Instructables
I know this is elementary stuff for most of you. But, we all aren't engineers. For those of us who like to disassemble things and scavenge the parts, I thought you might like to know the different kinds of common springs and what they do. I have buckets full of these things and they come in very useful.

This Instructable is open to collaboration. I would like to include "real" examples of these different springs in use. If you have an image, load it up and file it under the particular type of spring. Don't worry if it is incorrect or may fit more than one category. I may go in and rearrange for clarity.
 
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Step 2: Extension Spring

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The extension spring stretches apart to create load. They often have little loops on the ends to attach to things. You may find these on the screen door hinge, garage door hinge, and bouncy decorations that hang from the ceiling. The Slinky(tm) is a very weak extension spring.

Step 3: Torsion Spring

The torsion spring rotates around an axis to create load. They release their load in an arc around the axis. They are commonly found in mouse traps and rocker switches. They are good for things that rotate less than 360 degrees.

Step 4: Constant Force Spring 1

Also called a "clock spring", because it is often found in clockworks. This spring is made of a band of steel wrapped around itself a number of times to create a geometric spiral. The idea is to create a rotational force that releases a constant amount of load, instead of a quick burst of power. Besides clocks, they are found in all sorts of wind-up toys. Be careful when removing these from a mechanism. They tend to unravel with a dynamic flair and much excitement. They are great for things that need to rotate many times and still have a reasonable amount of force to apply and release.
123mani2 years ago
We are on a project which needs springs that can bear a minimum of 30kg and should compress about 25cm. Are they available in stores or we have to design ourselves. Please post your reply.
chs94 years ago
My friend and I have designed a spring loaded cannon, but before we commit the time and money (graduate school doesn't pay well, we have to be thrifty) I'd like to hear what you engineers think! I have a forum post describing it, an opinions are welcome!
http://www.instructables.com/community/Spring-loaded-cannon/
I have personally built a full-sized ballista using the larger leaf springs from an s10 truck.  The problems I ran into were mostly a result of my lack of any real engineering experience, and I'm sure you would be able to overcome such problems.  To winch it back, since I was on a budget, I staked it to the ground and pulled the draw string back with a truck.  I never measured the actual tension force, but it tossed a six-foot long sharpened piece of standard reinforcing bar (rebar) clear through a car from about fifty yards off.  Never had the room to fully test the range or accuracy, but the materials are viable.
whiteoakart (author) 7 years ago
This Instructable is open to collaboration. I would like to include "real" examples of these different springs in use. If you have an image, load it up and file it under the particular type of spring. Don't worry if it is incorrect or may fit more than one category. I may go in and rearrange for clarity.
can i be a collabortaor?
whiteoakart (author)  sharlston5 years ago
Absolutely! Collaboration is open to anyone. I know I have glossed over a few, so any additions will only make this resource better.
have you added me? ill upload pictures of springs in action like in squirt bottles and suspensions
whiteoakart (author)  sharlston5 years ago
I can not find the control to add a collaborator. When I published this Instructable, there was a link to add people. Any ideas how to do it now?
What about leaf springs? Don't suppose anyone knows how easy/hard it is to replace one on a Mercedes Sprinter?
its pretty hard when i was little 3 years ago my uncle was replacing his mates hes a mechanic and it took him 3 days i cant remeber what he did
yoshhash6 years ago
you also missed the A-shaped compression spring, like the big one in the hydrofoil:

http://www.instructables.com/id/How-to-Fly-a-Human-Powered-Hydrofoil---the-Aqua/

speaking of which.....does anyone have any suggestions on how i can find or salvage such a spring? I am thinking of laminating one out of many layers of wood, but it would be better if i could find one ready made.
stu27456 years ago
A good cheap source for this type of spring (of a useful size) would be the pull starter mechanism of a petrol lawn mower.
you missed one, a torsion spring used on catapults and other midevil devises like my torsion spring catapult (launch it!)
Step 3 is a torsion spring. It is identical in concept to your string version, even though, visually, they look different. BTW, I like your catapult. Have you tried the version that shoots bolts (arrow or spear, not the threaded fastener)? It is made with two torsion springs, like yours, mounted vertically. The two arms face toward the center and push a bolt along a track. It is one of the historically early designs of catapult.
sorry bout that i didnt read the steps i just skimmed the pictures
thanks
your talking about a ballista ( ballista kit ) i havent tried to build one but maybe ill give it a try. i did make a ballista shaped object that uses a rubber band on a track to shoot stuff however it broke often and had little range

