How to fix things

[houseoftang]

A lot of people here probably aren't as handy as they'd like to be.  And knowing how to fix things is a very important skill, even now when new stuff is still being manufactured cheaply and in volume.

It's my observation that many people, more women than men, learn things by "rote" or "procedure". How do you repair a dryer?  Follow these steps. . .   This works fine if you're trying to do one thing at maximum efficiency; but in most of the real world where you're just doing it once, you run into a lot of things that the instructional can't cover, and you have to improvise and innovate.  Rather than a recipe, you have to be an Iron Chef, working from first principles and prior experience.

I've been taking things apart since I was old enough to lay hold of a screwdriver, and putting them back together almost as long.  I've become really good at doing it, in fact.  Nowadays my job is mostly putting things together, but I fix stuff plenty often.  Taking things apart and putting them back together are two sides of the same coin, the process in reverse (but not always exactly the mirror image), and knowing how something goes together and comes apart is the majority of knowing how to fix it.  Add in how it can potentially break, and you're 90% of the way there.  A very nice side effect of this kind of knowledge is that you can also build stuff on your own to do what you want rather than what someone else thought you might want.

There are almost too many principles, even generally speaking, to enumerate, but I'm going to try. You want to know how basic machines work; how to combine them; what the properties of various materials are; how to modify materials to do what you want; how various materials interact; how things tend to be put together; and probably a zillion other things.  I'll try to be as organized as I can, but no promises.  I figure this will be something like Megadoom's thread on treating gunshot wounds; part tutorial, part question and answer.  I hope others who know how to fix stuff will join in and help me out.

I'm not intending this to be a specific how-to guide for, say, your specific model of dryer or sewing machine or bicycle.  But I think examples are helpful, so if you have something broken, maybe we can help point you in the right direction (and in the process help you to learn how to learn to fix things).  At the very least we can maybe help you figure out what might be wrong.

Later tonight: simple machines, the building blocks for all the more complex machines we use.


General principles for fixing stuff:

• Know how it works.  When you're fixing something you're trying to make it work the way it was supposed to.
• Understand how it was put together.  This helps you put it back together once it's apart.  You can also see how the designers intended it to be disassembled--and the intended way is usually the easiest way, in the short and long term.
• Think about the weakest points and what parts are most likely to break.  Usually it's one of the weaker parts which has failed.
• Start with more likely causes of the symptoms (including various reasons why a certain sub-system or function which is your likely culprit might have failed) and more toward less likely reasons and those more difficult to repair

[Six Gun Jim]

Good idea. The classes of fix it material would be pretty awesome to discuss too. Might help people stock up. -James

[freeyourmind]

Hmmm, simple machines are really an interesting topic. Are there 4? Are there 6? Should basic electrical devices count? Interested to see what direction you go!

[houseoftang]

It's not only the name of the forum engine, it's the name given to the basic devices that allow us to work more efficiently.  These are the building blocks of all the tools, gadgets, machines, and toys we use.

First, read the Wikipedia article:  http://en.wikipedia.org/wiki/Simple_machine

To summarize, a simple machine is a device that changes the direction or magnitude of an applied force.  There are 6 (or, arguably, fewer):, the Lever, Wedge, Inclined Plane, Wheel and Axle, Pulley, and Screw.  These actually cross over quite a bit--a screw is an inclined plane and a wheel put together.  Simple machines can be used to provide mechanical advantage, which basically means that rather than directly applying a force all at once, you spread it over a longer distance.  With a crowbar (lever), for instance, you apply a smaller force over a longer distance on one side, to get a much bigger force over a shorter distance on the other (like lifting a washing machine with the crowbar--you move the long end of the bar maybe 3 feet to get the washing machine to lift maybe 3 inches).  With a knife (wedge), you apply a smaller force over a broader area (the handle), and it converts that force into a much greater force over a smaller surface (the sharp end of the blade).  An inclined plane, like a wheelchair ramp, allows you to spread the lift over a greater distance--rather than just lifting the person in the wheelchair straight up, you lift it gradually over the length of the ramp (it'd still be easier if you were dragging the person in a chair up the ramp without the wheels).  With a wheel on an axle, you convert the greater force on the axle, which is applied over a short distance (the circumference of the axle), to a lesser force over a greater distance (the circumference of the wheel). A pulley is similar to a wheel in that it spins, but it directs the force differently.  A wheel is attached to the axle, but the pulley rotates on it, redirecting the force.  Pulleys are more useful in multiples; connect a few different size pulleys with a belt, and you can get mechanical advantage, having one turn faster or harder than the others.  Connect a few of them of the same size and you can get a block and tackle, splitting up the lifting between multiple ropes, so you pull a longer distance but gain greater force.  And as I mentioned above, a screw is an inclined plane and wheel put together; you can cinch things down tightly or lift heavy things slowly, because you have mechanical advantage by moving the "nut" as it were over a longer distance with a lesser force.

