Questions tagged [mechanical]

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Remove stripped screw inside of a tube

I have a stripped screw inside of a tube (see picture): The size of the screw is M2 and it seems to be glued. This is part of a camera objective so I want to avoid impact (e.g. tapping with a hammer)....
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What are some interesting applications of G2/G3 Continuity? [closed]

I've heard of CNC tool paths using splines to approximate G2 continuity to create smoother motion. Also, rollercoaster designs use G2 continuity to reduce shock from sudden changes in curve radius ...
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Failure criteria for CFRP single plate bolted joint

Which equation can be used to find failure based on ply orientation. Tension,shear & bearing faliure to validate against fem analysis
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How does the retrofit mechanical system work in the rear brake pistons of cars (dual hydraulic + mechanical)?

I discovered recently (when changing the rear brake discs/pads of a car) that the piston cannot be pushed back without setting a rotation to it in the same time. This is due to the dual system with ...
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1 answer
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How can I understand shear flow in a beam cross section?

I am trying to understand shear flow and I am just not getting it. For example, one of the problems in Beer has an I-beam and there is both a horizontal and vertical force acting on it. So it has ...
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Clarification of a piston and crank dynamics question

Yesterday, I had an Engineering Mechanics exam which involved a Piston and a Crankshaft engineering dynamics problem, which I was a bit stumped about. I sought clarification from the teaching staff ...
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Is there a geometry that meshes exactly with a rope?

I'm in a use case where the outer surface is a gear driven by a motor (that's the easy part) and the inner surface meshes with a metallic (iron) rope. When the part rotates, I want the motor and ...
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What are the different ways to measure mass, for mechatronics

I’m trying to build a small mechatronic device and want to know the different ways of measuring mass. The ones that I’ve found so far are vibration and directly measuring mass using weight or a scale.
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Why were handcuffs ever made with a chain between them?

I've noticed that modern handcuffs are always attached directly to each other, without any "chain" of any length in between. I guess I can understand why that make them safer and more robust....
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2 votes
2 answers
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What would I search for to find a combination of a cap screw and a set screw?

I'd like a (hex) cap screw that at the non-head end has a (smaller) keyed opening, allowing tightening the screw from the inserted end (because the screw will be into a threaded hole with an open end, ...
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1 vote
1 answer
83 views

What type of ball bearing is this?

I don't have engineering background. I'm looking for this telescope' altitude bearing below. I understand it's a type of ball bearing, but does anyone know the exact name of this type? There are 2 ...
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Incremental rotation that snaps in place

I'm developing a board game and it needs a mechanism of incremental rotation in which the rotated object will snap to one of five possible angles. I have been trying to search for examples of ...
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1 answer
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Connection to periodically electrify equipment

I am designing a system where I have a set of 4 electrical components rotating in a circle. In the bottom stage, the electrical component is submerged in water. In the top stage, the electrical ...
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1 answer
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How to make a circle spin from the edges

I have an issue where I need to make a large wire through a bearing spin in 3" diameter circles, and have a weight hanging from the bottom of the wire. Essentially, I need a hole that moves in a ...
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1 answer
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I need a coaxial gearbox that translates reciprocating clockwise & counterclockwise rotation to unidirectional while increasing speed of rotation?

I am a noob engineering student. I want to design a coaxial gearbox that takes an input shaft that rotates reciprocally (clockwise then counterclockwise) and increases the speed of rotation ...
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2 answers
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Between the front wheel and the rear wheel, what is good for maintaining speed? [closed]

A car weighing 13,000 N is driving at a speed of 50 km/h, overcoming a resistance (Fd) of 450 as shown in the figure. If the coefficient of friction between a wheel and a road on a frozen road is 0....
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Designing a grabber

I designed a grabber for grabbing strings and yarns. the movement that I need is straight up and down to grab a piece of yarn. I wanted to know if this model (in the video) works in real life or not. ...
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1 answer
99 views

How to find clamping force from bolt preload?

