What's a Better Spring Shape?

Catsies likes springs.
Can I confirm, what you really want is the two square bars to push out away from eachother whilst remaining parallel and you want the central area clear?
I shall sketch away...
Del

Del, I'm suprised. This is an ideal application of a simple bow on each end, or recurve, or whatever, you're the bow guy. It's only 20 mm, nice little spring steel bow with the ends bent in to go into the holes. I think his design will bend down the wrong way. I presume he wants to keep everything in the same plane.

This is an ideal application of a simple bow on each end, or recurve, or whatever, you're the bow guy.
That's what I've done...Each vertical line in the pic represents a tapered limb ideally.
I didn't have the time to do a better drawing, and tapers aren't practical if the design is implemented with wire....
Del

With beryllium copper flat stock, you can punch/forge, in one operation, any shape and vary thickness throughout its length. Then form and heat treat. One-offs would be expensive but volume lowers price and there are small job shops itching _{(subliminal command)} to do it.

You could probably accomplish the same thing with simple leaf springs, perhaps with some pre-curvature formed into them. Squeeze the leaf springs together, and the two square bars come together. Release them, and the two bars return to their natural position...

A simple "square," with the corners including an angle of about 100°, and the side bulging a little.

Or 80^o with the sides curving inwards...

Could be. I am envisioning a square hollow with a groove at some depth, into which the spring should expand, leaving a maximal open area in the middle. Some OP clarification, maybe with a drawing, would help. Your first design might be viable, but the OP's sketch had inward loops that would encroach toward the center of the otherwise open area.

Ain't guesswork fun?

I assumed it was only engaging in two edges (left and right in the pics).
Del

how about some variation on this? It could be either wire or 2mm flat spring. doesn't have to be square, but radius curves or sinusoidal.

How about a large internal circlip that engages in a slot on the inside of the bars. They are cheap and readily available. This leaves open a large circular area in the middle. Other designs seem to encroach quite a bit on the open area, reducing the diameter of a shaft passing through it, if it is a shaft passing through it.

More info on the application might help.

How about sliding tubes (one inside the other) surrounded by a standard round spring?

What would be wrong with inserting a std round circlip?

There's some good thoughts here.

Maybe the leaf spring would work.

I can't use the round circlip as I need a clear square area in the centre. The comment about my loops encroaching into the clear area is correct, I would have to make the assembly rectangular to compensate.

In use the 2 bars would be squeezed together using circlip pliers in the central holes, moved into place then released below a couple of tabs. This will retain a component underneath the circlip.

If I get a chance this week I'll have a go at making one.

ya we need more design information to work with.. (or at least I do. )

Chris

What about the springs they use to hold a watch strap in position:-

Obviously you'd need corresponding holes in your square bars, and, may need a way to hold the whole assembly together. This meets your design requirement:-

"ensure that the arms of the springs remain about parallel"

The really good thing is that they're cheap as chips and readily available.

That's a nice thought, wouldn't work for us unfortunately, the finished assembly will be in vacuum & those would be hard to pump out.

I don't think they're well enough made to form a seal.

No they won't be sealed but any entrapped volumes slow down the pumping time.

D'uh!
Just dawned on me, you can make a square circlip, if the 'gap' is at one corner it should close nicely for fitting/removal as the ends of the gap are pulled together.

Sketch being done even as we speak..

Selective thinning of the material could help to induce flex where required to aid insertion/removal.
Gotta be a winner... give the cat Tuna...

Del

You beat me to it! The only difference was that I would have drawn the corner angles at about 95°; i.e., sprung a little more open.

I don't know an easy way to machine a groove into the internal wall of a square tube. A drawing of the original concept, or a more detailed description, would help in understanding the constraints.

There wouldn't be any groove, the construction of the assembly the circlip goes into would be a metal/ceramic layered construction with the circlip fitting under some tags. An angled face on the clip locks it into position.

My design is a bit sketchy just now but I will see if I can upload more detail by the end of the day.

No tuna yet, I did think of this shape but it would flex at the corner opposite the circlip pliers making insertion a bit difficult.

I still like the leaf spring idea, if the springs were etched the shape could be optimised to make it bend in the best way.

I did think of this shape but it would flex at the corner opposite the circlip pliers YES making insertion a bit difficult.NO.

I don't see why it should make insertion any more difficult than a standard circlip? The inward force of the pliers should reduce the length of the two diagonals allowing it to fit.. (assuming you make the gap big enough, to make it close enough)
I could draw dotted lines on my pic, but my dotted pencil is bust
Del

I looked at replacing the spring in my original image with a leaf spring as per Del's suggestion but that has sort of morphed into this idea.

This shows it in the assembly.

The pale blue part is what I am trying to hold, the yellow tag forms the top of the circlip 'groove'. The clip also has to carry volts from the yellow tag to the face of the pale blue part.

So it's a retaining clip for the Dilithium crystal, all part of the warp core?
Del

Spot on- for the Scalextric Enterprise.