/r/engineering

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r/engineering is a forum for engineering professionals to share information, knowledge, experience related to the principles & practices of the numerous engineering disciplines.

r/engineering is NOT for students to ask for guidance on selecting their major, or for homework / project help. Read the sidebar BEFORE posting.

If you see any post or comment that violates these rules, please report it so the moderators can respond in a timely manner. Thank you.

  1. No questions related to university, school, major selection, GPA, coursework, etc. NOTE: Asking for help on homework will result in an instant ban. DO NOT DO IT.

  2. No questions on "how something works" — try r/AskEngineers.

  3. All workplace topics and questions asking for career advice must go into the Weekly Career Discussion Thread.

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  • No misleading or sensationalized titles. All sources are subject to moderator evaluation.

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  • Crowdfunding: Must be relevant to engineering and submitted as a self-post (not a link). You are allowed one submission, and you must be active in the comments to answer any questions.

  • Submission Flowchart

    Comment Rules
    1. Keep the discussion civil. Overly insulting or crass comments will be removed. Multiple violations will lead to ban. Racism, sexism, or any other form of bigotry will not be tolerated.

    2. Be substantive. No low-effort one-liner comments, memes, or off-topic replies. Limit the use of engineering jokes.

    3. Do not comment outside your area of competence. If you do not know about a topic, do not attempt to answer somebody's question. If you paste a comment that appears to be from an AI source, it will be removed. Multiple violations of this will result in a ban.

    What is r/engineering for?

    r/engineering is a forum for engineering professionals to share information, knowledge, experience related to the principles & practices of all types of engineering: civil, structural, mechanical, electrical, aerospace, chemical, computer, environmental, etc.

    Questions about current engineering projects you are working on, how to interpret codes and standards, and industry practices are all encouraged. Engineers should help each other to make the world a safer and better place.

    Images and videos related to engineering are acceptable, provided they are relevant to engineering. Completed projects, destructive test results, and unique machinery and hardware are all acceptable and encouraged. Lead-in comments are required to provide context to the readers.

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    Pick an engineer from the list of volunteers below and send him or her a PM indicating that you would like to conduct an interview:


    Directory of Useful Subreddits

    Engineering Fields
    Engineering Topics
    • LearnEngineering: Learn & discuss engineering concepts
    • CAD: Computer Aided Design
    • CFD: Fluid Dynamics
    • FEA: Finite Element Analysis
    • PLC: Programmable Logic Controllers
    General Science
    Textbooks
    Other Links

    /r/engineering

    588,803 Subscribers

    2

    What is this Hinge Called

    I need to source this hinge and am coming up blank on what to call it. The tubing is approx. 3/4" OD and the tubing end of the hinge goes inside the tube. I am not certain on how it couples together.

    https://preview.redd.it/jub0502zdlde1.jpg?width=1512&format=pjpg&auto=webp&s=6e14a3463dec592f919eaba5672e060a4ca63641

    5 Comments
    2025/01/17
    17:51 UTC

    4

    Advice for Making Watertight Clear Cylinder

    I want to create a relatively large (~20'' diameter, ~10'' tall) cylinder that is transparent (for use in a laser system) and watertight (to serve as a tank). The base does not need to be transparent.

    These are uncommon dimensions and difficult to find a vendor that sells anything close to these dimensions. Some vendors like UVacrylic (https://uvacrylic.com/plexiglass/acrylic-tube) do offer open-ended tubes that I can cut to the desired height and attach to a custom base, but these are 1m long and expensive, so there will be a lot of waste.

    I'm wondering if anyone has advice or suggestions on how I can custom fabricate it? I have access to a machine shop, including a CNC machine. I'm also open to using glass, and outsourcing certain tasks. I have a budget of $300 but would prefer to get this done as cheaply as possible.

    One idea is to take acrylic sheets and bake it in the oven. Then bend it to the shape of a cylinder and use waterproof epoxy to seal it. Then finally, epoxy it to a base. However, I am concerned about the watertight-ness as well as the structural integrity due to the water pressure. Any help is appreciated, thanks!

    10 Comments
    2025/01/16
    23:27 UTC

    5

    Anyone in Industrial Automation?

