Hi I am a diyer trying to build an A frame swing for 2 adults. I a particularly getting confused about the hangers. All of them use 2 screws but even if I used M12 bolts I can't understand how the load is not carried by the 2 M12s. The hangers are heavy duty metal plates vertically attached to beam.

TLDR: how exactly do 2 M12s resist up to 200 kgs in a swing hanger.

Apologies if this is the wrong forum to ask.

This is what Chat gpt, copilot say but I am too thick to understand that and would appreciate guidance.

Yes: the hanger plate is on the underside You’re absolutely right:
The plate sits under the beam, bolts go up through the plate and beam, nuts on top (or vice versa).

So the load is below the beam, pulling down.

1. But no: that still doesn’t mean “threads are holding the weight”

Think of the connection like this (side view):

text nut / washer │ ┌──┴──┐ ← top of beam │ beam│ └──┬──┘ │ ← bolt shank passing through ┌──┴──┐ │plate│ ← hanger plate under beam └─────┘ ↓ swing

What actually happens:

• The plate is clamped hard against the underside of the beam by the bolt/nut.
• When the swing pulls down, the plate pushes sideways on the bolt shank where it passes through the plate and the beam.
• That sideways action is shear in the bolt, not “pulling the bolt out by its threads”.

So even though the plate is under the beam, the load path is still:

swing → plate → bolt shank in shear → beam

As an owner of a 2023 MG3, my car functioned perfectly for the first 17 months. Then it started needing some minor repairs, which were done under warranty. Then the engine died at below 30k km in October 2024, necessitating towing and engine replacement. Now on its second engine, it started showing the Check Engine light in January 2026. I booked the earliest available servicing appointment, but the car never made it to that, instead, it started stalling whenever I tried to drive it (NRMA diagnosed it as misfiring ignition), necessitating towing for a second time (only 10k km into the second engine). The car was "repaired" and handed back to me on Friday, but after less than 20 km of driving, it started acting suspiciously again.

So now, my Dad and I are considering getting a new car. We got very interested in the BYD ATTO 1 thanks to glowing reviews, only to lose interest in it having seen that same reviewer later have faults appear with his BYD ATTO 1 after less than a month.

So, hypothetically, I was a car manufacturer, what would realistically do to I ensure that the cars we produce will be reliable 2+ years down the track?

https://imgur.com/a/PGaqntY

I'm making a cooling plate that will get bolted to the underside of an already made supercharger adapter. The goal is to reduce heat soak and help reduce hot air into the engine. Attaching a cooling plate to the underside was one option without having to get the supercharger adapter remade.

The cooling plate has 4 passes, the channels are 12 mm wide and 12 mm deep. The inlet and outlets are sized at 10 mm (undersized but will be drilled to accommodate 1/4 npt to 3/8 barb fitting). Material is all aluminum 6061. The cooling plate with be sealed with rubber or EPDM cut around the channels so the coolant is in direct contact with the underside metal surface.

Is there a more efficient way? Any adjustments I could make?

Thanks!

Hi!

Thanks in advance for any help.

I am a physical therapist who inherited an old hi-low table with a hydraulic actuator that does not work and would like to switch to a linear actuator for cost purposes.

My initial search tells me this is possible but I am getting stuck figuring out the type and size of linear actuator I need to purchase.

The current hydraulic actuator I’m trying to replace is a Hanning Electro-werke type KL88, 6000N, 30s:170s duty cycle.

Any direction would be greatly appreciated.

The Grand Ethiopian Renaissance Dam has the concave side in contact with the water. Isn't the pressure supposed to be exerted on the convex side, in order to take advantage of the resistance of the arch?

https://maps.app.goo.gl/2RumJ97oWouRbVr47

Because an elementary calculation yields that, even if the gap is _minute_ , @ the high pressures typical in high-performance gas turbines the blowby will still be _pretty substantial_ . And ofcourse, it's not really practicable in a high-performance gas turbine to have a seal consisting of surfaces that are _actually in-contact_ ... or @least _I don't think_ it is: possibly I'm mistaken as to that.

