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Discuss electric RC on-road vehicles here. Also discuss brushless motors, speed controllers, brushed motors, etc
User avatar
by: dragger
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.

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)
by: blue
i should define the term "gear ratio" right from the start. In its simplest form, it defines the relationship between any two gears. Usually this will be the "pinion" gear (found on a motor in electric cars and on the clutch bell of a nitro car) and the "spur" gear (which more often than not is found on the drive axle of a car).

Pinion gears come in all shapes and sizes, as do spurs but for our example we'll say hat the pinion gear has 18 teeth and the spur gear has 90 teeth. You often see in car specification charts we publish in Racing Lines a gear ratio of 18:90. Often it is divided into its lowest common denominator which would be 5:1 after we divide the number of teeth of the pinion (18) into the number of teeth of the spur gear (90).

[attachment=1]Axial Gear Chart 48 pitch odd_zpsstzjjsgn.jpg[/attachment]
[attachment=2]Axial Gear Chart 48 pitch even_zpsrd9pvhyl.jpg[/attachment]
[attachment=3]Axial Gear Chart 32 pitch odd_zps0mmatlxe.jpg[/attachment]
[attachment=4]Axial Gear Chart 32 pitch even_zpsv9so1uk2.jpg[/attachment]
Axial Gear Chart 48 pitch odd_zpsstzjjsgn.jpg
Axial Gear Chart 48 pitch even_zpsrd9pvhyl.jpg
Axial Gear Chart 32 pitch odd_zps0mmatlxe.jpg
Axial Gear Chart 32 pitch even_zpsv9so1uk2.jpg
User avatar
by: mambo
Gearing is simple. If you want more speed, you install a larger pinion gear. For more run time, reduced motor heat, or stronger acceleration, do just the opposite and install a smaller pinion. If you’re a bit experienced, you know that messing with the spur gear works just the opposite – smaller spur equals more speed. Most enthusiasts also know that a single tooth change on the pinion has more impact than a single tooth change on the spur. That covers the basics.

Gear Pitch:

Most of you know that gear pitch indicates the size of the gear’s teeth – the larger the pitch, the smaller the teeth – but people probably don’t know how pitch is determined or why a large pitch number equates to small tooth size. Pitch (specifically known as the pitch diameter) actually refers to the number of teeth that can fit around a 1-inch diameter (specifically known as the pitch diameter). A tooth size that permits 48 teeth to encircle a 1-inch gear is 48-pitch. To have 64 teeth on the same 1-inch gear, the teeth must be smaller, and that explains why 64-pitch gear teeth are significantly smaller or finer than 48-pitch. The pitch of the gears in your car has no effect on the ratio. 100-tooth spur/20-tooth pinion combination is a 5:1 ratio whether you use 32, 48, or 64 pitch gears. That said, certain gear pitches are better suited to certain applications.

32 Pitch:

Nitro vehicles often use 32-pitch gears because the larger teeth are durable. It’s important to note that some vehicles such as 1/8 scale buggies and truggies have 1-module gears, a metric size that works out to 25.4 pitch (more on metric gears in “Metric Pitch”).

48 Pitch:

Rob Robinson of Robinson Racing gets the credit for bringing 48-pitch gears to RC. Until Robinson introduced this in-between pitch, racers had to choose between the bulky 32 pitch and the more fragile 64 pitch gears. Back in the day, Rob was a competitive racer and missed the A-main at a large national-level event due to stripping out two 64 pitch spur gears. This led him to contact outside gear manufactures in a search of a more appropriate pitch for electric off-road use. He found 48 pitch gears, and this new pitch quickly caught on, as 48 pitch gears offer a good mix of ratio options and durability and are now the standard for 1/10 scale off-road use.

64 Pitch:

This is the pitch of choice among on-road racers mainly because of the huge number of available ratios and extra-smooth mesh of the fine teeth. Since on road cars don’t have to endure jumps or more specifically the shock of landing, 64 pitch gears hold up fine even when subjected to brushless power.
User avatar
by: crome
For a higher top speed go for a larger pinion gear (with more teeth) and a smaller spur gear (with less teeth). The trade-off here is that you will gain a higher top speed at the expense of slower acceleration and a higher motor/esc temperature. This set up is ideal for long straight runs and large areas with few corners.

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by: blue


User avatar
by: crome
Speed for what ? For drift or for drag or race

If you want to make a high speed and high performance car , u need a high quality servo and good transmitter , because when you drive your car faster, u should drive the car very well. You havent a good steering servo your car not go on the line . If you havent profesional a transmitter and receiver you can not make good adjustments.

requirement list:

1. Under the 10T motor - a good engine

2. Spur and pinion - gear set for nitro cars

3. Have a quick reaction servo

4. Pro transmitter and receiver

i think

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