be presented to the cars that display the best finish, workmanship and overall appearance
• Concours entries are not limited to race participants
• Concours contests may be held at the discretion of the race director

Remember, these rules only apply to races set up by Tamiya. Other company's might have other rules.


Starting From The Beginning
So you get your first car. You open it up, put it together, and put on a Plasma Dash. You take it down to a nice looking track with a handsome bridge and a few jumps. You slip in a pair of Tamiya 1000 mAh Ni-Cd batteries. Now you turn on the switch, and let it run. Zoom! It runs for about two seconds, and after reaching its top speed, suddenly flies off a jump. Your car zooms across the air, and lands on the ground hard with a sickening CRACK! You go over to take a look. Your chassis has snapped in half and both your motor and batteries seems to be caught in a bit of smoke.
Why do you think something like that would happen. Is it because the car can't take the speed? Is it because your tires are made of rubber and not sponge? Nope, not at all. It's because you simply took a brand new car without adding any hop-up parts except for a fast motor. You just thought your car would be the best just because of the motor. Well, that's wrong. Putting together a high-quality Mini 4wd isn't that easy.
Then what is right? Consider this: In a car, you want the highest possible speed, the most effective way to run your car, and the power to stay on the track. Let's start talking about the speed factor.

Speed
For the top speed, you must first observe the track you will be running on. For a straight track, look for a motor with more RPM (revolutions per minute), and for a technical track, look for a motor with more torque. Or, you can even build your own motor. After getting an idea of your track and the right motor, it's time for the gears and wheels.
You should know that gears have different ratios, like 4:1, or 2.3:1. But what does that mean? The number on the left represents the number of times a motor rotates, and the number on the right represents the number of times the wheel rotates. A 3.5:1 gear ratio would mean that if the motor rotates 3.5 times, the wheel would rotate one time. It's really not complicated. But to put the motor, gears, and wheels together, well, it's a bit more difficult. For a motor with less torque, use a larger gear ratio (ex. 5:1) and large diameter wheels. For a motor with a lot of torque, use a smaller gear ratio (ex. 2.3:1) with small diameter wheels. If you get that right, then you're all set for top speed. Now let's talk about effectiveness.

Effectiveness
Top speed is great, but without an effective way to use that speed and power, top speed won't be the best anymore. Effectiveness relies on your rollers, the type of bumpers your using, the wheels, and even the design of the body of your car. For example, if you only have a bumper in the front and don't have a rear roller stay, your car won't be stable and will shake around as in runs, therefore slowing down your car. However adding a rear roller stay and a few good rollers will help keep your car running straight, and making full use of the speed from the motor.

Staying On The Track
The two points above are the main points. But with all that speed and effectiveness, your Mini 4wd might still fly. I bet you've seen a car doing great at first, but when it reaches a sharp turn or goes on a bridge, it suddenly flies off the track. A car that flies is a horrible sight, and preventing that takes some deep knowledge.
Those are the three factors that you must remember. But when you get a Mini 4wd, you don't need to consider any of the above yet. What you want are three things that go for any car: ball bearings, gold plated terminals, and hard shafts. You need ball bearings so that the shafts of your car can rotate more freely with less friction, therefore making it faster. Gold plated terminals are a must have because it conducts electricity better, so it makes your motor faster. When moving at high speeds, normal shafts might get bent and twist, changing its shape. Hard shafts are much stronger, so it's more dependable.
After adding those three things to your car, then you can think about those three factors. These are what I consider the basics. But that's only a tiny bit of knowlege, because Mini 4wd is much more complicated than that.

Wheels

Every Mini 4wd runs on wheels (how else would it run?) And on those wheels are tires. In the world of Mini 4wd, there are many types of wheels and tires. Different types of wheels can greatly affect a car. In order to start off, let's talk about wheels.
Wheels can be divided into four categories two types, and two sizes. The categories are normal wheels, one-way wheels, aluminum wheels, and lock-nut wheels. The types are small diameter and large diameter. The sizes are narrow and wide. Each of those wheels will be explained thoroughly below.

