Call for Engineers: Tell us about your job! (2020)

I found lots of catalogues and engineering tables that help you find the dimension for a ball screw that you need for your project. I didn't manage to find any that do the same but for bi-directional ball screws. Are there any? Is the addition of the second nut complicating the calculation beyond simple set of instructions?

Just to be clear, I mean a ball screw with 2 nuts going in opposite directions, not a double nut ball screw. I think I should be able to just calculate it the same way as a one nut ball screw, especially with the middle being held in place by a bearing, but this I'm designing it for my thesis. There should be differences in torsion etc. and I'm not sure how to account for that.

Any info is greatly appreciated.

I live in a dorm room of my college in an extremely hot and humid city with temperatures exceeding 40°C. Our hostels/dormitories don't have the capacity for ACs in the room and thereby do not allow it. However I managed to fit in a portable air conditioner with the exhaust pointed towards the window and it has a built-in pipe which blows out cool air into the room. I have added an additional longer pipe on top of it to allow it to directly blow air onto me since it's not capable of cooling the entire room. I need advice on how to increase the pressure or flow of the cool air coming from the pipe. My understanding goes along the lines that if you squeeze/pinch a water hose at the end then even if the originating water pressure is the same, the output is higher. Similarly, since air is also a fluid, can I do something within the pipe to increase the flow or the pressure with which the air comes out?

Hello,

I've been trying to calculate the required force for a given change in tension and subsequent change in pitch using the vibrato arm on a guitar with a floating bridge

The bit that i'm finding tricky is understanding the following interaction:

(assuming a correctly setup guitar) the bridge at rest is in its neutral position, that is to say, the string tension (on the front of the guitar) is equal to the spring tension (in the rear of the guitar); not only that but the tremolo arm/whammy bar provides a mechanical advantage but force is being applied in a direction that is approximately perpendicular to the load

I believe a guitar with a 25.5 inch scale length (647.7mm), gauge .010-.046 strings and tuned to E standard will produce a tension roughly equivalent to 47kg

I'm majorly struggling to reconcile all of this with the fact that moving the tremolo a little bit when in its neutral point is super easy and requires very, very little force and i can't figure out how the equal spring/string tensions and load perpendicular to effort are affecting the dynamic (if at all)

The distance from about tip of the tremolo (point of actuation) to its mounting socket on the bridge is 140mm - the distance from the mounting socket to the pivot point of the bridge is 20mm, as is the string anchor points to bridge pivot point too e.g. string anchor points are collinear with the tremolo mounting point for anyone that wondered.

Can anyone shed some light on which way is up for me at the minute? I can't seem to intuit even a little of what is going on here :(

For context, this prototype is supposed to be a streamer, forming a water screen for a projector.

Images: https://imgur.com/a/OzpAF7s

Video : https://streamable.com/d7znwp

I have been using GDTbasics.com but I am struggling to gain a cohesive understanding between all the GDT rules. I have tried digging on YouTube and linkedin learning but it is still confusing sometimes and the information is not as structured as college a course. Is there a good textbook or an affordable online course available?

I have a lidar, one found in vacuum home robot. The rotating lidar head is powered by an inductive coupler. The system is DC (battery power source).

1. Considering that one coil rotates, is DC capable of generating a DC current at the other end? I understand that AC is necessary for stationary power transfer.

2. I am able to drive the rotation of the head. Could that help me figure out whether it is DC powered, and what voltage should be applied to have something like 5V at the rotating end?

I have included a picture of the board and the inductor terminals. The inductor pins are those identified by P1 (top left). It looks like one of the pin is connected to a bunch of transistors (Q2-3-5-6 - not 100% sure all). Could that be a rectifier there?

Edit: I used an oscilloscope and couldn't measure anything when rotating the head... Like it should show something right?

I want to build some sort of robot that massages my shoulders similarly to human hands. I have some programming skill and I'm good at math so I figured maybe it'd be challenging but I could be able to figure it out? Have never really tackled a mechanical engineering project like this before, so I thought it'd be good to ask here first. I thought about maybe attaching some sort of sensors to someone's hands as they're massaging someone's shoulders and using that data for the program that will control maybe a microcontroller for the system? I don't really know where to even start with the hardware to be honest, so I'd appreciate if someone could give me an overview of some approaches on what kind of hardware I'd need and how I'd go about integrating the software. I'm hoping I'm not biting off more than I can chew on this as a beginner.

Just learned about graphene aerogels, which Wikipedia claims have a density of 160 g/m^3 (in vacuum) and Young's modulus of 50MPa. So if you wrapped a sphere of this in plastic and pumped all the air out, it would float in air. Can anyone do the math to see if it would crush or not?

