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

The US has spent billions over several decades trying to build mid-phase interceptors for ICBMs.To this day it’s still considered highly unlikely we could stop a significant attack.

I’m imagining a space based satellite system resembling a THAAD battery. As a lay person, it seems like it’d be easier to hit Phase 2, mid course missiles in space, from space, instead of ground launched options.

As engineers, what are the biggest challenges to doing something like this? Are there reasons it wouldn’t be feasible?

Hi, my name is James.

I could use some help, I'm working on something cool I'm trying to build a itashi (cringe worthy car) but at scale. Specifically a model scale of 1/24th scale.

I bought this model kit last year to do some experimenting with. I wanna be able to engineer a safe and functional battery operated LED light system.

I could use some help, I thought maybe. Fairy lights, but I'd rather be able to control the color with a remote, although I'm willing to tried to single color use.

So what I specifically more so need help with is what kind of LEDs can I use? I thought maybe strips and using flat connectors and wiring the system to a watch battery (CR type) and placing it in a plastic 3D printed case inside the chassis of the car, either in the hood where there is 80% free space or between the layers.

If anyone can tell me where I can look, what type of material I need, what examples can be visual shown, especially diagrams and video, as well as the safest method to hook it all up, id appreciate it.

Heard about a salvage operation in the area where I live, recovering a barge from 30-40 meters after a year, do fully submerged structures corrode at that depth, if so how fast?

Hello all. I am working on a problem involving a cylindrical US transducer designed for radial emission. Positioned vertically (axial length perpendicular to the ground), the transducer emits energy circumferentially in 360° from all points along its curved, axial shell (Surface Area: 37.699 mm^(2)). Power is supplied continuously for 10 seconds to the transducer and distributed uniformly across this curved emitting surface. ~50% of the electrical energy input is converted into heat, and the remaining ~50% is converted into mechanical/ultrasound energy.

  The transducer dimensions are as follows: Axial length/height = 6 mm, radial length (non-emitting diameter) = 2 mm, Radius of curvature = 1 mm. The transducer operates within a biological lumen (37°C), held coaxial with the lumen by an inflated cooling balloon. The balloon circulates cooled normal (0.9%) saline of known volume and flow rate. Wave propagation from any point on the transducer’s emitting surface travels radially through: (Medium 1: 4.2 mm of cooled, circulated saline), (Medium 2: 1.3 mm), and thereafter through (Medium 3). The material properties for all media (e.g., acoustic impedance, density, speed of sound, etc.) are well-defined.

  I am seeking advice on physics-based approaches, simulation tools, or accessible models capable of accommodating radial ultrasound distribution from a curved surface, fluid circulation’s impact on wave propagation in Medium 1, and propagation through three homogenous, but distinct, media. Importantly, I aim to avoid reliance on advanced coding or scripting. A practical, cost-effective solution suitable for academic or small business use is especially valuable. Any guidance – whether through simulation platforms, existing models, or expert recommendations – is immensely appreciated. Accurate modeling of wave propagation and energy distribution is vital and thank you very much for your time and any assistance!

The engineering club at my University will be presenting at an engineering event(mostly curated towards kids but everyone is welcome) next year and we’re trying to brainstorm things that we can present. Our main goal is honestly teach kids about what engineers but not let it be super boring.

Hello engineers! I'm looking for a product that will sit on floor or mount on a base, to whose top I can attach a device weighting approx. 4lbs and is roughly a 6" cube. I need a range of height adjustment of 24" or so. Also pan/tilt/ball motion at the head. Most important is it needs to lock once in position. While the weight of the device on top is not much, it contains a small motor which will have a pendulum action and there will be lateral forces of up to 15lbs.

Ideally, I'd love some sort of articulated arm, but it may have to be a behemoth in order to resist that level of force extended to 24" or greater.

Of course in the end I am may be forced to use a more traditional tripod with ball type head which is fine. I just thought I would ask about other options I may not be aware of.

Thank you so much!!

My idea is to use a cardboard box to be able to link one 6" inline duct fan with two 4" carbon filter canisters, and have a flat filter (mpr2200 or HEPA) in the box separating them, which will further filter the air and especially take out any carbon dust coming off the canisters themselves.

Image of my proposed design here: https://imgur.com/a/ASoY9r3

I am looking on any expertise on whether this works, will be effective, might be dangerous, etc - and how to possible do it better.

It is based on the "AC Infinity - Duct Accessories - Air Filter Box"
https://acinfinity.com/air-filter-boxes/
(which may not actually be for attaching a canister filter at one end and a fan at the other?)

