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

My headliner has failed and I want to ensure 100% that every drop of glue is properly clamped down and i won't need to do this again. I'm spending extra on good fabric and would rather it not fail.

My question is , would a simple extra extra large plastic bag , say for a mattress be sufficient in applying pressure to headliner fabric > headliner backing?

I'll use a 110v vacuum continuously if need be

Hi all,

Just started a new gig at a startup. Part of the company involves two components that are shipped to sites across the world. These components are fitted to rigs at these sites.

I’d like to track the history of each individual component, alongside the history of each site (current component config and past component swaps).

I’ve accomplished most of this in Jira WM but it’s janky.

Anyone have any free or low cost ideas to accomplish this?

Cheers! Thank you!

Mom built front & back porch without permits 10 years ago. Currently the porch feels and seems solid but I'm worried 10+ years later it might collapse. Not sure if I should install structure pillars just to be safe.

Multiple pictures of the porch.

Pictures of porch where I would implement structural pillars (in red).

Should I hire a contractor to install "Porch Post Columns"? Or to make things easy, can I just buy a Jack Post and call it a day? Or would it be easier to call a contractor to remove the whole porch?

Thank you in advance.

Hello, I have a general question regarding BLDC motors that I would like some insight on. I am designing a system using a 2-pole, 3-phase BLDC motor with a 6-step communication scheme.

I am curious if someone can explain how to calculate the number of discrete positions that the BLDC can be held at.

From my understanding, there are six unique commutation states and since there are only two poles, then there would be 6 positions in which the motor could be held at. If there were four poles, then there would be 12 positions. I am confused how the number of winding slots may affect the number of positions that can be held.

Additionally, if an encoder was used with higher precision, would the motor theoretically be able to hold in between steps? Any insight would be appreciated.

Hi all,

I’m trying to get a better understanding of CIP (clean in place) best practices. I am aware the fluid velocity should be high enough so that you achieve turbulent flow.

I’d like to know a little more about the relationship between fluid velocity and pressure drops. Using a centrifugal pump, I’m cleaning a line that has a maximum head of 10 feet along with a few 90 degree elbows. Bernoulli’s principle relates a lower pressure to a higher velocity, and vice versa.

So, when designing a CIP line, should I not think of pressure drops as harmful if they increase the fluid velocity, which is what I want? Am I correct in assuming that in a closed loop, with steady flow, the flow rate will remain constant throughout the line despite these pressure drops due to bends?

Thanks in advance for the insights.

I’m 100% overthinking this, but I’d like to get new pivot bolts machined for my full suspension mountain bike. The current bolts are 6k series aluminum and the hex drive commonly strips out requiring new bolts. Yes I use bits that fit, yes I use a torque wrench. It’s a common problem for this brand and pivot. I want a harder material that won’t strip out so I’m considering SS, Ti, or 7k Alloy. With Ti and SS I fear thread galling, and with SS or 7k aluminum I’m afraid of galvanic corrosion. An obvious solution would be anti seize, but a recent Torque Test channel video has me concerned that anti seize would result in overtorqued bolts (10nm spec). Looking for solutions to my analysis paralysis

I was talking to my manager about upgrading our 3D printer to open up a bottleneck on our prototyping capabilities. He said he doesn't think we should be running a printer at all and that production/operations should run it and make the parts for us. I'm curious what other companies out there are doing and how people feel about it.

I thought since they use cheaper water then should be quite wide spread. Also if building a small scale air wash what would you have to keep in mind compared to an air purifier? How do you find the right amount of air pressure, so that the water doesn't splash but the air is still forced through the water?

Hi! I recently built a plexiglass rig for a video shoot-it’s a 1/2” thick 4’ x 5’ piece of plexiglass bolted to four sturdy wooden stools about 2’ off the ground. I (110lbs) have stood & jumped on it repeatedly & it’s held great. The model for the project is about 170 lbs. Is there a way to calculate if it will hold their weight so I can be 100% sure?

I am building a vacuum system to use for stabilizing wood and I have found that a standard vacuum pot is not ideal for my application because I intend to stabilize quite long pieces.

However I found these so called gastronorm containers that would be perfect for me.

Container 1

Container 2

The problem with them is that they are quite thin, container 2 is advertised as only 0,8mm although I believe some are slightly thicker.

So my question is how much reinforcement would I need to do for a container like this to tolerate 0.3Pa vacuum?