If I have a piece of rubber between two steel plates, and four bolts (at equal preload) compressing the plates, will the total compressive force on the rubber be Preload x 4?
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Euler angles from angular velocity pseudovector

According to wikipedia page https://en.wikipedia.org/wiki/Angular_velocity Euler proved that the projections of the angular velocity pseudovector on each of these three axes is the derivative of its ...
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1 answer
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Need new pressure switch mechanism for a 3 phase compressor using a 220V AC Drive

I've bought a vintage Quincy 216 air compressor. Actually there are duel Quincy 216's - each has a separate 3 phase motor. One motor is 1.5 HP and the other motor is 2 HP. The compressors share a ...
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4 answers
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When we replace supports distributed reaction by point reaction in thin beams, is that considered an application of Saint-Venant principle?

I read about Saint-Venant principle which is about the effect of replacing forces by equivalent forces system that effect on the same small region of a rigid body, all examples I come across are on ...
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0 answers
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backrest angle mechanism for a Cargo Bike seat [closed]

I'm looking for a joint with an integrated rotating and locking mechanism, that can hold the load of a back leaning onto it. I have attached a dirty render of the concept. Hope this will make the ...
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1 answer
71 views

Max Stress on Weld

Part is welded to a plate, based on the below free body diagram how would I determine the max stress in the weld? It seems half the weld is in tension and the other half is in compression.
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3 answers
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Can tubes for fits & tolerance be purchased or only manufactured?

I'm currently designing a steel structure for a gym machine. I want to assemble two rectangular tubes, one being able to slide inside the other, for height adjusting. I intend to use a spring ball pop ...
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1 vote
1 answer
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Bushed 3" V-belt pulley with unkeyed 3/4" shaft?

Shortly I will have two 3/4" unkeyed shafts needing 3" type-A V-belt pulleys, one each. They'll each have their own motor driving them, and will need to run to 5000 RPM and possibly higher ...
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3 votes
1 answer
679 views

Why/when do we use a transition fit?

I'm self-learning a bit about preferred fits and tolerances and was wondering why transition fits were even a thing. Clearance fits I understand, applications where you don't want parts to touch and &...
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1 vote
2 answers
59 views

Heavy machinery/loader attachment with custom tube

I spotted this heavy machinery/loader attachment at a road reconstruction job site in Ontario: The device a has horizontal tube that is cut off at an angle. The tube is attached to a vertical ...
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5 votes
3 answers
225 views

Why does this thing that is not a screw have a screwdriver slot?

I am (partially) disassembling an old sewing machine to clean it up. While removing the bobbin winder, I found this thing that has a screwdriver slot, but it isn't a screw. This is the part: It came ...
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2 votes
4 answers
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Inverting motor polarities automatically to close and open a door

Hi, I need to build a device that opens a chicken coop door. The idea is quite simple, a motor connected to an axle that pulls a string up just like a wench. It would be activated by a relay timer ...
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1 answer
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How can I measure gear efficiency?

I am doing a experiment on various gear combinations and am wondering How I can measure the efficiency (Torque loss) of each gear pair), I have a input shaft connected to the first gear and is also ...
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1 vote
1 answer
72 views

Why is the torque of an ICE low at low rpms?

Let us consider a basic 4-stroke single cylinder, direct port fuel injected naturally aspirated engine which is given a constant throttle. Now, why does it produce very low torque at low rpms, meaning ...
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3 votes
2 answers
157 views

Parallel beam load cells, force transfer and maximum load

I'm going to experiment with a parallel beam load cell like this one: https://cdn.sparkfun.com/datasheets/Sensors/ForceFlex/TAL220M4M5Update.pdf. I've read somewhere that for a setup shown on this ...
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Cargo box opening system below

I am currently trying to make a delivery drone similar to ones Amazon did. Basically the cargo box which carry the package must open to below in order to drop the package. What I want to do is exactly ...
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2 votes
2 answers
44 views

HPU minimum oil temperature

Two different HPU systems in different locations with slightly different oils Chevron Ranco HD 68 and HDZ 68 have the same minimum oil temperature 55. Their flash points are are 455 and 414 F ...
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1 vote
1 answer
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Why would anyone "pull the stem out and stop the wristwatch at night or when not wearing it" in the context of mechanical watches?

