Questions tagged [friction]

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2 answers
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Smallest possible rolling resistance

So, question is how to achieve the lowest possible friction in a scenario where there is a steel bar rotating AGAINST the circular frame at high rpm. Now, when it comes to sliding friction lowest ...
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1 answer
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Force Required to Keep Ball Rolling

I am attempting to recreate a demonstration that someone told me about. A hollow steel ball rolls around in a non-metalic bowl, electromagnets keep it going. I obtained a steel ball and a glass ...
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2 answers
26 views

Collecting a released rope with a proper speed

To simplify the problem, I liken the problem to a ship approaching the shore and a device wants to collect the rope in such a way that the rope is neither stretched too much nor released to the extent ...
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1 answer
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Can you explain mathematical and mechanics formulation of equation in Junker 1969 paper on self-loosening of fastener by vibration?

Can you help me to understand how the first equation in the paper 'New Criteria for Self-Loosening of Fasteners Under Vibration' by GH Junker, 1969 is derived? I'm not able to understand the ...
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2 answers
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Most efficient electricity generation in a wide flow of water

I'm wondering what the best method is for generating electricity in a wide river. The assumptions here is that it's a strong flowing river. It is very wide and we're allowed to put an electricity ...
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1 answer
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Can Friction Pendulum Bearing/System (FPB/FPS) suppresses the effect of an earthquake from every direction or only from one direction?

Can Friction Pendulum Bearing (FPB) AKA. Friction Pendulum System (FPS) suppresses the effect of an earthquake from every direction or only from one direction? Please take a look at the tests which ...
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1 vote
2 answers
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Passive magnetic bearing coefficient of friction

Imagine two axially-magnetized ring-shaped permanent magnets in a repulsive configuration where one is levitating on top of the other (and somehow radially constrained so the PMs remain ~concentric). ...
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Do asperity junctions break every time a machine starts to rotate?

After reading CONTROL OF MACHINES WITH FRICTION by Brian Armstrong-Helouvry, some questions rised. The main question I ask you is: Suppose two metal surfaces in relative motion first in static ...
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2 answers
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How to create a friction-based cable exercise machine?

What would be the best mechanism to create a friction based cable machine? The point of this machine to only have resistance to movement not when the cable's stationary and without the momentum of ...
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1 answer
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To reduce friction losses, is it better to have one single large ratio stage, or multiple smaller stages for worm gear?

If I wanted to have a 49:1 total reduction, would there be less friction losses with a single stage of a 49:1 or two stages of 7:1 and 7:1? Google has not been much help. My gut says that I should use ...
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2 votes
1 answer
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How friction between stator and rotor is dealt with in an electric engine/motor

This YouTube video https://www.youtube.com/watch?v=nlG2dsYRagI shows how an electric engine is made but I don't understand how friction between the stator and rotor is dealt with. At 3:50, we see the ...
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POM-c/POM-c (dynamic) coefficient of friction

I've googled around but can't seem to find the value for the coefficient of friction (dynamic preferably) of POM-C sliding with POM-C. Does anyone have information on this?
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One way locking mechanism linear movement

Sorry for the English in advance, it is not my native language :) I am working on a design which involves moving two steel plates in a horizontal linear motion together to clamp around a box. After ...
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2 answers
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How to calculate press load for an interference fit with no friction coefficient between the materials (shaft & hub)

Press-fit load calculation always takes friction into consideration and gives you the load expression as follows, $$F = µ\cdot PA$$ where µ is the friction coefficient, P (Interference Pressure) is ...
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1 answer
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Examples of Materials with a Coefficient of Kinetic Friction Very Close to or Equal to Coefficient of Static Friction?