    I’m specifically work for a distributor but our lines include robotics, motion & control, safety, RFID/Sensors/vision, pneumatics, linear actuators, aluminum extrusion, etc. pretty much covering anything on the factory floor.

    Anyone here in a similar industry or involved with it?

    19 Comments
    2025/01/16
    02:41 UTC

    1

    2/3 Stroke Linkage Question

    Greetings,

    I'm trying to reverse-engineer a machine for home use (please see attached video).

    I have a good grasp on the internal construction, except that the extension must be 2/3 of the total cycle (retraction being 1/3).

    I have a feeling this can be solved with a four-bar linkage, but I haven't spent enough time with them to know for sure. Perhaps there's another linkage I haven't considered?

    Any thoughts are appreciated, thanks in advance.

    1 Comment
    2025/01/15
    21:12 UTC

    2

    Woodworking screws in CAD

    Hi guys

    In EU, so no imperial please.

    When you design structures that use e.g. a metal frame to which a wooden panel gets screwed. How do you manage the details like holes (countersunk, regular, slot, ...) and wood screws? Are there standards you use for manufacturing in Europe and China? With bolts it's easy and built-in (currently using SW) but with wood screws I'm a bit lost.

    Thanks for any help!

    3 Comments
    2025/01/15
    17:56 UTC

    4

    Trying to identify this air flow tester

    I have run across one of these before in my search for CFM airflow testing. I found one very much like it in France, but with a different number of rings. There is one currently on eBay which is identical aside from the gauge. Does anyone have any information on this or a set of instructions?

    https://preview.redd.it/bsfyw398z0de1.jpg?width=3024&format=pjpg&auto=webp&s=b639ede1b2189ba2680a37ebfc827163c31816ba

    Airablo link

    eBay link

    1 Comment
    2025/01/14
    21:01 UTC

    0

    Here’s an engineering problem for you..

    I’ll provide below a short description of the problem with given circumstances and you come up with a solution you believe to be most cost effective and practical.

    A 40’ shipping container needs to be moved approximately 20’ transversely to its length. DL is 10kips (contents included) and currently sits atop 3 railroad ties.

    Conditions: The container is in a pasture full of grass with surface conditions slick enough to get a 3/4 ton pickup truck stuck (2WD).

    Railrod ties are $20 ea.

    It would cost $450 to have a piece of equipment come out and move it from the dealer.

    It would cost $700 to rent a t770 bobcat

    A gas 4cyl 1963 Ford 2000 tractor is available https://www.tractordata.com/farm-tractors/000/2/5/255-ford-2000.html

    And a neighbor with a similar tractor is also available.

    If the tractors aren’t able to pull it due to slick surface conditions as well, how would you move the container with cheapest option?

    You can ask whatever questions you want and they will be added to the post to help others.

    26 Comments
    2025/01/14
    19:47 UTC

    1

    Sources

    Hello everyone,

    I wanted to ask if anyone could recommend any good sources or materials for studying engineering mathematics. I’m looking for something that explains the concepts clearly and provides useful practice problems.

    7 Comments
    2025/01/14
    19:14 UTC

    7

    Weekly Career Discussion Thread (13 Jan 2025)

    # Intro

    Welcome to the weekly career discussion thread, where you can talk about all career & professional topics. Topics may include:

    * Professional career guidance & questions; e.g. job hunting advice, job offers comparisons, how to network

    * Educational guidance & questions; e.g. what engineering discipline to major in, which university is good,

    * Feedback on your résumé, CV, cover letter, etc.

    * The job market, compensation, relocation, and other topics on the economics of engineering.

    > [Archive of past threads](https://www.reddit.com/r/engineering/search?q=flair%3A%22weekly+discussion%22&restrict_sr=on&sort=new&t=all)

    ---

    ## Guidelines

    1. **Before asking any questions, consult [the AskEngineers wiki.](https://new.reddit.com/r/askengineers/wiki/faq)\*\* There are detailed answers to common questions on:

    * Job compensation

    * Cost of Living adjustments

    * Advice for how to decide on an engineering major

    * How to choose which university to attend

    1. Most subreddit rules still apply and will be enforced, especially R7 and R9 (with the obvious exceptions of R1 and R3)

    1. Job POSTINGS must go into the latest [**Monthly Hiring Thread.**]((https://www.reddit.com/r/engineering/search?q=flair%3A%22hiring+thread%22&restrict_sr=on&sort=new&t=all)) Any that are posted here will be removed, and you'll be kindly redirected to the hiring thread.