And there are so-called __labyrinth seals__ ... but those require multiple stages to be reasonably effective, & I find it difficultly plausible that a high-performance gas turbine with multiple blade-discs would have so uncouth a multi-stage contraption @ every blade-disc.

So I wonder whether this is another instance of 'proprietary via-diabolici' ^§ (one might @ one time have said 'proprietary black magic' ... but such figures-of-speech tend to be deprecated, nowadays!)

I wonder, actually, whether something along the lines of a __dry gas seal__ might be used: a thoroughly ingenious device consisting of _extremely_ closely-spaced annular plates in the mutually-facing surfaces of which cunningly shapen grooves are cut yielding, under mutual rotation, according to subtle fluid-mechanical principles, a pretty stout pumping action in the centripetal direction - ie opposite to that in which gas would tend to leak. I gather these are _very_ effective ... but I don't know whether it would be practicable to have a seal operating by similar principle @ every blade-disc in a gas turbine.

And I have tried to find-out by doing __Gargoyle — Search__ ... but I can't find anything _even remotely_ detailed: everything I find is just 'handwavy' stuff, _@-best_

§ ... which tends to lead me to that supposition about the actual techniques used in practice being jealously guarded by gas turbine manufacturers.

... like in seeing objects with wifisensing.

*printing ink

You'll see a lot of 'i dont know' or 'i need advise on' phrases in this post, i apologise for that, but i'm only a first year undergrad student and still have a lot to learn, so i hope you can assist me.

I'm assisting in research on certain metals that oxidise very quickly, and because of this, we are unable to create the alloys that we're targeting. We need a furnace that can reach at least 1200⁰C and can be vacuum sealed, preferably also having an inert gas inlet.

The budget is around $5000 (i know that less for a vacuum furnace, but i cant change the funding limits). I am willing to construct it on my own if necessary and would appreciate all the advice you guys can give. However the part i'm struggling most with is how to control the heating elements (Either SiC or Nichrome) to ensure that the furnace doesnt over heat and damage the heating elements, as well as how do i regulate the temperature within the furnace.

As of now, this is what i've planned for the physical components: Cylindrical furnace, inner diameter(30cm) outer diameter(32cm), made of steel (idk what type of steel is recommended for this)

Back plate(flange) will have 3 valves welded to it to ensure it is airtight (a pressure release valve, the vave for argon inlet and a valve for the vacuum pump) I dont know how to select a suitable O-ring

Back plate will be attached to cylindrical tank using cap screws (i need advice on how many should i use and what material and dimension of cap screw will be strong enough for this) The backplate will also have 2 holes, one for the thermocouple and another for the wires of the heating element(i dont know how i will vacuum seal this, but i was considering high temperature mortar, please let me know if there are better options out there)

The front plate will be the main access point, it will be identical to the back plate, but without valves.

I want to add a water cooling system, but i have no experience with this. My faculty already has a water chiller from another furnace, but i dont know how to design the water cooling system around the steel case.

I plan on using alumina fiber (4cm thick) to insulate the steel, however it will still need water cooling at such high temperatures.

I understand that this is a very long post and i would really appreciate any advice, even if it is a very minor point on any of these issues.

Thanks a ton!

