Straight Spring Help

[houdini16]

I am moving this thread to this forum, I didnt see it before.
Hello all, I am trying to find if a material exists in this state.
I am looking for a Stainless steel wire (.078-.08")that has spring properties.
I have ordered 303/304 stainless wire with spring temper, but it doesn't seem strong until you cold work it into a shape, coil etc..
I have ordered some music wire (spring steel), but Im sure it will have the same outcome.
I need the wire to be a strong spring while it is straight, it doesn't need to be formed into anything.I prefer stainless.
Anyone have a clue where I can get this material, or do you know if there is a way to heat treat it into this state?
Thanks

 

[CoryPad]

Austenitic stainless steels do not harden via heat treatment. Rather, spring temper is produced via cold deformation. So, you should order the material in the spring temper, e.g. Type 304, 1/2 Hard according to ASTM A666. Better still would be Type 302, 3/4 Hard or Full Hard according to ASTM A666.

 

[houdini16]

OK, Im not a materials Engineer so i want to make sure I dont mess things up.
If I look for 304 1/2 hard wire or 302 3/4-full hard wire. Am i to assume this is a spring temper? and the material isn't just hard? Do I need to be looking for the parameter ASTM A666?
I checked the net for a minute and I dont see anything in wire like this, the only one I found that was exactly this was in a coil and it needs to be straight.

Link

It doesnt mention anything about spring temper... Is that assumed or is this wrong thing?

Thanks

 

[desertfox]

Hi houdini16

Can you explain exactly what it is you are trying to do, a straight piece of wire will not make a very good spring.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[houdini16]

Sure, it is a regular 3 piece hinge, upper and lower stationary, with the center pivoting. the wire is the shaft for the hinge. here is the difference. the hinge opens from 0-90 degrees. it uses a pieces of thicker plate material. the pivot plate has the fulcrum corner rounded over, but it is larger than the tangent from edge 0 to 90 edge. so it has a cam effect when opening and closing. the center pivot plate is relieved in the shafts hole from either end but the center is a net fit on the shaft. this allows the spring shaft to flex and apply pressure as the hinge is moved over the cam are, so as to snap and stay at either 0 or 90 degrees . I have built a prototype, works good, I want more pressure, I will try to increase the cam difference from the current .003 to .006, if its too thick move down or up until desired. but I am not sure yet if the fulcrum/cam difference is the problem or the spring strength is not high enough.

 

[desertfox]

Hi

Can you provide a sketch with dimensions and some pictures, I can of follow but there a lot of information that you can clearly see but I can't.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[houdini16]

 

[houdini16]

As you can see from the top view the green hinge piece is setting at 0 degrees, flat against the stationary blue part, or you can rotate it out to 90 degrees. you can see the radius on the corner of the green hinge part it is .003 larger than it can be for a net fit rotation, there for if you start rotating it from zero it would get harder and then stop. but the shaft has flex, and the shaft hole in the green hinge piece has been relived more than the .003 difference in either end so only the center 1/3 is a net fit. so as you open the hinge piece out towards 90 degrees the green plate wants to roll out away from the stationary part,with the high point being the middle of its travel(45 degrees) then roll back at 90. and with the flex in the shaft it can. so it is spring loaded towards either side of the movement and locks at either 0 or 90 degree. even though at 90 degrees it only has that small flat at the far right to sit against it works perfect, but I want more snap to either side, either a larger displacement at the cam on the fulcrum, or a stronger spring than the 304 spring temper I have now. scale=blue block is 1.75" tall

 

[MikeHalloran]

I have bought 'stainless music wire' as big as 1/8" diameter, I think from McMaster-Carr.
It was hard but formable, as any music wire should be, and did not rely on my cold forming for the hardness.

It's a clever design, but will be sensitive to edge radius of the swinging door, and probably high wear of those corners and the mating surface, if that's an issue. If you want it stiffer, the easiest way might be to make the door thicker, at least at the hinge end.

This would probably be a good time to analyze some parts for stress, in particular the complex bending of the hinge pin and its contact areas on the stationary portion, which gets interesting when you start allowing the hinge pin 'beam' to deflect angularly, as it must. I suspect you will find that even the best music wire will not be adequate, which is probably why more typical designs separate the centering spring function from the hinge pin.

Have fun with it, and good luck.


Mike Halloran
Pembroke Pines, FL, USA