How to Make Your RC Car Faster Pt.3: Basic Gearing

In the last part of our series we talked about how to make your RC car faster by upgrading the battery. Now we're going to move on to gearing. So let's get started.

    Your transmission is made to transfer power from your motor to your wheels. In the transmission of a typical RC car there will be two gears, the pinion and the spur. The pinion gear is the gear that is connected to the motors output shaft. You can identify the spur gear as the gear that is larger than the pinion and mounted to the drive axle. The spur gear is larger 99% of the time. So when the pinion gear moves, the spur gear moves, and the spur gear moves the drive axle which moves the wheels. Simple right?

    The gear ratio is just the relationship between the number of teeth on the pinion compared to the number of teeth on the spur gear. So if you have a spur gear with 80 teeth and a pinion with 20 you have a 80/20 (eighty to twenty). But of course you can simplify that ratio. To do this you divide the spur gear tooth number by the pinion gear tooth number. So 80 divided by 20 equals four so the ratio is 4/1. That means that about every four times the pinion goes around the spur goes around once.

    Now that you hopefully understand that gibberish let's get to the fun part. Okay, so if you increase the number of teeth on the pinion your car will have a higher top speed but less acceleration. So that means if you leave the pinion the same but decrease the number of teeth on the spur you will get the same result. Your probably wondering why you would get the exact same outcome. The reason is that in both of these cases your increasing the gear ratio. For example if I had an 80 tooth spur and a 20 tooth pinion my ratio would be 4/1. Now if I increase the pinion by five teeth and leave the spur alone (80/25) the ratio would be 3.2/1 (which is a higher ratio than 4/1). If I decrease the spur gear by 5 and leave the pinion alone the ratio would be 3.75/1. That's not exactly the same ratio but you'll get the same result of a higher top speed and less acceleration.

    So if lowering the gear ratio gives the car a higher top speed and less acceleration then raising the gear ratio will have the opposite affect which is better acceleration but a lower top speed. To decrease the gear ratio you can either switch to a pinion with less teeth or switch to a spur with less teeth.

    Hopefully you now have a very basic understanding of RC car gear ratios and how they affect speed and acceleration. If you have a question just leave it in the comments!

A higher gear ratio = higher top speed, less acceleration

(to get a higher ratio move to a pinion or spur gear with more teeth)

A lower gear ratio = more acceleration, less top speed

(to get a lower ratio move to a pinion or spur gear with less teeth)

How to Make Your RC Car Faster Pt.2: Upgrading the Battery

In the previous part of our How to Make your RC Car Faster series we learned how to pick the right motor to make your RC car faster. Now that you have that monster motor your RC car will be draining your battery pretty fast. So it's about time you learned how to upgrade your RC car battery.

                                 Upgrading the Battery
    Upgrading your RC car's battery is one of the easiest, cheapest, and effective upgrades you can do. The battery as you know, supplies power for the motor, servo (steering), receiver and ESC. So by the time you finish reading this you should be able to understand all those numbers you'll see when buying a battery.

NiMH Batteries
    NiMH batteries, also known as Nickel Metal Hydride, are one of the most problem free types of batteries you can find. Pretty much the only problem with them is that they may self-discharge more than other batteries and that many of them don't hold their charge as great as other batteries. But you can find many high capacity NiMH batteries to keep your RC vehicle powered for a good long time. NiMH batteries tend not to suffer from voltage depression (also known as "memory effect"). Memory effect supposedly occurs when the battery is not fully discharged between charging cycles. Then when you have a partway full condition the battery will "remember" the shorter cycle and is reduced to a lower capacity which means less run time. For example: you use 60% of your batteries power and then charge it. The battery will then only charge to 60% of its potential. The way people keep this from happening is by completely discharging the battery before recharging. But the good thing is that NiMH batteries don't suffer from this problem!

Pros: High capacity is available, Safer than other types when overcharged, Less of an environmental problem, no memory effect problems.
Cons: not always the advertised capacity, heavier than other battery types (typically 400grams), some won't hold a charge well.