    1. **Do not request interviews in this thread!** If you need to interview an engineer for your school assignment, use the list in the sidebar.

    ## Resources

    * [The AskEngineers wiki](https://new.reddit.com/r/askengineers/wiki/faq)

    * [The AskEngineers Quarterly Salary Survey](https://www.reddit.com/r/AskEngineers/search/?q=flair%3A%22salary+survey%22&include_over_18=on&restrict_sr=on&t=all&sort=new)

    * **For students:** [*"What's your average day like as an engineer?"*](https://www.reddit.com/r/AskEngineers/wiki/faq#wiki_what.27s_your_average_day_like_as_an_engineer.3F) We recommend that you spend an hour or so reading about what engineers actually do at work. This will help you make a more informed decision on which major to choose, or at least give you enough info to ask follow-up questions here.

    * For those of you interested in a career in software development / Computer Science, go to r/cscareerquestions.

    11 Comments
    2025/01/13
    06:01 UTC

    659

    Google AI responses appear to be degrading

    172 Comments
    2025/01/13
    05:15 UTC

    9

    Converting roman concrete formula for cold weather environment

    I never use reddit, however a clients request has me stumped. They are planning a project to build a home using middle-eastern / roman building practices and techniques in USA climate zone 3-4. The plans for this are relatively sound albeit a bit strange for the region they have picked (namely a large courtyard) but have made significant efforts to accommodate for this. Their budget is essentially unlimited. One particular request that they have been an immovable object on is the composition or formula for the concrete used to lay the foundation, first story walls and facade. They are insistent that it is not just similar, but the exact same composition found in ancient roman architecture like the pantheon and whatnot (volcanic ash, quicklime, aggregate, pumice, etc.)

    I'm worried that it won't be as structurally sound as other concrete mixes, especially given a freeze-thaw cycle in northern climates. As ideas to perhaps modify or add a material to increase structural integrity?

    14 Comments
    2025/01/13
    03:45 UTC

    0

    Fuck, marry, kill: cast iron, HDPE and titanium

    Fuck, marry, kill is a type of question like "would you rather", except you have to choose what would do "fuck" (maybe do some side projects with, or some really cool shit), what would you "marry" (use for the rest of your life etc), and what would you "kill" (never use ever again)

    16 Comments
    2025/01/12
    15:46 UTC

    1

    Resources on the Magic of Engineering

    Hey all,

    I'm looking for resources (books, YT channels, twitter accounts) that teach the magic of engineering. I don't have a specify area of interest atm.

    Thank you!

    4 Comments
    2025/01/11
    23:34 UTC

    15

    What are the strongest and weakest points of this bridge?

    61 Comments
    2025/01/11
    19:45 UTC

    0

    What are the practical limits (size and distance) on launching a giant balloon?

    Totally serious here. I would say the requirements are 100-meter accuracy with 10-meter accuracy preferred. It needs to act like a water balloon, which means that it "explodes" on impact, releasing the water. Ideally it would be good to send it 10 kms, but let's say if it's not at least 1km it's probably not worth doing. Bigger is better, the equivalent of a helicopter water drop is the target I would pick.

    What are the challenges? Needs to be a material that will contain the water and not break in flight, while opening on impact without causing secondary damage. Needs to be a shape with a predictable aerodynamic profile, to minimize aiming error. Has to be able to be filled in minutes, and transported in bulk (along with the launcher) to a fill spot.

    I doubt this is a wholly original idea, and based on my search I don't see a great solution. What I don't know is how far people have pushed-- has it been tried & failed, does the physics just not work? Could you even employ something like SpinLaunch and have a range in the hundreds of miles?

    24 Comments
    2025/01/11
    18:02 UTC

    3

    Hoop Stress and ultimate failure

    I have a question. I have a cylinder with semispherical heads. Size is 140mm diameter, 350mm overall length, 210mm between the head seams. The vessel is a strap-restrained elastomeric bladder. Circumferential straps are of high strength webbing (UHMWPE/Dyneema), webbing width is 30mm wide x 1mm thick, spaced in contact side to side.

