# Questions tagged [friction]

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### statics exam question about friction

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 ...
170 views

### Ideal funnel design for powders

I'm designing a funnel/bottle for a powder. My goal is to have all of the bottle's powder contents come out when inverted. However, the powder has a tendency to stick to itself (like flour or brown ...
56 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 ...
1k views

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

I have a gearbox adapter that bolts onto a flange and I need to work out how much clamping force is needed to prevent the faces from slipping and keep the bolts in tension rather than shear when ...
365 views

### Does a washer really increase static friction force?

Suppose I have a bolt that goes through a hole in a plate and is under tension. If I place a washer between the bolt head and the plate, does static frictional force (torque actually) really double? I'...
447 views

### Materials to use for a low friction cable-pull

I'm posting this question on this stack-exchange site, because it appeared to be the one made for this kind of questions. If this happens to not be the case, I'm sorry, I didn't know better. Also ...
601 views

### How Can You Calculate Force to Overcome Friction From an O-Ring Seal?

I essentially have a piston in a tube that is sealed with an O-Ring and actuated with a solenoid. The friction of the O-Ring however, is higher than estimated (guessed as far as I can tell) by the ...
233 views

### Pan and tilt mechanism

this is my first project that i am working on. I want to make a IR sensor mount using stepper motors. I seen this on youtube and would like to make a similar design. I plan on using aluminium ...
48 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 ...
407 views

### Mechanical device that creates friction when rotating?

I am designing a mock-up aircraft throttle, like one of these: In an airplane, it it slides forward and backward to control the thrust of the engines. The problem is, I am not sure how to go about ...
299 views

### Multilayered Bearing Spinner

I have a few questions relating to a multiple layered spinner that uses ball bearings to reduce friction, kind of similar to a fidget spinner. The image below is an example of the multilayered bearing ...
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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 ...
108 views

### Building a machine from an ideal physics problem

I have a physics professor for whom I'd like to build a machine. Featured in a problem he is notorious for assigning students, originally from Kleppner and Kolenkow's "Mechanics," the machine causes ...
93 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 ...
530 views

### Does oil actually “attract” dirt?

The conventional wisdom consistently holds that "oil (or grease) attracts dirt", giving rise to the need for seals and dry-lubricants. But I've always considered that to be loose thinking, the truth ...
1k views

### Brake pad materials for use against an aluminium surface [closed]

For a project that I am a part of, we are in need of a brake pad material for use against an aluminum surface without causing any damage to it. So far through my research, the only safe alternative ...
92 views

### Dimension of the unidirectional mechanical clutch

This is a problem from the book Engineering Mechanics Statics vol-1 by Meriam Kraige. The elements of a unidirectional mechanical clutch are shown in the figure.A torque $M$ applied to the outer ring ...
479 views

### Normal force between two boards

This is a problem from the book Engineering Mechanics Statics vol-1 by Meriam Kraige The rectangular steel yoke is used to prevent slippage between the two boards under tensile loads $P$ .If the ...
45 views

### Can the hysteresis phenomenon be considered as a (type of) friction

I was wondering whether the hysteresis (in particular, mechanical motion systems) can be considered under the class of friction. From theory, I know that the frictional forces are direction, and ...
68 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 ...
910 views

### Is a gear usually held to a shaft by friction or an adhesive?

So, where I work, we have this arcade game, which is a classic claw machine. IN order to raise the claw up and down the machine makes use of a worm gear, like so: (although for the meticulously ...
2k views

### Good material for friction disk for a torque hinge?

What kind of material(s) would make a good friction disk, or disks, for a friction hinge, or torque hinge? This will be for the hinge on an arm that needs to be adjustable and also hold it's position ...
136 views

### Recreating Focaults Pendulum

I am having issues building a recreation of Focaults Pendulum (basic, inexpensive, undergrad project). At this point, I am going to purchase aircraft cable or suspension cable unless someone can ...
1k views

### Applications with combination of high friction and low wear?

What would be some common applications involving high friction and low wear rates? for example, gear-driven mechanisms which require high friction between the gear teeth but ideally low wear between ...
826 views

### How do I model the friction on a rolling pulley wheel, which holds weight, on a horizontal cable?

I am currently designing a motorized zipline trolley that will carry a person on a horizontal cable, so I am trying to calculate the friction on the wheels to determine what kind of motors I need. I ...
465 views

