Cracked Hinge on Mac Portable

JDW

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I wonder if the mentioned dental scaler would work for removing this metallic covering?
If you look closely, the tips are all sharp hooks...


For my plan to work using DCM solvent, my flat PC rectangular piece (shown in red in my previous post) would need to lay flat across the ribs with virtually no grit or scratches on the backs of those ribs because DCM doesn't fill gaps. So my concern about using a spinning-hook dental cleaning instrument is that it would basically remove the chrome paint and roughen up the surface of the plastic too, making less surface area for the DCM to do its job. That's my guess anyway.

With that said, I still haven't figured out how to get that chrome paint off cleanly though.
 

JDW

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And so it begins…

IMG_7588.jpeg
 
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JDW

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Cutting out only this tiny 27 x 10 mm piece for reinforcing the back of the 5 ribs was tough, even though the polycarbonate is only 2mm thick. It was cold in my room before, but now sweat is pouring off my brow! 💦 But I can’t use that until I have tried to close the crack with the solvent, and after that finely sand off the backs or the ribs somehow to they are perfectly fat and level to be solvent-welded to this 27x10 piece I just cut out.

IMG_7589.jpeg

I have no good ventilation inside my home and it’s now dark outside, so the solvent-weld of the crack must wait until tomorrow.

I also cut out another piece for testing…

 
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Paolo B

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Cutting out only this tiny 27 x 10 mm piece for reinforcing the back of the 5 ribs was tough, even though the polycarbonate is only 2mm thick. It was cold in my room before, but now sweat is pouring off my brow! 💦 But I can’t use that until I have tried to close the crack with the solvent, and after that finely sand off the backs or the ribs somehow to they are perfectly fat and level to be solvent-welded to this 27x10 piece I just cut out.

View attachment 24887

I have no good ventilation inside my home and it’s now dark outside, so the solvent-weld of the crack must wait until tomorrow.
Was just about suggesting using some metal reinforcement…
 

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JDW

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Cutting 2.0mm thick polycarbonate zapped all my energy, so I can only imagine how precisely cutting METAL would be!

ChatGPT suggested I use fiberglass mesh tape that has adhesive backing and then put JB weld on top of that. Why mesh? Because the JB Weld would be able to go through the gaps in the mesh and make contact with the polycarbonate surface underneath, making a better bond overall, rather than just trying to pack it on top of something.

But for that JB Weld to stick, I would need to scrape off all of the metallic paint, which is probably going to be the most painful job of all. How in THE world can I get that off? I really have no idea. The gaps between the ribs don’t really make it that practical to sand out. Using a box cutter with a fine tip is the only thing I can think of.

The only thing is, photos on Amazon are not very detailed, so I couldn’t tell how wide the fiberglass mesh was until it actually arrived, and the mesh gaps are fairly wide.

IMG_7595.jpeg

🤷‍♂️
 

JDW

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The order of steps would be as follows:

  1. Weld cracked together with DCM liquid solvent.

  2. Scrape off as much metallic paint as possible with a small box cutter in between the ribs. Then apply the fiberglass mesh and JB weld.

  3. Somehow, perfectly sand off the metallic paint on the backs of the five ribs and ensure they are completely level. Then use DCM solvent to weld the 27 x 10 mm polycarbonate piece to the backs of those ribs.

There is barely enough clearance for my 2.0mm thick polycarbonate piece. It won’t touch the metal drive bracket but just barely.

IMG_7594.jpeg
 

Oelmuvun

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But for that JB Weld to stick, I would need to scrape off all of the metallic paint, which is probably going to be the most painful job of all. How in THE world can I get that off? I really have no idea. The gaps between the ribs don’t really make it that practical to sand out.
Use the technology of the sanding block.
You want to mate these two surfaces into each other, so use them together. Either use the sandpaper between them or use an abrasive lapping compound between them.. or both. In this case I would imagine the sandpaper to be enough, but if you really want to get fancy you could go extreme.

For between the ribs there are probably dremel attachments that would work. flap-discs, wire brushes, etc. Or wrap the sandpaper around the end of a strip of your polycarbonate and stuff that in there?
 

JDW

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Well everything is now only hold due to my compete lack of knowledge about chemical solvents and the SHEER STUPIDITY of ChatGPT.