Sadly due to private life issues I could only begin working on my thesis a bit late into the semester. It's not really a big deal, I can work really efficiently under pressure and I already have the plans and the 40 or so pages of the thesis where I describe my process of designing and the sizing of the systems. The only thing really left is the literature review. I would be happy for anything, case studies on wineries, technologies used in wineries etc. I know I can google, and I'm doing that as well, but I tought this would be a great place to ask! Mainly from an HVAC or water/sewage point of view would be great.

Sorry if my post is out of place! I used the "Mechanical" flair, because i'm a mech eng, but i don't really know in which category my field falls in other countries.

Btw the deadline is the 29th of april but I only need to write 15 or so pages for the literature review.

Thank you in advance.

Edit: I'm located in Hungary, Europe

Hi Wizards of the Internet,

I am looking for requirements around around screen freeze/flicker. This can happen when a video card can't keep up with a game, or when your streaming tv loses internet for a some period of time. Is there a measure for what is the maximum number of frames/freeze to be perceptible? Is there a specification for maximum allowable time for a freeze in a military application? In a aircraft application (like ATC or similar)?

My struggle is when I am searching for freezes I get thermal requirements, and there is nothing for dropped frames or other terms. If there is a better term to use for search, let me know.

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Can I use a sound generator in a chamber that ranges from 0 to 10°C for an experiment on fruit ripening? Is there a risk of damage? It would stay inside the chamber for three hours for two weeks.

I would like to have a short DM conversation with someone to see if they think it is feasible to create a coating for tennis or pickleball courts which would temporarily, reversibly and repeatedly change color at the impact spot of the ball to help players determine if the ball landed in bounds or out of bounds.

My research indicates it might be possible with current tech but I am not finding specifics or a path to actually proceed and don't have access to (or understand) all the latest literature and research.

Happy to pay someone with knowledge and expertise for their time.

Heated debate with coworker surrounding what construct is more an engineering marvel. Take it as you will and respond as you will, no right answers!

I'm using a clip-on constant force spring to pull a trolley down a track. I'm already using the lightest COTS spring I can find on McMaster (0.2lbf), but the acceleration of the trolley is still too great. (it's very light). I need a way to control the acceleration of the trolley along the entire length of the track. The movement of the trolley is subject to stopping at any point along the track, therefore, at any point along the track, it can accelerate from 0. I've considered rotary dampers, however, this would require that the track is redesigned such that it has teeth to engage with the damper. I'd like to avoid this if possible. Are there any other simple COTS solutions that I can use to control the acceleration of the trolley along the entire length of the track?

Hi everyone,

We run a clothing vintage store where we each piece is unique. We sell both online and in the store. Our problem is that it can be hard to find specific items physically in the store that were sold online (and should be taken out of the store and shipped). That can be quite time consuming. So I was wondering if we could use a indoor positioning system where the pieces that we put online would have tags attached to them which would allow us to locate them precisely in the store quickly.

It seems as if there is either BLE or UWB as a tech option, but it seems as if BLE is not precise enough (should be less than 1 meter accurate). Do you know of specific products that could help us with this?

One problem is the price, as we have several hundred products online the tags would need to cost less than say 3 dollars otherwise the investment would be too high for us right now.

Worst case we could just try to find cheap tags that make a noise when we "call" them, but I hope that there would be something beyond that since we have music in the store and it would be great if the employees can collect the clothes during their regular shift (and the beeping might annoy customers).

I would be glad over any suggestions :)

Hopefully this type of post is allowed: I'm not an engineer but I play one in bed when I can't fall asleep for hours. I've wondered if you could somehow convert energy to lift weight and when power is needed, allow the weight to fall and through the use of some mechanical transfer, spin a magnet to generate electricity.

I'm operating on the assumption that the energy needed to lift the weight would equal the same energy generated by the weight falling (save for heat loss due to friction)? If this is the case, could ultra dense (wet sand, or denser?) weights be used to store energy in a practical application? I imagine a dam spinning a turbine which, through the use of gears, slowly lifts a set of weights (or even a wind turbine or PV panels using electricity). And through the use of clutches and gears and mechanics I'm not totally sure of, when power is needed, the weights fall just enough to generate the electricity needed.

I guess my question is, why wouldn't this work? Or why hasn't it? Is the weight/height needed too large to store a quantity of electricity that would be worth the build? Would too much energy be loss in the transferring/friction? Is there some other law of physics this layperson is not considering? Or is it really a law of economics?

Edit: Thanks to some suggestions, I read about Energy Vault, and why they later gave up on the idea.
https://www.canarymedia.com/articles/long-duration-energy-storage/why-energy-vault-went-from-disrupting-batteries-to-selling-them

Example, you scale an F1 car to 2x size. would it be significantly faster?

(Side question) If so, why hasn’t the land speed record been beaten by a very large car?