I'm looking for examples of frictional materials that have a coefficient of kinetic friction that is as close to equal to their coefficient of static friction as possible. What is an example of that ...
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3 answers
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Rack on rack vertical force

I have a locking mechanism in mind, that is made with two racks. Rack 1 is fixed and then we push down rack 2 to lock something. After that a horizontal force is applied to rack 2. I calculated the ...
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1 answer
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Head loss coefficient for a valve with respect to both the open position and flow rate

This question talks about the head loss coefficient for a valve, i.e., $K_{L}$ for $h_{L} = K_{L} V^{2} / 2g$ where $h_{L}$ is head loss. First, head loss coefficient for a valve with respect to the ...
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4 answers
186 views

Derivation of static & kinetic friction formula

We know formula of static friction & kinetic friction = μsN and μkN. I have searched online a lot about them. I do know what is the formula & how to use it but I couldn’t find any article ...
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1 answer
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On Which Side Will The Tyre Wear Out More?

Whilst watching a F1 race recently I noticed the commentators talk about how all the cars on that race day started observing more/faster wearing down of the tyres on the front left of the car relative ...
2 votes
3 answers
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Eliminate cat ear and nose shocks during the dry season

My cat, George Valentine, really enjoys being pet. However, when the air here in Canada gets very dry (mid-fall), this activity creates static charges. Once the petting starts giving him relentless ...
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3 answers
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Which of these two cases will have the most friction?

I have a structure colored in blue which we are looking directly downwards on (birdsview). Its high up in the air, and the only thing keeping it from falling down is the friction surface (red) between ...
1 vote
1 answer
58 views

What rubber to use to grip stainless steel?

I need to secure a plastic bobbin on a 316SS shaft so it can be wound in a winding machine. There is a potential for undesirable axial and rotational drift that I need to prevent. My initial thought ...
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1 answer
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Water dynamics in aluminum pipeline for dummies

This topic is totally alien to me, so I may be asking something very obvious. I am designing a cooling system. In the bulk of aluminum, I drill 3mm holes and then I connect them one to another to ...
2 votes
3 answers
72 views

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

Is there a positive displacement pump that experiences only rolling resistance? One with no sliding friction and diaphragm stretching?
4 votes
3 answers
318 views

Equivalent viscous damper for friction damping

I have a friction damping system which is exited by a harmonic force FE (depicted on the left side). Is there a way to convert the friction damper to a linear or nonlinear damper, such that the ...
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How much actual performance is lost with extreme negative camber / "stanced" vehicles?

I recently had a discussion with a friend, who's intuition is that "stanced" cars with extreme negative camber angles are losing a huge fraction of their performance, such that a 5.0L V8 ...
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1 answer
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Rover Steering Torque

I would like to calculate the required motor torque to turn a rover wheel whilst the rover is stationary. I have modelled the friction force as a distributed force acting equally along the width of ...
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1 answer
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Inconsistant load cell readings - (static) fiction perhaps?

First off I'm not an engineer so please excuse the simple language I use to explain my question! I have an arrangement whereby I have a steel plate suspended from basically a bridge. The plate is free ...
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1 answer
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Friction in Wedges: finding the mass of the block C on the verge of slipping

I need to solve for the mass of block C that is in the verge of slipping. All surfaces have a coefficient of static friction of 0.11. The cable connecting the wedge B and C is parallel with the ...
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2 votes
1 answer
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Determine the minimum horizontal force to disturb the equilibrium

Three blocks of 1N 2N and 3N are placed one over the other respectively. If the friction between the topmost 1N and the middle 2N block is twice the friction between the lowest 3N and floor then ...
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3 answers
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How to guess direction of friction in any case

Here , in case of a death well situation as an example. Q How is direction of friction going to be opposite to mg or in upwards direction ? Why not: In case of like circular turning , direction of ...
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2 votes
2 answers
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Effects of rolling resistance on wheel angular and vehicle longitudinal speed

The differential equation for wheel speed can be given as: In here, $T_t$ is driving torque (not braking), $F_x$ is longitudinal force of tyre, $J_w$ is wheel inertia, $\dot{w}$ is angular speed of ...
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2 answers
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Find minimum horizontal force required to keep the block and wedge stationary?

In the adjoining figure, the coefficient of friction between wedge (of mass M) and block (of mass m) is μ. Find the minimum horizontal force F required to keep the block stationary with respect to ...
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1 answer
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Are there any frictionless objects or is it possible to create frictionless objects?