NiCd (NiCad) Batteries
    NiCad batteries (nickel cadmium) are good for beginners and cheap to buy. Sounds great, but the catch is... these batteries suffer from memory effect. They are more durable than NiMH batteries, so they can get hotter and take more abuse. Eventually NiCad batteries will be banned because of their environmental effect, so now companies have stopped developing them and are focusing more on the NiMH batteries.

Pros: Cheap, durable.
Cons: Old technology, lacks power, lacks capacity, heavy (typically 350 grams), has memory effect.

LiPo Batteries
    Lipo batteries (Lithium Polymer) are lightweight, unlike both NiMH and NiCd batteries. They don't suffer from memory effect like NiCd batteries do. They hold a better charge than other battery types. About 20-30% longer life for the same capacity as a NiMH. LiPo batteries also don't self-discharge, this means you can charge them a week before you use it and it will still have close to, if not the same amount of power. The downfalls of LiPo batteries are that if overcharged or punctured it has been known to burst into flames.

Pros: Relatively cheap, Light (typically 250grams), No memory effect, Powerful, Great capacity.
Cons: Dangerous if overcharged or punctured (may burst into flames), not recommended for beginners.

    So those are the three main types of batteries. Now we dive deeper into the meaning of all those numbers (the different ratings) you're sure to see when picking the perfect battery.

mAh (Milliamp Hours)

    Probably the biggest thing you'll see when picking a battery is the mAh rating, which stands for milliamp hours. You can think of Milliamp Hours (mAh) as how much gas a car's tank can hold. So a battery with 5000mAh will run way longer than a battery with 1200mAh. Milliamp Hours don't have anything to do with your RC car's speed just the run time.

V (Volts
    If mAh is how much fuel your car can hold then volts would be how much power that fuel can give. If you have an 11.1 volt battery (11.1v) it will give your motor more power than a 7.2v  battery can. But before you get a higher voltage battery make sure your RC motor can handle it (Just look up your motor model to find out.).

C-rating
    C-rating is a rating you'll find when looking at LiPo batteries. There are two C-ratings you'll find. One stands for max continuous discharge potential and the other for max burst discharge potential. The continuous discharge potential is how much power the battery can discharge at any given moment. The max burst discharge is the amount of power the battery can burst to. Usually the burst is only towards the beginning, when the battery is fully charged. The max discharge is always double the continuous discharge. Now that you know what the C-rating is you need to know what it means to you. Well with a higher C-rating your car, truck or buggy will have a lot more burst or acceleration when coming out of corners. A higher C battery will also keep a cooler temperature than a lower C. Higher C-rating can also improve top speed. A common misconception is that a higher C-rating will discharge faster and give you less tun time. That's not true, a higher C-rating just means your battery has more power to give at any time you wish. So all in all you should go for the highest C-rating you can get.

S (Cell Count)
    The cell count is how many separate battery cells are put together in one pack. For example: 2S1P = 2 cells in one pack, 3S1P = 3 cells in one pack. Easy. Every cell has about 3.7 volts of power, so a 3S battery would give 11.1 volts of power. This may be important if your motor or ESC says specifically.

Making Sure It Fits
    Making sure your battery fits is just as important as making sure your motor fits. You don't want to buy a battery that doesn't fit. So measure the area where your battery would go and look at the battery's dimensions to see if it will fit.

                                                                         Up Next...
    Hopefully now you understand the different ratings and numbers you'll see when buying an RC battery. If there's something you don't understand then just leave a comment and it will get answered. Up next we'll be talking about making your RC car, truck, or buggy faster with gearing.

How to Make your RC Car Faster Pt.1: Upgrading the Motor

    There comes a time in every RC car owners life that you feel what you have isn't fast or powerful enough. You want more speed and you know it! So we started this new series on how to turn your bone stock and sluggish RC car into a speed demon, scratch that, a speed demon's worst nightmare. Are you ready? Well let's get started.