AI is such an idiot most of the time that I have to call into question the entire process!

While reading through the instructions that came with the DCM liquid solvent, it says very clearly that the protective gloves need to be PE…

IMG_7596.jpeg

And when I chastised ChatGPT for having told me to buy Nitrile gloves, even though it knew I was buying DCM liquid solvent, it merely had this to say…

I gave you nitrile-glove recommendations earlier because nitrile is the right general choice for many lab/repair tasks and for many solvents — it’s a common default for handling adhesives and general chemicals. That was an oversight: I should have checked DCM compatibility specifically before recommending. DCM (dichloromethane / methylene chloride) permeates nitrile and PVC rapidly; the DCM instructions specifying PE are correct. I should have caught that sooner. I’m sorry for the mistake and for the wasted time.

What a complete moron! And we’re supposed to fear this kind of stuff taking over the world? Replacing workers? And where are all those self driving fully autonomous cars? Oh yeah…

We live in a world of lies.

This is why I was hoping I could find a firsthand experience from someone who’s actually done this kind of stuff before, but I seem to be forging new ground.

For now, I need to place an order for PE gloves, but since today is a national holiday and I have to start work tomorrow, I probably need to put it on hold until the next weekend. What a mess!

😡😤
 
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JDW

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Ah yes... Now ChatGPT says that even the DCM manufacturer-recommended PE is not enough...

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Naturally, all those EVOH and specialist gloves are outrageously priced or so thick it's impossible to do precision work.

Maybe I should just use the Nitrile and turn a blind eye to it all? Maybe use bare hands? It's all a huge shot in the dark anyway because none of us are chemical engineers, and my attempt to gain the attention of engineers on Reddit has been a complete failure.

WHY CARE?

Because, sadly, you have to POUR OUT the DCM from its glass bottle into its smaller plastic bottle so you can add the syringe attachment in order to properly dispense it to weld plastic joints together.

There's a secondary reason too. The DCM printed instructions say that heat from your hand alone can inadvertently cause the DCM laid to shoot out or flow out unexpectedly, prompting the need for some kind of gloved hand protection.

🤷‍♂️

 

JDW

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I'm not buying a face shield. And I may not even glove at all. At the end of the day, of protection prevents me from properly dispensing the liquid in a very precise manner, what good is the DCM solvent in the first place?


I decided to go to the chemistry sub-reddit and found interesting advice from chemsts about handling:

DISCUSSION #1

DISCUSSION #2

As you can see in those discussions, some say double-glove with Nitrile gloves, while others say use bare naked hands because any DCM will penetrate gloves quickly and once penetrated, the DCM would stay on the skin longer than if no gloves at all were used.

So what I did was join that group and posted the following (still waiting for moderator approval):

1763948224684.png


LINK to the above.

I will do whatever the forthcoming recommendations suggest. That will probably be to do it without gloves. But I wonder if I'll get good advice about how to properly DISPENSE the DCM, with the crack tightly closed (like ChatGPT suggests), or apply it while the crack is open, then quickly close the crack. THAT is the bigger question!



UPDATE: When checking in a web browser, it shows still awaiting moderation, but when checking in the Reddit app, it says my post was deleted...

IMG_7597.jpg

So I retitled and eliminated some references to ChatGPT, and posted in the r/OrganicChemistry subreddit here. No silly "awaiting moderation" and has 27 views as of this writing. Fingers crossed.
 
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JDW

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OK, guys...

Only one fellow on Reddit replied, first by complaining that I wrote too much (which told me he's a millennial or younger), and then he initially provided scaremongering rather than any direct answer to my two questions. Knowing his youth, I used brief responses that was able to engage his limited capacity to read text. Several messages were exchanged, but ultimately learned nothing I already knew from reading the posts of others in the Chemistry subreddits. I then checked his profile and found his is in two "teenager" subreddits, which confirmed my hunch about his age. I don't mind being a youth because I was once one myself, but I suspect some people are on Reddit to get upvotes rather than speak from a truly informed (and therefore helpful) position. Moreover, he said he has no experience welding plastics together.

And so, despite all my hours in vain of checking online in a quest to find out how to be SAFE and how to DISPENSE the DCM properly, I decided to just go outside and do my test. Heck with it! When nobody else knows or helps, the adventurous press forward, accepting the risks.

