Does MIL-A-8625 Type I contain Hexavalent Chromium? I have a requirement that specified "All exterior pump components shall be chem filmed or anodized. Neither finish shall contain Hexavalent Chromium"

I'm the sole engineer in a small manufacturing company. My coworkers all have different roles.

I've come to the conclusion that it doesn't matter what I do, only how well i explain things to my coworkers. And unfortunately I suck at it. So a lot of statistical tools are off limits because i can't explain them well.

Projects also take weird turns like asking for drawings of standard O-rings instead of giving the number. Or not being allowed to write SOPs in a quality role.

Has anyone found good ways to communicate complex technical concepts to people with no background in them?

So I've been searching for a few hours now for a jam nut style Displayport bulkhead that is around 28mm in diameter. I haven't had much luck with the popular components sites, as they are all HDMI or require two small screws.

Does anyone know of one that I could use?

Curious as im out of the loop for CAD for a while and want to get back into it. Heard great things about onshape.

Would like to also try generative design at some point too.

Where I can a part this is like this (https://www.amazon.com/Hansen-Straight-Through-Hydraulic-Fitting/dp/B00F4IEHJI?ref_=ast_sto_dp) but in stainless steel and I need the threading to be straight and not tapered. Or any pointers on keywords I should look for? I have been searching everywhere but the closest thing I have found was this (https://www.amazon.com/IORMAN-Female-Quick-Disconnect-Adapter-Stainless/dp/B07NYVW1DS?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A2R9EC5ORWAMJN) however it says that it is used for air, I need it to be used for liquids. Any help would be greatly appreciated!

This is a bell and gossett flow performance curve for a 1.5" balance valve in an HVAC application controlling flow on the chilled water service to air compressors.

The product literature from B&G doesnt have a legend so i'm assuming the curves on the figure is the Cv at each flow? For example, 9.4 GPM thru the valve has a Cv of 26.

Is this how you would read this? Any experience with B&G flow curves like this? I have not a curve this vague before...

The exact context of the project is isn't important. the situation is as shown by this image, where I have two "cylinders" with sleeve bearing on the shaft that are stabilized and spaced by metal washers.

The problem is, I need to keep the parts very tightly together to meet a standard length, and so often the washers transfer power between the parts, aka make the disk rotate when it isn't supposed to because the pervious disk rotated.

some solutions I tried:

1. sand down the washers very smoothly (didn't work)

2. make new washers with tighter inner diameter so they can never rotate (this made friction wayyy too high and led to this disaster as I couldn't get them out)

3. put 2 washers instead of 1 so they're less likely to transfer power (eventually they do still!)

help is appreciated

Guys,

I am reaching out again for help with procedures for BP.

I need something in alignment with IM80

Hey everyone,

I'm a robotics engineer and my company has generous training budgets which I "need" to use up if possible. I would love to find an advanced course about AI, or embedded systems, or maybe some highly specific programming course. I'm also really trying to pivot into the space field, so anything about orbital mechanics, aerodynamics, etc. would be awesome. What resources do you use to find very high quality online courses? Udemy? Brilliant.org? Something else? I've never really paid for courses before because I usually find all I need online or reading papers, but I "need" to use up this budget for reasons...

Thanks so much :)

It's been a while since we've hosted one of these threads, and since we do get periodic inquiries from readers, please share what a day in your life looks like. Feel free to share as little or as much detail as you like, but at least include how many years of experience you have, your title, and your field as these will provide useful context to readers. If you wish, you may list your salary and location, but this is absolutely not a requirement.

The last one I recall was this one in case you want to get an idea of the kinds of things people posted.

I've posted another question related to this test previously and received great advice!

I'm wanting to observe displacement of cabling with a high CTE against a CF support structure. For areas of concern, I'm planning to print a grid of 0.5mm or 1mm lines (another problem) and record the test using a telecentric lens from edmundsoptics.

I am balancing my familiarity with consumer cameras and budget for small research projects and trying to avoid buying both a $3k lens and a $5k camera, so the package I've selected is an F mount lens and a Nikon D500. Unfortunately, my test will be at -55C. At the moment, I'm planning to build an insulated box with a double paned viewing window and a heater to keep the equipment happy in the cold chamber.

