8 votes

Can epoxy bond two Aluminum alloy beams?

It does nothing for aerodynamics, the cavity makes the thing bigger and hence producing more drag (a very hypothetical reduction of Cd cannot change that). The point is simply the weight. Perhaps it ...
Vladimir F Героям слава's 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 ...
Transistor's user avatar
  • 10.7k
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 ...
Bart's user avatar
  • 1,184
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 ...
joojaa's user avatar
  • 3,577
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 ...
Transistor's user avatar
  • 10.7k
5 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 ...
Dave Tweed's user avatar
  • 6,884
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 ...
alephzero's user avatar
  • 12.5k
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. ...
Olin Lathrop's user avatar
  • 11.4k
5 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 ...
Transistor's user avatar
  • 10.7k
5 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 ...
mart's user avatar
  • 4,771
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 ...
kamran's user avatar
  • 22.4k
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. ...
Phil Sweet's user avatar
  • 4,755
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. ...
Fred's user avatar
  • 9,637
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 ...
Transistor's user avatar
  • 10.7k
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 ...
blacksmith37's user avatar
  • 6,134
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 ...
fred_dot_u's user avatar
  • 7,097
4 votes

Derivation of static & kinetic friction formula

Coulomb friction is an empirical law. It was observed that the force required to move an object was proportional to its weight. Regarding static and kinetic friction it is possible to use graphs like ...
NMech's user avatar
  • 24.3k
3 votes
Accepted

Applications with combination of high friction and low wear?

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 ...
Chris Johns's user avatar
  • 15.2k
3 votes

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

The numbers for static and kinetic friction in aluminum-on-aluminum interactions, cited by @albseb back in 2016, are unreliable. Strangely though, they're the only published values. I'm a physics ...
Colson Sapp's user avatar
3 votes

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

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....
Chris Johns's user avatar
  • 15.2k
3 votes

Refute my assumption: Bearings Don't Improve Efficiency

Bearing have rolling elements specifically designed to insulate the two moving surfaces from coming into contact with each other and let the move freely (almost). There are many types of bearings, ...
kamran's user avatar
  • 22.4k
3 votes

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

The explanation is due to the fundamental physics of momentum transfer. In all cases of continuum flow, including laminar, transition, and turbulent flow, the zero (no-slip) boundary condition ...
ttonon's user avatar
  • 417
3 votes

Calculating Bending Force on a Fixed Metal Plate

In my view, you are attacking this from the wrong angle. The pipe will expand by about 150 mm. You need to give your pipe run the required space to do so. Look if you can use existing bends (this is ...
mart's user avatar
  • 4,771
3 votes

A quantity to measure whether brakes should be repaired

Indicators to warn that brakes need repair do exist. They are on many cars, but not all and are called pad wear indicators. These are small (usually copper or brass) metal studs held in an insulator ...
Solar Mike's user avatar
  • 15.7k
3 votes
Accepted

Find minimum horizontal force required to keep the block and wedge stationary?

What you are learning here is the effect of the "inertia force" due to motion. In order for both blocks to move together, we can simply write the equation, $F = (M + m)*a$, by the law of ...
r13's user avatar
  • 8,174
3 votes
Accepted

Inconsistant load cell readings - (static) fiction perhaps?

When you are raising the plate you are also raising the bearings and since they need to roll there is the frictional component pulling down on the bearings and pulling down on the plate. When you ...
Jim Clark's user avatar
  • 496
3 votes
Accepted

Equivalent viscous damper for friction damping

In general this is impossible, because for a given value of $F_e$, the friction damper dissipates a fixed amount of energy per cycle of vibration independent of the vibration frequency. This is (...
alephzero's user avatar
  • 12.5k
3 votes

Is there a positive displacement pump that experiences only rolling resistance?

Rolling diphragms have been around for many years now. See... https://www.diacom.com/rolling-diaphragm-theory With or without the spring. (With enough vacuum in the top you can get the membrane to ...
Jim Clark's user avatar
  • 496
3 votes
Accepted

Examples of Materials with a Coefficient of Kinetic Friction Very Close to or Equal to Coefficient of Static Friction?

Steel/Teflon - $\mu_s = \mu_k = 0.27$ Glass/Teflon - $\mu_s = \mu_k = 0.1$ Ice/Ice - $\mu_s = \mu_k = 0.01$ See table here.
r13's user avatar
  • 8,174
3 votes
Accepted

Why is the open-front bike stem design so widespread despite that it may be inferior to the closed-front design?

For starters, I think you have to differentiate between "theoretically inferior" and "practically inferior". Judging by the hundreds of thousands of bikes with open-faced stems out ...
MaplePanda's user avatar

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