In the latest StarTalk NDT says that without friction space crafts would not be able to slow down when reentering orbit. The friction against the air slows it down from 17,000 miles per hour down. ...
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2 answers
478 views

Wheelbarrow minimize wear

I have a question about the design principle. To explain my problem I made the sketch "wheelbarrow". To minimize wear, which design is preferred?
1 vote
1 answer
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For cleaning food and objects, power scrubber vs. electric rotary toothbrush?

I'm asking about cleaning produce like potatoes and melons, NOT human organs here. This handheld power scrubber looks like your average rotary toothbrush! Indubitably I know that a toothbrush's brush ...
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0 votes
1 answer
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A quantity to measure whether brakes should be repaired

Suppose you can record some suitable parameters each time a driver uses the brakes of a vehicle (assume it's a heavy truck if necessary). Is there a reasonable formula for a dimensionless quantity $Q$ ...
1 vote
2 answers
108 views

Jamming & linear guiding

For a linear guiding I need to know the concept and understand the jamming limits. See picture. If I choose concept 1 or concept 2, what will be the value of X? How can I calculate this?
2 votes
3 answers
131 views

Forces acting on a weightless member

A weightless bar is pinned at the top of a triangle with N weight. Both rests at the horizontal plane. There is a horizontal force F acting on the weightless bar, and a given coefficient of friction μ ...
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1 vote
1 answer
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Pressure drop in a CFD simulation of an air flow too small

I am simulating a turbulent air flow through a rectangular channel with the goal to match measured velocity profiles and the static pressure at certain points. My problem is that the pressure drop in ...
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1 answer
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Required force to start the motion of a leaning bar

A uniform bar weighing 343N leans on a heightened plane (see figure). What force P is needed to start the bar moving? Coefficient of friction (on all surfaces) = 0.30 The blurred length is most ...
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1 vote
0 answers
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Force necessary to resist motion due to torque on a drum brake

A drum is subjected to a counterclockwise torque of 16 in-lb. What horizontal force is necessary to resist motion? Coefficient of friction = 0.40 Weight is neglected. I'm having a hard time on this ...
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2 votes
2 answers
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Find frictional losses as box exits ramp

I have a box traveling on a ramp just before the ramp levels out. At this point all values are known: I want to calculate the frictional losses from this point to when the box is completely off the ...
2 votes
1 answer
38 views

Friction versus ratcheting pawl

We are working to design a lock mechanism and need to hold a square plunger out of a hole for extended periods of time (potentially years). The square plunger is under pressure from springs to return ...
2 votes
2 answers
252 views

How to add friction to a rope without using abrasion

I have a pay-out winch. It is a spool of rope that has a disk brake attached to it, so I can control the torque required to rotate the spool. When the torque is very large, however, the rope begins ...
2 votes
1 answer
253 views

Calculating Bending Force on a Fixed Metal Plate

At work we've had a steel pipe support break on us, and I can't for the life of me figure out what happened. Here's some background info: A long (125m) steel heating pipe (ø51mm) is suspended, resting ...
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1 vote
2 answers
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Disc Brakes - Swept Area , why is larger better?

I am trying to understand why a bigger swept area on disc brakes provides higher braking force for the same force being exerted on the brake lever/pedal by the rider. If we use the same exact brake ...
7 votes
4 answers
3k views

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

The Darcy friction factor is defined as: $$f_D =\frac{64}{Re}$$ with $Re$ I mean Reynolds number (global). I was wondering why Darcy in laminaire flow is independent of pipe roughness (wall roughness)?...
2 votes
2 answers
174 views

Acceleration of spool on conveyor belt

A spool has a mass of 500 kg and a giration radius of $k_G = 1.30m$. The spool lies on the surface of a conveyor belt, the static coefficient of friction is $\mu_S=0.5$. The spool is not moving at ...
1 vote
0 answers
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Where do I learn about jewel bearings?

I would like to take a deep dive into the world of jewel sourced watchmaking components (including, but not limited to, bearings) but I am having trouble finding any textbooks on the subject. Are ...
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