### Are “interference fit” equations appropriate for calculating barrel stress?

I am curious about calculating stress at various points along a barrel as a bullet is being fired through it. The interference fit (press/friction fit) equations immediately come to mind, but I am ...
187 views

### Understanding net torque from an actuator

This will probably sound like a silly question, but here goes.... Let's say I have an actuator, with a torque rating of 1 Nm. I then connect it to a wheel, which starts rotating at a constant ...
247 views

### Apply constant load to an electric motor - low tech way

I want to know how much I can over-drive a small electric motor. Its speed at the rated voltage is too slow, so I want to find a higher voltage that won't blow it. It will only be used intermittently, ...
57 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 ...
2k views

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

Is there a material that has higher kinetic friction than static friction? You can assume it's sliding on any surface you want. Better if you come up with one that has this property on a standard ...
121 views

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

I have a dry film moly-graphite lubricant (CoF=.075) and a lubricious CVD coating (CoF=.05). The CoF of each of these lubricious materials was determined using the same ASME standardized test. The ...
446 views

### Can a 2 HP motor move a 1,000 lbs flat-bottom boat across a flat material surface?

There is a small 13' long x 6' wide, 1,000 lbs (total weight of everything) all-fiberglass white pontoon boat with dual flat-bottom fiberglass pontoons. (Each flat pontoon bottom is 2' in width, with ...
769 views

### Determine coefficients of friction based on the torque required to rotate a part on a shaft

I'm trying to model a part that rotates on a shaft. I measured empirically that it has a static torque of around 500 N·mm and a dynamic torque of around 400 N·mm. I want to simulate it in CAD but my ...
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### Pacejka Formula - natural values

For my racing game I am using a simplified Pacejka Magical Formula: $\mu_{lateral} = \mu_{0} * \mu_{1} * D * \sin(C * \arctan(B * x - E * (B * x - \arctan(B * x))))$ Where: $\mu_{lateral}$ is ...
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### Not a good idea to rub two of the same material against each other?

I've read that it's not a good idea to rub two surfaces of the same material against each other, e.g., plastic against plastic, metal against metal. Plastic against metal is preferred. Why is this the ...
21k views

### Why use bushings of different material than what they contact?

I've heard that materials that need to slide against each other should be of different materials. Why is that?
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### Suggestions for low friction surface materials for a “beltless static treadmill”

I'm currently developing a treadmill for clinic gait research. If I were to build a flat treadmill with no moving surfaces what materials or coatings would be worth exploring as walking surface. ...
826 views

### Design of Wheels/Tires for a RC Car [closed]

Background Information: My design team is trying to create a small RC car that can climb a 30 degrees incline that is 6inches high. We have two motors on a 3 wheels vehicle with the motors powering ...
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### Sumo-bot Wheel Help - Sticky tires or Wide & less friction tires? [closed]

I am building a sumo-bot and our competitors have thin sticky tires, while we have wider and less sticky tires. The diameter is the same, and the gearbox/motor is the same. Who will win? PS: Sticky ...
2k views

### Practical uses of superfluids [closed]

I am wondering whether and how superfluids (possibly at room-temperature, if that is possible at some point) can be of any practical use in mechanical or electrical engineering or other fields. I ...
125 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. ...
235 views

### What type of ultrasonic transducer would be suitable for ultrasonic welding? [closed]

Project background: I am working on a project where i need to weld plastic using ultrasonic transducers. Problem: Since I'm still learning engineering, I have a hard time figuring out what all the ...
2k views

### What causes friction in magnetic bearings?

Magnetic bearings work by levitating a rotating shaft so that it is not in contact with its supports. This greatly reduces the friction of the system. In all of the literature that I have seen on ...
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### Are jeweled bearings commonly used for applications other than mechanical timepieces?

Jeweled bearings use a metal spindle with a jewel lined pivot hole (pictured below). They have been important in the manufacture of mechanical timepieces since the early 1700's. Their importance ...
7k views

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

I want to attach something small to the smooth metal shaft of a small motor (2-3 mm in diameter), like fan blades, but I want it to be temporary. If I make it too loose, then the fan won't turn at ...
7k views

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

This is inspired by a project I undertook for my Physics class last year; I'd like to apply it in the future. Background: For the project, I and a few classmates were required to build a small car ...