I was thinking about TIG welding 20x3mm stainless flat bars with some interval to the sides and bottom, sort of like this bridge.

0.3Pa is the advertised ultimate vacuum of my pump.
I plan on using a 12mm tempered glass lid with a 10mm drilled hole for fittings.

Thanks and I apologize in advance for any English errors.

Hello. The company I work for has a concrete 3 story building. The roof is a large parking garage with about 350 spots. My company has been cramming cars up to 3 wide down the aisles effectively doubling the amount of cars parked up there. I worry for the safety of the people who work on the bottom floor. Cars are even parked on the ramps going up to the 3rd floor. Everywhere they can fit a car. These are heavy luxury cars. How do I know if it is safe? What city department is this under?

Hello there. First time poster here. I am currently looking a bit into Lidar sensors because I was recently working with a camera (DJI Ronin 4D) which had this amazing lidar sensor which helped me alot for pulling the focus on that shoot. The sensor gives you a "top down" view of everything in front of it. The result are clusters of white pixels that can give you an estimate of the objects in front of the camera. A bit like a radar "waveform". Now I am looking into similar sensors, because the dji system sadly only works with this camera. I found quite a few to use with a Arduino but they are all singlepoint. And my robo vacuum for example gives me the same top down view but with a single point Lidar combined with a rotating mirror. And thats sadly not an option because hand held camera can be quite rough and a rotating mirror wouldn't be reliable. I had to think of the iPhone lidar sensor. That seems to be a relatively cheap multi-point lidar sensor without a mirror. But I couldn't find any lidar multi-point components to buy. Can someone point me in the right direction?

So I want to understand what woods and sealants go hand in hand to produce the best outcome. I am looking at pine, cedar, redwood, oak, maple and mahogany. For treatment, I am looking at borate, pressure treatment, oil based sealant, water based sealant, chemical preservatives and marine grade sealants. I want to know which combination will yield the best results in damp, and lit environments (regular sunlight and rain)

For example, a 2.0 liter naturally aspirated engine from 2004 made somewhere between 140-160 horsepower, meanwhile today it can be easily over 200. Forced induction is a different thing altogether, but for the sake of keeping everything else equal let's just focus on the power increase of NA engines.

Do engines today have mechanical components or materials that allow them to create more power than 20 years ago? Or is it just mostly faster electronics and faster software that can more precisely calculate how much fuel to inject?

I purchased a M16 long shank eye bolt which comes with a nut, they fit together perfectly:

https://www.gsproducts.co.uk/16mm-200mm-stainless-steel-long-shank-eye-bolt/

I also purchased some M16 threaded rod:

https://www.gsproducts.co.uk/16mm-threaded-stud-rod/
(From webpage - metric coarse right handed threaded, with a 2mm thread pitch)

Problem - they do not appear to be the exact same thread, they do go together but feel loose fit which I'm worried about the SWL using it like that.

Are there different type of threads used in M16 marine grade A4 stainless steel? And how do I differentiate between them?

3D Prints and attaching Ball Bearings

Hey good people of Reddit.

I am working on a 3D print involving a ball bearings and a threaded axis and I am having some difficulties understanding how to properly attach a spinning threaded axis onto my project using ball bearings.

See attached graphic for an overview of the design.

The current struggle is not so much attaching the ballbearing itself to the 3D print, as I have used a fitting design, where the 3D print will contain small circular balls which the ballbearing is press fitted into to, providing a stable and solid attachment onto the 3D print part itself.

My current struggle is attaching a threaded axis into the ball bearing where it is then ocked in place preventing any vertical movement while still allowing for a spinning motion utilizes the features of the ballbearing.

So it comes down to these two issues.

My first issue is that my threaded axis/wheel, which is the same size as the inner diameter of the ball bearing, minus a minor amount, can rotate freely within the inner race of the ball bearing, without the ball bearing spinning at all. This means that I could just remove the ballbearing itself entirely as it serves no purpose.

If the threaded wheel gets any larger, it would be to big to fit within the inner race of the ballbearing itself, so I don't see how a larger axis is the solution.

My second issue is I am not sure how to properly use bolts, which I am supposed to use right?, to limit the horizontal travel.

Is one supposed to use bolts that has an inner diameter the size of the threaded axis and a size of the outer diameter(bolt itself) so that when attached to the threaded axis only presses against the inner race of the ball bearing and not the outer race?

