6 ms·

Workmanship standard for crimping, interconnecting cables, harnesses, and wiring

180 points by throw0101c 2y ago

OldGuyInTheClub 2y ago
Before I worked in aerospace, I wondered why that industry cost so much. Now I understand that every requirement within each requirement document has to be "flowed down," maintained, verified, documented, and that compliance has to be proven along the chain from design to operation. The number of these documents grows at some beyond-linear rate with project complexity. Of course, this is not all the source of cost but it is a good chunk. But, if you're building spaceflight hardware that can't be repaired once launched, it is necessary.
- mschuster91 2y ago
  ... and all of the documentation has to be kept around for decades, same for the knowledge of how it was constructed and maintained. That's what makes missions like Voyager or even the ISS possible in the first place - a lot of the people who did the early work on either are probably dead now.
- tekla 2y ago
  When I worked on some aircraft, every single line of code that was added or changed had a digital and paper record of the change and the reason for it.
- neilv 2y ago
  Inspired by very serious traceability, like for aerospace engineering, I did a very-very simple and lightweight system, for the security practices & assurances of a non-aerospace startup. I was proud of not only of how effective yet non-encumbering the practices, and how smart our external assurances, but the lightweight way of implementing traceability between the two. A single, short internal document tracked not only practices, but sections were annotated with all the external documents/instances that made assurances wrt to those practices. So when we did need to change something, we knew what was easy and hard to change. (Interface vs. implementation.) Of course, the very first externally-shareable document side of this, I explained to our enterprise salesperson that it would convince the partner's savvy IT people that we were fully competent and diligent, and said a bit about how everything in there was carefully designed and traceable... Well, maybe you can guess how that went. Not everyone is familiar with building things that really have to work correctly, nor with how a little bit of judicious process can actually make things dramatically more efficient, nor with any kind of traceability rigor. If you're not familiar with that, or aren't aligned with that, then the most efficient thing in your mind might be to quietly change a copy of engineering document, to say whatever is most expedient in the moment. And don't tell anyone that you changed a copy of an engineering document, since that would not be a happy vibe when everyone likes what you're saying, and so not a good use of your time. :) (I default to confidentiality about such things, even in absence of NDA. But I can mention this anecdote, in this professional practice discussion within the field, since the company is no longer in business, and there are no unresolved liabilities.)
  - newsclues 2y ago
    I think it may be seen as a feature not a bug when there is cost plus contracts and regulatory capture limits competition.
    - OldGuyInTheClub 2y ago
      I will agree that there is a lot of overhead per engineering hour in this market area. But, I also think there's a great deal of misunderstanding about how government contracting works. Cost-plus fixed fee means the fee is agreed upon at the outset. If you overrun you may get the cost of the extra work performed but you get no fee (profit) on it. When the corporation sees that dilution, there is usually hell to pay. If the government gets tired of the overruns, it can and does cancel the contract. There are different contract types with award fee and/or incentive fees each with its own peculiarities. The Federal Acquisition Regulations (FAR) make for interesting reading: https://www.acquisition.gov/far/part-16 https://www.acquisition.gov/far/part-16 " Part 16 - Types of Contracts"
      - newsclues 2y ago
        The government contracting scam is to agree to a set percentage of the total cost as profit, so the contractor has an incentive to increase the total cost in order to maximize the dollar amount of profit they can extract. And that’s without using subcontractors to transfer even more wealth. The business is: If profit is % of X Then maximum X
  - OldGuyInTheClub 2y ago
    > If you're not familiar with that, or aren't aligned with that, then the most efficient thing in your mind might be to quietly change a copy of engineering document, to say whatever is most expedient in the moment. You might be joking here but in case you're not, there is serious configuration control and change management at play. Documents go into a controlled repository, are watermarked, and have other protections applied to them. Anyone trying this especially on a government contract is risking a lot.
- euroderf 2y ago
  Oh but we're bringing in some hotshots from McKinsey who have some ideas about how we can trim all this unnecessary overhead. They have assured me that absolutely nothing can go wrong.
