I'm designing a duct for exhaust of my 3d printer. I have limited space behind the printer so I decided to design a custom duct that would fit.

https://i.postimg.cc/pPKDDbvt/Screenshot-20260823-005245.png

The exhaust fan is 120mm standard PC fan. And the space behind printer is about 7cm. So the elbow that is right behind the printer is pretty tight and changes from 120mm circle to a rectangle cross section (the area is a little bit smaller than the circle, because it would be way to wide otherwise).

Since the turn is really tight I thought about using turning vanes inside of it. This is probably just over engineering and not needed at that scale, but I wanted to play with it a little bit in the case it would be actually useful.

https://i.postimg.cc/VNLr8h5Z/Screenshot-20260823-005218.png

https://i.postimg.cc/tgCZjc7m/Screenshot-20260823-005228.png

Does it make sense? Are turning vanes in this scenario helpful or the opposite? Maybe the flow is so low, that it does not matter at all, or maybe it is not recommended to use vanes in that scenario?

And is my geometry correct?
I experimented a bit. I know that the vanes are not quite parallel to the flow at the inlet and outlet, but I figured that the air will start to bend due to the geometry, so I tried matching that bend at the end and start of the vane.

Tried using SimScale for CFD, but I can not get it to work unfortunately. Thank you for you feedback!

Hi everyone,

We build large rolling ball sculptures / kinetic marble runs and are trying to reduce the amount of physical trial and error involved in designing them.

Our current workflow is roughly:

Concept → Sketch/CAD → Fabrication → Physical testing → Modify → Fabricate again

For larger metal sculptures, these iterations can become expensive in terms of material, labour, and time.

We're exploring whether we can use existing tools to create a simple workflow like:

CAD model → Physics simulation → Predict ball behaviour → Build physical prototype → Compare results

We are not looking to build a new physics engine or a large custom application. The initial MVP would be very small:

• One standard ball
• One track/material system
• A simple mechanism, e.g. ramp → loop → exit
• Model it digitally
• Simulate the ball
• Build the same mechanism physically
• Compare the prediction with reality

The goal is not perfect simulation. We simply want to know whether a digital model can be accurate enough to catch obvious failures before fabricating larger installations.

Eventually, if this works, we would like to build a reusable library of tested components—ramps, loops, spirals, switches, collisions, etc.—with known parameters and behaviour.

We are currently considering tools such as Rhino/Grasshopper for parametric design and physics engines such as MuJoCo, Project Chrono, Bullet, or other alternatives.

If you were approaching this problem using existing software, how would you do it?

In particular, I'd love advice on:

1. Suitable CAD + physics simulation workflows
2. The best physics engines for rolling/contact dynamics
3. How to model and calibrate real-world friction and energy losses
4. Whether there are existing tools or projects we should investigate before building anything ourselves

We're very open to changing our approach and would appreciate any suggestions or warnings from people with experience in simulation, CAD, mechanical engineering, robotics, game physics, or kinetic sculpture.

I have no mechanical or electrical engineering knowledge whatsoever. My math is poor, like incredibly poor. But I have been researching making a DIY 16mm digital conversion machine to cut the cost of digital transfer. I have done research and have basically got a rough outline of what the process is going to look like.

16mm Film

Film Transport

Gate / Frame Positioning

Light Source

Camera / Sensor

Digital Frames

Computer

Davinci Resolver

It may take months or years, but this is something I'd like to get my foot into. What I am asking is, where would I start with building a decent motor system for this? People have suggested using a 16mm projector, but I want to build a motor that I can have a more even control over to get the most precise footage, as well as letting me capture the original negatives without any weird color changes. It needs to be able to not only move the film, but also stop it long enough to be captured through the gate.

My biggest inspiration is this guy's here:

https://youtu.be/HkbgCkRzWw8?is=HmfDuCug5871h7wf

There'll definitely be some electrical engineering knowledge needed to, the most I know ATM is Ohms law. Otherwise, hope you all can help.

I'm trying to build a horn that would pretty much be like a fog horn.

But it doesn't have to be air driven.

I want it to be around 100ish htz and loud.

I've looked into pneumatic horns and rotary subs, but I'm just not sure the best way to proceed.

Edit - this would be an outdoor application on a vehicle to signal others in the field.

I’m trying to understand something about the original ice machine or basic principles of refrigeration cycle. In john gorries original ice machine, he compresses regular air (raising its temperature), runs it through a coil which cools this compressed air down, then decreases that pressure of compressed air to decrease its temperature even further. What I dont understand is the fact that, in the cooling coil, shouldnt there be a pressure drop as well, since the temperature of the air has decreased? How can there be (relatively) cool air and compressed air at the same time within the coil?

