Compound Gears Explained: Calculate Gear Ratio

What is a Compound Gear Train? How are compound gears different from Idler gears? How do you calculate the gear ratio in a compound gear train?

By creating compound gear trains it is possible to produce enormous gear ratios that would be impossible to produce with just a simple gear set made up of two gears. In this video we take a look at compound gear trains. Calculating the gear ratio for a compound gear train is not hard but it is important to recognize that the two gears which share an intermediate shaft share angular quantities not tangential quantities. Even though there are four gears in a compound gear train, there are only two lines of action between the input and output shafts and really only two gear sets.

The subject of Compound Gears often come up in both high school and college physics and engineering classes. They are found in Project Lead the Way (PLTW), Principles of Engineering (POE) and AP Physics.

[cupostuff]

Good video. I really liked how clearly you drew the connection between the math that was being done & what was actually occuring between the gears.

[josiemaylinn]

straight and right to the point, i couldn't recommend this guy enough

[Shabazza]

Best explanation I've seen so far. Easy to understand.

[MrScienceMaths]

Beautiful explanation of Compound gear, thank you😊

[Ryan-dksn]

Thank you for this video! It's the best one I've found for explaining the gear ratio of a compound gear train.

[py-skdn]

This is one of the top best explanation on youtube

[sbugwama]

There's isn't any explanation better than this.

[goodfriendscrappycars]

This was extremely helpful in helping me solve a manual transmission gear set curiosity!

[erinbentson]

Thanks! This helped so much. I wish you were my teacher!

[wbriggs]

Thanks, you hit the nail on the head.

[LouisG-gwno]

Great video. Is it possible to ask for further instruction on this topic?

[JohnDoe-otle]

Thank you,
I have a question, compound gears have the same speed (rpm) so normally they have the same Torque, However torque is related to distance as per T= Fxm (Torque equals to force x distance) here distance is the radius of the gear. So normally as per the definition of Torque they shouldn't have the same Torque as they have different distances away from the center of rotation. Any explanation? Thank you.

[ptyptypty]

nicely done! Your dedication to Detail is amazing. thanks for that effort. I do have a question, the Middle Gear can also be thought of as a Wheel And Axle machine. So, when considering the Forces at the Interfaces.. it seems like the Wheel And Axle Mech Advantage is ignored. I guess we'd have to look at the Torques... anyway.. nicely done.. :)

[markthurst]

Is it possible to calculate torque reduction in a compound gear train like this one? would the torque be reduced to a quarter of the input?

[troyam]

is there a calculator for when you have a set of gears and you need to find the right combination when all you have is input turns and output turns? IE: milling machine table to dividing head via gearing; 1 turn of the table equates to 5mm direction dividing head is 40:1? all i have at the moment is 30 turns is the lead of the table so 64t driver and 48t driven will turn the dividing head 1 rotation

[spookydaily]

Showed this to my friend who called me a dumbass for making these as a fun side project. Thanks.

[dave]

Hi Guys, I am working on a design that requires Indexing Gears. And so, I need to know how fast can an Indexing Gear spins. And where would I be able to find detailed information on this type of gear.
Thanks very much everyone.

[realstatistician]

Wouldn’t it be more straightforward to flip the ratios?
Then you’ll get that rotating the first shaft 1 time rotates the last shaft 4 times.

[sirazulislam]

I have a question,
How to select Covering machine gear stretch wise.
1.Take up gear.
2. Drafting gear
3. Feed gear.
please formula?
Thank you

[thatdrh]

If your 50 tooth is the drive side, that first stage is 2:1, not 1:2, and you indicated.