    Properties of Dyneema:

    Tensile Strength, Ultimate, 3500 MPa, 508000 psi ; (I de-rate that by 25% to 2,625 because the strands in webbing aren't parallel to the load).

    Modulus of Elasticity, 110 GPa, 16000 ksi ;

    Tenacity, 3.53 N/tex, 40.0 g/denier.

    Breaking strength 1640 DaN

    Working pressure 500 kPa (Design safe working 5x 2500 kPa)

    Hoop stress at working pressure, I should get Stress Sigma 35mPa and total tensile load 1050 kg.

    Hoop stress at design pressure (2500kPa) I get sigma 175mPa and load 53.535kg

    Where I'm running into trouble is backing that data into the tenacity/breaking strength of the material to select thickness of the webbing

    1 Comment
    2025/01/11
    04:49 UTC

    0

    I want to resolve your problems!

    Hey engineers! I am not an engineer, but it is a pathway I am very interested in. I love CAD design specifically. Enough about me though, I wanted to know if any of you all had any engineering “problems” you’ve had to solve. I want some real world situations that I can practice coming up with cad designs or modeling already thought out ones. Thank you all!

    17 Comments
    2025/01/11
    04:05 UTC

    6

    r/engineering's Monthly Jan 2025 Hiring Thread for Engineering Professionals

    # Overview

    If you have open positions at your company for engineering professionals (including technologists, fabricators, and technicians) and would like to hire from the r/engineering user base, please leave a comment detailing any open job listings at your company.

    We also encourage you to post internship positions as well. Many of our readers are currently in school or are just finishing their education.

    **Please don't post duplicate comments.** This thread uses Contest Mode, which means all comments are forced to randomly sort with scores hidden. If you want to advertise new positions, edit your original comment.

    > [Archive of old hiring threads](https://www.reddit.com/r/engineering/search?q=flair%3A"hiring+thread"&restrict_sr=on&sort=relevance&t=all)

    ## Top-level comments are reserved for posting open positions!

    Any top-level comments that are not a job posting will be removed. However, I will sticky a comment that you can reply to for discussion related to hiring and the job market. Alternatively, feel free to use the [Weekly Career Discussion Thread.](https://www.reddit.com/r/engineering/search?q=flair%3A%22Weekly+Discussion%22&sort=new&restrict_sr=on&t=all)

    ## Feedback

    Feedback and suggestions are welcome, but please [**message us**](https://www.reddit.com/message/compose?to=%2Fr%2Fengineering&subject=Feedback:%20Quarterly%20Hiring%20Thread) instead of posting them here.

    ---

    # READ THIS BEFORE POSTING

    ## Rules & Guidelines

    1. Include the company name in your post.

    1. Include the geographic location of the position along with any availability of relocation assistance.

    1. Clearly list citizenship, visa, and security clearance requirements.

    1. State whether the position is *Full Time*, *Part Time*, or *Contract*. For contract positions, include the duration of the contract and any details on contract renewal / extension.

    1. Mention if applicants should apply officially through HR, or directly through you.

    * **If you are a third-party recruiter, you must disclose this in your posting.**

    * While it's fine to link to the position on your company website, provide the important details in your comment.

    * Please be thorough and upfront with the position details. Use of non-HR'd (realistic) requirements is encouraged.

    1. **Pandemic Guidelines:**

    * Include a percent estimate of how much of the job can be done remotely, OR how many days each week the hire is expected to show up at the office.

    * Include your company's policy on Paid Time Off (PTO), Flex Time Off (FTO), and/or another form of sick leave compensation, and details of how much of this is available on Day 1 of employment. **If this type of compensation is unknown or not provided, you must state this in your posting.**

    * Include what type of health insurance is offered by the company as part of the position.

    ## TEMPLATE

    ### !!! NOTE: Turn on Markdown Mode for this to format correctly!

    **Company Name:**

    **Location (City/State/Country):**

    **Citizenship / Visa Requirement:**

    **Position Type:** (Full Time / Part Time / Contract)

    **Contract Duration (if applicable):**

    **Third-Party Recruiter:** (YES / NO)

    **Remote Work (%):**

    **Paid Time Off Policy:**

    **Health Insurance Compensation:**

    **Position Details:**

    (Describe the details of the open position here. Please be thorough and upfront with the position details. Use of non-HR'd (realistic) requirements is encouraged.)