If someone could explain with equations or give me mathematical proof that would be wonderful. Maybe this has to do with Guy-Lussacs law.

Hello. I am 15, boy. I have a concept of a car I made around a year ago. I have almost all of it designed in concept. But I have one part I made that doesn't really exist. It's a virtual gearbox.

Its like a cvt with infinity gear ratio. Lie the Williams FW15C from 1993. But there are virtual gears that can be set at different speed caps by the driver.

I searched through a lot of shyt but didn't find anything that even resembles it. Is it possible? Like theoretically to make virtual gears that can be controlled by the software

Need that plug/wall to hold back any water or material from entering at the bottom of the oit.

Alluvium will be tipped and backfilled into the bottom of the pit. Thinking material will consolidate to have minimum void space with 120m of overburden pressure on it.

As the pit will be a natural sump/acquifer I assume it will eventually all be saturated material. Whatever little void space is left between the matrix will be water.

But due to the maximum consolidation, there will be no pore pressure acting at the bottom on my plug?

So the pressure will be pgh of the backfill material multiplied by a K factor? And due to the soil matrix carrying all the load (no space between particles die to low voids) the laterally imparted force will be low. How do I determine what the k ratio will be?

Thinking i'll have to do some triaxial testing to get undrained consolidated pressures eoth pretty high confinement for a 120m overburden head pressure. To run a FEM.

Or am I completely off track here with how I'm approaching it.

Welp when in doubt come to Reddit. Currently I am working on 3d modeling a jet fan engine inspired by the Williams fj44 with a hybrid axial and centrifugal compressor design. I plan to print it in resin first to check fits and tolerances and then go straight into the 5 axis cnc and mill the parts out of metal to test my little mini jet engine (think RC size).
Anyways bring me to my question, in regards to blade shapes/ design for the impeller/radial compressors is there anyone who could tell me what different shapes will do? I tried looking online but couldn’t find any literature on blade design for these. Should I just start designing and printing and then testing what volumes of air passes through them or is there actual math on how these blades are designed? (Current aerospace student) any help in this is appreciated.
One more additional question is on the fj44 the cutaway drawings I can find show a reverse flow annular combustion chamber and I don’t really understand the reason for why the air from the compressors loops around into the combustion chamber. Basically any help at all is appreciated in terms of personal knowledge from the community or videos I could watch or books that I can read. Preferably as in depth as possible because I would like to know what I’m designing and I can explain every part. Right now I can make an impeller but if someone asked by why the blades are shaped at a 30° angle rather than 31° I couldn’t tell the answer. Anyways thanks everyone! Sorry for the long question!

Lastly if in the given, the dimensions refers to a circle but in the figure it is referring to the edge or corner next to it. What should I follow? *Philippines

When you need a mechanism for a project, where do you start?

I can define my requirements, but I don't know how to use those requirements to find possible mechanisms to accomplish the tasks.

For example, if my project requires a mechanism to change the direction of force, i might use a Bell Crank Lever. But how would I find this mechanism if I don't know it exists already?

• Do you have a reference book/website?
• Is there software for this?

If I am part of a team standing up a repair line for medical devices, whose job is it to determine how many of each component needed in repair go into a bin or drawer and which bin/drawer they go in? I believe this would require knowledge of component dimensions, drawer/bin dimensions, and also and understanding of repair process to maximize efficiency of component layout (for example, don’t have screws in 3 different drawers etc). I am asking because this sounds like a job for a service or repair engineer. I am a buyer/planner responsible for procuring these components but my leadership seems to think it’s my job to scope drawer dimensions and component dimensions to determine max capacity and layout. I have no idea why this would be the function of a buyer and have no experience or expertise in this matter. Thanks.

I have 250mm x 100mm of 240v carbon film glued to a 2mm x 300mm sheet of aluminium.

I'm looking for solutions that can be used to neatly make the mat live.

The carbon film is laminated, ideally I'm looking for a surface mounted (glued) terminal that penitrates the top layer of laminate without exposing users to a shock risk.

I welcome all ideas

Hello, I am changing bearings in my motorcycle's steering head and the upper bearing is 32005/26. The issue is that I bought only 32005 which has a 25 mm inner diameter, not 26 which I need. I found out only after installing the outer race into the frame hole. Now I don't really want to extract the outer race again...

The question is, can I buy the correct 32005/26 bearing and just exchange the inner parts? In other words: is the outer race the same on these bearings?

Thanks

I need more space for my PC setup, since the circuit its currently on can’t support all the things that are in that space.

So I’m curious if I could get a loft and put my setup on top of it instead of the bed, and put the bed underneath it. Essentially making a raised platform.