nickt 2y ago
There were some good comments last time around, I can’t believe that was 9 years ago! https://news.ycombinator.com/item?id=9905875 https://news.ycombinator.com/item?id=9905875
Modified3019 2y ago
A personal favorite, the Fastener Design Manual: https://ntrs.nasa.gov/citations/19900009424 https://ntrs.nasa.gov/citations/19900009424 In particular >Lockwashers >The typical helical spring washer shown in figure 14 is made of slightly trapezoidal wire formed into a helix of one coil so that the free height is approximately twice the thickness of the washer cross section. They are usually made of hardened carbon steel, but they are also available in aluminum, silicon, brome, phosphor-bronze, stainless steel, and K-Monel. The lockwasher serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking.
- petee 2y ago
  Someone on YT did a demonstration on a paint shaker, and the bolts loosen nearly as fast as having none. Internal/external tooth washers or nylocks are the way to go
  - cuSetanta 2y ago
    Nordlock washers are the best, but they are expensive and a little space inefficient.
- deleted 2y ago
  [deleted]
- analog31 2y ago
  One useful property is that when partially tightened, they allow slight re-positioning of an assembly, before driving the fastener all the way home. In other words, they're actually used as springs.
- perihelions 2y ago
  (OCR error: s/brome/bronze/. Just pointing this out as a warning because I read it literally, and was very confused and spent some time search querying silly things).
cuSetanta 2y ago
As a spacecraft Assembly, Integration and Test (AIT) Engineer, one of my areas of expertise is harness manufacture and routing. So this naturally involves an awful lot of crimping. I am a certified crimping operator and inspector under the ECSS standards (which go a bit overboard at times in their requirements when compared to the NASA standards). I am lucky to have built a large amount of harness has/is/will fly on many spacecraft for many customers. There are a lot of unique challenges to crimping for spacecraft harnessing, but in almost all circumstances the main issue has be schedule. Very few project managers that I have worked with, even those who have a lot of experience, plan for enough time to complete the harnessing side of a project. Depending on the number of crimping configurations that are present in a system, it can take days to calibrate all of the crimp tools before starting. Every crimp needs to be inspected before the heatshrink can be shrunk, and often before the next crimp can be performed if the routing is critical. Routing involves labeling, gluing of tie-bases, bundling of harnessing, and the shielding.... jesus christ the shielding can be a nightmare... Man I love making harness, honestly one of my favourite things to make. Not sure if anyone cares enough to have questions, but happy to answer them if they exist.
- goy 2y ago
  I'd like to know more about the education & career path that lead you there ...
  - cuSetanta 2y ago
    At undergraduate level I studied Physics and Astronomy, and then did a research MSc as an optical astronomer, which I hated and drove me away from Physics and Astronomy as a whole. I spent a few years working in IT Support before deciding to go back to University to study Spacecraft Engineering at Surrey University. Which was a wonderful course, that gave an incredible overview of how one builds a spacecraft. More than most of the Master programs I have seen in the field since, the guys at Surrey had very real experience building quite a few spacecraft, which shone through in the projects and courses. After that I started a PhD in Southampton that had an industrial sponsor, who eventually ended up offering me a job to build spacecraft before I finished the PhD itself (which was a little complicated in itself), which I took. After I started with them, I basically apprenticed under an experienced AIT engineer who was coming up to retirement. This is where I really learned a lot. If you ever get the chance to work under someone in the later stages of their career, you really can learn a lot from them. That was at OHB Sweden, which was an excellent place to see a broad range of things in the industry. I go to work on multiple spacecraft and various stages of development, from proposal, to qualification, to final assembly and test, and to launch as an operations engineer. Really a super experience I am not sure I could have been luckier ending up there. After that I joined a very small team building the ispace lunar lander, which I am fairly certain will remain the pinnacle of my career. Never have I worked with such a great team on a great project. Everything just worked between us, and a small team really achieved something spectacular (even if it ended up in a crater on the moon). Now I am working in Ireland for a data acquisition system developed for flight and launch vehicles. Learning the ins-and-outs of ethernet communication and analog circuitry. So far my complete lack of understanding of electronics hasn't been a problem, somehow.

