User Reviews

Since the early days of automobiles, engineers have been at work trying to find new ways to make their steering more efficient and practical. Even 80 years ago, a remarkably advanced concept of steering, called differential steering, was being used on a variety of vehicles. This short explains, in even better simplicity than modern textbooks, how this type of steering works. Basically, if you have a group of motorcycles or other vehicles moving together in a tight circle, the driver on the outer edge has to adjust his speed to keep pace with the one on the inner edge. This is because the wheels on the former's vehicle have to travel a greater distance, but in the same amount of time. Surprisingly, this never used to be a problem since early cars had one (but only one) of their wheels connected to the engine, meaning the wheels could already turn at different speeds. However, this came saddled with the downside of the 1 wheel drive being woefully underpowered. 1930s cars had both rear wheels connected to a single axle, but this meant one of them always slid when making a turn. This is where the wonders of differential steering come in. A device attached to the rear axle of the car is responsible for making this type of steering work. The film goes on to explain how a crossbar connects two separate axles attached to each wheel to each other, so that the wheels can both turn at the same speed when the car is going straight. When making a turn, a pivoting bar of metal shifts toward the right or left wheel (depending on the direction of the turn), which allows that particular wheel to continue moving, but stops the other one. It's similar to how if a tank needs to turn, one of the treads needs to come to a halt. Further, gears are used to drive each axle. Connected to this entire assembly of gears is a large gear on the left that meshes with a smaller one which is attached to a source of power. This is the driveshaft, through which the engine provides power to the rear wheels. The driveshaft is difficult to incorporate into the car, since if the engineers build the floor of the car above it, the car won't have enough room inside unless the top is raised. If the driveshaft is built above the floor, it'll be an obstacle in the car's interior. Thankfully, there's a solution. By angling the shaft slightly, it is able to be connected to the differential at the bottom of its big gear, which has the benefit of making it more quiet. Finally, we're told that this relatively straightforward but revolutionary invention has made cars more capable than ever before. I thought this short was decent. Because it's barely 10 minutes, there's not much to say. It's also another one of those anomalies that has barely any ratings on here but has over 15 million views on Youtube. People there have said it's amazing how an 85 year old film can explain this concept better than many modern videos, and I concur. I think it's because actual engineers worked on this short and gave their expertise to it.

Ford Motor had its own industrial film production unit, but General Motors, in particular Chevrolet, farmed out its work and in this one, the people at Jam Handy explain how an automobile's differential gear works and how it engages with the drive shaft.

It's nicely done, and the ending, with some pretty girls bouncing along on top of the barrels they have substituted for tires, is a nice bit of performance. However, while each step of logic and reasoning involved in the evolution of the differential and power transmission is perfectly explained, by the time they get to the end result, a fine piece of involved milling technique, I have no idea how they got there. I suppose my mind just doesn't work that way.