Normal Wheels
These are plastic wheels that comes with a Mini 4wd kit. They are simple, heavy, and shouldn't be used for a fast car. However, a few of the wheels that come with certain cars perform better than average normal wheels. These wheels get loose after pulling it off and putting it back on the axle a few times.

One-Way Wheels
One-way wheels are made of plastic, but are a lot better than normal wheels. Normal wheels spin together at the same time. When it's time for a curve or turn, the outer wheel gets dragged, therefore slowing the car down. One-way wheels, on the other hand, has a special type of movement. Each wheel spins on its own, so that during a turn, the outer wheels moves faster than the inner wheels, allowing the car to pass a curve easier.

However, there are bad parts about these wheels as well. Just like normal wheels, they get loose after a while. One-ways wheels have many gears inside them, making it heavier, and creates a power loss. It is only recommended for technical tracks. Never use them on straight tracks!

Aluminum Wheels
Aluminum wheels are definitely the best type of wheels you can find. Unfortunately, Tamiya doesn't make them. They are light and strong, and looks a lot better than any other wheels. They are either locked onto the axle with screws (the best type), or slipped onto the axle with a rubber tube inside the wheel, making them very dependable during a race. These are definitely the wheels you want for the fastest cars.


Lock-Nut Wheels
These are wheels that slip on, and are locked tightly so that it won't fly off during a race. When I say lock-nut, I simply mean any other type of wheel that can be tightly locked without being pushed on to the axle. Lock-nut wheels don't get loose, simply because it's not possible. This a type of wheel you should consider for straight tracks.
Now you know all the categories of wheels. You should be able to choose the right ones for your car. Remember, different tracks require different types of wheels. Now that you have the wheels, you'll need to know the types of tires that go on the wheels. Luckily, there's only two main types of tires, so it won't give you such a headache, and they'll be explained below.

Rubber Tires
These are tires that come with a Mini 4wd kit. It grips the tracks quite well. However, it is on the heavy side.

Reston/Sponge Tires
Reston/Sponge tires (from now on, will be talked about as "reston") are very light. They grip the tracks very well. But, they get dirty very easily, and require a lot of cleaning.

Of course, since wheels have small diameter/large diameter and narrow/wide, tires have these selections too. What I'll be talking about below relates to both the tires and wheels.

Small Diameter vs. Large Diameter
Small diameter wheels/tires are good for technical tracks, as they lower the center of gravity. Large diameter wheels/tires are for speed tracks. So without knowing anything, you might think that large diameters are the best for a fast car. However, I wouldn't ever suggest using large diameter wheels/tires. They may be fast, but are only good with a weaker motor and a larger gear ratio (for example, 5:1).
Small diameters are supposidly fit with a stronger motor (more torque) and a smaller gear ratio (3.5:1). So small diameters would definitely be your choice for the perfect car.

Narrow vs. Wide
Narrow wheels/tires have less contact with the tracks, causing less friction and less drag, allowing the car to go faster. Wide wheels/tires have more contact with the tracks, causing more friction and more drag, allowing the car to be more stable, but slower. So, which type is better?
I would suggest using narrow wheels/tires on both the front and the back of the car. Narrows may not be as stable, but through my experiences, they work out just fine, and are faster than wides. However, if your car really appears to be unstable and tends to fly at times, try wide wheels/tires on the back.
Now you probably know a lot more about wheels and tires, and know how to pick the best ones. Good luck!

Rollers

Every Mini 4wd has to have rollers. Without rollers, it would be impossible for a car to run on tracks. Rollers come in all sizes and shapes. The current rollers can be divided into five categories: plastic rollers, plastic rollers with ball bearings, aluminum rollers, aluminum rollers with ball bearings, and ball bearing rollers. Below I'll talk about these different kind of rollers.

Plastic Rollers
These are rollers that come with a Mini 4wd kit or hop-up parts (ex. Sliding Dampers). Some of these rollers have rubber o-rings on them, and others are just plastic. For those of you using these, I have one thing to tell you all: these are the worst kind of rollers ever! They are plastic, and of course, breaks much too easily. The ones with o-rings are even worse because o-rings slow down your car. But no matter how bad these rollers are, they are still useable.