Here are the photos of the aftermath...

Note the spillage:
tempImageKjeDwa.png

Closeup showing the tiny air bubbles (zoom into the full resolution photo to see them more clearly).
tempImageQ5E0su.png

Here's a photo from the opposite side (the side I did not apply any DCM to):
tempImageWvHiNP.png
(As you can see, the DCM flowed to that edge and stopped, which is nice.)

Here's what I did after removing the protective plastic scratch cover on my transparent polycarbonate board:
  1. I used my Nitrile gloves and double-gloved. A bit tight but nicely form-fitting and my hand could move well enough. Even though the printed documentation said to use PE gloves and so did ChatGPT, all the PE gloves I saw on Amazon Japan were NOT form-fitting (they are all too big) and therefore, the sheer size of the PE gloves probably would have caused an accident. That's why I just went with my Nitrile gloves instead.

  2. I tested putting the syringe cap on the plastic bottom and pulling it off BEFORE I did anything else. I found it takes a good amount of force to pop it off the bottle, and I therefore knew that if any liquid was inside, it probably would splash out as a result of my popping off the cap. So I experimented and found that a gentle pull while twisting the cap could get it off more smoothly, and without inadvertent jerks on the bottle that could cause liquid to leap out.

  3. I removed the cap on my glass bottle and got only a very faint whiff of something, but it wasn't a strong smell at all, maybe because I was outdoors, although no wind was blowing at the time. I held my breath and poured into the tiny plastic bottle, filling only 1/5th of it. Sure enough, some spilled out onto a brick below, but nothing touched my glove that I could see or feel. I put the cap back on the glass bottle and put the syringe cap on the plastic bottle, and then I watched as the spilled liquid evaporated very rapidly. I think after 10 seconds the spill was entirely gone from view.

  4. It didn't take much pressure on the plastic bottle to get it to squirt out, and a bit more than I wanted came out as I moved the bottle to the edge I wanted to squirt it onto. You can see the spillage atop the transparent PC in my photos. That spillage is permanent and is evidence the surface of the plastic in that area was melted by the DCM. So that is basically what will happen when and if I use the DCP on my Mac Portable's hinge. But Mac Portable plastics aren't clear, so spillage won't matter. But I suspect the excess will create bulges at the back of the ribs that would need to be sanded down, on top of the sanding required to get the metallic paint off.

  5. I had to hold the plastic piece and press down on it longer than I initially thought. It was easily movable for well over 60 seconds, and it really didn't start to firm up at all until after a few minutes. So a 5 minute hold time seems to be about what is needed. Note though that there are many tiny air bubbles in my photos, and those will be the weak points where no bond was made. The bond is technically not cured for 24 hours, so I will need to wait until tomorrow night after work before I push on it and see how strong the bond is. I am going to leave it outside for a few more hours before bringing it in the house. That will ensure there is nothing left it evaporate into the air in my home.

  6. After all that, I removed my gloves, went into the house, and washed my hands with soap and water.



By the way, my post in the r/Chemistry subreddit ended up getting deleted by a mod who misused the rules...

1763967833819.png


I wrote them back telling them I wasn't seeking any such advice at all. I wrote about a page of info for the mods. I then deleted my post and left that subreddit. So I'd suggest steering clear of that one. Thankfully, the r/OrganicChemistry subreddit is much more friendly, if not entirely helpful (so far).



Hilarious. My daughter who lives in California has no idea I am touching chemicals but she just now sent me this video citing how funny it is:


It's funny, weird and unsettling, all at the same time! :LOL:
 
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stepleton

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first by complaining that I wrote too much (which told me he's a millennial or younger)
I find this kind of casual age-based dismissal unfortunately common in the retrocomputing community, even now. I'm a bit older than those age categories, but I've been part of the scene since making a webpage about the Apple Lisa in 1994, and back then I got my fair share of aspersions cast once people knew my age (but not before, strangely!). I'd hoped we'd moved along since then.

The most dynamic hardware expert in the Apple Lisa community has just finished undergrad and is in the first years of graduate school. The amount he's done for the community is truly remarkable --- he was the first to get the Lisa OS compiled after its source code release several years ago, his hard drive emulator is incredibly cheap and capable, and thanks to his (basically solo) efforts, we are weeks away from fully having a Lisa running on an FPGA. All of this stands in some contrast to the presumptive lack of attention we're a bit too quick to ascribe to his generation, not to mention folks who are only about ten years away from an AARP membership (note that the oldest millennials are around 45 today, depending on your definitions).