Yes, there are mathematics that go with this, but for our purposes, it's not really that important.  We're not trying to engineer things here, and most of the time when you fix stuff, you just kind of guesstimate.  This generally results in stuff being overengineered, if you do it right.  Or underengineered if you do it wrong.

There are, of course, things like hydraulics and electronics which also multiply force or redirect it.  These are also simple machines, in a way.  Hydraulics can allow you to move things gradually or in a different direction in a lot of different ways.  You can input force on one end of a hydraulic system over a big or small surface, and then have it come out over the opposite (think squirting liquid through a syringe).  You can put it through a tube of one sort or another, and make it come out somewhere else.  You can even store energy hydraulically, like in a water tower.  You can do similar things with electronic methods, what with solenoids and motors and such.

If anyone would like to add on, please do.  I'll give some examples of how complex machines are composed of simple ones a bit later.

Next up:  common parts (fasteners and others).

[Shamaness]

This is an awesome idea for a thread, tang!  I'm more of a conceptual learner - I like to understand, so I CAN improvise and tinker my way through. 

Really looking forward to reading more here.  Thanks so much for taking the time to work on this discussion!   

[residualheat]

Brill! Look forward to more. Always been interested in achieving things with small amounts of technology.

[Annihilatrix]

Awesome idea--thanks and can't wait to read this!

[urbanfarmer]

Pictures too please! Words hurt my right brain. 
My friends have always said that if I could see it and handle it, I could figure it out. That is why electrical stuff is a problem for me.  I have put in several light fixtures, but I hate working with electricity. But the more I know, the better off I'll be.

[houseoftang]

Don't worry, there'll be pictures galore.  I've got a whole post (or probably two) on screws, but I have to find pictures to go with it.  Now that things are calming down in the thunderdome thread about me, I'll probably jump back on this thread.

[houseoftang]

I'll get some pictures for the next couple posts on screws when I get a chance (or if someone else wants to help me out, you can dig some up and I'll integrate them).

In any list of common parts, the most common category will be fasteners.  Especially in our mass-produced economy, but also sometimes when you're making things from scratch by hand, the easiest way to build things is to fasten pieces of stuff together, be it clothing that's pieces of fabric sewn together rather than a garment woven in one piece, or an automobile with thousands of pieces and many thousands of nuts, bolts, screws, washers, and other parts.  I intend to write a whole section on ways of putting things together (and the corresponding ways of taking them apart), because that's the majority of the work when you're building or fixing things.  If you weren't fastening a part to the whole, you'd be replacing the whole thing, by definition.

You can tell a lot just by looking at fasteners.  First off, you can tell what tools you'll need to install or remove them (most of the time; but there's always something you didn't realize you'd need).  By looking at where fasteners are located, you can often determine how things are put together.  You can also tell which points are stronger than others, because you don't usually fasten to a weak point.  The number of fasteners, together with the strength of each fastener, at a given joint can indicate the level of stress that joint was intended to take.  Strong joints will have strong joining (many weaker fasteners, or a few strong ones).  Weak joints will have a few weak fasteners.  Also, the type of fasteners can often give you an indication of the quality of what you're looking at, even when you don't know what materials were used.  Better products, or ones made to be easily repaired, tend to have fasteners which can be easily removed and put back without destroying them.  And if you can see multiple ways to take something apart, but one way wouldn't break any fasteners, that's likely the way to go about doing it.