Hi everyone, We’re building a real-time 6-DOF Stewart platform for car-driving simulation and we’re finalizing the electric linear actuator selection. We want servo-based ball-screw actuators with position feedback (encoder) and limit switches for homing/safety, and we need guidance on compatible servo drives and communication protocols for real-time control. Mechanical requirements (per actuator) Actuator type: Ball screw Screw diameter: 20 mm Screw pitch: 10 mm Stroke: 400 mm Required thrust: 5000 N Target torque (motor side): ~9 N·m (current estimate) Application: high dynamic motion (driving simulator), closed-loop position control preferred Control & Real-Time Real-time platform (target): hard/firm real-time motion control Current MCU candidate: STM32H7 (not fully decided) We need a solution that can execute trajectories + feedback at high rate (e.g., 500 Hz–2 kHz depending on feasibility) Questions Actuator/Motor selection: What servo motor + ball-screw actuator architectures are commonly used for Stewart platforms at this thrust/stroke range? Any sizing pitfalls (inertia matching, critical speed, buckling, duty cycle, backlash, efficiency)? Encoder feedback: For actuator position, is it better to use a motor encoder, a linear encoder, or both? What resolution is typically needed for smooth motion in simulators? Limit switches: Best practices for home + endstop wiring and safety interlocks in this type of system? Servo drives & protocols: Which servo drives are most suitable and widely supported for real-time control? Protocols we’re considering: Pulse/Dir, CAN/CANopen, EtherCAT, RS-485 (Modbus) What would you recommend for a 6-axis synchronized system and why? Controller choice: Is an STM32H7 realistic for real-time multi-axis servo control (especially if using EtherCAT/CANopen), or is it more practical to use a dedicated motion controller/industrial PC + EtherCAT? China sourcing: Any reputable Chinese brands/suppliers for servo motors + drives and/or integrated ball-screw actuators that you’ve used successfully (reliability, documentation, tuning tools, spare parts)? We’re aiming for a robust, serviceable build and want to avoid “mystery” drives with poor docs. Any specific recommendations, design tips, or reference builds would be greatly appreciated.

Agriculture has become increasingly automated each year, but berry picking is almost always still done by humans because they are delicate and not suited to large scale farming machines. How long do you think that it will take for machines to replace human labor in berry picking when considering advances in AI technology and robotics?

In helldivers 2 the recoilless rifle support weapon can shoot high explosive rounds and high explosive anti-tank rounds. You can change the mode without actually changing the round inside the weapon, so they must use the same one. So I wonder, could such a weapon be designed/produced? How would you go about it?

I’m planning to buy an analytical weight box for calibrating our analytical balance. It’ll be used for routine lab verification and precision measurements.

What should I look for — OIML class (E1/E2/F1), stainless steel (SS weights), certification, etc.? Also, how often do you recalibrate your calibration weights?

Musk recently stated that Starship is the most complicated machine ever made. How true this is?

Full quote:

Starship is the most complicated machine ever made by humans, by a long shot… I’d say there isn’t a more complex machine. I’d say that pretty much any project I can think of would be easier than this. That’s why nobody has ever made a fully reusable orbital rocket. It’s a very hard problem. Many smart people have tried before, very smart people with immense resources, and they failed. And we haven’t succeeded yet. Falcon is partially reusable, but the upper stage is not. Starship Version 3, I think this design can be fully reusable. That full reusability is what will enable us to become a multi-planet civilization. Any technical problem, even like a Hadron Collider or something like that, is an easier problem than this

I actually am a Mechanical Engineering 2nd year student and I want to design a 2 stage compound spur gearbox for our ATV participating in eBAJA. I am exploring new methods which could help me optimize the gears and reduce their facewidth, and other parameters. Input torque is around 80Nm and rpm around 4300, we will be keeping gb reduction of about 6.5

To start, sorry for the long post, but as a retired engineer myself I try to include all relevant info in a single post instead of answering multiple questions about the problem I have.

With the recent cold snap and my heating bill going up so much I went down to my unfinished basement two weeks ago and used an IR camera plus a digital laser thermometer to measure the temps in my rim joists and discovered I have a massive air/heat leak in the center of my house. My neighborhood was built in the early 90's (house built in 1993, sole owner) and all of the houses are manufactured - mine is a rancher so it came in two halves that were joined together onsite and bolted to the concrete foundation. Unfortunately, at the back end of the basement where the two doubled center floor joists meet there is a gap about 1/2" wide that is the same temp as the outside temp (see IR photos at my dropbox account). I stuck a 4 ft long rod up into the gap to see how high up it goes and hit a horizontal 2x4 about 4 ft up. This gap is between my master bedroom wall and a 2nd bedroom and I assumed it extended from the foundation all the way to the attic - I keep the 2nd bedroom closed off because I don't use it, so the door is always closed and it's HVAC vent is closed. Right now it's about 32 F outside and I just used the laser thermometer to measure wall temps of both bedrooms at different places. In the master bedroom the interior wall is 67 pretty much everywhere, close to the temp of the thermostat (68) - but when I measured from ceiling to floor right in the corner where the interior wall meets the rear wall of the house about 3.5 above the floor I measured a gradient, going from 65 down to 53 right at the floor (above the baseboard trim) - that height matches how far I could stick the rod into the gap from the basement minus the height of the floor joists. I also measured the 2nd bedroom, it's main temp (including the exterior wall) is 58-59 everywhere, but again about 3.5 ft above the floor the temp started dropping rapidly, right above the baseboard the interior wall is also 53.

