NEVER be confused by GEAR RATIOS again - EXPLAINED in the MOST VISUAL WAY using LEGO

Today's video is a follow up from our previous video where we used LEGO and lego motors to explain the concepts of horsepower and torque.

In today's episode we're going to add gears into the equation to see how they can be used to manipulate torque and speed.

So here again we have our two motors. The large motor generates 0.14 newton meters of torque and the smaller motor generates 0.03 newton meters of torque. Last time we have seen that the small motor couldn't generate the torque needed to move this heavy arm. Now we're going to use gears to enable the small motor to move the heavy arm.

Instead of trying to move the heavy arm directly with the small motor, we're going to connect a gear to the motor's shaft and we're going to attach another gear to the heavy arm.

We're going to call the gear on our motor the driver gear. Because this is the gear where the force input is and this the gear that does the work. This gear has 8 teeth We'll call the gear on the heavy arm the driven gear, this gear receives the force input and has work done on it. This gear has 40 teeth.

How do we obtain the ratio between the two gears? We simply divide the number of teeth on the driven gear by the number of teeth of the driver gear. And the result is 5, this is our gear ratio.

So what does the gear ratio tell us? It tells us how much we have increased the torque using this gear arrangement. Our initial torque on the small motor was 0.03 Nm. To figure out the new torque output value at the large gear we simply multiply the initial torque with our gear ratio. So 0.03 Nm x 5 gives us 0.15 Nm. This means that with the help of gears the small motor is now outputting more torque than the large motor.

So why does this gear arrangement increase the torque coming from the motor? The answer is pretty simple...it's because the large gear is larger than the small gear. To fit a larger number of teeth onto a gear you must increase it's radius. By increasing the radius you're increasing the physical distance between the force input and the force output. In other words by increasing the radious you're increasing the leverage provided by the gear. The gear acts like a lever, and as you probably know or have experienced yourself the larger the lever the larger the force output.

The torque increase coming from larger gears comes at a price and the price is rotation speed.
Our small lego motor has an initial torque of 0.03 Nm that we have increased to 0.15 Nm using a gear ratio of 5. But our gear ratio of 5 also reduces speed.
Our small lego motor is capable of doing 275 full rotation in one minute. It spins at 275 rpm. It's significantly faster than our large lego motor which does 146 rpm. But as you can see after we install our gears to increase the torque the small lego motor actually becomes slower than the large motor. How much slower? We can again easily calculate that using our gear ratio. We simply divide the inital speed with the gear ratio to get our new output speed. So 275 divided by 5 is 55 rpm. This means that to have more torque than the larger motor the small motor had to it's speed. By becoming five times stronger it also became 5 times slower.

So why does this kind of gear ratio decrease speed? The answer is again simple and again it's the gear size. To fit a larger number of gears we need a larger gear radius. A larger gear radius also means a larger circumference, or the total length along the edge of the gear. The larger the circumference the more distance needs to be covered to make the larger gear achieve one full rotation. Our gear ratio can aslo be expressed as 5:1. It tells us that for every 5 rotations of the driver gear the driven gear makes only one rotation.

All of this explains why gear ratios of a typical car transmission usually look something like this.

The lower gears reduce speed and increase torque. This because we need the most torque to get the vehicle going from a standstill in first gear and we also need torque to help increase acceleration to get the vehicle up to speed. But once we're up to speed the vehicle has a lot of inertia and we don't need as much torque to push it along, what we need is increased rotational speed or an increased number of wheel rotations per minute to allow the vehicle to achieve even higher speeds.

A special thank you to my patrons:
Daniel
Peter Della Flora
Daniel Morgan
William
Richard Caldwell
Pepe
Brian Durning
Brian Alvarez

#d4a #lego #gearratio

[SECX]

You know, Jason from Engineering Explained is a nice and knowledgeable guy. But your style of making these concepts truly visible is at least for me the key to a good understanding.

[LouisWritingSomethingCrazy]

This video is really the difference between teaching and explaining. A lot of other YT channels merely explains a topic. But through simplified means, examples and practical demonstrations you did more than explain it - you taught it, in a method we all can understand. Thank you for doing this.

[madmangaud]

Really love how you make things understandable

[cameronhicks]

To have watched and understood this at 5:30 in the morning before work, I commend you sir! Great explanation and a very intriguing visualization. As a very visual learner this material is priceless

[non-neurotypicalstudent]

I finally get it!! Thank you so much for explaining the connection between rpm, torque and speed.

[mohammadyaqoob]

Really needed someone to explain it in this way ❤👌

[hamidmaroof]

What 30 pages of a textbook take hours to read n comprehend u do it in a mere 8 minutes. Hats off buddy. Excellent. Thank u.

[atfsgeoff]

A big semi truck engine might put out 495 horsepower which is roughly the same as a new C8 Corvette. Yes a C8 Corvette engine COULD be used in a semi truck to haul large, heavy trailers. BUT to do so effectively it would need to be screaming at 6500 rpm all the time to achieve maximum power. The huge diesel engines usually used in semi trucks, can make that same horsepower at ~1600 rpm, meaning it will last much, much longer at full power output than the Corvette engine which has to spin 4x faster to generate the same horsepower. That's why semi truck engines last for millions of miles routinely, where as a Corvette that's driven flat-out in endurance races, might need a new engine after just 5, 000 miles.

[seattleshare]

Using the overlay of math with the visual demonstration made what is going on very clear - and using Legos was fantastic! 👍👍

[iamlugee]

That was a very interesting demonstration and explanation. Concepts were presented clearly and your explanations are paced well. Awesome content, as always!

[catnipleaf]

going back to the torque vs power video, the power at the output shaft of the driven gear is still the same (assuming no frictional losses are present of course). what changes is the force and the speed. for instance at the gear ratio of 5, the output shaft is applying 5x the force at a fifth the speed, so it still means that the small motor is still putting out 0.0013HP. just we have sacrificed RPM in favor of torque.

great video as usual! whatever you're doing to make these videos, keep doing it!

[jhuntosgarage]

A good explanation of a granny gear in a 4WD vehicle.

[nats]

At times, how you explain it makes one finally gets it instead of still being stuck asking for more questions.

[coolmailsonly]

Can't tell you how incredibly helpful this video is. I was wondering about this since few months and now I find perfect answer through your video. Thanks for the wisdom.

[davidplante]

Well explained demonstration on torque, speed and gear ratios. Two motors of equal horsepower can have completely different sizes, weights, and shaft sizes solely dependent upon speed. This is especially noticeable in electric motors. Keep up the great videos.

[honestboy]

wow, I gave up learning these concepts way before college, now with great examples I can grasp the concept with ease.
Massive thanks!!

[someperson]

I'd be fascinated to see you gear both motors to the same rotational speed so they could work work together to turn one shaft.

[DroidX]

Many thanks for this! I've been unable to understand gear ratios for the last 24 years until today haha!

[oribt]

The only place in the internet that actually explains this good. Thank you so much, I'm so glad I finally understand this!

[vishwanathsharma]

Dude I was scratching my head regarding the selection of motors for my project. Now with the introduction of gear ratio, I have much more clarity. Thank you!