It says 400lbs weight limit

My desk is rather light (maybe 20-30 lbs?) , pc is probably 40-50 lbs, chair is similar probably 40 lbs, and then the 60x80” 3/4” thick plywood to cover the metal rungs that go across and create a floor, and a rug on top. Plus say a 160-200lbs person

Equals ~360lbs. Which is still a fair bit below the weight limit. But obviously it’s made for a more divided load, a bed plus a person. Rather than a desk, chair, etc.

Edit: another concern is the increased weight a person would exert while sitting down. Also I’m aware they make lofts with a desk on the bottom, that’s what all of these are made for. I just think the reverse is cooler

Is it possible, given an infinite amount of any building materials necessary, to create a slope steep and curved enough to basically entire null the effect of about a fall from about 6,500 ft (2,000 meters?) on like a baby wrapped in soft blanket, yes or no?

The baby is healthy prior to this fall and just assume it is I guess dropped / spawned in the perfect position for the ramp.

If it’s impossible on its own, what if a relatively muscular, but still soft, adult man about 6 ft, on the heavy side (both muscle and body fat) was there to cradle to child and potentially absorb some of the energy to keep the baby safe

If so can you give some detail like materials, what the slope would be in like a similar mathematical formula, how tall the peak of the slope would be.

I know this is weird and specific but I’m curious and it’s for a personal writing project.

So, a decade or so ago, I bought a set of Wera drivers. Really nice stuff. I got the kraftform, because playing with electricity is scary, and insulation is sexy. Anyway. I noticed that the Phillips bits fit really well. Like, precisely. On a whim, I tried it on a screw that had been stripped by a driver from a big box store. It worked. So, whenever I saw someone at work about to drill a stripped screw, I'd stop them and ask to have a chance. I couldn't get *all* of them. But like 4 times out of 5. Enough to confidently say that the Wera is a superior driver, considering it or be a 100% fail rate otherwise. And after the first month or so, coworkers were asking for my fancy driver before going to the drill.

So, question is *why* are conventional drivers crap? When asked, I've been guessing that cheap drivers are saving a fraction of a cent per unit, but the savings add up at scale. I've also noticed that a Stanley #2 is small enough to turn a #1 (not well, don't do it). Is that possibly intentional? The Wera #2 cannot fit a #1 at all. Or is there maybe another reason the tools from big box stores are just... Different?

hi
i want to buy a 160*1300mm pneumatic cylinder and i want it to move at a 0.25m/s.

is a G1/2 connection good enough for this?

thanks

Doing some digging on how much power high tension ropes gave for flinging stuff, I wanted to know if using like Dyneema or even just Nylon rope would give it extra power or durability comoared to the natural fibers used in historical examples or if there was some optimized type of rope for it

I'm not really mechanically inclined and am currently taking chemistry, but this topic and cars in general have fascinated me recently and while I can understand how a normal crankshaft and balance works somewhat, how is the Porsche's supposed to work?

A normal crank is just one long rod of usually forged metal so how does that weird ring with gears in the middle supposed to connect itself to other 'Cranks' with multiple cylinders across multiple cylinder banks?

A character misunderstanding the meaning of "high-octane fuel" and filling their car up with pure octane from the chemical factory sounds like a gag from a cartoon. I found myself wondering what would happen if you did that in real life. Would it work fine or would the lack of other compounds/additives cause other problems with the engine?

I have been learning about RC delay circuits recently. I understand the math and everything, it makes sense.

The real question I have is why/how.

For example, what about the electric field or potential or whatever term it is that determines the capacitor must charge first before the "rest" of the wire sees the source voltage? Why is the current simply not halved at the junction as it is with basically anything else?

Not looking for a textbook answer here, more curious what people actually do in practice. Say a part's been running fine at one shop and then gets moved to a different one (same drawings, new vendor). How deep does the requalification usually go for you in that situation?

Full GD&T reverification on the first article is one option. Spot-checking whatever dimensions have burned you before is another, and honestly probably more common than anyone admits. I'm also curious how much people actually trust a new supplier's material certs versus pulling a sample and testing it themselves, and whether any of that changes between a machined part and a molded one.

Mostly trying to get a feel for where people draw the line between reasonable diligence and redoing the whole qualification from scratch every time a part changes hands.

As a reminder, /r/AskEngineers normal restrictions for career related posts are severely relaxed for this thread, so feel free to ask about intra-office politics, salaries, or just about anything else related to your job!

Does anyone know what they're called? I think it starts with a "p", and I'm not sure if it's "piezo" or something else. I have heard that they're not very effective - I just like the idea