                              Upgrading the Motor

    When you first think about upgrading your RC car the motor is probably the first thing that comes to your mind. There are a few things you'll need to know before you pick your new motor. 

Brushed vs Brushless

    You will see two types of motors when looking, they are brushed and brushless. We won't go into detail on what this means today (we will in a more advanced motor guide). Basically a brushless motor makes more power and has hardly any parts that will wear out, and if they do wear out you can change the internal parts. Whereas the brushed motor has more parts that are more likely to wear out, and once something internal is ruined you can't replace the parts. Pretty much all brushed motors are cheaper than brushless that's why they are what most RC cars come with. In short, if you want a nice powerful RC car don't get what you'll find in a stock RC car, get brushless.

    

What does KV mean?

    So first let's talk about KV. KV is how the motor's power is rated, like horsepower is for cars. It stands for RPM (revolutions per minute) per volt. What that means is that for every volt of power the motor is given, it will turn that many RPM (revolutions per minute) more. So for example, if you have a 7,000 KV motor and give it 5 volts of power then your motor will be spinning at (7 x 5 = 35) 35,000 RPM. Well okay, now you know what KV means but what's faster more or less KV? Good question. The higher KV you have the more top speed get but with less torque. The lower the KV the more torque and acceleration you get but with a lower top speed.

What does Turns mean?

    Now let's talk about turns. Turns are another thing you'll encounter when choosing a better motor. They are another way of rating the motor's power. Turns are abbreviated with the letter 'T'. The number of turns a motor has is how many times the copper wire is wound around each pole of the armature inside the motor (don't worry you don't have to understand). With lower turns you get a higher KV and less torque. With higher turns you get lower KV and more torque. Here is a simple way for you to look at it:

Less KV/More Turns = Higher torque (acceleration), less rpm (top speed), and longer battery life.

Higher KV/Less Turns = Less torque (acceleration), more rpm (top speed), and shorter battery life.

Sensored vs Sensorless 

    Sensored motors have a little port on the back for connecting the motor to the ESC (Electronic Speed Control). The reason they connect is so that the ESC can monitor the position of the rotor and deliver the power to the motor smoothly. You really only notice this when you first punch the gas, once you get up in the higher RPM range it doesn't matter much. Sensored motors require a sensored ESC to go along with it. The price difference between a sensored motor and sensorless motor (regular motor) is about $20-$30. It may or may not be worth it to you depending on your budget. You can check out the link below and look at the related products on Amazon to get a feel for the price and what you can afford.
Hobbypower 10 turn, 3900kv, Brushless Motor for 1/10 Rc Car or Truck
Making sure it fits
    Making sure your motor fits is obviously very important! Your going to want to look for the length, diameter, and shaft width of the motor. The shaft width is how wide the piece that the pinion gear (the pinion gear is the small gear on the tip of your motor shaft, the large one is the spur gear) will go on. Make sure it's not some crazy size your pinion gear can't fit on. You'll also wan't to look at the motor's spacing of the mounting holes so it will fit on your mount.

Don't forget to upgrade your ESC too!
The ESC (Electronic Speed Control) is the mediator between the battery power and your motor. It's like the negotiator almost. It connects to the receiver and gets the signals from your remote telling it how much power it should release. So for all the power to be able to go through and reach the motor, the ESC must be able to handle it without getting fried. So when you upgrade your motor you will have to upgrade your ESC as well. You will need to look at your selected motor's wattage, max amps, and continuous amps. Then find an ESC that is a little better than what you need, just in case. For example: my motor has a continuous current of 150A (Amps) so it would be smart to get an ESC that can handle 170A or more. But don't stress to much over this because most websites and stores will tell you what ESC you need.

What's next?
So now you know everything you need to about upgrading your RC car's motor. What's after that? Well the next thing we'll talk about in our series is the battery. So stay tuned folks!