8

It is lithium grease aka white grease. It is often sold in aerosol can packaging. It adheres well to moving parts and tends to work well for long term lubrication of low to moderate load mechanisms.


5

There are two types of losses in magnetic bearings, windage and electromagnetic losses. Windage or aerodynamic loss is the dissipation of rotational energy due to the viscosity of air or other gases trapped between the rotating and stationary portions of the system. These effects are more significant in high speed applications and clearly non-existent in a ...


4

No, it does not. I do not think that adhesive science people have managed to come up with a fancy name like the lubrication folks.


4

The bearings themselves may have ideally 0 friction, but there will still be some losses of rotational energy in the system as a whole. Even if the vacuum was perfect, anything that conducts electricity even a little becomes a transformer secondary in the presence of changing magnetic fields. Conducting material in the rotating thing will dissipate power ...


4

Friction is not a property of a material, it is a property of the interface between two objects, which may be the same or different materials. One interface I can think of that has that property is a thin layer of grease -- the force required to move increases with velocity.


3

The best option would probably be "clock oil" which is intended to be long lasting, non-acidic, and (importantly) non-spreading. If you apply it in small enough quantities, it will stay where you put it, and not move around through capillary action. Sewing machine oil is probably a reasonable alternative, but the fact that it is formulated not to mark or ...


3

As mentioned in the comments you don't actually want high friction between gear teeth, the tooth profiles are designed to roll over each other indeed the ideal is to minimise any sliding friction between the teeth. Obvious examples of devices which use sliding friction are brakes and friction clutches, these will have a limited wear life depending on the ...


3

The crosshead bearing slides within a track and connects to the conrod and then to the crankshaft. In a vertically oriented engine the pressure on the bearing is always downwards, resulting in a depleted lubrication film on the lower contact surfaces of the bearing shell. To supply lubricant to the entire bearing, high pressure oil is injected into the ...


2

You actually don't need to know the force on the wheel to work on the power. Just look at the kinetic energy of the powder. Kinetic energy = $(1/2)mv^2$. For 0.013 kg of powder, the kinetic energy is $(1/2)(0.013)(104.72)^2=71$ Joules. You need to provide that much Joules every second, so the power is just 71 Joules/second = 71 Watts. Of course, this ...


2

Sliding friction must, logically always be less than static friction. This becomes obvious when you look at it in terms of forces rather than coefficients. Consider a block resting on a flat surface. You apply a small force to one side of the block to try to slide it along. Initially it doesn't move as the reaction force provided by friction increases in ...


1

I'm trying to approach the problem at the high school level. The vertical force is proportional to the tangential force acting at the other end of the rod, the ratio of these two is called the static coefficient of friction. Here the applied forces are due to robotic arm and the weight of the rod: $$(F+mg)\mu_s=25\ [N]$$ or: $$F\mu_s=25\ [N] - mg\mu_s$...


1

As mentioned in the comments you don't want high friction between gear teeth, but if you're asking about the materials who exhibits higher friction with low wear rate, it depends on several parameters, such as, the nature of the two counterfaces, the environment, the applied load, the hardness, velocity, etc In general there's cubic crystal oxides, with a ...


1

Apparently Aluminium - Aluminium (clean and dry) has a higher coefficient for kinetic friction than static friction. The numbers I've found listed are: Static: 1.05-1.35 Kinetic: 1.4 source source


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