My primary design modification ideas:

• use a cardboard box, not metal
• use either a MPR 2200 3M Filtrete or HEPA filter in the box
• downstream side of box: make a 6" hole, for inline fan (402 CFM with speed control)
• upstream side of box: two 4" holes, each with 4" carbon filter (max 195 CFM)

Purpose:

• filter reduces any carbon dust coming off of carbon filters (it's unclear if this is necessary?)
• box allows for the use of one 6" fan with two 4" filters rather than needing a seperate fan for each carbon filter

Questions:

• how much CFM reduction is likely for filter(MPR2200/HEPA)?
• might the added filter or box design, cause a pressure problem?
• is cardboard an adequate material (with all joints taped up)?
• is cardboard adequate for fan's vibratiosn and possible heat?
• does direction (up/down/horizontal) of fan or filters matter?
• does size of box / flat filter matter?

Possible alternatives to the above idea:

• use a box simply to link the two 4" filters with the 6" fan, and then put a filter (MPR2200 or HEPA) downstream of the fan, i.e. outside the box.
• OR... simple design that still captures carbon dust: 6" fan with 6" filter upstream and MPR2200/HEPA filter downstream.

Thanks!

With DU being harder than tungsten but less dense than gold, what exactly is it about the extraction of U235 that makes the waste/depleted material so hard? Any good resources/further reading on the subject?

I watched a video by Neil deGrasse Tyson where he said that it’s a common misconception that atmospheric re-entry is a problem for aerospace engineers. He said, no! It’s a blessing! We love it! Because it’s air-braking.

Tyson argued that without an atmosphere, you’d need to fire retro-rockets to slow down on Earth re-entry. That requires fuel. And carrying fuel is the enemy. So atmospheric re-entry is a space shuttle’s friend because it reduces the fuel it carries.

I get that, but if there were no atmosphere, wouldn’t that reduce drag on the way out? So isn’t it more or less a wash in the end?

If Earth had no atmosphere, would the space shuttle require less fuel?

I am making a robot for a hobby project with some friends, and we need to figure out what motors we have to buy, but we are unsure how much torque this application would need.

I will provide some stats, but feel free to ask for more as needed:

• Weight: 17lbs (~7.75kg) with load
• 6 wheels - 5.5cm radius
• 6 motor drive, direct drive (unless you recommend gearing)
• max speed 12-17mph (somewhere in that range)

Please suggest me how much torque and some motors if possible, that would be good, and any other tips. Thanks!

Potentially a stupid question, but I have 2 plastic bolts where the majority of the bolt's threaded length is "sticking out". I want a stupid easy way to create a handle, so I was thinking about threading eyelets on the free end of two bolts with a rope to connect them. In this configuration, is it reasonable to model the free part of the bolt as a cylindrical, tip loaded cantilever. And if so, would the cross-sectional area of this "hypothetical cylinder" be the tensile stress area? I feel like it's generally reasonable, but it also feels wrong to be looking at a bolt in bending.

I’ve been hearing a mysterious sound in my home that I can’t seem to reproduce. It’s not connected to any water activity or other appliances as far as I can tell. The sound happens intermittently and lasts for about 30 seconds.

Here’s the link to the audio recording of the sound: https://jmp.sh/ljeXYqFX

Does anyone have any idea what this could be? I’ve checked for common issues like water hammering or HVAC noises, but nothing seems to match.

I’d appreciate any insights or advice!

Location of room: https://ibb.co/yyZysVF

Hello, I've done some research, but I'd like some personal opinion / input as well.

I'm looking into mechanical vibration standards for low-speed rotating equipment. This particular piece of equipment is rotating at 25rpm.

I'm finding conflicting information into what standard should be used to determine whether the vibration indicates failure or is normal. One party claims ISO 10816-3 should be followed, however, my understanding is that his has been withdrawn, and replaced with ISO 20816-3, but in any case, this is only for rotating equipment between 120 and 30000 rpm.

This equipment is not a wind turbine, so ISO 10816-21 should not apply.

I'm left with ISO 20816-1:2016, but I do not fully understand it to be honest.

Any guidance as to where should I look next, or am I heading in the right direction?

Thanks in advance.

PS. First time posting in this subreddit, if not allowed, delete.

Hi, first of all i'm not an engineer (but I wish I was!) I'm learning on my own at my shop.

I've designed and built my own bldc motor and I want to test it's performance and get some metrics (Kv, Ke, back emf...) I've built a small test rig where I have a known comercial bldc motor controlled by a FOC controller coupled to my MUT(motor under test) motor that is in turn controlled by a ESC. I can use the FOC to simulate forces and measure rpm under load and at free spin.