Avoiding this kind of nonsense over in Lisa-land meant that we didn't turn away someone who has proved to be a really awesome community member. Do you have to draw the line somewhere? Sure, maybe. ChatGPT is about three years old at this point and judging by experience here, that may be a little young yet ;)

Best of luck on the repair: I have a Portable hinge of my own that could use the same fix at some point.
 

JDW

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I find this kind of casual age-based dismissal unfortunately common in the retrocomputing community…
I apologize for possibly misreading what you wrote, but I don’t really know what you’re trying to say to me. 😅

So allow me to clarify what I said and emphasize the point I was and still am trying to make. It will be a small distraction to this thread to do that, but based on what you wrote, I feel it necessary to do that now.

If your chosen word “casual” is defined as being “flippant,” then that doesn’t describe my previous post because I thought it out a lot before I even wrote it. I wrote my words deliberately, thoughtfully, and factually based in my experience with others.

CORE ISSUE
I don’t like it when people complain that I write too much.

It happens all too often, and unfortunately, by the same age groups. I want it to stop, but I’m powerless to change it.

Those who complain about the length of what I write are dismissive of me. So it’s rather odd that I would be accused of being dismissive of those who are dismissive of me.

It’s really that simple.

Regardless of your age, don’t complain about the length of what I write, and we can get along just fine.

That’s especially true these days when people use things like “TL;DR”.

I deliberately write a certain amount of text in order to avoid a long back-and-forth that could take days. I try to write everything necessary at the beginning so people who respond have all the facts. Again, it’s that simple.

The fellow on Reddit clearly didn’t read everything I wrote, he basically admitted as much, and he didn’t even try to answer both of my questions as a result. And although you could argue that pretty much anybody could act the same way, in my experience, the people who do that the most, tend to be the younger ones, such as my son and daughter who are 19 and 22 respectively. It’s not like I’m coming from an uninformed position here. Nor am I dismissive of people younger than myself when they act appropriately. And by acting appropriately, I don’t mean acting exactly like me. I mean don’t complain about the length of what someone writes.

And it’s not like I’m discriminating against anyone either. Act right, and everyone will love you, regardless of age. Act less than right, and you’re going to have your detractors.

So why did I even mentioned the age of that fellow on Reddit? Because it’s what I experience all the time. It’s what I experience from my kids from time to time. People who are in certain age groups need to try harder to get beyond the TLDR mentality. It’s pervasive these days.

Furthermore, as I said in my earlier post, even I was young once and still remember how I thought and felt at that time. It was at that point in my life that I learned how to write more to avoid long and drawn out discussions that often happen because you didn’t write enough to begin with.

What’s most amusing about all this is that I had to write a lot of text just now in order to explain myself and I really shouldn’t have had to.

I don’t complain when somebody writes a lot of text because I usually read it and appreciate it. All I want is others to do the same for me. And if you’re a younger person and do that, I have all the more respect for you because you are bucking the trend of extreme brevity.
 

PL212

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Well, irregardless of everything else, I think we can all agree we shouldn't be use a transformers-based token sampling model for material safety advice! 😅 At least it will apologize for misleading you as you suffer...
 
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JDW

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Okay, friends. I have test results for you.

Here is a closeup of the bubbles again, this time shot from the bottom of the polycarbonate board...

tempImageubqpAf.png

Here's a video I made of the testing, showing you what it took to break the bond...


Here are photos take after the break...

tempImageZRyRmD.png tempImageVwPv2q.png

tempImageJVXkbv.png

Would love to hear your thoughts.
 
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Stephen

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Two questions for my fellow Portable owners, including @techknight

Question 1: What is the step-by-step procedure to clean and lube stiff hinges?

Question 2: My Portable’s screen was always hard to open, requiring me to press very hard on the right side of the handle to open it. Tonight I learned why. My right side hinge is cracked open as shown below. I have 24-hour Cure JB Weld epoxy. Is that enough to fix this? Any advice?

View attachment 24791

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Video:

View attachment 24792
Is this portion of the chassis removable - a subframe? I haven’t had my portable open in a long time.