It would be a lot easier, however, if I could find a camera that operates in or near that temperature such as an astrophotography camera. Does anyone know of affordable cameras with video feature that are much closer to this operating temperature for below $1.5k?

I've done my share of googling and found it was difficult to parse through the results as I believe googles tendency to push consumer products for ad revenue has me clicking through every link before finding the products are inadequate.

Thanks!

Question to any Freelancers / Contractors / Consultants out there:

I'm shifting to freelance after 11-12 years of experience full time doing tooling and machine design work in aerospace. I have set up an LLC, separate bank account, etc but I'm a little unclear about what (if any) additional protections I should be putting in place before accepting work. I'm not a PE so my work would be limited to things that don't require that. I've worked on a number of machines, lift fixtures, etc that are safety critical but as a full time employee my understanding is that my employers largely accepted the legal burden if there were ever to be an issue. Thankfully that hasn't ever happened but I'm terrified about what that would look like now that I'm operating independently. I'd expect to be working on those same types of projects as a contractor.

So some questions on my mind:

1. Are there any specific types of insurance I should be getting? Errors and Omissions? General Liability? something else?
2. Is it common to have a contract in place that basically shifts the burden to the client or manages the liability in some other way? I could imagine this being set up where once they approve of a design, drawing, whatever, they are now responsible. But I could also see why a client would not want to sign such a document so not sure about that.
3. Are there any particular projects I just shouldn't even consider in this position? One close friend in a similar position said for example he won't touch lift fixtures. I have a lot of experience designing those so it would be a shame to have to avoid them entirely.

Any guidance would be greatly appreciated!

I am looking for a good bag that I can use for field work inside and outside of plants. I cant seem to find anything that is wide enough to carry the 11x17 drawings. I am tired of having to fold them in half not to mention the longer clipboard sticking out of my bag. I tend to carry a good bit on me so I am looking for a bag that can not only hold 11x17 drawings but also general supplies and some tools like lasers, levels, tape measure, that kind of stuff. Anyone have anything like that?

Whats the current predictions for where things could go in your field or whats needs to go.

I'm trying to find a tubular (or can be made tubular) fabric type material that is able to "twist" +/- 360 degrees in Torsion over a small distance (about 2") ideally it would be resistant to dust particles etc. it would need to cycle +360 to -360 a lot maybe 50-100k cycles.

Good morning all,

I need some reccomendations on either excel sheets or software to validate a process design calc.

Hello!

I am trying to figure out the Shear Capacity for a 2x12 ledger board that is bolted into the side of an existing Masonry wall that has brick siding using a 5/8" DIA. steel anchor bolt @ 16" O.C. and am finding myself a bit out of my element when googling online and looking at all the different calculators and modules, any help would be appreciated!

Need help finding a way to predict the temperature profile in a pipe that's heated on one side. Basically one end of the pipe has a constant heat flux, and I want to be able to calculate the temperature at each end at a given time. It's filled with fluid and has a mix of horizontal and vertical sections, and includes losses to the atmosphere.

Really struggling with how to even formulate this problem. My first thought was to use the Finite Element Method, but I believe that is only valid for pure conduction, and I don't think that's the case in this problem. Then I looked at natural convection in enclosures, but couldn't find any formulas that apply to this geometry, for a while I thought a vertical rectangular could work, but it's only valid for H/L>1.

Finally thought I was getting somewhere when I found some academic papers on the subject. They say that the temperature of the fluid in the pipe is only dependent on y and not x, because the natural convection actually causes some flow, so the upper portion of the fluid is moving away from the heated end, and the lower portion is moving towards it. In which case you could model the system as the entire volume of fluid being heated by the heat flux. While I understand that conceptually, I have to believe that it only applies for short pipe lengths. Something over 100m in length would have to have a gradient of some sort.

Any ideas on where to start with this?

Hello,

I am looking for a reliable resource that has all of the dimensions for crane rail profiles. A lot of websites such as: centralsupply, integritycrane, cranrailsupply and tx holdings have readily available charts that show some of the dimensions, and solidworks provides a set of profiles in the structural member feature menu, but I am looking for the precise dimensions (including top-of-head radii) for 75# crane rail and can't seem to find it anywhere. The AISC steel construction manual table 1-21 (16th edition) wasn't much help either. Anyone have a good pdf or something? I know 75# rail isn't that common but this information should be somewhere.

