Questions tagged [mechanical]

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3 answers
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Mechanical advantage of the 3-ring release system

I'm quite curious about the 3-ring release system used in parachutes, as described in this Wikipedia article: https://en.wikipedia.org/wiki/3-ring_release_system I wonder why is this system so ...
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6 votes
1 answer
167 views

Identify this bomb disposal equipment

A recent news item featured this photo of a WW2 bomb being prepared for detonation. Can anyone identify the purpose of the large widget sitting on the bomb? it's got a lot of cooling fins on it, and ...
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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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4 votes
2 answers
8k views

What is Saint Venant Principle?

I am having problem with the application of Saint Venant principle.I have heard that quite often we use that knowingly or unknowingly.I would be very greatful to anyone who would explain this very ...
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4 votes
1 answer
484 views

4 Gears in a Circular Pattern - Calculating the Proper Distances for Meshing

I have recently been working on a gearbox for a robot. I have this pattern of 4 gears with each gear connected to its 2 neighbors. It looks like this: You will probably notice something though. ...
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  • 43
4 votes
1 answer
441 views

Quick return mechanism for spring-loaded screw

I am looking for a way to convert rotary motion to linear, but it should take less energy to get back to initial position than when going from initial position to the end position. Specifically, a ...
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  • 83
3 votes
3 answers
6k views

Moments of Fixed-Fixed Beam

I have a quick question related to the topic of mechanics of materials. If I were to have a beam that is fixed at both ends and has a central point force, do moments develop at the fixed supports? e....
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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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3 votes
3 answers
396 views

Torque and RPM calc

started by designing the gear meshing, and now I need to calculate some parameters to determinate if this meshing works for me. The system considers an electric motor, which technical parameters are: ...
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3 votes
1 answer
50 views

Clutch role in a micro hydropower

I've recently visited an old (about 60 years old) micro hydroelectric standalone installation. Total electric power is about 3 kW A/C. A local told me between generator + fly-wheel and turbine there ...
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3 votes
2 answers
1k views

Why do 2-stroke engines burn more oil?

Of course, most 2-stroke engines require oil to be mixed with the fuel (I appreciate there are 2-stroke engines that don't require this). Therefore, it makes sense to me that oil will be burnt during ...
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3 votes
1 answer
49 views

Scanning and modeling my personal vehicle for aerodynamic simulation

I have this pickup truck that I love dearly. I often change the aerodynamic configuration of the truck when I use my camper shell, or roof top tent, etc. Is there a reasonably easy way to create a ...
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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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2 votes
4 answers
99 views

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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  • 21
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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2 votes
2 answers
324 views

Explain tolerances in technical drawing

I'm not a mechanical engineer and am not used to looking at mechanical drawings. I'm trying to understand what these tolerance features mean. There is a positional tolerance feature, which ...
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  • 287
2 votes
4 answers
732 views

When calculating a force, why do I get different result when I try to calculate via torque vs via sum of forces at an axis?

If I just do it by writing that the sum on y axis is 0 I get $100+x=200$ $x=100$ If I try torque around the top: $x*800=200*500$ $x=125$ So what am I doing wrong?
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2 votes
1 answer
242 views

Vehicle Train Towing [closed]

Why can I not tow 50,000 lbs (40,000 cargo and 10,000 Trailer bed) using multiple pickup truck each individually capable of towing 30,000 lbs? I was told that the towing capacity does not "Add up" ...
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  • 51
2 votes
2 answers
57 views

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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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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2 votes
2 answers
74 views

Most efficient orientation of exhaust vents on top plate of chassis for air flow with regard to heatsink fins?

I'm looking for some advice from an ME or anyone who understands heat transfer,convection, etc. I'm currently laying out in Inkscape a top panel for an audio amplifier I'm building. Now, my question ...
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2 votes
1 answer
71 views

Is there a way to convert a short throw in one direction into a long throw in two directions

I have a motor that I have created a simple adapter for; this lets us attach any parts we might design to solve the final problem: I would like to convert the motors motion to oscillating motion in ...
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  • 131
2 votes
1 answer
36 views

What are the characteristics of a motor that will generate current and is powered by a 30 cc, 2-stroke small engine?

Problem: I am trying to hobby-build a generator using a (old, working, throw-away gas, yard blower) 30 cc, 2-stroke engine. The 2-stroke engine will spin a motor and I want the motor to generate DC ...
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2 votes
2 answers
199 views

How does a two dimensional elevator work?

If you watch this video, you can get a sense of how an elevator can operate in two dimensions. But, what I can't figure out is how it is driven. If you consider a conventional elevator, there is a ...
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  • 163
2 votes
1 answer
138 views

How did the snifting valve in Newcomen's steam engine work?

Its function was to expel the air that came inside the cylinder along with the steam to prevent the engine to become "wind logged". Since the valve was non-return, how did Newcomen stopped steam from ...
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2 votes
2 answers
1k views

Heat transfer Calculation, for Cooling for an aluminium box

To go into more detail, I basically have a controller and its housing is basically an aluminium box that I need to add heat sinks to. But first I need to calculate how much heat is being dissipated by ...
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  • 41
2 votes
1 answer
189 views

Latch Mechanics

I want to make a sprung latch mechanism which keeps a door in place until a certain force is applied to the door. In the diagram attached, the force the door must release at is Fd, and the latch ...
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2 votes
3 answers
981 views

One way/locking mechanism without springs or flexible members

There a few neat mechanisms that allows only one way motion without the use of a pawl or ratchet. This is one of them: https://www.instructables.com/id/LEGO-Technic-One-Way-Gear-Mechanism/ What I'm ...
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  • 141
2 votes
1 answer
55 views

Hinge or similar that breaks at a certain change in acceleration?