TLDR:

How do I secure a threaded axis / wheel into a ball bearing.

https://imgur.com/a/6zq45ZS

I am in my first year in french engineering studies (prépa) and I have to do a ISP (Independent study project) about a thematic around the wind energy. I came up with this problematic :

How to reduce a drone's electrical consumption using wind energy ?

I know it has a lot of chances to fail but I want to know if there is some technical sources I can use to make the statement that it is doable or not ?

Thanks for your potential answers !

Water and thinner fluids are just that. Fluid. they slosh around. Thats why water / milk / gasoline etc, trucks have baffles inside of them. but how do non newtonian fluids react. what about different viscosities of shear-thickening fluid. like silicone suspensions? What if it was in partial vacuum? or under pressure? How would that change its characteristics? How can I find research on this? or who can help me with some more insight? Please and Thank-You in advance.

Hey! I am a small time valve automation shop that has steadily been growing. I’m very well versed in autocad - 2D type work, so the actual drawing component does not bother me. However, I have a customer asking me to make these drawings for an order I have. 3”150 WKM utilizing an Airtorque.

My question is where do I find out the regulations of all the info I need to put on these drawings? In the Notes, scale, etc info? Is there a standard? Thanks!

Light hobbyist here and need some help... My dad likes to be on the porch swing and rock, but can't rock by himself because he's paralyzed below the waist. I want to make him something that can push him/pull him to allow for continuous motion back and forth. He also likes building things, wiring stuff up, and figuring things out. He doesn't know about this project yet, but I'm trying to piece together all the parts so we can solder and assemble together.

If anyone can help me out or point me in a direction, that'd be awesome. I don't really even know where to begin when it comes to trying to calculate the size motor needed. If you have any comments beside the motor size, leave those too. Anything helps! Thanks all!

Here's the numbers:

• Has to push around 400lbs for 2 people & swing.
• Move the swing like a gentle rocking (maybe 2ft from the center point in each direction)
• Doesn't have to go fast, just would like it to be efficient and small if possible.
• Ideally powered by a solar-powered battery pack, but outlet would work too.
• The quieter the motor, the better. Even if that means an initial push off is needed from the person swinging (he has a grabber thing he currently uses to push).

I have a pressure chamber designed to use a cast acrylic tube as the body, with aluminum end caps. The chamber will be mostly filled with distilled water and then pressurized with compressed air up to a max of 80psi. I'm using a 7.250" OD, 6.250" ID, 7" length tube, with an M180 thread machined into the ends. Due to the thread cuts, the minimum OD as ~6.9587", or a minimum material thickness of ~0.35".

using Barlow's formula P=2St/D, with P= 150psi (~designed safety factor, roughly double the max pressure), t = .35" and D = 7.25" (more conservative value), I get 1550 psi as my hoop stress.

looking at the mechanical properties of cast acrylics, I see the tensile strength ranging between 8,000 - 11,000psi. Assuming the low end, that puts my hoop stress as ~1/5 to the tensile strength. (In reality, my max pressure possible 80psi results around 1/10th of the tensile strength.)

The tube is held in compression by the end caps, tightened together externally with bolts and rods. One end cap has M180 threads and the acrylic will screw into it. How do I account for the stress concentrations from the machined threads?

I am seeing online sources saying that acrylic tubes aren't rated for pressure, as opposed to the standard ratings for PVC/ABS. I was originally satisfied with my design values, but now I'm concerned that I should not be using the acrylic tube. So, I ask, can I use the acrylic tubing for this design, or do I need to pivot to a different material?

I am evaluating the safety of a testing setup and am trying to determine how far the snapback distance of our rope under tension couple be. I know the cross sectional area, length, and material (therefore Young's modulus) of the rope, as well as exactly how much tension it will be under when it snaps back. Can I calculate snapback distance with this?

Note that nobody will be remotely close to the test setup, I'm just doing this for my own curiosity.

Hi everyone! I am hoping to get some opinions/advice if possible 🙏 We are installing a 20'x40' pool in our backyard and recently received 2 quotes from a landscaper based on the pool layout being perpendicular vs parallel to our house. The pool will be on a slope and will require about a 6' high wall in either layout. One quote put the retaining wall at 1255 SQFT/197 LF and calls for 690 TONS of 3/4" clear limestone backfill. The other quote at 960 SQFT/185 LF and calls for 460 TONS of limestone backfill.

