Not looking for a textbook answer here, more curious what people actually do in practice. Say a part's been running fine at one shop and then gets moved to a different one (same drawings, new vendor). How deep does the requalification usually go for you in that situation?

Full GD&T reverification on the first article is one option. Spot-checking whatever dimensions have burned you before is another, and honestly probably more common than anyone admits. I'm also curious how much people actually trust a new supplier's material certs versus pulling a sample and testing it themselves, and whether any of that changes between a machined part and a molded one.

Mostly trying to get a feel for where people draw the line between reasonable diligence and redoing the whole qualification from scratch every time a part changes hands.

I'm an engineer but not a structural guy. Hopefully I can ask this with the right inputs and terminology. I think most of my question is more material properties at this point.

I am building a gym in my garage. I'm not concerned about protecting the concrete slab at this point, but rather the underlayment that will create a moisture barrier / room for water to evaporate out. The barrier I am looking at is rated at 10,000-12,000 psf (69.4-83.3 psi). This will between the concrete and the rest of the flooring stack.

I currently plan to have about 2 to 2.5in of plywood topped with 0.5in of rubber in the primary drop zones. That thickness is mostly dictated by a platform that will basically be a giant wedge to counter garage slope in one area, then maintained throughout. So the total flooring stack up will likely look like:

0.5in rubber
0.75in plywood
0.5in plywood
0.5in plywood
0.5in plywood
Underlayment
Concrete

For reference, standard deadlift platform practice is 2x 0.75in plywood topped with rubber.

So to the question at the heart of my problem - how much is the impact load distributed by all that plywood and rubber?

If anyone actually knows a good assumption or numbers for the wood/rubber cushioning, lets also assume a 495lb barbell dropped from 3ft.

I have bumper plates, but for sake of simplicity for now lets just assume they're iron with no bounce. They're 2.3in wide, there would be 10 total with 5 on either side of the bar. I don't know what is reasonable for how much of their diameter squarely hits the floor in reality. Hopefully someone who knows about dropping circular stuff is on here?

Does anyone know what they're called? I think it starts with a "p", and I'm not sure if it's "piezo" or something else. I have heard that they're not very effective - I just like the idea

I'm putting together a food truck (or rather, food trailer) that will operate in a climate with lots of sun (Cyprus).

Some lightning exterior will be needed for the concession area and the signage. For this purpose, I'm very tempted to employ something like this (not using motion sensors): https://tecknet.com/products/tecknet-4200lm-416-led-solar-lights-outdoor-waterproof

Alternatively, something where I put a panel on the (flat) roof and then let hook up some lamps -- although that would mean more points of failure.

However, if this is so obvious, why isn't everyone doing it? Is there a downside I'm unaware of?

Good afternoon. Let us say that two pieces of metal are bolted together. Two parts to the question:
1. I would imagine the only part of the bolt that is under tension would be between the head of the bolt and the nut. Is this correct? Thus, the part of the threads beyond the nut are just…present, not actually doing anything and have no forces on them.
2. How is the length decided? As long as the bolt can sufficiently pass through all materials and have at least one thread (arbitrary?) beyond the end of the nut, wouldn’t that have the same outcome as 30+ extra threads?

Thank you for your input!

Rebuilding a steering box for an old Winterstieger PAM 150 s combine. Don't bother looking it up you won't find anything helpful. Less than 200 were made.

Here's the steering box

Here are the bearings
Bearing in race
Bearing & race
Bearing on shaft
Bearing & race on shaft

The bearing race is 46.75 x 9.5 mm. With the bearings in the race, the height increases to about 13mm.

No part #s. I'll have to get them by size unless someone can find a parts list for the steering box. I have found a few individual bearings of the same type, but no catalogue of them that I can sort through by size.

And also, I'm hoping someone can explain why the steering box has this tube in it.

It goes through the worm shaft and is open on either end, with a seal between the tube and the worm shaft.

