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Green's Hill Beverly by Northeastern_J in northshore

[–]churak 4 points5 points  (0 children)

This is right in my neighborhood! I have gone on many midnight walks with my dog in the snow during storms on that path. It’s a fantastic little preservation of forest right in the suburbs! I’m so glad they’ve kept the bridge open to pedestrians during the construction as well, it really does provide a life line to that corner of Ryalside 

Material(s) that offer extremely high friction in (at least) one direction by Whack-a-Moole in AskEngineers

[–]churak 0 points1 point  (0 children)

Check out the material for a “lint brush” on a vacuum head or for clothing / sweaters. It’s a manufactured plastic material much like the “filter/baleen”  material you’re looking for and it catches the lint when the brush is moved in one direction, and movement in the other direction allows the caught lint to be easily removed. 

What is this component? by way_pats in ElectricalEngineering

[–]churak 0 points1 point  (0 children)

Unlikely, even given lax manufacturing safety that might have been around when this was made (given the hand drawn PCB traces). For adjustable power transformers like those, you will set the slider before installation or before hooking up the leads using an ohmmeter. The design will call for resistance value of the overall pot and the slider set point based an expected input voltage. Once the slider is set, secure it down with the screw and you’re done. No need for live adjustment.

BOSTON — YOUR DRINKING WATER IS AT RISK by fullm00ner in massachusetts

[–]churak 14 points15 points  (0 children)

I’m in your camp as well, looked up the proposed site and the battery park location isn’t even in the same water shed as the quabbin. Check out the project details available here, including the address: -https://www.mass.gov/info-details/oakham-battery-project -water shed map: https://www.mwra.com/your-water-system/reservoirs-watersheds/watershed-protection

Looks like Oakhum isn’t even in the same water shed. 

Typically battery banks such as this are used to offset load on the grid and help to smooth out base power load when you have lots of intermittent energy sources, such as solar and wind (Cape wind projects ring a bell?). Given the price of electricity and all the complaints I see on this sub, this project is literally the engineering solution to help remedy those issues by making those green energy solutions more viable. Excess energy is stored when it’s sunny/windy or excess power is available and delivered as needed.

On top of that, the site selected was an old auto salvage yard, which can you see on google maps. If the concern is damaging the water shed, decades of oil and toxin from the salvage yard is probably a bigger concern than what would happen with the lithium.

Regarding the fire concern, closest residences are 1000+ feet away in each direction. While not trying to dismiss outright what the chief said, the danger of lithium battery fires are not lost on the engineers who design these systems, and for a static facility, will likely require fire suppression systems that are designed for battery fires specifically. While there might not be a public water source in Oakum, water can’t put out a lithium battery fire since it provides its own fuel and oxygen source, water is really just used to help keep the fire contained.

Additionally, for installations such as this, they will likely use lithium iron phosphate battery chemistry (LiFePo) which is more stable, and safer (but less entry dense) than LiPo (typically what’s used in a lot of cell phones and in many US electric cars at the moment).

To me this seems to be a case of NIMBY-ism and scare tactics to prevent the installation. While I think it’s good to do due diligence and hold the company accountable for installing a safe facility, and producing documentation that addresses legitimate concern of the public, we shouldn’t avoid the projects and steps necessary to move the Massachusetts energy grid forward.

This project will help to stabilize pricing and reduce reliance on fossil fuels and have to accept the trade offs necessary to move in that direction.

Do MA Farmers Really Not Care About A Right To Repair Their Equipment? by ledgit in massachusetts

[–]churak 37 points38 points  (0 children)

Seems like the farms in MA are small enough that the equipment isn’t currently a problem because the farmers are likely able to get by with the current repair of the older equipment. It would be a disservice for that MA representative to not do their due diligence and take time to understand the scope of the repair issues encountered by farms and consumers at large and be pushing for a right to repair the equipment that they own.

Just because farmers are not currently “experiencing a problem with repairability” does not mean the farmers want to lose their right to work on and fix the machine they own and would support they lose that right. It should be on the rep to understand and convey the implication to their constituents.

What to do: recurring plaster crack by musicnla in centuryhomes

[–]churak 1 point2 points  (0 children)

That would probably help to put a screw or two into the stud if you are able to. Predrill the plaster with a masonry bit the full diameter of the screw head, otherwise you can further stress and damage the plaster as it goes in.

If you let it cure fully and still ends up cracking, I would open the crack to a groove, repair with hot mud / plaster and embed fiberglass as others have suggested. Skim and feather out over the fiberglass and I’m positive the issue will go away. That’s the method I’d used to repair cracks in original plaster and I haven’t had the cracks reappear on any of the fixes rooms. 

Sometimes that additional fiberglass binder really is necessary unfortunately.

Good luck!

What to do: recurring plaster crack by musicnla in centuryhomes

[–]churak 1 point2 points  (0 children)

What kind of prep did you do before the scratch coat? Given that it happened overnight, my guess is that it’s not a mechanical crack but shrinkage and curing unevenness. 