    2 Comments
    2025/01/09
    07:01 UTC

    3

    Looking for light recommendations for syringe inspection

    Operators 100% inspect clear syringes filled with a water-like fluid. They use a white/black background with a 2000 lumen black light.

    We ran a gage RxR and roughly half the operators failed, the other half got 100% accuracy.

    21 Comments
    2025/01/08
    16:52 UTC

    9

    Cast steel porosity and density

    I'm repurposing some large 10,000lb cast steel weights for a project. They were in a deadweight transducer calibration frame, so I know they were 10,000lb (at the original location's gravity). They're very old, 1960's ish.

    Considering the parts' dimensions, I'm getting 0.26 lbf/in^3 (7.19 g/cm3). The porosity of this weight would be 8%. Is that something you would expect, or am I missing something?

    I have a little aluminum casting knowledge, but none with steel. Modern aluminum casting for industry uses lots of technology to keep porosity to ~1%.

    I realize the material and the times have changed, so it may be perfectly normal. Just trying to sanity check myself before continuing.

    Any casting engineers in here care to shed some light?

    6 Comments
    2025/01/08
    00:41 UTC

    2

    Prompt Engineering

    Really? This is a thing now? FFS

    12 Comments
    2025/01/07
    15:01 UTC

    10

    Help: Low Outgassing epoxy to seal between metal and PCB for vacuum sealing?

    I'm looking to seal between an aluminum flange and a PCB assembly that will pass thru the flange. This will act as a vacuum sealing barrier, and hopefully operate just fine down to 10^-7 mBar. Of importance for is low outgassing of the epoxy after curing (think NASA low outgassing, ASTM E595).

    Does anyone have any recommendations?

    22 Comments
    2025/01/06
    22:10 UTC

    1

    Weekly Career Discussion Thread (06 Jan 2025)

    # Intro

    Welcome to the weekly career discussion thread, where you can talk about all career & professional topics. Topics may include:

    * Professional career guidance & questions; e.g. job hunting advice, job offers comparisons, how to network

    * Educational guidance & questions; e.g. what engineering discipline to major in, which university is good,

    * Feedback on your résumé, CV, cover letter, etc.

    * The job market, compensation, relocation, and other topics on the economics of engineering.

    > [Archive of past threads](https://www.reddit.com/r/engineering/search?q=flair%3A%22weekly+discussion%22&restrict_sr=on&sort=new&t=all)

    ---

    ## Guidelines

    1. **Before asking any questions, consult [the AskEngineers wiki.](https://new.reddit.com/r/askengineers/wiki/faq)\*\* There are detailed answers to common questions on:

    * Job compensation

    * Cost of Living adjustments

    * Advice for how to decide on an engineering major

    * How to choose which university to attend

    1. Most subreddit rules still apply and will be enforced, especially R7 and R9 (with the obvious exceptions of R1 and R3)

    1. Job POSTINGS must go into the latest [**Monthly Hiring Thread.**]((https://www.reddit.com/r/engineering/search?q=flair%3A%22hiring+thread%22&restrict_sr=on&sort=new&t=all)) Any that are posted here will be removed, and you'll be kindly redirected to the hiring thread.

    1. **Do not request interviews in this thread!** If you need to interview an engineer for your school assignment, use the list in the sidebar.

    ## Resources

    * [The AskEngineers wiki](https://new.reddit.com/r/askengineers/wiki/faq)

    * [The AskEngineers Quarterly Salary Survey](https://www.reddit.com/r/AskEngineers/search/?q=flair%3A%22salary+survey%22&include_over_18=on&restrict_sr=on&t=all&sort=new)

    * **For students:** [*"What's your average day like as an engineer?"*](https://www.reddit.com/r/AskEngineers/wiki/faq#wiki_what.27s_your_average_day_like_as_an_engineer.3F) We recommend that you spend an hour or so reading about what engineers actually do at work. This will help you make a more informed decision on which major to choose, or at least give you enough info to ask follow-up questions here.

