Stainless Wire Thinning

Ok... I have an idea to pitch to a buddy to offer him a "superior" product to one he is making and selling now. For me its just a way to
help a buddy. It requires substantially thinning about 1/3 of a short piece of stainless spring wire. Right now he is using a cludgey looking crimp sleeve to join two different size pieces of wire. It works. It sells. He warranties a fair amount when the crimp sleeve fails. I think minimum failure would be if it were one piece of wire.
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Its subject to continuous flexing and vibration when in use.
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wrote:

Its subject to continuous flexing and vibration when in use.
===============================================================Bob,
What's the original diameter & reduced diameters and over what distance is it reduced?
Are you talking "piano" wire size?
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========================================>
"Real" piano wire covers a range of sizes. I'll measure one and give some more specifics. Probably in the ball park of .045" down to . 03". Maybe 6" or 7" total with 1/3 thinned to the smaller size. The transition could cover .75".
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On Wed, 18 Apr 2012 23:44:17 -0700 (PDT), Bob La Londe

That's within the range of infeed centerless grinding, which is cheap if done in quantity. It's usually not expensive even in small batches.
However, a lot depends on the loads you're talking about.
--
Ed Huntress

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wrote:

-Probably in the ball park of .045" down to . -03". Maybe 6" or 7" total with 1/3 thinned to the smaller size. The -transition could cover .75".
You could slowly lower the wires into an etchant to taper them, but you might have to inspect under a microscope for stress concentrators at defects.
jsw
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wrote:

I had thought about hard points and figured the final transition to the smaller diameter probably should be a tiny cove rather than a hard angle. Irregular pockets from etching could certainly create small hard points though out.
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On 4/19/2012 12:33 PM, Bob La Londe wrote:

It might be worth trying, though.
Beechcraft used exactly thins kind of "chemical milling" on aluminum skins as far back as the late '50s.
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Bob La Londe wrote:

Could he use something pre-exisiting such as a double butted stainless steel bicycle spoke. They're readily available in a number of lengths and diameters in the sort of range you're looking at.
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Centerless grinding?
Or grind serrations in the ends to give the crimp something to hold onto?
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On Wed, 18 Apr 2012 23:20:58 -0700, Bob La Londe wrote:

Volumes?
* Draw the wire down (note -- I don't know how to do this, but it sounds easy if someone else is doing the work!!) * make a nice stainless collar, and braze * butt weld a .03 wire onto a .045 wire (presumably mechanically)
Whatever I did, I'd be worried about fatigue if the thing is stressed or vibrated at all. I think drawing the wire could be made to have the smoothest -- and hence most reliable -- transition.
--
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The heavy side may have occassional sudden shock forces of about 50 pound +/- , and occassional continuous loads of 3-20 pounds +/-. Best case it would experience those forces 20-50 times in a day. Worst case it would not experience them at all.
The light side will have continuous vibration or flexing of upto 1 inch (more like 1/4-1/2 inch normally) at a flex rate of about 3-10 times per second. (I'm guessing here.) Additonally the light side might have occassional greater flexing at about the same rate as the sudden loads on the heavy side.
There is a product that does this with all lighter wire, and it some times fails on the load side costing the user the load. Failure is not unreasonable if the rate is not excessive. Loss of the load will sometimes make a user cry.
There are products that do this with all heavier wire, but at the cost of the vibration and flexing. It works, but the extra vibration of the lighter wire is a desireable attribute and increases the appeal of the product.
My buddies product is a hybrid of the two and it does work. The weak link is the join. I believe he spot welds the wire side by side, and then slides the crimp sleeve over it to keep forces from working directly on the weld and the HAZ. The sleeve by itself is not enough.
The dual diameter pieces would still need to be formed using conventional wire forming techniques afterwards.
If it worked out end quantities would probably be a thousand units at a time +/-. A test run of a couple hundred would not be unreasonable. Currenty he makes a couple hundred end product at a time.
There is a caveat. I believe that a dual diameter wire might make for a superior product in several ways, however the ugly (in my opinion) crimp sleeve does draw attention to the very nature of the concept of dual wire sizes. One for strength, and one for greater vibration. It might not be better marketing to make the product prettier.
I'll measure the two wire sizes when I get out to the shop and post that info later.
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On Thu, 19 Apr 2012 09:17:50 -0700, Bob La Londe wrote:

I forgot to ask how hard the wires are.
Bicycle spokes are (or were) available double-butted, with larger diameter wire at the ends and thinned down in the middle. I don't know how it was done -- but it was affordable enough that a lot of racer wannabes got the opportunity to discover the difference between a wheel that saves an ounce of weight, and a wheel that'll survive potholes with aplomb.
So the notion of a dual-diameter wire is out there in at least one market. It seems like there might be some specialty wire shops out there that one could order from -- or one could develop a machine and do it the old fashioned way.
Hardness probably matters. The fact that it's stainless probably makes the job harder, because of work hardening.
If you want to draw attention to the dual-sized wire, make a little black plastic sleeve and force it down the wire to cover the tapered portion-- that'll make things obvious, without introducing stress risers like his current design.
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Does that larger OD section have to be perfectly round and smooth?
If not, why not go the other way? Start with a piece of the smaller diameter. Work out some way of rippling [1] the part that needs to be larger so that its effective diameter is big enoungh.
[1] Or knurling or crimping. Or flatten ever so slightly and twist. Once set up, a little machine to do this should turn out a lifetime supply in an hour.
--
Mike Spencer Nova Scotia, Canada

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writes:

That is certainly an outside of the box solution. On the surface it doesn't sound right for the application to me, but I'll think about it for a while. Its not about size, but about strength on the larger size side.
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Should be able to roll it - have two rollers each with a half-cylinder groove the size of the small end you want, spin them against each other and feed in wire the size of the big end, stop when you have enough small wire and reverse. May have to feed the wire in and out a couple of times as you bring the rollers together, depending on the two diameters, but with a limit switches that the small end hits to automatically reverse the motor you should be able to get each wire in maybe 10 seconds?
----- Regards, Carl Ijames "Bob La Londe" wrote in message
Ok... I have an idea to pitch to a buddy to offer him a "superior" product to one he is making and selling now. For me its just a way to help a buddy. It requires substantially thinning about 1/3 of a short piece of stainless spring wire. Right now he is using a cludgey looking crimp sleeve to join two different size pieces of wire. It works. It sells. He warranties a fair amount when the crimp sleeve fails. I think minimum failure would be if it were one piece of wire.
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