Types of Mechanical Springs

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.

Step 1 Compression Spring

A compression spring squeezes together to create a load. You will often find these inside switches, automotive suspensions, and jacks-in-the-box.

Comments

[123mani]

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.

[chs9]

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/

[survivalengineer]

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]

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.

[sharlston]

can i be a collabortaor?

[whiteoakart]

Absolutely! Collaboration is open to anyone. I know I have glossed over a few, so any additions will only make this resource better.

[sharlston]

have you added me? ill upload pictures of springs in action like in squirt bottles and suspensions

[whiteoakart]

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?

[brettyourgoals]

What about leaf springs? Don't suppose anyone knows how easy/hard it is to replace one on a Mercedes Sprinter?

[sharlston]

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

[yoshhash]

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.

[stu2745]

A good cheap source for this type of spring (of a useful size) would be the pull starter mechanism of a petrol lawn mower.

[i make shooting things]

you missed one, a torsion spring used on catapults and other midevil devises like my torsion spring catapult (launch it!)

[whiteoakart]

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.

[i make shooting things]

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

[Clayton H.]

I built a balista in 6th grade for a science project. I might still have it.

[legan]

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]

thanks. btw, if you use the REPLY tag at the end, it posts a message back to their profile page that someone commented.

[jtobako]

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]

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.

[jtobako]

it looks like a bent washer, not cone shaped. is it called the same thing?

[gzusphish]

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]

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.

[jtobako]

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?

[trebuchet03]

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

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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]

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.

[dataphool]

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]

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.

[HamO]

Very nice instructable, congrats. Well done.

[Shark500]

I love learning!

[HamO]

I'm learning love.

[whiteoakart]

me too!

[trebuchet03]

ooooooo! Open this up for collaboration :) I've got a book of springs and can add a few types and details :)

[whiteoakart]

It is open and your name is already filed. I am more than happy to accept your input.

[Myself]

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]

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.

[trebuchet03]

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 :)