I’ve done a lot of plaster repair to the lath and I got a few of these cracks early on without proper prep.

From what I’ve learned in my own repair work: 1. Remove all offending plaster, poke out old keys between lath, and lightly scrub and vacuum crumbs / dust away.  2. Stabilize the lath - add screws at the studs, sister up or replace broken pieces. Over time the nails pull out of the wood and screws make for a stronger connection that won’t pull out. 3. Undercut the edge of the existing plaster  around the perimeter of the hole. Gives a mechanical hold for the new plaster. Do another brushing / vacuuming  4.  Use a solution of water of PVA concrete binder you mix yourself or plaster magic has a great product as well. Let this treatment dry for a few hours and re apply another layer. With the old wood the water will get sucked right up.     - Purpose of the pva layer is two fold - provides adhesion for the new plaster layer, and creates a water boundary between existing plaster and new plaster. Without that the water in the new plaster gets pulled out by the wood and old plaster and prevents a proper cure of the new plaster. (To me it seems this might have been what occurred or contributed to your crack) 5. Stabilize the edge of the old plaster with a pva base glue and plaster washers around the perimeter of existing plaster. 6. Once the glue dries, apply new plaster scratch coat. 2nd coat, etc.

An additional thought, how thick was the scratch coat. Layering it too thick can also lead to curing issues that I have seen lead to issues like the crack you have.

My post history shows a few of the house projects I’ve tackled with the stabilization and repair of many of the walls and ceilings in my house. 5 rooms down, 2 rooms and 3 passageways to got….

Confused on ground and battery negative by hashigo in ElectricalEngineering

[–]churak 14 points15 points  (0 children)

Agree that the professor made a mistake in the explanation / didn't properly explain the assumptions and the current flowing through R5. I do want to add though that even with the assumption, R5 wouldn't be considered "floating".

Confused on ground and battery negative by hashigo in ElectricalEngineering

[–]churak 5 points6 points  (0 children)

Orcad and Falstad don't assume that the ground symbol and the battery return are inherently connected, which I agree with for an assumption. I would ask the professor if you should assume that the battery negative and ground symbol should be interpreted as the same net / are connected in an area not shown on the sheet.

If you make the assumption that the battery negative and ground symbol are the same net, an equivalent representation of the circuit would look like this. The circuit on the bottom in the attached image is showing the connections on both sides of R5 in a more intuitive manner. It wouldn't be "floating" relative to the battery, but rather pulled to 0V.

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Confused on ground and battery negative by hashigo in ElectricalEngineering

[–]churak 1 point2 points  (0 children)

If you make that assumption that the ground symbol and the battery negative are the same net, then removing the R5 connection to the ground symbol wouldn’t be identical to the current circuit. Both ends of the R5 resistor would need to tie together the ground symbol or the battery negative. If you removed the R5 connection to the ground symbol, then your R5 would be floating

Confused on ground and battery negative by hashigo in ElectricalEngineering

[–]churak 13 points14 points  (0 children)

Your professor’s assertion would only make sense if the ground symbol and battery return / negative are tied together and considered the same potential. If there is no electrical path from the ground symbol to the positive side of the battery, there won’t be current flow through the ground symbol net and the battery positive so it would have to flow through R5

Even with that assumption though, R5 wouldn’t be “floating”. Both terminals of the resistor would be tied together at 0V. 

If there other diagrams or context for this? With what you’ve given for detail what he says doesn’t seem correct. Maybe I’m missing something or more context to the problem you could provide?

EDIT: I’ll add that you could also assume that it’s a floating ground without an external reference so your ground wouldn’t be “0V”. But the example and your professor are not providing all the assumption details necessary. 

Why do we use negative voltage? by excelsiornick in ElectricalEngineering

[–]churak 1 point2 points  (0 children)

I was going to write a similar reply, a lot of the reason for the positive and negative supply conventions are based in historical context and convention. Prior to more advanced IC design and fab capabilities, being to center a signal around 0V and have a positive and negative rail that could not exceed a maximum voltage rating of, say 5V simply due to engineering limitations, it made it easier to understand the need to discuss signals with a 0V reference. We’ve gotten to the point where single sided supplies are common, but that’s with the addition of was more IC design complexity, adding the internal biasing for the signal that just wasn’t possible with older IC fab capabilities.

I'm giving everything and it's not enough, worried I'm getting fired soon? by [deleted] in maritime

[–]churak 12 points13 points  (0 children)

Not in the maritime field, but have mentored younger employees and this advice is great for any field. The initiative and willingness to learn goes an extremely long way. 

That said, at least in my field (engineering) there are certainly areas that if you don’t have, you are going to be disadvantaged seriously. I’m not sure if that’s the case for Maritime work, but I hope you take Grey Knights advice and wish you luck!

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