I’m not gonna lie – I learned something from this viddy. Thanks, Cory!

This brings up something I’ve long advocated – mandatory auto shop in high schools. Hardly anyone but gearheads understand how cars work, but almost everyone uses one. Hands on experience, like Muse above states, is a great learning tool. By learning how a car works and how to do basic repairs, there are a number of applied sciences at work, including physics, chemistry and math. Once kids have gone through a one semester auto shop class, they’ll be more self reliant on taking care of their vehicle, have a better understanding of some basic science concepts, and we’ll have safer, more well maintained vehicles on the road.

I’ve built dozens of lego and model differentials in my time, and still couldn’t figure out the principles of how they worked. Simply observing them in action it’s just a whirlwind of gears.

The rod explanation is pretty brilliant.

Dig the video though… For some reason, between this and the video about the atom with Walt, it really makes me wish that Disney would get back into the nature and science videos gig (yes, I know this isn’t a Disney video).

Question #1: When the car is going around a curve, is the slower wheel still getting as much power from the transmission as the faster wheel? Or once the differential’s inner wheel starts spinning past the slower wheel does it stop transmitting (much) power?

Question #2: I had an old motor scooter, and I was told that the reason you could still rev the engine while applying the breaks, or rev the engine with the front wheel against a wall without the wheels spinning, was because of the differentials. But in this video it would seem that if both wheels were stopped the transmission would not be able to keep turning. Am I misunderstanding the mechanism, or is the differential in a motocycle designed differently?

To OP: Thank you so much for posting this! I get the feeling that if you found one of these for each part of my car, I could save $1000′s per year at my mechanic’s!

I want videos like this for all the parts of my car.

#2: I don’t think motorbikes have a differential at all. Are you thinking of the clutch perhaps?

Automatic transmissions are complex beasts in of themselves — IIRC it’s able to drain the power from the engine if the output shaft is locked, but it can’t be too good for the mechanism if the different in power between input + output is too great.

Clutches/Manual transmissions simply disconnect the input power shaft from the transmission when the clutch is engaged, so the internal combustion engine can continue to idle.

Technically electric vehicles don’t need clutches, since they can full-stop.

re #1 — I’m curious too of the loss of power, if any by going through the differential and at different turn ratios.

I also found it fully inspirational:

It makes me want to a) go out and invent things b) take things apart to understand them c) disseminate my limited knowledge in Important Tones so as to Impress.

Thanks, Cory. Daymaker.

Your 4WD Colorado is a “Part-Time” 4WD and is NOT Designed to be used in dry weather on roads with good traction. You will experience abnormal tire wear, and could even damage the front differential or your transfer case.

This is not a design issue, it is an operator issue. The Part-time system has a couple of superior aspects including better traction in very challenging conditions. Simply put, your wife’s Subaru system is great for a street with a few inches of snow, while your colorado could actually go off-road with a fair amount of success.

If you read your owners manual you will find that your Colorado 4WD should only be used in low traction situations.

Regards,

Joe Dokes

Thanks for the answers, all!

http://auto.howstuffworks.com/differential4.htm

The limited-slip differential is how you get around the problem of all the power going to the wheel with the least resistance.

If one wheel wants to spin faster than the other, it must first overpower the clutch. The stiffness of the springs combined with the friction of the clutch determine how much torque it takes to overpower it.

Getting back to the situation in which one drive wheel is on the ice and the other one has good traction: With this limited slip differential, even though the wheel on the ice is not able to transmit much torque to the ground, the other wheel will still get the torque it needs to move. The torque supplied to the wheel not on the ice is equal to the amount of torque it takes to overpower the clutches. The result is that you can move forward, although still not with the full power of your car.

I think I get it! Weee!

Basically, it’s made of a drum connected to the wheel with a rotating friction pad set inside it that’s connected to the motor.

The friction pad set is held together with springs, so that as it speeds up, centrifugal force makes the pads spread apart and press against the drum, connecting the motor to the wheel.

This shift of torque between wheels can cause slip and is a reason the basic differentials like the one in the video are rarely used by themselves or are replaced by more exotic variants in today’s cars:

http://en.wikipedia.org/wiki/Differential_(mechanical_device)#Loss_of_traction

http://www.youtube.com/watch?v=WAwDvbIfkos