    * For those of you interested in a career in software development / Computer Science, go to r/cscareerquestions.

    16 Comments
    2025/01/06
    06:01 UTC

    8

    Measured force through rubber hole

    Hi everyone, I am trying to calculate the force required to push a stainless steel cuboid through a hole in another cuboid of neoprene rubber and can't seem to find a good formula to calculate it with.

    The data is as follows: It is a stainless steel cuboid of 0.04" (1mm) by 0.04" (1mm) by 0.32" (8.25mm) deep, the hole cut in the rubber is 0.023" (0.6mm) by 0.023" (0.6mm) by 0.32" (8.25mm) deep, it is a rubber cuboid of 0.197" (5mm) by 0.197" (5mm) by 0.32" (8.25mm). The exact material is ultra strength neoprene rubber with 70A durometers, 2,500 psi tensile strength, and a tolerance of -0.020" to +0.020" at 1/8" (0.125").

    T.L.D.R. ——-(Basically the steel is larger than the rubber by a margin 0.4, how do I calculate friction?)——-

    Suppose that the rubber cuboid is fixed surrounded by a steel rectangle.

    How much force in Newtons would be required to push this rod in accounting for friction and all, and what would be the formula to calculate it?

    Also, what would be the optimal shape if other than a cuboid to generate the highest amount of friction and therefore require the most force to push it in?

    Thanks! Hoping this enlightens me and others because I couldn't find a way to calculate this.

    18 Comments
    2025/01/04
    09:09 UTC

    0

    What's a good free (or very cheap) calculator iOS app akin to the TI-36xpro?

    10 Comments
    2025/01/03
    18:38 UTC

    7

    Questions about older engineering books

    I double majored in comp sci and accounting and am trying to self-teach myself engineering. I got some (older) textbooks from thriftbooks to give myself a bit of a crash course on just general stuff.

    Here is a list of the general subjects i got books in and the years that they are and I just wanted to make sure I wasn't going to read anything super outdated even though I am pretty sure alot of mechanical engineering has been set in stone for a very long time.

    Fluid mechanics (2005)

    Mech E design (1988)

    Dynamics (2001)

    Thermodynamics (2010)

    Mechanics of materials (2012)

    Machining fundamentals (1993)

    control systems engineering (2000)

    If im missing anything that is going to give me a gaping hole in my general knowledge which I probably am can yall let me know

    Thanks

    25 Comments
    2025/01/03
    16:41 UTC

    0

    Should I consider myself an "Inventor" or a "Maker"?

    I have been making smart devices with ESP32 boards, sensors, relays, LCD screens, etc. Recently I made my own smart thermostat for a natural gas heater in my detached garage. I design and 3D print my own cases and enclosures for these devices. I'm learning how to use KiCAD to make my own schematics and eventually make my own PCBs. I use SolidWorks and Inventor to make my designs. I code everything myself. I also have been dabbling with resin casting by making 3D printed molds and things out of silicone and urethane. I haven't sold any of these things or designs to anyone yet so I don't think I can consider myself an Inventor. Am I a "Maker"? Most of these things I've made are for my own enjoyment, or to make my life easier. A lot of times I just experiment to learn a new skill.

    13 Comments
    2025/01/03
    03:06 UTC

    18

    I Wrote a Handbook on Simulation in Python with SimPy

    Hi folks,

    I wrote a handbook on discrete-event simulation with SimPy, designed to get you building simulations using Python. Kind of like the official documentation but on steroids.

    I have used SimPy for over a decade. Discrete-event simulation is useful for modelling real world industrial systems such as factories, mines, railways, etc.

    My latest venture is sharing my know-how on how to do this.

    If you do get the handbook, I’d really appreciate any feedback you have. Feel free to drop your thoughts here in the thread or DM me directly!

    Here’s the link to get it: Handbook Link

    For full transparency, why do I ask for your details?

    Well I’m working on a full programme which will be all about real-world modelling and simulation with SimPy, and I’d love to send you keep you in the loop. If you found the handbook helpful you might be interested in the programme. That said, you’re completely free to hit “unsubscribe” after it arrives if you prefer.

    19 Comments
    2025/01/03
    00:14 UTC

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