I've been hearing about droughts and that one of the main sources of inefficiency in dam lakes (ex in California or in Mexico City) is that a lot of it is evaporated. Is this true? And if so, how effective / costly would it be to cover the lakes with like, a giant plastic bag?

I recently finished high school and will be starting a degree in electronic engineering soon. I am looking for something cheap to build so that I can deepen my understanding and get a bit of hands on experience. (also, i am bored.) Preferably something that can be used in daily life.

Experience: I have a little bit of experience with very simple circuits and have some theoretical knowledge of hardware and components and high school level physics. I know a little bit of basic python.

Budget: My ideal budget is $ 20 but could be stretched to $ 50(I know it is way too cheap but yeah)

Tools: I have a soldering iron, a pair of pliers, screwdrivers, screws and nuts

I also some good quality wires and some pvc pipes lying around. I have a few parts and covers of old phones, an induction, a few broken watches, a few small magnets and old toy cars lying around(if these could be used) and lego

Some more parts I have: a few leds, five dc motors, 3 switches, a mini fan(not sure what it is called exactly), some copper wire

So I see car manufacturers advertising that their car has a Continuously Variable Transmission, but then in the next breath, say it's a 6, 7, 8, 10, 12, etc speed transmission.

Isn't the point of a Continuously Variable Transmission that it's Continuously Variable, and there is no set speeds?

And wouldn't setting speeds mean that you end up with defined wear points on the drive cones if it walkways goes back to those points?

One like this: https://img.fruugo.com/product/2/31/332174312_max.jpg

I understand that there is a (metal?) membrane that oscillates at a high frequency and that this somehow generates the mist.

But how does the water come from the bottom side to the top side of the metal sheet? Are there tiny holes in the metal? Or is there a gap that opens and closes as the sheet oscillates?

If so - how wide is this gap / are these holes and by what force is the water moved to the side where it's atomized?

Right now, air ships achieve buoyancy via balloons of helium, and formerly they used hydrogen. But helium is not renewable and hydrogen is dangerous. Would it be possible to build a rigid vessel strong enough to resist implosion when evacuated, but light enough to achieve buoyancy via vacuum? What would such a vessel entail?

Original post, https://www.reddit.com/r/AskEngineers/s/7t9BwFinGj

There is a hole. Fully closed the hole leaked.

Our welder suggested jb weld. It worked. Only needs to hold 20 psi of nitrogen.

McMaster never emailed me back. Didn't worry, I won't let the cold shoulder keep me from ordering parts every other week.

Have a good weekend y'all.

I'm working on a prototype project that will have two people sitting in an uninsulated plywood enclosure about 200 cubic feet in volume (Roughly 5' tall, 5.5' wide, and 7.5' long). They will spend a couple hours at a time inside, and there will be some small electronics operating in the enclosure as well. Nothing extreme, mainly 4 or 5 monitors and maybe a small form factor computer or two. The whole assembly will be in an air conditioned area and we would like to utilize the conditioned air to keep the inside of the enclosure comfortable. My question is are there any general guidelines for such a situation? I haven't found much info on human comfort, just safety recommendations. I don't really need a super detailed analysis, I just need to keep the space at room temp/ humidity. Is there a specific number of ACH that should work? Would a bathroom ventilation fan with the proper cfm to achieve this theoretical ACH and a separate intake vent on the other side of the enclosure work, or should we mount a fan or two blowing air into the space with exhaust vents opposite of them? Very generic questions, I know, but hoping someone can provide some direction or insight. Thanks!

Does anyone know of alternative ways to measure the phase compression of a mixer? Looking for a good alternative to compare against the PNA Phase compression measurement option?

Hi Engineers, after looking at the James Webb telescope and seeing how its sun shield works I was wondering if a number of them were built and some how parked up between us and the sun could this be used to cook the earth? Similar yet very different to Mr Burns device 😂

Could the shields be made larger, maybe like roll out solar panels and at a distance far enough away that it would provide some cooling?

I appreciate it would be able to cool by a lot. It I would be a start.

I'm looking to see if there's a relatively simple way to quantitatively express the benefit of a suspension change I'm looking to make to my car. Say there's a crappy road that I hate driving down because I can feel how bumpy/bad it is from the driver seat. I'm hoping to reduce the overall effect of these impacts by replacing worn bushings in my suspension, or getting re-valved shocks, or something along those lines. I'm interested in taking before/after measurements so I can objectively show the difference this change makes.

Is there a measuring device you would recommend that would be well fit to measure this impact, from the drivers' seat?

I understand why you need draft angles for plastic injection molding, you want to be able to extract a part easily without damaging it or the tool.

But what if I want to make a perfect cube with all right angles. If I add even a small draft angle, won’t that mean it won’t come out as a cube? And instead will come out as something really really close to a cube, but not a cube because it doesn’t have all right angles?

I feel this is such a dumb question because I can’t easily find this answer online so bear with me please