One of the most common fasteners (perhaps the most common overall nowadays) is the screw.  Remember that simple machine?  When used for fastening, screws typically have a fairly flat angle on the inclined plane that's wrapped around the shaft, so that you can easily turn it and sock things down tight (this is as opposed to the screw in something like a Yankee Screwdriver, which is designed more to convert the force along the axis of the screw as you push down into rotation at the bit).  Screws are great because they're almost always re-usable.  In fact, if you're taking something apart and don't intend to put it back together, it's probably worthwhile to save the screws because they're relatively hard to manufacture (thus why they didn't come into common use until fossil fuels made it cheap to automate the process).  Notice that most folks who survived the Great Depression have cans of screws lying around?  Screws originally from your washing machine might fasten duct work together really nice some day.

Screws are almost always one piece (in fact I can't think of a screw which isn't).  They're usually made from a small cylinder of metal that gets turned through a die which cuts the threads into them.  Generally a screw has a head that's wider than the shaft, with some kind of slot or shaped recess that fits some kind of screwdriver, so you can turn it.  The shaft, as I mentioned, has threads--that inclined plane which spirals down the length of it.  Sometimes the shaft is the same diameter the whole way, and sometimes it tapers at the tip (and it could conceivably taper at other points if you had some special purpose).  Tapered tips are usually for screws designed to push some material apart as the screw pushes into it, be it a screw for wood (wood screws) or a screw for sheet metal (sheet metal screws).  These kinds of screws sometimes have a notch in the shaft to facilitate the screw's cutting through the material.  If a screw does not have a tapered shaft, it's usually designed to go through a pre-drilled hole the entire length of it (though it may poke through at the tip), and for the threads to catch a something with matching threads on the other side (like a nut, which is a hole with threads around the inside).  This kind is often called a machine screw.  Screw heads come in all shapes and sizes.  Larger heads relative to the shaft can spread the pressure of the screw over a larger area (or you can use a washer to do the same thing).  A head with a beveled underside can fit into a tapered (countersunk) hole so the top of the head is flush with the surface of the material it goes through.  It can be knurled or ribbed to bite into a surface better.

Obviously, screws and other fasteners can be made from any number of materials.  While some materials are more expensive than others, there are good reasons to use almost any material for a fastener (or any fastener) even in high-quality products.  Plastic screws don't scratch stuff up, for instance, and if you don't need much strength, they could be a good option.  Brass screws are expensive and thus not usually found on cheaper products, but they're weaker than steel screws even if they look better.  The only times you can definitively say, in general, that the material of a screw (or other fastener) is sub-standard is first of all when it makes it difficult or impossible to remove something that should be removable, and second when it reacts with the likely environment or other materials and degrades (like screws rusting on a bike when they ought to be stainless steel).

Bolts are basically big screws.  Thick and long, they often have a head shaped like a hexagon or square so you can turn them with a wrench.  Carriage bolts have a rounded head with a square under it, so you can't turn it with a wrench (it gets tightened by tightening a nut on the other end).  This keeps folks from accessing it from one side, or from tearing their clothes on it (typical uses are fastening the hasps of locks or picnic tables).

Machine screws and bolts mate with nuts, either integral to a material or separate.  Separate nuts are, like the heads of many bolts, often in the shape of a hexagon or square so you can turn or hold them with a wrench.  Some of these are lock nuts, with some plastic or nylon in part of the area where the screw goes through, to prevent it from unscrewing from vibration.  If you see a lock nut, you know that it was intended to resist vibration, which tells you something about how the device was designed.  Integral nuts are nothing more than threads cut into the material (it's effectively what happens when you put a wood screw into wood, but when it's in metal or plastic it's easier to take it in and out multiple times).

A note on threads.  The size of screws is generally expressed in either standard (Imperial) terms, as the size of the shaft and the number of threads per inch (for instance 10-24, being a size 10 screw with a diameter of .190 inches from the outside tip of the threads, and with 24 threads per inch, or TPI), or in metric terms as millimeters.  I really don't know how the millimeter measurement works, except that a 5mm screw should be 5mm in diameter.  Sometimes you'll see Imperial measurements for the diameter of screws--like a 1/4" screw, or a 3/4" screw.