if u liked my catapult check out my sling shot
I built a balista in 6th grade for a science project. I might still have it.
legan7 years ago
jtobako, I'm in the springs industry, though I hail from the far east. What you are looking for is known as a curved spring washer. You can get them easily in the States
jtobako legan7 years ago
thanks. btw, if you use the REPLY tag at the end, it posts a message back to their profile page that someone commented.
jtobako7 years ago
there is a bent washer made out of thin spring steel, not a lock washer-it's much thinner and doesn't have the cut in it. any idea what it's called? i'd like to use some to take up the play in toy joints so they stay in postion.
whiteoakart (author)  jtobako7 years ago
trebuchet uploaded the image on step 6, called a Belleville washer. Is this what you are looking for? There is a similar type with a wavy surface, too.
it looks like a bent washer, not cone shaped. is it called the same thing?
gzusphish7 years ago
So a lock washer is just a single-turn compression spring? and a rubber band is an extension spring. I would have never made the connection between the two. This is great: thanks for the instructable. Sometimes, if you want to learn about something that you know absolutely nothing about it helps to know where to start. Instructables such as this help prevent people from wasting time by introducing them to the place where their understanding of the topic should begin. The alternative is to drop them directly into the complexities of the topic ( equations and errata ) with whatever preconceived notions they may have and possibly misunderstand what they're trying to learn. I think the proper word would be clarification
whiteoakart (author)  gzusphish7 years ago
is a "gzusphish" that little thingy I see on the back of cars that looks like a fish-like loop, sometimes with the word "jesus" enclosed within? Anyway, yes, I guess a lock washer is a single-turn compression spring. I had not thought of that in this way. And it would not be a "stretch" to call a rubberband an extension spring. They do perform the same function by definition. You are absolutely correct on your thought of simple definitions. This came up for me, because I was writing an Instructable on a Live Mousetrap. I started spec'ing a torsion spring and realized that a lot of people might not know what I was talking about. Thanks for your comment. It is helpful.
jtobako7 years ago
is there a simple or common way to measure/order springs by force and deflection? i can get standard springs, but how do i know how strong they are if i'm not strong enough to test them?
Well, if you're picking out a spring to buy.....

Hooke's Law

F=-k*x

where:
x is deflection
f is the load
K is called the spring constant x


K is a common value to find in catalogs. You can also find wire diameters and other dimensions of the spring. Unless you have the equations to calculate the spring constant, it's not particularly helpful in determining the load. If you want, I can post a scan of the equations and some of the tables that go with them (it can be a little scary though :P).


As for the units of K..... Well, it's kinda weird... Kg/s2 :P So, stick with F=K*x :)


You can use hooke's law to find these values on unknown springs... But it's much easier to look them up on a table (as whiteoakart mentioned) or less desirable, do some hand calculations (assuming you know the material) :(
whiteoakart (author)  jtobako7 years ago
I know there are some websites that list all the attributes of their stock springs. I will look it up for you tomorrow and post it here. For some real fun, you can order big, metal boxes full of assorted and compartmentalized springs for your workshop.
dataphool7 years ago
Congratulations! This is a very good start to basic mechanical arts. You have not taught me any thing, but the review is constructive, and many people do not know these basics. It reminds me of the time, a quarter century ago, when I asked my wife to pass me "the pliers" that were by her left hand. She looked, and saw "wire cutters" which I know as diagonal pliers; we both learned something that day.
whiteoakart (author)  dataphool7 years ago
Thanks Dataphool. That is my goal. All of us take what we know for granted. I work with springs a lot. And they always seem to be popping out of things that I take apart for fun. I know it helps me, while trying to figure out how to make some wacky mechanism, if I know which spring does what.
HamO7 years ago
Very nice instructable, congrats. Well done.
I love learning!
I'm learning love.
whiteoakart (author)  WesDoesStuff7 years ago
me too!
trebuchet037 years ago
ooooooo! Open this up for collaboration :) I've got a book of springs and can add a few types and details :)
whiteoakart (author)  trebuchet037 years ago
It is open and your name is already filed. I am more than happy to accept your input.
Myself7 years ago
So I guess the "buckling" spring found in an IBM keyboard mechanism is just a compression spring whose behavior when unevenly compressed is known? I'm reminded of the "flagpoles" on the old Fisher-Price castle, which were extension springs without the end hooks. They were also used for their lateral load behavior, as kids could flick them and they'd make a wonderful "Sproing!" sound, plus they weren't too likely to poke an eye out. How about the doorstop springs? They're wound like tension springs but no tension's ever put on them.
whiteoakart (author)  Myself7 years ago
Oh Yeah! As an annoying 6 year old, I could sit for hours by the front door going, "sparoinnnnnnngggggggah!" over and over. I have seen both extension and compression springs used for sideways deflection like that.
How about the doorstop springs? They're wound like tension springs but no tension's ever put on them.

They are designed to act as a solid bar when small loads (that won't damage the door) are placed on them. But, when a door is opened too quickly (or in the case of a heavy door) the spring will buckle preventing damage to the door and (hopefully) to the wall. Plus, if you were to accidentally run into the stop, it won't hurt ;)

Have you ever seen an advertisement sign that was supported on a stand made of extension springs? It's the same concept -- so, if there's strong wind, the springs will buckle until the wind dies down :)