180 points by throw0101c 2y ago

Before I worked in aerospace, I wondered why that industry cost so much. Now I understand that every requirement within each requirement document has to be "flowed down," maintained, verified, documented, and that compliance has to be proven along the chain from design to operation. The number of these documents grows at some beyond-linear rate with project complexity. Of course, this is not all the source of cost but it is a good chunk. But, if you're building spaceflight hardware that can't be repaired once launched, it is necessary.

mschuster91 2y ago
... and all of the documentation has to be kept around for decades, same for the knowledge of how it was constructed and maintained. That's what makes missions like Voyager or even the ISS possible in the first place - a lot of the people who did the early work on either are probably dead now.
tekla 2y ago
When I worked on some aircraft, every single line of code that was added or changed had a digital and paper record of the change and the reason for it.
neilv 2y ago
Inspired by very serious traceability, like for aerospace engineering, I did a very-very simple and lightweight system, for the security practices & assurances of a non-aerospace startup. I was proud of not only of how effective yet non-encumbering the practices, and how smart our external assurances, but the lightweight way of implementing traceability between the two. A single, short internal document tracked not only practices, but sections were annotated with all the external documents/instances that made assurances wrt to those practices. So when we did need to change something, we knew what was easy and hard to change. (Interface vs. implementation.) Of course, the very first externally-shareable document side of this, I explained to our enterprise salesperson that it would convince the partner's savvy IT people that we were fully competent and diligent, and said a bit about how everything in there was carefully designed and traceable... Well, maybe you can guess how that went. Not everyone is familiar with building things that really have to work correctly, nor with how a little bit of judicious process can actually make things dramatically more efficient, nor with any kind of traceability rigor. If you're not familiar with that, or aren't aligned with that, then the most efficient thing in your mind might be to quietly change a copy of engineering document, to say whatever is most expedient in the moment. And don't tell anyone that you changed a copy of an engineering document, since that would not be a happy vibe when everyone likes what you're saying, and so not a good use of your time. :) (I default to confidentiality about such things, even in absence of NDA. But I can mention this anecdote, in this professional practice discussion within the field, since the company is no longer in business, and there are no unresolved liabilities.)
- newsclues 2y ago
  I think it may be seen as a feature not a bug when there is cost plus contracts and regulatory capture limits competition.
  - OldGuyInTheClub 2y ago
    I will agree that there is a lot of overhead per engineering hour in this market area. But, I also think there's a great deal of misunderstanding about how government contracting works. Cost-plus fixed fee means the fee is agreed upon at the outset. If you overrun you may get the cost of the extra work performed but you get no fee (profit) on it. When the corporation sees that dilution, there is usually hell to pay. If the government gets tired of the overruns, it can and does cancel the contract. There are different contract types with award fee and/or incentive fees each with its own peculiarities. The Federal Acquisition Regulations (FAR) make for interesting reading: https://www.acquisition.gov/far/part-16 https://www.acquisition.gov/far/part-16 " Part 16 - Types of Contracts"
    - newsclues 2y ago
      The government contracting scam is to agree to a set percentage of the total cost as profit, so the contractor has an incentive to increase the total cost in order to maximize the dollar amount of profit they can extract. And that’s without using subcontractors to transfer even more wealth. The business is: If profit is % of X Then maximum X
- OldGuyInTheClub 2y ago
  > If you're not familiar with that, or aren't aligned with that, then the most efficient thing in your mind might be to quietly change a copy of engineering document, to say whatever is most expedient in the moment. You might be joking here but in case you're not, there is serious configuration control and change management at play. Documents go into a controlled repository, are watermarked, and have other protections applied to them. Anyone trying this especially on a government contract is risking a lot.
euroderf 2y ago
Oh but we're bringing in some hotshots from McKinsey who have some ideas about how we can trim all this unnecessary overhead. They have assured me that absolutely nothing can go wrong.

nickt 2y ago

There were some good comments last time around, I can’t believe that was 9 years ago! https://news.ycombinator.com/item?id=9905875 https://news.ycombinator.com/item?id=9905875