A note on heads.  There are far more types of screw and nut drivers than I can list, or even think of.  These are of all kinds of shapes, and often each shape has numerous sizes.  Common types include Phillips, shaped like a + sign (Phillips #2 is the most common size), flat head (the - sign), square drive (Roberts), hex or allen (hexagon) of both inside (where you use a hexagon shaped key to fit into a similar recess) and outside (like a bolt), torx (kind of like a circle with waves going around it), and various security bits (like a three-pointed "Phillips", or like hex and torx with a little raised pin in the middle) designed to keep most folks from fiddling with stuff.  These can all tell you different things.  Security bits, of course, tell you that something wasn't designed to be accessed except by professionals (not that it means you shouldn't access it yourself).  Torx and hex are generally used in applications where you want to be able to repeatedly remove and reinstall a screw without damaging it, and are indicative of something that's of decent quality, made to last.  You find these on things like bicycles and guns and cars.  Often you'll see a hex screw as an adjustment, or that allows you adjust something.  These types of heads provide good grip and because you stick something into the recess that fits tightly, tend not to strip out (become rounded) as easily.  Phillips screws are sometimes used as adjusters or for things that are designed to be removed and replaced (like the door to the battery on an alarm clock), but their use shows that the product wasn't designed to be truly durable, or that the screw wasn't designed to be used all that often or be tightened very much.  This is because Phillips screws tend to strip out rather easily, unless you put a lot of pressure on the screwdriver and keep it keenly in line with the axis of the screw (lean on it and keep it straight up).  Phillips screws are also used in many applications that aren't meant to be removed, like construction.  In these cases it's a sign of higher quality than the alternatives (flat-headed screws or just nails), because screws don't back out as easy as nails and hold things tighter.  Phillips screws (and square-drive screws) are easy to put in with power tools.  Square drive screws are good for applications where you want to put a lot of torque on the screw to drive it really deep or hard, but don't want to risk it stripping out as easily as the Phillips.  Flat headed screws strip out easily and aren't used very often nowadays.  Their one big advantage is that you don't really need a screwdriver to open them--you can use a coin or any other flat object.  It's great for things like holding sheet rock knives together, so you can open them with a nail or screw or coin or whatnot.  Flat head screws are probably easier to manufacture, since you just have to cut a slot in the head rather than mold or machine a shape, which is probably why they were the most popular type of screw in ages past.  Flat head screws may indicate something old, and you can usually confirm by the degree of weathering on the screw's surface.  If it's beat-looking, it's probably old.
 
Accessories you'll often see with screws include washers of various types.  Plain, or flat, washers spread the stress of the screw's pressure over a larger area, or allow a smaller screw to be used in a larger hole, or take up room so that a screw isn't sticking out so far, or allow a screw to turn somewhat without loosening.  Lock washers can do many of these functions, but have a split or other method of pushing against the screw to prevent it from turning.

With screws especially, but also with other fasteners, you'll save a lot of time when you learn that certain applications have standard sizes.  In construction, you often find hex bolts and nuts which fit a 1/2" or 9/16" wrench.  Lug nuts on cars are usually 15mm.  The bolt on the seatpost of a bicycle is usually 5mm.  This allows you to carry only the tools you need rather than an entire assortment of them (although there's always the one thing you didn't think you'd need that you do!)

A link to the excellent Wikipedia article on screws:

http://en.wikipedia.org/wiki/Screw

[pamela]

House, this is such a great idea! thank you for doing this!

[houseoftang]

Make sure to poke me with sharp objects to keep me working on this! 

[pamela]

oh you bet! lol
 

[amfortas]

What about those who "Walk by, and get it done.."


?

Some of us figure it out fromn first principals.
Some of us never forget what weve read...including tech-manuieals.


How Deeep is my Well??

[jock]

Scrap wood, scrap glass, screws, and a favour called in. Poke.