Gearing up, Gearing down, and Gear Ratios

Gears are helpful for many things, such as changing direction, transferring power to other parts of the robot, increasing speed, or increasing torque. This post is about the last two, and is also about how gear ratios are calculated.                                                       



Gearing up
(Gear ratio = 5:3)



How do you make a gear spin faster?

If you want to make it spin faster, you gear up. When you gear up, you transfer the energy from a larger gear to a smaller gear (see picture on right). This may sound funny to you at first. Shouldn't it be called gearing down if you move the energy to a smaller gear? Well, they named it gearing up and gearing down based on the speed at which the gear is spinning, not how the sizes of gears are changing. Gearing up is great when you're trying to make something on the NXT spin really fast and you've already reached the 100 power limit, but BEWARE! Increasing speed also decreases torque.

What is torque?

Torque is the amount of circular force applied to an object. It equals the amount of force being applied perpendicular to the object times the distance from the object that force is being applied. If that doesn't make much sense to you, don't worry! You don't have to know the scientific definition of torque in order to use it. Simply remember that the more torque you have, the better chance you'll be able to move a heavy object.



How do you increase torque (strength)?

Gearing down
(Gear ratio = 3:5)

You can increase torque by gearing down. When you gear down, you transfer energy from a smaller gear to a larger gear (see picture on right). Once again, it's called gearing down because it decreases speed. An example of a good time to gear down is when you're trying to lift something heavy, not when you're trying to make something spin really fast.

What are gear ratios?

Gear ratios simply compare the gears you are using. If you're using two 8 teeth gears, the ratio would be 8:8, which reduces to 1:1. If you're using a 8 tooth gear and a 24 tooth gear, the ratio would be 8:24 or 24:8 depending on which one is attached to the motor. Remember this simple rule: when you gear up, say the larger number first. When you're gearing down, say the smaller number first. Gearing up would make it 24:8 (reducing to 3:1), and gearing down would make it 8:24 (reducing to 1:3). Always remember to reduce the number. 

I hope you found this post helpful. Please ask if you have any questions!

Where to start- Tips for the Very Beginners

When I first got my Mindstorms set, I had no idea where to start. So many pieces, so many choices, so many possibilities. My advice is to start by building the model that comes in the instruction booklet. It gives you a feel for where pieces are supposed to be used, how to use them, and why they are important. And, it's a great NXT to learn programming on. Another tip I have is whenever you think of something you'd like to build in the future, write it down! I've often gone months without building due to lack of creativity or inspiration. Inspiration can also be found from the contests the LEGO Mindstorms team hold every once in a while (I make a post here whenever they have one, and try to enter all of them). After you are done with the beginner model LEGO gave you in your instruction booklet and are ready to move on to your own creation, keep it simple at first.

Also, keep in mind that you can ask any questions you have about building and programming on this blog. I may not be able to answer all of them, but I will definitely try. Thanks!

Building

Perhaps you're thinking, "What in the world is that piece supposed to be used for?" Or maybe you can't decide what to build next. Would you like to share your favorite creation with us? Here is a discussion page for anything you have built, are currently building, or are planning to build. Enjoy.