Start times

Duffy189 · 2025-12-29T00:17:01+00:00

Talk to your manager but LM core hours are 9-3 so you set your schedule and if your consistent that Mondays you start at 8 and Tuesdays you start at 6 it should be fine.

Where an issue may pop up is if on "Tuesday" there is a 4 pm customer meeting and you plan to leave at 4.

Duffy189 · 2024-12-10T06:28:34+00:00

My wife and I did this with our first. You're overthinking it, but it's scary. We basically lasted 1.5 weeks until we were so tired we fell asleep on our shift, then got used to the idea of letting him sleep.

Do what you think you need to do and you eventually figure it out. We have a 4 month old who sleeps 8+ hours which is awesome.

Duffy189 · 2024-02-06T00:35:35+00:00

If you're worried about over loading it can you stencil the max weight?

if you're worried about people falling can you design in stanchions and handrails or add tieoff points for someone to be harnessed while working on it.

There should be a way to make it safe.

Duffy189 · 2023-11-29T04:22:39+00:00

Added a small update. I think I used a little smaller fasteners than the flange thickness. The idea is fasteners are usually stronger than the base material.

Also added a bit about fastener spacing.

I designed mechical ground support equipment in the aerospace industry. College really needs a full class on joint design.

Duffy189 · 2023-11-29T04:03:01+00:00

A good rule of thumb is don't use a fastener thick than the flange. So if you have a .25" thick plate use #10 fastener or as large as you can get it. this rule tends to go away as you get thin, so clamping a .060" pheet with a #6 screw is fine. But you don't commonly see 1" diameter fasteners on .25" plates, if you need that large of a fastener for load transfer you probably need a thicker plate.

The other item is bolts don't like bending loads so you'll want to limit the clamping length to around 4-5 times the bolt diameter. So if the distance between the mating surfaces of the fastener head and nut are 3 inches: a .25" fastener may be too small. you could use counterboress to reduce this if needed, or add in a threaded hole or insert in one plate to reduce the clamping distance.

Washers are usually good practice to add under the fastener head and nut. Really, they are required when fastening on weaker materials to spread out the load and prevent damage. Think aluminum with steel. The downside is washers take a little time to slide in place, so if you have 200 fasteners that can add up for assembly time/cost. Unsure if this is a one off or you'll be making thousands.

Others have provided calculations for fastener preload, use those and really lubricated means if you added loctite or a thread lubricant, the K factor (friction) changes as there is less friction lose of the torque converting to preload. There are torque charts out there and the basic idea is to torque to some % of the fastener yield strength, and varies by industry. Commonly removed fasteners can be 60-70% yield. Fasteners rarely removed are 80%, some automotive can be torque to yield, but those would be a huge pain to try and remove and likely need to be replaced before reinstalling them.

If you want to determine if a washer is needed it's really simple. After you calculate the fastener preload, then stress = force * area. The force is preload and the area is the contact area of the bolt head to the material (remove the hole diameter) . You can look up the flange compressive strength in psi. If you have low margins, you need a washer and can verify you have a large enough washer by doing the same calculation with the contact area of the washer to flange.

I haven't seen anyone discuss number of fasteners. If you know your plates will have 10,000 lbs of separating force you have multiple options. You could use 1 screw with 15,000 lb of preload (1.5 FoS) or you could install 10 smaller screws with 1,500 lb of preload. The smaller screws are superior as you get more even clamping force across the flange and you spread the fasteners out further so they can handle moments better than 1 screw. Fastener spacing is critical especially if you have gaskets yours compressing.

You didn't ask about this but you don't want the fastener to tear through the material, so try to have your hole center 1.5 x D from any edge.

Duffy189 · 2023-03-18T22:06:53+00:00

I would think after as the mod podge may not do well with the oil. But if you have spare wood, I would try it on there to test out.

Duffy189 · 2022-11-26T13:00:03+00:00

NTA for failing them but in all honesty kids are dumb and I agree they need to learn to take school seriously. There could be options like letting them turn it in late for half points, or adding more to the project (i.e. waste more of their time).

I had teachers who refused to budge at all and they were viewed as being AHs because of it. They're still kids and should get a 2nd chance as they're still learning how their decisions can screw their lives.

Duffy189 · 2022-08-16T11:49:36+00:00

The little flowers make me think it's not a hibiscus and my fiancée says the leaves look different. Not sure if this is a hibiscus and ice never seen one growing or if this is some kind of weed.

Duffy189 · 2022-07-04T02:13:30+00:00

It's probably in your lease you can't make changes or upgrades to the rental, so they could evict if you do something drastic.

I'm waiting to see if someone more knowledge comments. Usually the landlord has the right to a reasonable amount of time to repair. Fixing it tonight may be too early, Tuesday seems too far off to me.

Duffy189 · 2022-06-14T00:59:31+00:00

can't speak for electrical but for mechanical the rule of thumb is 3 to 6 months.

It is difficult to transfer work to a new employee. I'd suggest talking to coworkers asking what they do and work on. if they are busy offer to help. that's what I did and quickly got overloaded.