I read this the other day while discussing mechanical pocket and wrist watches: Plus it is common practice to pull the stem out and stop the wristwatch at night or when not wearing it. You then have ...
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How can (many) mechanical watches keep track of the current day of the month when these vary so much over months and years?

Having dealt with dates and time in programming context for many years, I have realized what a nightmare our common calendars are, and how much they vary by the year/month/etc. Yet there are fully ...
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1 vote
1 answer
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Dynamic model of a two-mass electric drive taking into account the Gear Ratio

Two-mass rotational system has the following form and is represented in following structural diagram. where $\tau_e$, $\omega_1$ and $J_m$ - motor torque, angular velocity and moment of inertia $\...
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2 answers
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Torsion of continuous vs simply supported beam [closed]

Say that I have a 2 span of continuous beam subjected to torsion, is the torsion value smaller than those 2 single span beam subjected to torsion of same value ?? I think the torsion of continuous ...
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2 answers
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Effect of multiple shear pins used in combination in a coupling

Does using multiple shear pins under a limiting torque case reduce the minimum required shear pin diameter for the coupling or is the complete load distributed over the shear pins regardless of the ...
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1 vote
1 answer
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Do really "all mechanical watches need to be maintained properly"?

Somebody answered this on a different question: All mechanical watches need to be maintained properly. Every year or two they should be taken to a watchmaker for a service. This will include ...
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3 answers
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Are mechanical pocket watches inherently water-proof and last "forever"?

Recently, I bought a cheap (~$53) but elegant mechanical "retro pocket watch", newly made. That is, not an antique made in the 18th century or anything. So far, it's worked flawlessly and ...
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1 vote
2 answers
77 views

Looking for locking "lanyard" reel mechanism

I'm working on a system that requires a small cord (~3ft long) to retract up into a reel and lock in place so it cannot be pulled away from the reel. Sort of like a seatbelt mechanism after it's been ...
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166 views

Number of Kinematic Pairs

Kinematic pairs are the connection between 2 links that can have relative motion between them. But In six bar chain as shown below: There are five pairs for them to be a kinematic chain. But if I ...
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2 answers
156 views

How can a mechanical pocket watch wind itself from movement, and does it really get damaged if wound "too much"?

Today I received the mechanical pocket watch that I had recently ordered. It was this one: https://www.trendhim.se/guldfargat-mekaniskt-retro-fickur-p.html#full-gallery I find it extremely fascinating ...
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2 votes
3 answers
83 views

What is this mechanical pump called?

I am unable to find it again but I once heard of a type of air pump that involved a pair of offset archimedes screws inside a cylinder. The point of the device was that as the screws would turn ...
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0 votes
1 answer
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Peltier Module Set up isn't cooling

I have set up a peltier module with an aluminium heat sink, cooling fan, 12v, 7ah battery supply and thermal paste for the purpose of cooling water. At first, it performed well. It dropped down to 3.5°...
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1 vote
2 answers
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Professional threaded insert in plastic?

I'm getting some plastic parts (made with HDPE) CNC machined. A few of these parts require the addition of threaded inserts. I've printed the parts myself using a 3d printer and when I add the ...
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1 answer
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Shape of the shaft of knurling device

I'm trying to design and simulate a simple knurling device. The shaft ( blue part ) has a flat surface at the other end, where the small grey pin connect the green body to the shaft. I guess you can ...
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1 vote
0 answers
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Design a Jig and Fixture for 3-axis CNC Milling Machine

Newbie Here!!! This is my assignment task. I am required to design a Jig and Fixture for 3-axis CNC Milling Machine. The workpiece will be a simple aluminium block and it will be cut and shaped into a ...
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2 answers
297 views

how many power stroke in 3 cylinders, 4 stroke at 3000 rpm?

According to some answers, in 3 cylinder , 4 stroke we have power stroke each 240°, as we have 1500 rev. Of 720° in this rpm, so we will have this: 1500 x 1.5 = 2250 power stroke at 3000 rpm, is it ...
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