Modified3019 2y ago

A personal favorite, the Fastener Design Manual: https://ntrs.nasa.gov/citations/19900009424 https://ntrs.nasa.gov/citations/19900009424 In particular >Lockwashers >The typical helical spring washer shown in figure 14 is made of slightly trapezoidal wire formed into a helix of one coil so that the free height is approximately twice the thickness of the washer cross section. They are usually made of hardened carbon steel, but they are also available in aluminum, silicon, brome, phosphor-bronze, stainless steel, and K-Monel. The lockwasher serves as a spring while the bolt is being tightened. However, the washer is normally flat by the time the bolt is fully torqued. At this time it is equivalent to a solid flat washer, and its locking ability is nonexistent. In summary, a lockwasher of this type is useless for locking.

petee 2y ago
Someone on YT did a demonstration on a paint shaker, and the bolts loosen nearly as fast as having none. Internal/external tooth washers or nylocks are the way to go
- cuSetanta 2y ago
  Nordlock washers are the best, but they are expensive and a little space inefficient.
deleted 2y ago
[deleted]
analog31 2y ago
One useful property is that when partially tightened, they allow slight re-positioning of an assembly, before driving the fastener all the way home. In other words, they're actually used as springs.
perihelions 2y ago
(OCR error: s/brome/bronze/. Just pointing this out as a warning because I read it literally, and was very confused and spent some time search querying silly things).

cuSetanta 2y ago

As a spacecraft Assembly, Integration and Test (AIT) Engineer, one of my areas of expertise is harness manufacture and routing. So this naturally involves an awful lot of crimping. I am a certified crimping operator and inspector under the ECSS standards (which go a bit overboard at times in their requirements when compared to the NASA standards). I am lucky to have built a large amount of harness has/is/will fly on many spacecraft for many customers. There are a lot of unique challenges to crimping for spacecraft harnessing, but in almost all circumstances the main issue has be schedule. Very few project managers that I have worked with, even those who have a lot of experience, plan for enough time to complete the harnessing side of a project. Depending on the number of crimping configurations that are present in a system, it can take days to calibrate all of the crimp tools before starting. Every crimp needs to be inspected before the heatshrink can be shrunk, and often before the next crimp can be performed if the routing is critical. Routing involves labeling, gluing of tie-bases, bundling of harnessing, and the shielding.... jesus christ the shielding can be a nightmare... Man I love making harness, honestly one of my favourite things to make. Not sure if anyone cares enough to have questions, but happy to answer them if they exist.

goy 2y ago
I'd like to know more about the education & career path that lead you there ...
- cuSetanta 2y ago
  At undergraduate level I studied Physics and Astronomy, and then did a research MSc as an optical astronomer, which I hated and drove me away from Physics and Astronomy as a whole. I spent a few years working in IT Support before deciding to go back to University to study Spacecraft Engineering at Surrey University. Which was a wonderful course, that gave an incredible overview of how one builds a spacecraft. More than most of the Master programs I have seen in the field since, the guys at Surrey had very real experience building quite a few spacecraft, which shone through in the projects and courses. After that I started a PhD in Southampton that had an industrial sponsor, who eventually ended up offering me a job to build spacecraft before I finished the PhD itself (which was a little complicated in itself), which I took. After I started with them, I basically apprenticed under an experienced AIT engineer who was coming up to retirement. This is where I really learned a lot. If you ever get the chance to work under someone in the later stages of their career, you really can learn a lot from them. That was at OHB Sweden, which was an excellent place to see a broad range of things in the industry. I go to work on multiple spacecraft and various stages of development, from proposal, to qualification, to final assembly and test, and to launch as an operations engineer. Really a super experience I am not sure I could have been luckier ending up there. After that I joined a very small team building the ispace lunar lander, which I am fairly certain will remain the pinnacle of my career. Never have I worked with such a great team on a great project. Everything just worked between us, and a small team really achieved something spectacular (even if it ended up in a crater on the moon). Now I am working in Ireland for a data acquisition system developed for flight and launch vehicles. Learning the ins-and-outs of ethernet communication and analog circuitry. So far my complete lack of understanding of electronics hasn't been a problem, somehow.