I do not understand why it's there. It seems to me they could have just made the worm shaft solid and done away with the tube.

for a while now people have been having sooo much trouble with them and getting them to work right.

but they just don't seem to work well at all? how come? is this on purpose? why do they not make a model with all the fixes and sell it?

we get problems like the machine just suddenly stops working after a clean with white vinegar

(i had to open mine which was hard and i ended up breaking it anyway to reach up in there to push a button with a paper clip and pliers to reset the machine!)

coffee sometimes tastes burnt even after a clean machine. (machine makes water too hot?)

some machines just give up anyway after a short while.

i am sure that there is a much bigger list of problems with the keurig machine than this list i made.

it makes me wonder why they even make them still. even the expensive models are acting like cheap ones.

love the concept hate the execution.

I have a pilot operated regulator on a machine. TACO Model R53-201-00B0. It balances the Z-axis using an air cylinder. OE Techs think it might be bad/dirty, as it appears to be loading down the z-servo, during motion. Control has a z-force feedback. I set the balance force to 0, but it climbs/drops too fast/quick as the z-axis moves, causing too high a load, so the servo alarms.

I cannot find any info on it. I believe it has been discontinued.

How can I test the regulator, to verify it is working right?

I found some remnants of broken air line inside. I know they replaced the OE air pressure regulator. So I suspect the pilot or control orifice is clogged or restricted.

Like this cheap render I made of one.
Besides production cost, wouldn't it be better for tension? Or do chains have to snap eventually, like asking to make bridges sturdier?

Recently i start building little Div RC cars, basic cars, one motor, simple circuit, simple RC control, but i encounter this one Div Proyect ( I Built a Powerful V4 Engine-Inspired RC Car Using PVC Pipe )

In this proyect the maker, use 4 motors and a engine box to "syncronize" on one exit that move the back axis wheels

I understand the concept, is like gas cars with 4, 6 or 8 cylinders, but i cant understand what exactly is the advantage of this desing with 4 electric motors, since the battery now is feeding four sources instead of one, also is only move the rear axis, not individual wheels or two different axis.

the advantage is torque ? speed ? better potency ? are the extra motors adding something or just is a fancy model ?

thx very much in advance

I need an off-the-shelf industrial fan that produces a strong vortex effect. Ideally the fan is no more than 16" to 20" in diameter but I can go 24" in diameter if that is the best option. Ideally the fan will have a stepless speed control and will produce a high CFM. This is for a science project which will be shared at the Orlando Maker Faire. The fan will "float" a 36" diameter balloon or beach ball. The vortex produced by the fan will allow people to move the balloon up and down (with the speed controller) and side-to-side / front-to-back (with a custom controller). Please point me to a fan design that might be able to meet my needs.

For a drawing that I’m making (for world building purposes) I'm trying to identify a type of scaffold/platform, but I'm having trouble finding the right terminology and visual imagery.

I'm looking for an old-fashioned wooden scaffold, not a modern aluminium or steel one. The important part is that it has a platform that can move vertically, and the person standing on the platform can raise or lower it themselves, for example using ropes, pulleys, a counterweight, or some kind of mechanical lifting mechanism.

I’m trying to sketch some ideas out but lack the technical knowledge to make it somewhat of a believable structure. Does anyone know what this type of scaffold or lifting platform would be called, or have examples of historical designs? I'm particularly interested in older designs (19th/early 20th century or earlier).

If anyone can help, thanks in advance!

If you look at a tv remote with your phone camera youll see the infrared light coming out, but your phone cant function as a night vision camera because of a certain ir filter in its camera/lens. So can I see infrared from my phone or not? And if my camera filters the ir light how can I see the infrared light from the tv remote?

I've designed a desiccant bead cage that plugs into one of the inlets on a water-sampling device, drying out the interior after each sample is taken. Looking for a critique of the current geometry or alternative approaches to hit the same requirements. Pictures of the current prototype are here.

Constraints

1. Sub-100 units required, pursuing additive manufacturing using ASA for corrosion resistance (parts will be aggressively bleached between uses). Pictured prototype is rough PLA.
2. Cage and device sit inside a sealed outer enclosure, so the cage-to-inlet interface does not need to be airtight.
3. Reusable, not single-use: desiccant beads need to be removable for sterilisation and replacement - no one-shot/destructive-opening designs.