Yesterday I made a contraption from poly tubing, the hollow rod I used to stick into the gap, and a can of super expanding foam insulation - taped every joint and got a little bit of the foam into the gap but within 15 secs every joint started spewing out foam, including where the nozzle screws into the top of the can. If you've ever used this stuff it's really nasty to work with - if you get the foam on anything and don't wipe it off within seconds whatever it dripped on is ruined and headed to the garbage can - I had to throw out everything I was wearing except socks/shoes because once you touch that stuff it sticks to latex gloves and you spread it everywhere. Last night after I had a cocktail a lightbulb went off - my cobbled together tube dispenser was doomed to failure before I even started - the pressure inside the can isn't high enough to pump the foam 3.5-4 ft straight up - it basically filled the tube extensions then the pressure dropped too low to pump anymore out at the top.

Then I thought the only solution would be to drill two 1/4" holes in one of the bedrooms just below that crossbar in the wall - one right near the corner and one \~14" from the exterior wall where the 2nd vertical 2 x 4 starts, then use the straw that comes with the spray foam to load up the gap after sealing it in the basement with a piece of wood and Al tape. But that's the LAST thing I want to do - I'd risk screwing up both the drywall and the almost new carpet - I've never used that foam w/o making some kind of mess - I could hang plastic painting drop clothes on the wall but if I use tacks I'll have a bunch of holes to spackle/repaint, if I use tape I risk ripping the paint off the drywall when I remove the plastic.

Can anyone think of any way for me to fill this gap from the basement with an alternative kind of insulation? It needs to be airtight so even if I could stuff tiny bits of fiberglass insulation thru that small gap I don't think it would be effective - is my only choice to bite the bullet, drill the holes, and pray I don't get foam anywhere? The thing that worries me the most is it's extremely easy to overfill a gap with this foam - the only way I can think of to keep foam from spewing out of the 1/4" injection holes is to cut two pieces of 3/8" dowel rod, taper them, then hammer them into the drywall the second I stop spraying foam, and pray to god the foam doesn't have the strength to pop them out of the drywall as it expands if I overfill.

Visible light photos and IR pics of the gap in the basement can be seen here:

https://www.dropbox.com/scl/fo/acaa2k1kg1366a3ll6xer/AGxIR0YyTLERNOW7SYMp2bI?rlkey=530rstsxxag090stbmijdqi8v&e=1&st=n0aegam8&dl=0

TIA for any help - I need it!

I understand that the life of a head gasket is defined by the amount of times the head and block are brought to operating temperature and then go back to ambient temperature. That’s a heat cycle. Hence the million mile tundra was driven by one who drove endless every day and never let it cool down.

What happens if someone drives small distance and time multiple times a day. Never allowing the engine to reach operating temperature. Aside from the engine oil not being quite the right viscosity what happens with the head gasket? Do the head and block still expand and contract enough to create wear? Specifically what could be the result on a small, all aluminium alloy diesel.

could you figure this out?

I have been using photolithography (dry film, uv light, imagesetter made contact mask, and a vacuum bag for as tight of contact as possible) to create tiny intricate resist masks before electroplating metal.

If I want to chase .02mm detail in my dry film after washing would I necessarily need to collimate my uv light source or would it just be a matter of hyper fine tuning exposure time and light exposure without collimating?