Plastic Rollers With Ball Bearings
Unlike their cousin, the simple plastic rollers, plastic rollers with ball bearings are the best kind of rollers that gives your car top speed. These rollers have a very thin edge, making the lowest contact with the wall of the track, allowing it to go very fast. Ball bearings are in the middle, lowering the friction, and making the rolling process smoother. There's one thing that's not so good about this type of roller, though. Because the edge of these rollers are so thin, it gets worn out real quick, and the plastic roller needs to be replaced. Unfortunately, Tamiya doesn't produce this type of roller. Still, these are truly the best rollers you can find.


Aluminum Rollers
Aluminum rollers are the second best rollers after the plastic rollers. They are made of aluminum, of course, and is stronger than plastic. All these rollers have rubber o-rings, and if put on a car, slows it down greatly. So if you want to use these rollers, take the o-rings off. These rollers are not suggested for super fast cars.


Aluminum Rollers With Ball Bearings
Anything that has ball bearings is better than those without it, so naturally, these rollers are better than the aluminum rollers that doesn't have bearings. The aluminum rollers that have plastic o-rings and not rubber o-rings are the best, because creates less friction. These rollers are very common, but still aren't better than plastic rollers with bearings.


Ball Bearing Rollers
These rollers are simply ball bearings. They are quite effective, but are also quite heavy. It is useful to weigh down the front of the car so that it doesn't fly. 6mm Ball Bearings can also be used. They are very light, and makes your car go quicker compared to other ball bearing rollers.


Where To Put Them?
Now you know the basic roller types. But where do you put rollers, and what's the best place to put them? Let's first begin with the basics. A fast car needs a total of eight rollers; four in the front bumper, and four in the rear roller stay. With this design, you get two levels of rollers, giving you a much more stable car. That was all you needed to know, and eight rollers are what you need to add. Now let's go on to small details.
You'll notice that the front rollers are bent at an angle of up to 15 degrees. But why is that so? Mini 4wd has been designed this way so that a car won't fly. If you try to pull the head of the car to a 0 degree position, it'll definitely fly. As a car is running, the front of the car needs to have a force that pulls it down to the track, and that's what the angle does. So if your car flies alot, you might either want to pull your bumper down a bit more or sand the plastic which the bumper is screwed onto to make an even larger degree. But remember this: The more the degree, the slower the car will be, but has a less chance of flying. The less the degree, the car may be faster, but has a better chance of flying.
Flying is horrible, but there are even more ways to prevent flying. On some plastic rollers and aluminum rollers, you'll see rubber o-rings. These create friction and slow a car down. It also keeps the car on the track, therefore lowering the chance of flying.
After making sure that your car won't fly, it's time to study the height and positioning of the front rollers. The first two lower rollers usually should be attached directly underneath the front bumper. This type of positioning lowers the chance of flying off the track. The other two rollers would of course be located above the front bumper, usually 17-19mm away from the bottom rollers. The rollers in the rear would need to have a distance of 23-27mm away from each other. Of course, you don't really need to follow that rule. Just remember this: The higher your rollers, the more stable your car would be, but will become more slow. The lower your rollers, the more unstable your car would be, but will be faster.
Roller Sizes
Rollers come in different sizes, and are measured by their diameter. Different roller sizes used on a car can greatly effect its speed. The diagram above shows three cases which will be explained below.

1. Front and back rollers at the same size
The car will run straight. Minimizes the power loss, and is the best possible setup.

2. Rollers larger in the front
Front roller diameter is bigger than that of rear roller. Suitable for courses with many corners since this pushes your car towards inside of the course when rollers contact a wall.

3. Rollers smaller in the front
Smaller in front: Rear roller diameter is bigger than that of front roller. This makes your car run along with a wall. Gives stability during cornering, but creates power loss.
That's pretty much all the knowledge there is for the rollers on a Mini 4wd.