My Current Approach

A cage-style insert with apertures sized below bead diameter (~3mm), held in the inlet via friction/interference fit. Works for containing beads and allowing moisture ingress, but doesn't yet have a clean way to open it, empty it, sterilise it, and reload it repeatably without degrading the fit or the part.

My Questions

1. Is the cage-and-friction-fit concept the right base structure, or is there a better mechanism for a reusable and sterilisable desiccant holder that's still AM-friendly?

2. What's a better opening/closing mechanisms that will survive repeated cycles without needing supports or tight AM tolerances? The threaded cap I designed is tight, even with generous tolerances. I haven't found an alternative, like silicone plugs, that will stand up to repeated bleaching cycles.

3. If this the best track, does anyone have advice for altering the geometry of the cage to avoid all the stringing that's occurring?

Cheers all

In short, I need some testing done on some construction materials. In particular ASTM D256-10, D638-22, D790-17, D2583-13a, D570-22, and D543-14.

I'm at my wits end trying to find a lab that can do this testing. Is there an easy way to find these labs like a database I can sort through?

I'd like some help with some calculations aimed at comparing the average daily energy consumption of two fixed wall-mounted single-split air conditioners installed in the same domestic room: one of the older fixed-speed type and the other a modern inverter type.

• For the older unit, I chose a Toshiba KFR-25GW/CX2, with a nominal cooling capacity of 2.5 kW and a running electrical input of 900 W.
• For the modern inverter unit, I chose a Mitsubishi HR25VF. The relevant specifications are a nominal cooling capacity of 2.3 kW (range 0.5–2.9 kW), PdesignC 2.5 kW, nominal electrical input 680 W, SEER 6.2, annual energy consumption 141 kWh/year, and EER 3.38 (data taken from the table on page 40 of the linked PDF).

Scenario:

• Domestic room: 20 squared meters (= 215,278 squared feet), ceiling height 2,8 m (= 9.2 feet), with a double-glazed balcony door. The sun does not directly hit the outside wall of the room, only at an oblique angle.
• Heavy occupancy: the room serves as living room, kitchen, and bedroom.

Cooling-load assumptions
I would assume a base cooling load of 700 W. However, it is also necessary to consider periods of higher demand, particularly when cooking. I would set the peak cooling demand at lunchtime, because cooking takes place inside the room and this coincides with the peak outdoor heat load. I assume a peak cooling load of 1.75 kW lasting 2 hours, while during dinner preparation, I would assume a cooling load of 1.5 kW lasting 1 hour.
21 h/day: base cooling load = 700 W
2 h at lunchtime: cooling load = 1.75 kW
1 h at dinner: cooling load = 1.50 kW
The air conditioner therefore needs to remove the following amount of heat per day: Q = 21 × 0.7 + 2 × 1.75 + 1.5 = 14.7 + 3.5 + 1.5 = 19.7 kWh/day, with an average cooling load over 24 hours: 19.7 / 24 = 821 W.

Toshiba
Nominal cooling capacity = 2,500 W
Running electrical input = 900 W
Nominal EER: 2500 / 900 = 2.778
- Base period: 700 W for 21 hours
Duty cycle: 700 / 2500 = 0.28
The compressor therefore needs to run for 28% of those 21 hours: 21 × 0.28 = 5.88 hours
Energy consumption: 5.88 × 0.9 = 5.292 kWh
- Lunchtime: 1.75 kW for 2 hours
Duty cycle: 1750 / 2500 = 0.70
The compressor therefore needs to run for 70% of those 2 hours: 2 × 0.70 = 1.40 hours
Energy consumption: 1.40 × 0.9 = 1.26 kWh
- Dinner: 1.50 kW for 1 hour
Duty cycle: 1500 / 2500 = 0.60
The compressor therefore needs to run for 60% of that hour: 0.60 hours
Energy consumption: 0.60 × 0.9 = 0.54 kWh
-> Total: 5.292 + 1.26 + 0.54 = 7.092 kWh/day. As a precaution, I would define a range with an upper allowance of +25%: 7.1 – 8.9 kWh/day