Suppose I have a rope that is capable of lifting 100 Kg without breaking. But I would like the rope to break if it is exposed to a sudden change in acceleration (jerk). So if the rope was lifting 10 ...
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  • 121
2 votes
2 answers
1k views

How to calculate the gear ratio of planetary gear?

I saw this picture today: They give an ratio of 5/352. I think this is not possible with a simple gear. Maybe the upper sides ratio is the cause for it. Which formula do I need to calculate the ...
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2 votes
0 answers
32 views

High articulation joints

Looking for advice or suggestions for high articulation joints (>57°) for an automotive halfshaft. Peak operating conditions are in the ballpark of ~1000RPM, ~300ft-lb torque. I've considered u-...
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  • 121
2 votes
0 answers
134 views

How is motor torque related to capstan equation?

I know that capstan equation relates $T_{in}$ and $T_{out}$ as $T_{out} = T_{in}e^{u \cdot F_c}$, where $u$ is friction coefficient and $F_c$ is wrap (slip) angle. In my situation, the capstan is ...
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2 votes
0 answers
21 views

Is inverse hall-petch relation valid crystals larger than nanocrystalline?

The image shown here is of ceramics, where they varied the grain size and measured the strength. For example, let's take Al2O3. There we observed that strength first increased from 3 μm to 95 μm. But ...
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2 votes
1 answer
238 views

Calculate Torque Required

I am working on a school project that requires me to build a machine. I have designed the machine but I am stuck at torque calculation. The problem goes like this, the machine supposes to rotate a ...
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  • 21
2 votes
3 answers
419 views

Pivoting trailer gate on multiple axes

I am currently trying to design a rear gate to retrofit to an existing caged trailer (similar to image 3), with the goal of having a system where the rear gate can pivot down (on its bottom edge) to ...
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2 votes
0 answers
220 views

How to calculate torque requirement for vehicle with Mecanum wheels?

What are the changes specific to mecanum wheels when calculating torque requirements for a vehicle. I have the data for the vehicles mass, top speed and top acceleration.
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2 votes
0 answers
42 views

Epoxy/Adhesive to bond solid wood and acrylic

I am trying to bond solid wood with with clear acrylic, with requirement to able to withstand shearing force, not more than 6kg over an area of 100 sq.cm. Have tried to bond with result of the ...
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  • 21
1 vote
5 answers
350 views

What is a purpose of learning G-code?

I might be wrong here. The solid modeling done in CAD like Catia, NX, Solidworks,etc can be taken as input in CNC and the desired shape and size of piece can be obtained.The CAD itself convert the ...
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  • 143
1 vote
2 answers
82 views

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 vote
2 answers
115 views

Which frame is optimal for children's bicycle trailers? tubular or rectangular frame and why? [closed]

I need to construct a 3D wooden bicycle trailer for Kids. The weight of bicycle trailers must also be light! The Frame should be made of wood. what criteria should I use to construct a Frame,Children'...
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1 vote
1 answer
63 views

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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1 vote
1 answer
79 views

Bending moment when there are no constraints

I faced this problem in an old book (Hall Allen S., Theory and Problems of Machine Design; 1961) The answer according to the book is 592 [in.lb], but I think the bending moment should be 0 because ...
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  • 19
1 vote
3 answers
66 views

what to learn to design mechatronics device that move [closed]

I want to design an artificial leg for disabled people. The idea is design of a Device for patients with problems on one side of the leg from the knee down. This device first detects intent to move ...
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1 vote
3 answers
428 views

How much force/torque act on a wheel of a vehicle when vehicle moves a constant speed and suddenly got a bump or jerk?

I am working on disturbance rejection technique in a vehicle of a wheel. Suppose our vehicle moves with a constant speed 15 km/h. Since roads are uneven in nature, suddenly vehicle got a bump or jerk. ...
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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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  • 407
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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1 vote
1 answer
174 views

Hydraulic Brakes - Why motorcycle brakes more powerful than bicycle brakes?

I was wondering why motorcycle brakes have so much more stopping power than bicycle hydraulic brakes (Than can be found on mountain bikes for example). The rotor has a bigger size which gives better ...
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1 vote
1 answer
141 views

calculation of tension in curved chain for chain fountain (Mould effect)

https://royalsocietypublishing.org/doi/10.1098/rspa.2013.0689 A chain of some sort goes upwards, turns in a half circle (according to the drawn diagram), and goes back down. Focusing on the half ...
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1 vote
1 answer
41 views

How to constrain stepper motor inside case?

I have a stepper motor linear actuator assembly like this for example, but the stepper shaft seems able to move axially back and forth - hence when I change direction it has to do a few rotations, ...
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1 vote
1 answer
875 views

How do I find the vertical reaction forces?

The horizontal Force $A_x$ is easy but how did they get the vertical forces $A_y$ & $B_y$? I tried using similar triangles for the Force and length of the sides, somehow I can't manage to solve it....
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