Questions tagged [friction]

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Deriving the amplitude of a coulomb (dry friction) damped spring

This is my first time posting anything, but I could not figure out the derivation of the amplitude of the spring for the 4 first oscillations. I am not acquainted with the effect and calculations of ...
• 89
169 views

Calculating a pull force between two pieces of plastic

I have an HDPE pin, 2 mm high, 2 mm diameter, that I impress into a flat plaque of hot HDPE. It is not hot enough to melt the pin, but still hot enough that the material will shrink 4% in 24 hours. ...
• 353
190 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 ...
• 33
113 views

How do you calculate the chain tension required when compressing bulk material over a conveyor?

Bulk material is conveyed over a slat conveyor, and the material is leveled with overhead rollers while being transported in the conveyor to maintain an even material height. Most of these "levelers" ...
• 175
105 views

Regarding the ITTC Guidelines for Ship CFD applications

I was reading through the ITTC – Recommended Procedures and Guidelines - Practical Guidelines for Ship CFD Applications (https://ittc.info/media/4196/75-03-02-03.pdf) document and this little thing ...
• 21
118 views

Torque needed to keep a wheel spinning at high RPM

I have a treaded wheel which is 16'' diameter and 4'' across (trailer wheel). If I want it to spin constantly at 2750 RPM, what amount of torque do I need to apply to combat friction and air ...
• 121
62 views

how to calculate the speed ratio (Rotational speed to advancing speed) in friction stir welding

I am a student and I work in the friction stir welding of a hardened aluminium alloy 7075-T6, and I want to confirm about this information before I put it in the article. I found in the literature ...
1 vote
30 views

If building a DIY screw jack, would it be beneficial to add a gimbal to the jack nut, and/or to the screw attachment?

The screw jack will be used twice daily. It will be made out of M24 8.8 grade threaded rod and nut. The nut will travel 300mm, to raise a weight of 50kg by 800m, via a pivoting lever arm. The parts ...
1 vote
248 views

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 ...
• 149
1 vote
113 views

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 ...
• 33
1 vote
59 views

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 ...
• 111
1 vote
100 views

Bevel gear friction and inertia calculation

I want to calculate the friction and inertia between 2 bevel gears with straight teeth. I know how to calculate those parameters between regular gears with straight teeth. Is there any difference for ...
1 vote
2k views

how to calculate required torque and rpm to through a 160 gram cricket ball horizontally at 160km/h velocity?

I am going to design a bowling machine. In this design, I'm going to use two motors that are being placed vertically and their shaft are attached with two horizontal identical wheels with a space of ...
• 119
1 vote
322 views

In a statics exam I had the question in the picture attacehd and I had some trouble understanding it. The question is so Under the effect of torque Mo rotates a wheel (radius r) with constant ...
• 11
1 vote
74 views

Why increasing the coefficient of friction results in evenly distributed load in rolling machines?

I'm designing a rolling machine for reduction of steel ingots of $5 mm$ to $1.96 mm$ thick. I can convince myself using equations why increasing the coefficient of friction (in case of lubrication ...
1 vote
95 views

How to make machined plastic part slippery for small dry particles

We have a plastic part that is a receptacle for small ( < 1mm ) particles. It is a disk with a shallow cone shaped indent made using a drill. When a particle is placed in the receptacle it should ...
• 111
1 vote
101 views

Spinning a balanced load with DC motor

Enclosed within a consumer electronic, I would like to spin a small balanced load. The device will be rotated relative to gravity, but no other direct forces will be applied to the load. A coreless ...
• 111
37 views

Why do engines with cylinder offset not suffer from increased frictional losses on the compression and exhaust strokes?

I recently watched the D4A YouTube video on cylinder offset, and for the most part it makes sense. Longer power and intake strokes, lower frictional losses on the power and intake strokes, greater ...
65 views

Belt conveyor roller spring

I wanted to know if anyone could help in this area. I want to create an inclined conveyor belt where, when a cargo box reaches the top of the conveyor belt, the rollers sequentially move down (maybe ...
29 views

Friction coating aluminum parts in lieu of anodizing

I have an application, 6061-T6 aluminum cylinder, and piston - approx 6" dia for both, O-ring on position. The piston is under 80-100 psi, room temp and stroke are a couple of inches. Typically, ...
68 views

What would be the Force Balance on this situation:

I'm struggling to find the correct Force balance in the following situation: The black parts are hard stopers. The blue part is moving perfectly aligned with the Y-axis in the negative direction. The ...
62 views

Minimum power required to drive a vehicle with a Swedish type omni wheels

I'm trying to find the minimal power needed to drive an omidirectional 3-wheeled robot. I already asked in Robotics Stack Exchange and they didn't respond yet. From the equation $P=Fv$ I know I need ...
40 views

How can I reduce noise from pushrods in an assembly without using grease/oil?

I have an assembly which consists of a row of vertically-oriented nylon pushrods (each 5/16" in diameter, colored green in the attached pictures), and two black pieces of laser cut delrin ...
72 views

Why carrom coins have the circular profiles on them?

Why do carrom coins have these circular profiles on them? At first I thought that this will reduce the friction as area reduces, but quickly recalled that friction for solids don't really depend that ...
87 views

Calculate pipe size and friction loss for an agricultural project's water system?

I'm in the process of designing a water system for our regenerative agricultural project in the Horn of Africa. I'm looking to install a ≈1000L water tank on a 3 meter stand which will gravity supply ...
169 views

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 ...
• 1
122 views

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 ...
140 views

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 ...
• 111
41 views

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 ...
663 views

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 ...
• 1
88 views

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 ...
• 101
313 views

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 ...
20 views

Train decelerations in no power condition

Suppose a train is running at 30kmph and suddenly the power is switched off. How do we calculate the reducing velocity at intervals and what factors will affect the change in it?. Further how much ...
48 views

What type of bearing should I use to allow a ring to rotate around a fixed axle

What type of bearing should I use to allow a ring to rotate around a fixed axle. Axle is horizontal. The rings inner diameter can be flush with the stationary rod or have a gap as needed. What type ...