I was hoping someone could tell me if these numbers make sense? The amount of limestone they are quoting seems like an awful lot to me, but I am definitely not an engineer! It is really driving up the cost on the quote though at $26k and $40k for the backfill limestone material alone.

We just had a concrete guy come look at the space this week (he is also going to send us a quote) and when he heard 690 Tons of backfill material, he thought the other company might have accidentally added a zero on the amount of tons they listed.

I would be truly grateful if any engineers out there could lend an opinion. Thank you so so much for any thoughts/help/advice!

I am currently doing a small project making a calculator for pressure losses through a steel pipe specifically with nitrogen. However, from the Darcy-Weinbach equation, I get a head loss measured in feet. I specifically want to calculate pressure loss in PSI, so what is the formula I can use to convert feet from head loss to pressure loss in PSI? Already tried searching, and found only conversions that apply to water as the fluid.

Hello everyone!!

I have this smith machine that I have added a low row function with 2 pulleys pic related

The problem is with the low pulley that is attached to the bottom 43"x4" steel bar (0.23inches thick, m10 bolt)

There is excessive bending when more than 110lbs are being pulled (it bends upwards more than 1inch and I place some 45lb plates on top of the steel bar to mitigate this)

I thought of bolting an extra layer of 0.2 inches thick steel on top of it but would that be enough to withstand the forces?? (all the pulleys/ropes/etc are rated for 330lbs)

How can I calculate how thick should I go?

I appreciate the input

Edit: I can't bolt the pulley to the floor unfortunately

Background: I have a local dry air generator that uses an air compressor, funneled through an oil filter then through a micro-mist filter before being dried out by two tube desiccators. Finally, the air meets a regulator which allows a range of 0.5-1.5 L/min into a small enclosure to lower the dew point to below -30C to protect sensitive silicon sensors.

The problem I am facing is that, the summer humidity in Japan is getting crazy where dew point can reach above 20C and relative humidity increasing up to 80% if the air conditioner is in cooling mode and not drying mode. We cannot exactly control the environment of the room as well.

Sometimes during operation, there will still be some condensation inside the air tubes right before the first tube desiccator. It does not help as well that the filters are not exactly in an upright position most of the time due to the lack of supports. Today, I found out that one of the desiccators has been damaged and cannot vent out purge air (making it useless to dry out air). Thankfully, the setup can still run with one tube.

Apologies for the dumb questions:

1. Is the mist filter not being in an upright position not allowing it to function properly?

2. How often should the mist filter be purged?

3. Should I consider adding more layers of mist filter before the desiccators?

Any other suggestions would be welcome.

I'm not a native speaker to please have mercy regarding my probably bad technical english.

I am wondering if the the gradient of torque (Nm/s) has any relevance on the fatigue of material, for example a steel differential housing in a car. If so, what's the physics behind it.

Hi everyone, I have spent days looking for Capital Harness XC Tutorials. Finally my last hope lies here. If you could please guide me to any form of tutorials, it would be of great help. I am in dire need of this and my job depends on this.

Thank you so so much.

Hey guys, humble electrical engineer here. I am in the hydraulics world now, came out of power electronics, and haven't messed with power systems or the internals of electric motors in a long time. I am confused by a video that I watched yesterday about the wiring of a 3 phase e-motor. For the example, it's a 208V system (in my job its usually 460 motor and 480V system).

The video below talks about wye-start/delta-run wiring configurations. It says due to the nature of a WYE configuration, the windings will see the lower L-N voltage (120V ) and thus will see less current/less in rush for start up. I must be missing something because my brain wants to think that the current would be higher due to less voltage. P=IV. If P is constant, then I would go up as V goes down. The guy on the video mentions "mathematical trickery" and for some reason I am not seeing it. Perhaps one of yall have a simpler explanation?

https://www.youtube.com/watch?app=desktop&v=DpB-kdM2RA4

I was calculating the thermodynamics of an entire thermodynamic steam plant for funnsies and was looking at the numbers and wondered at which corner I could improve the efficiency. Feedwater preheating and superheating are of course established and don't need any further word. But the biggest energy budget share is wasted by the energy used to evaporate the water and liquefy the steam afterwards in the condenser.

