So next time you’re thinking adding another actuator to a project, take a moment to consider if a cheap and simple cam could do the job.

Camshapes and movement

Gear oil is different from motor oil in a number of ways. One is that it is much thicker, possessing a higher viscosity. This viscosity helps the oil stick to the gears as they gnash and spin. The other difference is that gear oil is designed to provide lubrication in the high shock conditions that accompany the meshing and occasional mashing or grinding of gears. The chemical compounds in the oil often contain sulfur, which also give the gear oil its unique, expired egg smell. The thickness, combined with the special chemical compounds of the gear oil, lubricates and cushions the gears as they shift. The gear oil is crucial to achieving the ultimate goal of the transmission, transaxle, differential or transfer case – to transmit the power of the engine through the axles and the wheels and then down to the ground – and managing to do it all again, day after day.

Step 2: Here is the new seal, ready to install. Note the spring on the back of the flexible seal. Be careful not to drop this into the transmission or differential.

I would disagree about cams being simple to design. The shape of the follower (flat, roller, arc) has quite a large affect on the relationship between angular position and lift. The no-maths workaround that I have used for this is to use CAD to draw the follower rotating around the base circle every few degrees, then join the tangent points with a spline. ie, draw the system with the motion inverted, with a static cam and rotating follower and join the dots.

Step 1: This seal has seen better days. One common way seals fail is when axles are removed, or installed improperly, thus tearing the rubber seal.

Cammechanism

Step 4: Seal and bearing race installation tool comes with different sized discs. Choose one that fits into the seal mounting point, yet is only slightly smaller then the seal itself.

The automobile contains a number of fluids that should all stay where they're supposed to be. Oil spots, coolant leaks, mysterious drips, and other signs of fluids leaving their rightful places inside the automobile are telltale signs that you should pay attention to. One of these parts crying for care by leaking gear oil all over the driveway or garage floor is an axle seal. Sometimes, oil on the outside of the case where the axles enter will be the only indication of a problem. A surefire way to determine if the leaking oil in question is engine or gear oil is to follow your nose. Gear oil has a unique, rotten egg type of smell.

Since the axles going into the transmission, and the transmission itself, are made of metal, the axle seal houses a flexible seal that rides on the axle and keeps gear oil in, and crud out. The flexible seal uses a small amount of the gear oil in conjunction with the seal itself to achieve this task. The flexible seal is housed in a metal carrier, which allows it to be pressed into the transmission or differential semi-permanently.

Plus that would just tell you where the follower would be, not where the base circle needs to be to make the follower be in a certain spot.

Camdesign

Gear oil Gear oil has this unique smell for a reason. The inside of a manual transmission, transaxle, transfer case or differential of an automobile is a truly harsh environment. Gear oil is manufactured specifically to handle the gnashing and spinning of gears as you shift from First to Second, from Third to Fourth, and so on.

Scotch yoke

Cams are especially useful when you need to operate multiple mechanisms from a single input drive, as [Teaching Tech] demonstrates with the 3D printed automaton of a polar bear attempting to swipe a seal. We’ve also seen cams on a mechanical 7-segment display, and they were used to safely fire machine guns through aircraft propellers up to the 1950’s.

Axle seal Since the ends of these spinning axles that extend into the transmission must share the same gear oil with the transmission, transaxle, transfer case or differential, the axle seal has two tasks. One is to keep the gear oil inside the case that contains the gears and the ends of the axles. The other is to keep crud, road grime and rocks out of the transmission, ruining the whole deal by converting the gears into rock crushers.

Computer-aided manufacturing

This is indeed an extremely simple introduction to cams. Cams are used in many more different configuration, and a quick search for “cam mechanism” will find many more variants.

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As much as you try to ignore it, that pesky spot of oil on the driveway isn't getting any smaller. Sure, you can put a tray of some sort under the car, or use cat litter or some type of space age polymers to sop up the drips. You can even try parking in a different spot, but the oil will keep on dripping. While oil spots on the driveway are certainly a nuisance, the fact that the oil is no longer in the engine crankcase or transmission can pose a real problem for your transmission and your budget.

CAM

Step 5: Next, seat the new seal level into the mount. Tap the seal level into place with the seal tool until the seal is fully seated. Be careful not to deform the seal.

With the availability of precision controllable actuators, it’s easy to overlook the simple but versatile mechanisms that got us here. In the video after the break, [Teaching Tech] explores the basics of cams and how to use them in your projects.

Cams are used to convert rotation into linear motion, and are probably best known for their use in engines and locking mechanisms. [Teaching Tech] first goes over the basic design and terminology in CAD, and demonstrates it’s use with a cam follower, locking mechanism, cam plate, and a knob that snaps to predefined positions. Of course a cam shape is not limited to a single lobe, but can have multiple lobes of various heights to create different motion patterns.

Also note you can buy “cam rollers” as standard industrial components. They are a combination of a ball (or needle) bearing with a thicker and stronger outer race, and a bolt in he center. Quite often these cam rollers are used in a narrow slot, the slot can push the roller forward and back and you don’t need a spring for the return action.

Axle seals can simply wear out, but the most common cause of failure is improper axle removal or installation. While the metal carrier of the seal is sturdy, the flexible seal is fragile and can be easily torn by a ham-handed installation of an incoming axle. Since installing new axle seals requires removal of the axles, a great time to inspect and replace them is during axle service.