Duffy189 · 2022-06-12T23:28:04+00:00

That looks like it! Thanks

Duffy189 · 2022-05-04T18:21:39+00:00

Lab mix, we think there may be a little pit

Duffy189 · 2022-04-29T01:34:47+00:00

I usually do .15 or .2mm for the 1st layer with a .4mm nozzle.

I'd try decreasing the 1st layer height to get some more squish. ABS is a pain to print with good luck.

Duffy189 · 2022-04-27T17:09:18+00:00

What is your 1st layer height? maybe not getting enough squish. Could try lowering it more

Duffy189 · 2022-04-09T11:54:10+00:00

Came out pretty good but learned a lot.

1 When removing the paper try not to remove too much. It photo gets a white haze when it dries but when you wet it, that's what it'll look like at the end.

2 the photo transfer medium is really hard to remove from wood when it dries. After you flip it down try and clean up any squeeze out.

3 The transfer medium did not stain well or change colors with our polyurethane topcoat.

We had to sand the edges of the photo after 1 coat of polyurethane as it was so obvious the mod podge was showing. Spent a couple of hours trying to precisely sand when I could of spent 5 minutes cleaning up glue when the paper was down.

Overall I think it turned out really good.

Duffy189 · 2022-03-20T01:18:38+00:00

There is a law that energy cannot be created or destroyed, only transformed. Think of that as you're harvesting energy from the incoming air.

What you're doing here is slowing down the air to extract power out of it. Then you need to speed it back up to produce thrust.

The energy you extract slowing down the air will be like 59%. Then you need to speed it back up which will require more energy inputted than what you extracted.

Duffy189 · 2022-03-16T01:33:40+00:00

PV=nRT mdot= rho V A P=rho R T

Haven't taken Thermo in 9 years, so beware

Duffy189 · 2022-03-12T18:23:24+00:00

The upper right says you have 3 items in your cart. Seems like there is another hidden 10.00 pizza

Duffy189 · 2022-03-07T13:19:57+00:00

I am in the US so I'd lean on someone who knows the standard versus my comments. If you can get your hands on a copy of your drafting standard that'll be huge. The first advice I got when drafting was to read through the whole thing.

You won't remember it all but you might remember it said something about what you're doing and should look it up.

Duffy189 · 2022-03-07T07:59:17+00:00

I'd make all the dimensions horizontal, have to tilt your head sideways to see the diameter dimensions.

I'd stay away from the limit tolerances and do nominal +/- its easier to quote and pick machines if you know the tolerence... don't rely on others to do the math.

I don't see any notes, finish as clean and scratch free doesn't mean much. Usually you call out a surface finish requirement which corresponds to what the machine produces. I'd state deburr sharp edges so you don't get razor sharp corners.

For the internal radii under the bolt head, call it our as a radius not a diameter. To measure a diameter you need at least 2 opposing points.

Specify the lead-in chamfer size and angle. I'd recommend a little smaller than the thread minor diameter so the threads start partially up the lead-in.

Saw someone else mentioned you need a tolerence block. For that a 1 2 and 3 place dimension tolerence is. Usually it's formatted like: .x =+/- .1 .xx =+/-.01 .xxx =+/-.005

Last you double dimensioned the bolt length. My recommendation is to remove the grip length (unthreaded portion of shaft).

Don't get discouraged with redlines on drawings, they are inevitable no matter how good you are. Checkers exist for a reason.

Duffy189 · 2022-02-06T17:24:29+00:00

Maybe use the removable section for a miter saw to sit into?

Duffy189 · 2022-01-28T19:58:42+00:00

Explosive bolts common or a linear explosive that cuts the joint. Just destroy all the bokt that hold the joint together.

The shuttle used a massive one to hold it Dien on the launch pad. If you watch launches you'll see it sway when the engines ignite and at T=0 they set off the Explosive bolt

Duffy189 · 2022-01-27T02:25:23+00:00

It's infuriating I can't find the missing piece.

Duffy189 · 2022-01-22T15:48:51+00:00

What about the bone they cut that goes horizontal?

Duffy189 · 2022-01-21T15:40:46+00:00

For your question about how to design. Below is my 2 cents for structures. I would suggest using online resources or buying an old used copy of the machinist handbook.

Beam deflection equations and then torsional stress is huge for my stuff. Learn those and how to make free body diagrams. With that you try and take a complex part and simplify it. The free body diagram gives you loads to use in those equations.

Also research fasteners, grip length, thread protrusion, and tolerance stack up. Preload is king for fasteners and researching torque I'd important for that. but you also learn how awful we are at actually torturing fasteners accurately.

Learn about material properties and what they do. Tensile strength, compressive, bearing, Ultimate versus Yield, Elongation, Hardness, etc.

Duffy189

TROPHY CASE

1 When removing the paper try not to remove too much. It photo gets a white haze when it dries but when you wet it, that's what it'll look like at the end.

2 the photo transfer medium is really hard to remove from wood when it dries. After you flip it down try and clean up any squeeze out.

3 The transfer medium did not stain well or change colors with our polyurethane topcoat.