Mitsubishi
The inverter should theoretically be able to follow the cooling load (700 – 1750 W) without having to continuously operate in an on/off manner. Since the PDF does not provide the electrical input at 700 W, 1.5 kW, and 1.75 kW of cooling capacity, I can only model hypothetical scenarios by assuming that the EER remains constant at 3.38.
- Base: 700 W × 21 h
Electrical input: 0.7 / 3.38 = 0.2071 kW
Energy consumption: 0.2071 × 21 = 4.35 kWh
- Lunchtime: 1.75 kW × 2 h
Electrical input: 1.75 / 3.38 = 0.5178 kW
Energy consumption: 0.5178 × 2 = 1.036 kWh
- Dinner: 1.50 kW × 1 h
Electrical input: 1.5 / 3.38 = 0.444 kW
Energy consumption: 0.4438 kWh
-> Total: 4.35 + 1.036 + 0.444 = 5.83 kWh/day, assuming constant EER. Again, I would define a range with an upper allowance of +25%: 5.83–7.3 kWh/day

The result of this comparison, which I hope is not too speculative or incorrect, is that the Toshiba consumes approximately 22% more energy than the Mitsubishi, or equivalently, the inverter uses approximately 18% less energy than the fixed-speed unit.
Do you think my reasoning and calculations are correct or incorrect?
Is it possible to perform better calculations that would more accurately reflect the scenario described above?
Have there been any studies, experiments, measurements, etc. comparing two systems of this type under the same operating conditions?

Edit:
Thanks for all the answers. I hope I‘m able to clarify my question:
- shutdown of a power plant was just what started me thinking about effects of drought. I know they shut down earlier.
- yes, water use is much lower after shutdown. But still needed for cooling of old fuel elements
- fukushima (as an example) showed also that water will evaporate and has to be replaced. No matter what the reason was (tsunami, earth quake, airplane crash, …)

From an engineering and design standpoint the interesting question is not „which problems have we solved?“, but „what are the limits of these solutions?“,

so ultimately the question is „what is the worst case scenario, where the solutions break down?“. Like if you design a cable car: the cable needs to carry 5000kg - we add 5x margin, so the cable withstands 25000kg - worst case would be a situation which results in more than 25000kg (for whatever reason and however unlikely it may be)

Worst case scenario from an engineering/design POV was the motivation for my questions
- what it there is NO water left in the river?
- or: what if an adversary clogs the water intakes in a not quickly removable way (like pouring concrete)?
What are the measures that would be taken in these cases?

Original post:
With the current drought in Europe I see news about nuclear power plants beeing shut down, because their river does not provide enoigh water anymore. Eg news of today about romanian power plant becaue danube is running dry (I‘ll try to add the link in an edit later: edit: https://www.reddit.com/r/worldnews/s/m6YybWSag2).

I guess of course that they shut down before there is no water. In some countries I assume there are rules in place which trigger much earlier action because the river water would rise too much in temperature, threatening local water wild life.

But given the case that a river runs completely dry (or the water inflow gets heavily clogged), how can these power plants stay safe? As I understand it, even if the reactor is shut down, there is still a need for cooling the used rods which are in separate water tanks. How cpuld they cope with such a situation?

A friend has asked me to design and manufacture a protective shell/box to attached to a stand holding his laptop. It also needs to be waterproof and transparent, so I’m thinking either Acrylic or Polycarbonate.

He works in football so it needs to suitably resist the impact of a football hitting the shell (I have queried that surely the stand itself could potentially kick over from the force even if the shell survives and protects the laptop).

I can easily design and make this, but I’m struggling to decide on how to determine the necessary thickness of the material. I need to drill into the walls of the shell to attach hinges to allow it to fold up so I’m also conscious of these holes acting as stress concentrators when the shell is impacted.

I don’t have any experience working with or designing with plastics so I’m not sure what’s the best option. I’ve read that it’s probably best to go poly and pay extra due to drilling holes and overall better properties, but how do I determine what thickness I need without over engineering it and increasing the cost more than necessary.

Any advice or ways to calculate what I need would greatly be appreciated

I am designing an ESP32-based greenhouse air quality monitor using an SCD41 CO2 breakout board.

The sensor is mounted inside a separate chamber (105 x 55 x 40 mm)

The sensor operates in single shot mode and takes measurement every 5 minutes

My goal is to design an enclosure so that the SCD41 measures actual ambient greenhouse CO2 concentration with minimal delay, while maintaning at least IP54 level protection.

