11 votes
Accepted

How do you attach something temporary to a smooth metal shaft?

I'd recommend searching for shaft couplings. These are a great option for connecting two rotating shafts in a non-permanent fashion. A set screw (as mentioned) can work in low load cases, but is ...
user avatar
  • 1,966
10 votes

Why use bushings of different material than what they contact?

As already mentioned in many contexts you will make one part essentially consumable in order to reduce wear on an expensive or difficult-to-replace part. Similarly if you have a situation like a ...
user avatar
10 votes

How do you attach something temporary to a smooth metal shaft?

A method which works extremely well and which does not require set screws and/or flats on the shaft and which can be added or removed easily and rapidly is a collet based connector. While any one of ...
user avatar
7 votes
Accepted

Why use bushings of different material than what they contact?

In addition to ashgetstazered's answer, some materials (Aluminum, I'm looking at you!) will gall badly when meshed against themselves, while moving reasonably smoothly against a different material (e....
user avatar
7 votes

Suggestions for low friction surface materials for a "beltless static treadmill"

While it is an interesting idea, I don't think a "static treadmill" is going to give you results similar to walking. A PFTE(teflon) surface would be really low friction, but I think there are some ...
user avatar
  • 7,444
7 votes
Accepted

Are jeweled bearings commonly used for applications other than mechanical timepieces?

Typically jewel bearings (as you've described) are not used in large scale industrial equipment. The main reason jewel bearings are used is their inherent hardness. The bearing material has very ...
user avatar
7 votes
Accepted

How to add friction to a rope without using abrasion

You need to separate the braking from the winding / unwinding. Have a look at a ship's capstan. You want a miniature version with very high friction between it and your rope so there is no sliding and ...
user avatar
  • 7,669
6 votes

How do you attach something temporary to a smooth metal shaft?

There are two methods that immediately come to mind. Attach it with a set-screw. Use a weak adhesive. This would be strong enough to hold the items in place while in service, but weak enough that it ...
user avatar
  • 10.6k
6 votes
Accepted

How can I improve traction on a wheeled vehicle yet reduce friction?

You need to control how fast you apply the power. Some sort of damper mechanism that would allow power to be gradually applied and not cause it to spin out. You could try and wrap the 'power string' ...
user avatar
  • 486
6 votes

Does a washer really increase static friction force?

No it doesn't, and it isn't meant for that either. A standard flat washer, that is. It's meant to give the nuts and bolts a better support, and it protects the material against the nut which may ...
user avatar
  • 1,164
6 votes
Accepted

Refute my assumption: Bearings Don't Improve Efficiency

Your initial assumption is a bit flawed. You can not just draw the conclusion that all friction is the same. It is like saying all birds i know of can fly thus all birds can fly. Which is obviously ...
user avatar
  • 3,360
6 votes

What is the exact concept of bearings?

If that is true, then would not be better off just to remove the whole setup and have the axis of rotation free from bearings ... Ball bearings change a system from sliding friction (as in a journal ...
user avatar
  • 7,669
6 votes
Accepted

Why is the friction factor in laminar flow independent of pipe roughness?

In laminar flow, you assume a fuild layer near the pipe wall with flow velocity = 0, and progressivly faster flowing layers towards the middle of the pipe. That's why it's called laminar. Because ...
user avatar
  • 4,618
6 votes
Accepted

How friction between stator and rotor is dealt with in an electric engine/motor

... there's no space between the rotor and the stator. There is always an air gap between the rotor and stator. Iron has a permeability of about 1000 times that of air so the trick for maximum ...
user avatar
  • 7,669
5 votes
Accepted

Not a good idea to rub two of the same material against each other?

Friction is probably one of the primary reasons; as friction also correlates to wear. Friction is much more complicated than the equation we learned back in physics. Published friction coefficients ...
user avatar
  • 7,444
5 votes

Adding a lubricant to an already lubricious material, how is CoF affected?

You can't calculate friction coefficients this way. At the atomic-scale level, the friction coefficient depends on the interactions of the two materials across the interface. If you measure the ...
user avatar
  • 12.5k
5 votes

What causes friction in magnetic bearings?

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 ...
user avatar
5 votes

Understanding net torque from an actuator

There are two things going on. First, even if this "actuator" can produce constant torque, the torque required to keep the load spinning will be at least in part a function of the spinning speed. ...
user avatar
  • 11.2k
5 votes

Wheelbarrow minimize wear

Assuming the same material and tolerance, I pick the right-hand detail. Due to having a larger resistance arm against shimmying and lateral shock when the wheel falls into an unsymmetrical pot-hole ...
user avatar
  • 20.9k
4 votes
Accepted

What causes friction in magnetic bearings?

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 ...
user avatar
  • 11.2k
4 votes

Is there any material that has a higher kinetic friction than static friction?

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 ...
user avatar
  • 6,729
4 votes

Why use bushings of different material than what they contact?

I haven't heard this bit of advice and as with most things in engineering it really comes down to WHICH materials and in what CONTEXT. I can think of one main reason why you might want to make them ...
user avatar
  • 386
4 votes

How to find required clamping force of bolts to prevent flange faces from twising due to torque?

The simplest way by far is to select a prospective bolt, calculate the clamping force this creates when it is torqued to rated torque, and use the bolt circle as an approximation of the moment arm. ...
user avatar
  • 3,381
4 votes
Accepted

Ideal funnel design for powders

The problem you have is more complicated than you think. Any industry that deals with the storage and movement of granulated/powdered materials has to deal with this and most have unique solutions. ...
user avatar
  • 9,382
4 votes
Accepted

Need help regarding working of drum brakes

... then how is it stopping the vehicle's car, that is bringing it instantly to rest. It's probably an error in your writing but brakes don't bring a vehicle instantly to rest. They decelerate the ...
user avatar
  • 7,669
4 votes
Accepted

Disc Brakes - Swept Area , why is larger better?

Brakes primarily convert kinetic energy to heat energy. So a large area can absorb more heat lowering the peak temperatures ;of course this is strongly affected by the thickness/mass of the discs and ...
user avatar
  • 5,728
4 votes

How to add friction to a rope without using abrasion

I've loaded a winch with Spectra line, not quite as abrasive as Kevlar, but similar in strength and size. The key factor in such problems is to load the spool while the line is under tension. I used a ...
user avatar
  • 6,117

Only top scored, non community-wiki answers of a minimum length are eligible