My first issue is that if I measure the rpm at a certain voltage and calculate the KV I get around 21, but if I measure the back emf from the MUT and calculate the KV front that I get around 28. I'm not sure if that's too much discrepancy, and if it is where can it be coming from? I've re-tesyed everything several times... Any help, suggestion or direction would be appreciated!

Here is a short video of the motor running https://youtube.com/shorts/igbXB_XZKwk?si=aqdPnJlUTCPhqemh

And values of the motor and testing:

Motor data:

• wire: .4mm diameter
• turns per slot: 43
• slots: 36
• pole count: 40
• air gap: 1mm

Calculated Data:

• kv: 20.16
• phase resistance: 4.5 ohm

Measurements: For KV: Run1 Rps: 6.5 V:20 A:0.2 -> KV=19.5 Run2 Rps: 3.5 V:10 A:0.2 -> KV=21 Run3 Rps: 8 V:24 A:0.2 -> KV=20 For Back EMF: Run1 RPS:17.5, V between phases: 37.5, ->Back EMF Ke: 0.341-> calculated KV from Ke =28

Why do i get 20 and 28 when they should be the same?

Oh, I'm from Spain!

Across my various hobbies and interests, I keep coming across people talking about how some fans/blowers have high cfm but low static pressure, or vice versa. And that sometimes an otherwise powerful device is inadequate because it is strong in the wrong metric.

Can you not simply restrict or increase the path of air flow to trade one for the other?

Simple examples:

1. Dust Extractors vs Dust Collectors for woodworking. Dust extractors have high static pressure and low cfm (they're basically expensive vacuums). Conversely, wall mounted dust collectors have high cfm and low static pressure.

Why can large dust collector not serve has a high-static-pressure vacuum by simply attaching a smaller hose to it? If they impeller is putting in the energy to suck 1000 CFM either way, doesn't this imply a higher pressure in a narrower hose?

2. Cooling fans. One youtube channel I enjoy has people sending in all sorts of unique, 3d-printable computer fans, and the channel creator pits them against one another to see which works best. In previous "seasons" of his channel, he's ranked them according CFM but he recently changed over to ranking by static pressure.

This has resulted in new designs being submitted to optimize for the new metric.

Why would this metric be any different? Doesn't a fan that can blow lots of air imply more pressure than a fan that blows less?

The mental model I have for CFM vs SP is that of any other simple machine - a pulley/lever/wedge lets you trade force for distance moved. Do not CFM and SP have a similar relationship?

Presumably my mental model is wrong.

Hello! I am working on a project that involves designing an opto-mechanical system that is very sensitive to temperature fluctuations/gradients. We are using thermoelectric cooling to regulate both sides of the device and can keep the temperature stable across the device within ~20 mK but this is proving insufficient. My gut feeling is that the mechanical design is susceptible to deflection when gradients are present. A previous iteration of this device was actually less controlled but had less issues so I think the mechanical design didn't translate thermal expansion into erroneous readings as much as my working prototype.

Does anyone know any textbooks or literature that are useful for the mechanics of thermal design? Particularly optical systems if possible, but anything would help. Thank you!

https://www.amazon.com/800-1000-Voltage-Inverter-Generator-Ignition/dp/B07C94LKNT/ref=asc_df_B07C94LKNT?mcid=749b1c450c82303bb92f7a453f4b2314&hvocijid=14550549123546047392-B07C94LKNT-&hvexpln=73&tag=hyprod-20&linkCode=df0&hvadid=692875362841&hvpos=&hvnetw=g&hvrand=14550549123546047392&hvpone=&hvptwo=&hvqmt=&hvdev=m&hvdvcmdl=&hvlocint=&hvlocphy=9015312&hvtargid=pla-2281435177618&psc=1

If I take this high voltage generator, hook the positive to the spark plug wire and the negative to ground the top of the spark plug (on its threads), will this create a continuous high voltage spark?

Can I incorporate an on/off switch on one of the legs?

Might not be the right place for this but here goes.

Typically in the past, the more energy we used the more fuel we consumed. With the rise of renewable power, the energy is "free" but we can't control the amount generated. It's also going to be difficult to produce all of our energy through renewables alone (you end up with too much or too little and having storage that covers the differences over the year is tricky). Nuclear has disadvantages to load following (financial as well as stressing the system). If grid controllers had access to not only energy sources but flexible/variable grid sinks as well, wouldn't this be a more favourable way to run the grid? One example might be hydrogen production ( fairly well known) but are there other industries that maybe with some help could also fit this role? And what might stop to the adoption of such a grid architecture?