Motors

Every car needs a good motor to run well. The slowest Stock Motor will drop from a loop. The top-speed Plasma Dash might fly off a bridge. Fast motors are for straight tracks, normal motors are for technical courses, and Stock Motors are for trash. But don't expect to just put on the best motor and expect the car to do its best. A car might fly off the track easily. Also, when purchasing a motor, don't just consider the RPM, but also the torque. Torque is a very important aspect of a motor. Below is a list of every single Tamiya motor.
Making Your Own Motor
If you think putting a Plasma Dash on your car will get you first place in races, then your're very wrong. Yes, a Plasma Dash may be the best motor available, but that's not even a fourth as fast as a motor that you build yourself. What do I mean? I mean that you can wind your own armature, get some really strong magnets, a good electric brush, put them together, and TADA! You've now got a motor that goes over 70 kilometers per hour. It sounds easy, but it requires a lot of brainwork and patience. It can be very hard for beginners. This guide is for people who already know how to wind their own motors, but still have questions.
You must remember one thing, torque is good for technical tracks and uphills, and RPM is good for straight tracks. For more torque, you need stronger magnets and larger commutators. Thicker wire is good for top speed, requires less winds, but takes up a lot of battery juice. Thin wire, on the other hand, is slower, but uses less battery power. Using these options, try combining different wires with different armatures and different magnets. Each way is good, but it's all for you to discover.

Chassis

The chassis is the main frame of the car. Most of the tune-up parts go on here. A car can't run without its chassis. Even if you take the cover off a car, the car still runs, because the motor and everything else is all on the chassis. The type of chassis can effect the way you tune-up your car, as some parts don't belong on certain chassis. So how many chassis are there? You'll be able to find out this page. Just take a look below.

BATTERIES

Many people might not think so, but batteries play an important role in the performance of a Mini 4wd. A good motor needs good batteries to run, or else the motor won't do well. Of course, the batteries I'm talking about are rechargeable AA batteries. To begin talking about batteries, let's first talk about the features of every battery.
First, you'll notice that on almost every pair of rechargeable batteries, there is a number written, followed by the letters mAh. A pair of Tamiya Ni-Cd Mini 4wd Batteries has 1000 mAh. That's milliampere/hour, or the capacity of electricity for the battery. The higher the number, the more space the battery has, but the weight increases as well.
Then you'll see the voltage. For example, 1.2 V printed on the battery.
And here's something you probably won't see on a battery: the internal resistance. Almost every conductor of electricity has some sort of resistance to the electricity. This is where electricity is lost. This is measured in milliohms for a battery. The higher the resistance, the less the electric flow, and therefore less electricity flowing from your batteries to your motor.
Now that we know the basic of batteries, let's look at the types of batteries.

Nickel Cadmium
Nickel Cadmium batteries are better known as Ni-Cd batteries. They are overall good and common rechargeable batteries, except that they have the memory problem. Before you recharge it, you must fully discharge it, or when you charge it up again, it loses a bit of it's capacity. It is very noticible, and shouldn't be tried. That's why you must always discharge your Ni-Cd batteries completely before you recharge them.

Nickel Metal Hydride
These are also known as Ni-MH batteries. Most people believe that these batteries have no memory effect, but in reality, they do. The memory effect is not as noticeable, though. I would prefer these batteries than the Ni-Cds simply because of the difference in memory effects.
So, is that all? There are many more types of batteries (Alkaline and Lithium Ion, just to name two), except those aren't commonly used for Mini 4wd, and to tell you all the truth, I don't know much about them, haha. To end the discussion about batteries, let's talk about discharging.

Discharging Your Battery
Discharging your battery is a very important thing to do before charging it, especially with Ni-Cd batteries. Discharging a battery takes knowledge too. When you discharge a battery, you want it to go all the way down to 0 V. Suppose you take a flashlight or a motor to drain a pair of batteries, which, by the way, is encouraged by' many people. At a certain voltage, the flashlight will not light up anymore. However, the battery is still being drained, therefore damaging the cell. A motor is also the case. Down to a certain voltage, the motor simply can't spin. In other words, using a flashlight, motor, or any other similar equipment to discharge batteries pretty stupid.
So how do you discharge batteries properly? Use a discharger! You can buy Tamiya's Mini 4wd Discharger or any other discharger. Just make sure you don't use a flashlight or motor.