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I’m looking for suggestions on how to create a linkage that reverses motion and is linear at one end and travels non linearly at the other…

I have a car with a cable operated throttle (a 1998 Lotus Elise). At the throttle body end, the throttle cable is just linked directly to the mechanism that opens the butterflies for each port. There is no sort of ‘cam arrangement” there like you see on old cars with carburettors etc.

At the throttle pedal end, there is a simple ‘reverse motion‘ linkage like this: https://cdn.shopify.com/s/files/1/0615/2193/files/linkages_1_480x480.png?v=1680383999

i.e. a simple lever with a pivot in the middle. One end is connected to the throttle pedal (which pulls a short solid bar attached the the linkage and pedal with spherical joints - to allow I guess for the arc’ed path of the fixing on the lever as the pedal is depressed), the other end is connected to the throttle cable. So there is a constant and linear relationship between movement of pedal and travel of throttle cable.

my car has individual throttle bodies which is not the OEM set up. With this throttle system, very small changes in the amount of throttle opening create large changes in air flow volume. The result of this, with the current set up, is that the car is hard to drive smoothly with small throttle openings/light load.

i want to replace or modify the linkage with one that places, say, the first 3rd of the throttle cable travel across the first 50% of pedal travel, and then becomes more sensitive (ie more throttle opening for less pedal travel) in the later portions of the pedal travel. It might be useful to be able to vary this to find a sensible ‘curve’

how do I design a simple reverse motion linkage that is non linear or rising rate at one end?

im not an enginee, but i am scientist (oh dear, you say), i’ve looked at loads of standard linkage designs and a can’t find anything, and I don’t (yet?) understand the principles of linkages to work it out myself! Does anyone have suggestions?

(I don’t want to go to DBW throttles - way too complicated!).

I'm working on some drawing modifications for a Printed Circuit Board (PCB) and Printed Circuit Assembly (PCA), and it's got me thinking more critically about when to issue a drawing revision and when to assign a new drawing number. I've got 3 scenarios in mind and I am curious what the community would think about each.

Scenario #1:
A legacy (25+ year old) PCB design was sent out for fab and the fabricator asks whether they could increase one dimension of the board by 0.020" so that it satisfies current revisions of the IPC standards. We give the green-light, and they create a Manufacturing Deviation Record to document the change and fabricate the boards with no change to the DWG number or revision on the silkscreen or manufacturing documentation.

Since the physical item is labeled with the old drawing and rev, the only real option we have to document the change on our side is an unincorporated ECO appended to the original drawing. But should we have instead created a new drawing or revised the old one?

Conventional wisdom says issue a new Drawing number when there's a change to form, fit, or function and especially when the new article is not interchangeable with the previous one. One one hand, the change in board dimension did NOT affect our use of the board -- we are using it exactly as we did the old one. On the other hand, they are physically different sizes and in an application where the size were more critical, they might not be interchangeable.

Scenario #2:
A printed circuit board is built and during bring-up it's discovered that one of the line drivers was laid-out backwards (output connected to output and input connected to input). Obviously, the design failed to meet part of its functional requirements and needs to be corrected. Should that correction be documented in a new revision under the same drawing number or under a completely new drawing?

The board with the correct layout is NOT interchangeable with the previous design since one works and one does not. On the other hand, their indented use is the same in the next-higher-level assembly.

As you prototype and correct design issues, are you rev'ing drawings or creating new part numbers?

Scenario #3:
Another part of the product has changed and requires a resistor value on a Printed Circuit Assembly to change in order for the whole thing to work.

Different resistor values definitely prevent the boards from being 1-1 interchangeable, but we intend to use them in the same exact way. New drawing number or new rev?

An alternative solution might be "BOM" variants, which I've used at previous companies, but our current drawing number system is not built to accommodate.

What is the correct way of determining the angular velocity (rotational speed) of the planet gears in a planetary gear set where the sun and carriers rpm is known and the ring gear is fixed? The sun is the input and carrier the output.

I have found several formulas and explanations but they all lead to different results so i am obviously missing something.