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Getting Your Gear Ratios and Slipper Just Right

Adjusting Your Electric RC Drivetrain Components

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Gears on an Electric RC

Gears on an Electric RC

© M. James
On a hobby-grade electric RC the most common adjustments you'll probably be making are getting your drivetrain gear ratio (spur gear/pinion gear) set right and making adjustments to the slipper clutch.

That's all well and good but if you're new to hobby-grade RCs it may also sound completely foreign. So, first things first. Let's get back to the basics and describe the key elements we're talking about here:

  • Drivetrain
    The gears, wheels, and axles of a radio controlled vehicle are known collectively as the drivetrain.

  • Spur Gear
    On an RC vehicle, the spur gear is a large gear that meshes with the pinion gear on an electric motor or the clutch bell on an nitro engine.

  • Pinion Gear
    On an electric RC, the pinion gear attaches to the shaft of the electric motor and meshes with the larger spur gear to provide power to the drivetrain.

  • Slipper Clutch
    Most commonly found on off-road RC vehicles, the slipper clutch protects the drivetrain from damage and excessive wear by allowing the spur gear to slip when the engine is delivering more power to the gears and wheels than they can handle at that point.

The links go to more detailed definitions and descriptions of each part.

Now back to those common adjustments.

Finding the Right Gear Setup for Your RC Vehicle

The gear ratio setup helps determine things like speed and power. Some gear setups provide your RC with a lot of get-up-and-go right off the line while others may have you starting off more slowly but give your RC more top end speed.

Changing your gear ratio setup is most often a bit of trial and error, mixing and matching different spur gears with different sizes of pinion gears. Often RCs will come with a selection of different size gears so you can choose the setup that works best for you.

Each of these tutorials talk about different aspects of finding the right gear ratio and other tweaks.

  • How to Understand Gear Ratios: Illustrated article from RC Car Action explains gear ratio, gear pitch, and offers the "golden rules of gearing."

  • Gettin' in Gear: Calculating your gear ratio and then ways to find the right gear setup. From Horizon Hobby.

  • Internal Gear Ratios Explained: Some Q&A plus a list of gear ratios for quite a few RC cars and trucks from Associated, HPI, Tamiya, Traxxas, Team Losi, and several others. From RCUniverse.

  • XMODSStage 2 Motor Upgrade: Choosing a Gear Setup. Part of an About.com tutorial.

  • Gear Spacing Tip: Setting the gap between the pinion gear and the spur gear. Also see this tip in a quick video from RC Car Action: How to Set Gear Mesh. Part of an About.com tutorial.

Adjusting the Slipper Clutch on Your RC Vehicle

If your RC is equipped with a slipper clutch you may find yourself making adjustments to suit the type of track or terrain.

  • On a short track you might want to tighten the slipper to give a little more punch around the corners and off the line.

  • You may also want to try tightening the slipper clutch if you're having trouble pulling wheelies with your RC.

  • Loosening the slipper slightly on longer tracks can help you maintain consistency on the long sweeping turns.

  • But on any type of track, long or short, if you have a lot of jumps you want to loosen the slipper a bit because it can put too much stress on the drivetrain during landings if it's too tight.

As with the gear ratio setup, it can take some trial and error to find the balance for your slipper clutch -- and you may want to tighten or loosen it for different driving conditions and for the experience of knowing first hand how different settings affect the performance of your RC.

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