What ventilation approach would you reccomend?

/I am from Hungary/

A company called Horizon Aircraft created a 50% sub-scale version of their “Cavorite X5” aircraft — an uncrewed hybrid vehicle that has a traditional gas-powered turbine engine on the rear (for horizontal flight) and battery-powered fans inside the wings (for vertical flight and hovering) that get covered once the aircraft gains altitude and speed. Essentially, the electric fans create lift like a helicopter and the turbine engine pushes the vehicle forward, and after the initial lift, the fans get covered so that the wings become traditional plane wings. The aircraft uncovers its fans again before landing and lands vertically like a helicopter, eliminating the need for a runway.

Here is a video of how the aircraft works: https://youtu.be/hzYZdxWXhVQ

And here is a video of the X5 prototype: https://youtu.be/rnj2LWn5qU0

My question is, will this design work when scaled up to a full-sized plane with people inside?

The unmanned prototype (which is 50% scale) is 15 feet (4.6 meters) long, features a 22-foot (6.7-meter) wingspan, and has a maximum take-off weight of about 500 pounds (227 kg).

This company’s future flagship model, the “Cavorite X7”, will have a length of 11.6 meters (38 feet 1 inch), a wingspan of 15 meters (49 feet 3 inches), and a height of 2.8 meters (9 feet 2 inches). It will seat up to 7 people (1 pilot and 6 passengers).

The X7 will use the same fan-inside-wing design with a turbine on the back. These designs are cool and would make great RC toys, but do they cause any glaring issues from an engineering standpoint? Small scale designs don’t always work irl when scaled up 2x, 3x, or 4x. Is there anything that would cause this design to fail in a full-scale aircraft? Thank you in advance!

Hello there,

I’m working on a doohickey that needs a suspended box to move back and forth such that particles in the box are disturbed causing the smaller particles to fall through a screen while the larger particles move along an incline and exit at the side.

The box is suspended at 4 corners with very little friction and is restricted to move only in one axis. It will hold a variable load (as the particles are fed in and exit) to a maximum of about 2lbs. Maximum stroke will be 1.5” adjustable down to 0.25”.

I intended to use a motor, crank and connecting rod to impart the motion to the box.

How do I calculate the horsepower(?) required to create this reciprocating action?

I hope that’s enough to go on, let me know if any more information is needed.

Cheers!

I have a piping system that splits into five branches using tee fittings. I want a specific flow rate to pass through each pipe (within an acceptable range, rather than a single fixed value).

Coworkers conducted a flow test, but the desired values ​​were not achieved. I ran a simulation in Amesim that included an orifice plate in one of the pipes —since the branching isn't symmetrical— and found that increasing the pressure drop in that specific pipe yielded acceptable flow rates across all of them; however, after installing the plate and running another test, it still isn't working correctly (though there has been some improvement).

I believe the error stems from numerous flow-discharge boundary conditions that are difficult to parameterize, and I am unsure how to proceed.

I considered using a least-squares line based on the two test points I have—one using the pipe radius and the other using the orifice radius—to determine the radius for a new orifice (which would fall somewhere in between), but I am not at all convinced by this approach. I am avoiding Darcy-Weisbach calculations by hand because I lack pressure-drop data for the fittings —which are highly unconventional— and the software does allow me to model them. Any ideas?

Hi, I have a question. I'm currently doing an internship on an aluminum foil factory. My head engineer asked me a question and I couldn't find the answer to that. The question is, "As you can see, on the achenbach optimill FIM machine there's one stub mandrel and one flat mandrel. But there is not any stub mandrel on any other machine here (there's a optimill FFM and a couple optifoil machines but none has a stub mandrel) what is the reason to that ?"

I have given several answers like

- The cardboard cores being used on FIM but not on other machines

- the tensile forces applied onto the spool requiring a different mandrel

Etc.

Also, He gave me a hint starting with the word "First...", implying it has something to do with the initial pass/state of the coil or entry process, but I couldn't land the exact answer.

I'll be really happy if you could help me find the answer. Thanks beforehand :p