Storing Batteries
Right after you recharge a battery, it starts to lose its electricity almost immediately. Of course, this is a very slow process. My suggestion to you is you should recharge your batteries right before a race with a quick charger, so that your battery will have enough electricity.
If you won't be using your batteries for a long period of time, you need to know how to store them. For Ni-Cd batteries, drain the batteries completely. For Ni-MH batteries, make sure that you have some electricity inside the batteries before storing them.

Old Batteries
Everytime you charge and discharge a battery, you lose some of its capacity permanently. And everytime you do so, the internal resistance builds up a tiny bit (this happens over a long period of time). In other words, as batteries get older, they start losing their original power. So if you ever want to race in a big-time race, you should buy new batteries, so that the power is full, and the internal resistance is the lowest it can be.

Motor Care
For a fast and long lasting motor, you must know how to properly maintain it. First of all, get a small screwdriver, sandpaper, modeling knife, a cup of either engine oil or kerosene, and grease that came with the car that you bought. It's thick grease, and works good for the motor. If you don't know how to open up a motor, here's how. On either side of the motor near the electric brushes (small metal plates at the top of the motor), you'll notice two tiny pieces of metal coming from the body of the motor (the can) that holds on to the top of the motor. Using a screwdriver, pull these two pieces up. Now you should be able to pull the motor apart. Now follow these steps:
1. First put the seperate pieces of the motor into the engine oil/gasoline for around ten minutes.
2. Remove the pieces from the oil and let it dry itself on a layer of tissues.
3. Put a little bit grease at the tip of the electric brushes.
4. On the commutator, you'll see thin lines of space. The commutator is the tube-like object that the electric brushes touch. It is located at the top of the armature, or rotor. With your modeling knife, gently scrape the lines of space to get some dirt out.
5. As time goes by, the copper plates on the commutator gets worn out as a chemical reaction is created when it's exposed to oxygen in the air, therefore creating a lot of electric resistance. The more the resistance, the slower your motor would be. Using the sandpaper, scrub the commutator in order to remove the oxidation.
6. Complete these steps by putting some of that thick grease on the commutator, and some more on the other end of the armature.
Now all you have to do is put the motor back together just like how you took it apart. If you put it back wrong and your car starts running backwards, simply open your motor back up and rotate the top of the motor (the part with the electric brushes) 180 degrees. The above steps should be done regularly. If you do all this, the life of your motor will be much longer, and will perform much better.

Oiling
The main thing about maintaining your Mini 4wd is oiling it. Without any oils or grease, a car's parts wear out quicker, and the speed gets cut in half. So where do you put oils? Remember, you put oils wherever friction could exist. What type of oil? You can use sewing machine oil, engine oil, or even baby oil.
Let's start this oiling process by oiling the ball bearings. Wherever there are ball bearings, whether it's in a gear set or inside your motor, you must add oil. Without oil, ball bearings doesn't help you much.
Next, add oil to any kind of gear, whether it's the pinion or the gears on the propellar shaft. Remember, don't add too much oil, as it attracts a lot of dirt, and not too less either. You'll also notice little areas where the propellar shaft can possible touch the chassis. Those areas must be oiled as well.
Finally, oil the insides of the rollers, whether it's a ball bearing roller or just a plain old roller.
That's all there is to oiling your car. As I've said already, oiling greatly improves the performance of your car.

Tire Cleaning
A dirty tire doesn't run as well, and also doesn't look as well. Currently in the world, there are two types of tires: rubber and sponge. To clean a sponge tire, use scotch tape. For a rubber tire, take an eraser and gently scrape the rubber. Be sure not to scrape off too much, or your tire will be ruined. That's all there is to tire cleaning.
And that's also all there is to maintaning your Mini 4wd. Remember to do these things often. Doing this is fun, and most importantly, keeps your car running smooth.