I was thinking: What if the energy rejected in the condenser is reintroduced via a feedwater preheater? Which brought me to the refrigeration cycle. I know that in common cases of heat pumps for houses, 4 kWh of Energy can be moved with 1 kWh of energy used to drive the HVAC. So, I went on an exploratory calculation binge. Here are, just for visualization reasons numbers I played through:

1. The steam generator consumes 291,312 kJ/h produces overall 247,633 kJ/h as 76.43kg steam per hour at 100 Bar and 3240 kJ/kg enthalpy/450°C temperature (superheated)* (efficiency = 0.85)
2. The mechanical energy produced is 20 kW (efficiency = 0.66, but should not be relevant in this question)
3. The condenser receives overall 197,480 kJ/h as 76.43Kg steam per hour at 0.1 Bar and 2392 kJ/kg enthalpy/45°C* and rejects the entirety of the evaporation enthalpy of overall 182,821 kJ/h. The water is now liquid and at 0.1 Bar and 45°C
4. Pumping losses for the circulation pump (circulation set to 6 x feed water throughput) and boiler feed pump are set to 0.345 kW overall together.

That means the overall system efficiency is calculated to 0.24. 63% of the energy inserted into the steam generator is lost for the evaporation enthalpy rejection inside the condenser / of the cooling water.

Steam plants, that send the exhaust steam through a feed water preheater before it enters the condenser have been done plenty of times. But what if we could somehow extract the entirety of the evaporation enthalpy with a refrigerant and reinsert this energy back into the feed water to reduce the wasted heat? Let's say:

• The exhaust steam entering the condenser contains 2391.9 kJ/kg evaporation enthalpy*(0.1 Bar)
• Water is the refrigerant in the vapor compression cycle
• It must enter the condenser/heat exchanger in the liquid state. Let's set it to 0.075 Bar at 40°C*
• The feed water/condensate is assumed to be 46°C warm and should receive as much energy as possible before entering the boiler
• In order for the refrigerant to reject its heat, it must be warmer than the feed water. Only the evaporation heat of the refrigerant is used / transported into the feed water. The refrigerant pressure after the compressor is set to 120 Bar

These premises would mean:

1. If all of the 182,821 kJ/h in the condenser are transferred to the H²O refrigerant at 40°C, at 2405kJ/kg*, we'd need 76 kg/h refrigerant circulation
2. This would consume around 0.3 kW compression losses (eff = 0.85), bringing the overall pumping losses to 0.645 kW
3. After the compressor, the now partially liquid refrigerant is at 120 Bar, at 1510 kJ/kg liquid enthalpy
4. The feed water is heated to the maximum liquid enthalpy at 100 Bar, to 311°C, thus receiving 1407 kJ/kg from the refrigerant, overall 107,537 kJ/h

These results would translate into the fact, that 107,537 kJ/h from the original 291,312 kJ/h entering the boiler can be spared. That would mean the energy inserted into the boiler could be reduced significantly by a third to 183,775 kJ/h with a power loss of 0.3 kW. The overall system efficiency would rise from 0.24 to 0.387, a rise of 61%!

The system can be tweaked:

1. The refrigerant still contains 2405 kJ/kg - 1407 kJ/kg = 998 kJ/kg enthalpy. Overall 78,848 kJ/h
2. When it return into the condenser, it will be at 0.075 Bar, at 40°C and contain 12.824 kJ/h overall, thus another 66,024 kJ/h can be inserted.
3. The evaporation of the full 76.43 kg/h of water consumes 100,674 kJ/h
4. Minus the 66,024 kJ/h, that can be inserted, this would mean 66% of feed water can already be evaporated, breaking the hard definition barriers between a feed water preheater and a steam generator

These results result into the fact, that 173,561 kJ/h from the original 291,312 kJ/h entering the boiler can be spared. That would mean the energy inserted into the boiler could be reduced significantly by more than half to 117,751 kJ/h with a power loss of 0.3 kW. The overall efficiency would rise from 0.387 to 0.59, reaching levels comparable to COGEN-systems and other 2-cycle concepts, but with a moderately smaller rise in complexity. It's not a swiss-army-knife and doesn't reach efficiencies of the most modern top notch power generation systems, that break well beyond the 60% efficiency sound barrier. But it might be a further option in the power plant concept toolbox and might have its niche of application.

I'd love to hear other people's opinions about it.

* = based on the steam table from https://www.thermopedia.com/content/1150/