2023 Bolt EUV 12v system - DC to DC provides up to 130A & up to 15.5v with a minimum of 13.9v.

Aftermarket amplifier can only handle 15.1v.

How can I allow any voltage up to 14.4v through to the amp while allowing full current to pass through?

I am surgeon. We have patients that require drains to sit in the chest, or through the nose and into the stomach. These tubes are very uncomfortable for most patients. I would imagine a smaller tube made from a softer material would be more comfortable. But smaller tubes will not drain at a fast enough rate, am I right? How can we get smaller, more flexible tubes to do the same job?

I was looking around for a tutorial on designing a furnace exhaust stack for wind/seismic/etc. and really not finding much useful online. There are a ton of software options to buy, and we used to use STAAD pro, but what I'm wanting to do is go through the hand calculations so I understand it better. I'm coming at this as a chemical engineer/process engineer who has to work with the mechanical/structural guys.

Is there anything useful out there as a reference? I'm tempted to just sit and read STS-1 over and over but after one pass through it doesn't appear to really give me what I need, it's more a reference regulating you once you already know what you're doing.

I must be losing my mind because I clearly remember you place your poles strictly inside the unit circle for stability, you can place zeros any place you like in the z-plane.

If, say, I placed a bunch of zeros right on the unit circle, then in the frequency domain I'd be filtering out the frequencies corresponding to the angles of the zeros I placed.

yet the following gives me a filter that is nowhere near that... clearly I'm forgetting something. but I can't quite figure out what.

from scipy.signal import zpk2tf,freqz
import numpy as np
from matplotlib import pyplot as plt
pole_scaling = 0.9
b,a = zpk2tf([np.exp(-1j*2*np.pi*k/600)*1 for k in np.arange(-150,151,5)],[pole_scaling*np.exp(-1j*2*np.pi*k/600)  for k in np.arange(-150,151,5)],1)
w, h = freqz(b, a, 10000)
fig = plt.figure()
ax = fig.add_subplot(111)
ax.plot(w, 20 * np.log10(abs(h)))
ax.set_xscale('log')
ax.set_xlabel('Frequency [radians / second]')
ax.set_ylabel('Amplitude [dB]')
ax.grid(which='both', axis='both')

I have a couple console humidifiers for my shop (guitar shop - keeping the humidity up is extremely important), each with two 5 gallon tanks. The valves are like THESE. There is no air valve at the top of the tanks, so the air to replace the water must be coming in from the same valve as the water exits. I, and one of my employees, have noticed that the tanks always empty one at a time, and it is the same order on each of them - left first, right second. Is this just chance? Is this a design choice? Is this weird?

In piston engines, the pistons are nearly the same diameter of the cylinder, but not quite, we can't make things run reliably with that close of a tolerance. So we have piston rings which are springy and act to seal the cylinder as the piston moves up and down. Given that there is still a tiny gap between the piston and cylinder, some of the pressure has to act on at least the top piston ring. How much?

Assume a vertical static load of uniform density, anchored at 2 points spaced horizontally . How can I calculate screw diameter?

Hanging curtains from wooden window frame on 550 cord, if that helps

Thanks so much

Joe

Hello! Not sure if this is the right sub for this, but saw a similar post a while back so here we go. I have a bottle of cologne here, and the piece of plastic that allows the cap to seat seems to have gotten stuck inside as shown in the pictures below. It is the gold circle under the 4 black notches, and nothing I am doing seems to be working. Does anyone have a fix to this? Thanks in advance!

Photos: https://imgur.com/a/pTRXgbi

Hi all

So as the questions suggests - is there an only company/a seller who sells silicone rubber tubing according to the above dimensions? Needs to be the above specs. Willing to purchase a bulk quantity i.e. a few metres etc, if it means making a custom order.

Have looked at a few rubber companies online but want to cover all angles.

It can’t be a hardness of less, and it needs to match the ID and OD range.

Best,
S

So imagine the situation is an off grid tiny home or Skoolie, it would already have a heat pump installed that would be running off a battery system fed by solar. My question is, as a back up for when solar is insufficient, would it be more efficient to use something like a diesel heater or would it make more sense to have a generator charge the batteries to run the heat pump.

Also, if a generator was used, how complex/worth it would it be to try and capture some of the waste heat? Would that essentially be the equivalent of the diesel heater minus losses to noise by the generator?

Getting some equipment put on a test bench. Issue is, the output shaft is tapered and they do not have a way to connect that.

I need a bushing that has a tapered bore and cylindrical OD. Most of what I have seen has been the opposite.

Would there be any off the shelf type thing for this?