Spring metal types- need insight/help

[tarbellb]

Im looking to do new product that incorporates a spring type fastener. It will need to flex approximately 1-2" over a 5" span, using 3/16"- 1/4" solid rod. And of course spring back to its original shape, not a lot of cycles over the life of it, maybe ~2000.

After doing some research ive found the following metals seem like they would work but im looking for input and suggestions as ive only worked with common carbon steel mostly.

Steel: 1074, 1075 (seems the best $) 1095, 5160, 9255?

Stainless Steel: 301

Anybody able to shed some more light on the characteristics, cost, and use of these or others?

 

[zmaxmotorsports]

Id say thats a lot of pressure youre putting on a piece of 1/4" rod flexing that much in that short of a span,can you post a drawing of what youre trying to make?

 

[HammerMechanic]

Where is the pressure focused on? One point? That seems like an incredible amount of flex across a 5" span. The 2 ends will be moving in over an inch each.

 

[larry_g]

I can't even get an idea of what your trying to do. Is the life time of this thing in minutes or decades? Makes a difference. Will you have to machine this spring/fastener? Makes a difference. Any safety or environmental concerns? Many things play into material selection and you have given nothing to go on.

lg
no neat sig line

 

[retrobuilder]

music wire or 300 tempered stainless.

 

[zkling]

Do you want the engineering answer or the WAG answer? For the former you are going to need to post a bit more info. A drawing would help to see how this will be loaded. Do you plan on prestressing the spring?

What is the frequency of the cycles? Operating temperature?

EDIT, also, what force/stiffness do you need the spring to exert?

 

[tarbellb]

All very good points fellas. I will work on a drawing right now, but you have to promise not to steal my product idea Keep in mind I would like to be able to all the fabrication in my shop. Jig bending, but probably not able to heat and quench? Need a production run of 50 or so pieces to begin with.

To address a few questions right now.
1) pressure would be focused on the two opposite ends.

2) lifetime cycles would be over years of use (~2000 over 2-10yrs)

3) I would like to either manually bend (w/ jig) or eventually have it machine bent.

4) No real safety concerns, but it does need to be weather resistent. Which can be a chemical, paint, or built in finish ie Stainless.

5) Operating temps would be normal outdoor conditions 45-110 degrees

Im using a very similar form to these weight lifting bar clamps. Same concept, same amount of pressure roughly. What metal do they use for these, is there a process they go through post forming to give it spring or is it built-in before before forming?

 

[PT Doc]

That is so different then what I thought. You likely have a few feet of metering there to distribute the force. Unless you are making a mini version with just 5" of material.

 

[tarbellb]

Yeah sorry, I know its always hard to a) describe in a clear way what your doing, b) understand what that person is describing.

Yes, there is more material then just 5" total, I imagine each piece will be linear length of about 18". What is unique to what im doing is the coil section will not be on the same plain as the flex. It will be turned 90 to the arms.

Here is my quick Skup drawing trying to show the rough dimensions and forces.

 

[kmacht]

You won't find a metal that will bend around those curves like that and still keep its spring rate. Whatever you choose will need to be heat treated after bending.

Keith

 

[APEowner]

I'd be looking for an off the shelf torsion spring and adjust my design to fit it.

 

[tarbellb]

You won't find a metal that will bend around those curves like that and still keep its spring rate. Whatever you choose will need to be heat treated after bending.

Keith

I was afraid to here that. Im hoping I may not need actual "spring" metal, and will be able to get away with something that has those qualities?


"I'd be looking for an off the shelf torsion spring and adjust my design to fit it."

Ive definitely started to consider this option, at least for beta testing. Ill keep you posted.

I also have made contact with a GJ'r and he has offered up some potentially awesome insight. Thanks guys!

 

[charle10]

Having designed, and made springs at a spring shop for the last 9 years, I would not even attempt to make that spring at home. I would seek out a local prototype spring shop that makes small batches, or a production spring shop that is willing to quote them for you. If you do take it on I would suggest being very careful forming 3/16 to 1/4" spring steel. Not only does it takes a ton of force to bend that size wire, it usually wants to go where you don't want it to. If that size wire slips while under the load of coiling it, it would have enough force to break bones, or take off digits.

There are steels that don't require heat treat after forming, but for ease of bending I would suggest a carbon steel 1050 to 1060 in the annealed state then have them heat treated when you are done. You can heat the 90deg bends to form them, but do not quench them as you will create microscopic (or larger) cracks in the steel that will eventually break. FYI, heat treat will "move" the springs bends quite a bit.

If you want another sounding board on the design, pm me and I may be able to offer some help. How much force do you need at the end of the legs?

 

[retrobuilder]

a few tips- more coils equal less spring rate given same wire size.

you can get torsion springs with bare free ends. Maybe look at mcmaster carr.

torsional and compression springs actually twist along the wire length so paint can crack or peel. Use of stainless steel helps dealing with rust unless just cosmetic? paint needs to flex- not brittle.

The spring rate is not proportional to wire diameter, actually increases by factor of a "square" or more..depends on load condition.

good luck..