# Questions tagged [mechanical]

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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 ...
• 2,155
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 ...
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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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 ...
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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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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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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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 &...
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: ...
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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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 ...
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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157 views

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 ...
• 131
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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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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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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### 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?
• 121
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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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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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 ...
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 ...
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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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 ...
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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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 ...
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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### 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 ...
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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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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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 ...
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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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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### 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 ...
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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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 ...
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.
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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1 vote
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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1 vote
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 ...
1 vote
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'...
1 vote
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 ...
1 vote
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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1 vote
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 ...
1 vote
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
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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1 vote
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
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 ...
1 vote
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 ...
1 vote
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....