Re: VP-mechanism: geometry symmetry and bearing friction

From: leop12345 <leop_at_lyradev.com>
Date: Thu, 28 Jul 2011 14:12:41 -0000

Tapio,

The 20 pounds of force, using a 10kg hanging mass, does not provide the stress necessary to get to the yield point of 0.35mm (about 0.0137") music wire. The wire will not straigten with that force. The average breaking point of 0.013" music wire is just over 50 pounds of force (hanging a 23 kg weight will do just fine). The yield strength of good music wire is about 85%-90% of the breaking strength. Thus, you would need to hang at least a 20kg weigh on the wire to see any straigtening.

One needs to be careful straigtening music wire by stretching with a weight. If the yield point is exceeded by too much, the wire necks down and weakens in some places (using stretching to straigten wire causes a permanent slight reduction in the wire diameter), so the wire should be checked afterward for sections that have thinned down by more than a few thousands of a millimeter.

When I need to straighten music wire (guitar strings, usually), I stretch it out tight. Then I further stretch it out by a bit more than 1% of the original length (1% elongation or 1 cm for a 1 meter guitar string). This takes about 45-50 pounds of force and usually gives a reasonably straight piece of wire. Most of the time, a 0.013" guitar string breaks where the it is wrapped around the bobbin at about 35-40 pounds of force (15kg-18kg of hanging mass). However, the guitar string is still fairly straight even then.

I hope this helps.

Leo

--- In Indoor_Construction_at_yahoogroups.com, Tapio Linkosalo <tapio.linkosalo@...> wrote:
>
>
> Thanks to all for the tips on the F1D prop shaft. As I wrote before, I
> have a scroll of 0.35mm wire from Blashewicz (ukraine), so I tried to
> straighten that. I calculated that the pull force would be about 4 to 5
> kilos, pulled it up to 10kg (20 pounds), but it remained curved. I then
> tried the "rotate and pull through an inclined hole" -method, but this
> only produced a wire with a nice corkscrew pattern... :-) Luckily I
> found another short piece of 0.35mm wire, where I managed to salvage
> enough straight parts for 2 hubs; this probably originates from my time
> spent in Montreal.
>
> I guess I need to go to guitar string shop next. I did that several
> years ago when I started to build pennyplanes or F1M's. That was not a
> good experience, but the strings that I bought were rather mellow steel,
> easily bent, but also lost their shape too easily. Are there different
> brands of guitar strings, and what to look for to get "springy" wire?
>
>
>
> -Tapio-
>
Received on Thu Jul 28 2011 - 07:12:48 CEST