RE: Re: VP-mechanism: geometry symmetry and bearing fri...
Good tip.
Think it would be much easier to stretch to an increased length. !% stretch would be 1/4" in 2ft. Advantage is you don't have to guess the yield stress. In fact if you measure force, you can calculate the actual yield stress.
Method works for solder, copper or ...
In the case of music wire, 60,000psi yield would recover .05" in 2ft regardless of dia. Besides being straighter, yield, fatigue strength and other properties would be microscopically improved.
Money back guarantee on all free advice,
H
To: Indoor_Construction_at_yahoogroups.com
From: themaxout_at_aol.com
Date: Mon, 25 Jul 2011 23:44:11 -0400
Subject: Re: [Indoor_Construction] Re: VP-mechanism: geometry symmetry and bearing fri...
All,
A way to stretch wire to make it straight and keep it's properties is to clamp one end and pull the other end to about yield stress. This makes it take a "set" of a straight wire. As a former millwright, the usual tactic was to use a "C" clamp on the fixed end and an "over pull" lever on the other end, the wire being wrapped around a 2' long rebar about 6" up from the pivoted end. No need to pull at your best Conan the Barbarian pull, just enough to give it some yield. Letting up on the pull and noticing the wire staying straight is a good indicator.
One could do calculations based upon the tension force required to yield the wire. The wire diameter and the yield stress of the particular wire used if need be are the parameters. I'm sure someone will reply with this info. This also works for small diameter coiled copper tubing when used for hydraulic line applications. That is why the tubing looks so straight on those big machines!
FYI: Stress = (Applied tension force) / (Area of the wire) and should be larger than the yield stress of the wire. Typical yield stresses of wire are in the 60,000-80,000 #/in-2. For a .010" dia ("pi" x "r"squared) => 60,000 #/in-2 (PSI) wire...that's about a force required of (Yield Stress)*(Cross Section Area) => 60,000psi x .00007854in-2= 4.71#...not much so you have to be careful.
Pulling to just better than 5# should do the trick, but find out the wire yield stress and do a similar calculation. It's not necessary to let the weight hang for a day or so...just bringing it above the yield stress works.
Rick
Rick Pangell
Editor of "The Max-Out" Newsletter of
The Magnificent Mountain Men FF Club of Colorado
In a message dated 7/25/2011 9:14:24 P.M. Mountain Daylight Time, laflyer100_at_yahoo.com writes:
on the machinist blog they straightening music wire but chucking one end in a drill motor with the wire running through a hole in a 1/4" plate or piece of wood. the tool is held at a 45 degree angle starting next to the chuck. Run the motor at a fairly slow speed and move the tool away from the chuck towards the end of the wire. I was amazed how well it worked.
From: Benjamin Saks <bensaks_at_gmail.com>
To: Indoor_Construction_at_yahoogroups.com
Sent: Monday, July 25, 2011 4:10 PM
Subject: Re: [Indoor_Construction] Re: VP-mechanism: geometry symmetry and bearing friction
It's worthwhile to straighten your music wire or guitar string before making prop shafts. Most strings come packaged in a coiled loop in a paper envelope. The coiled wire has a memory and I've found props wobble from this.
How do I straighten mine? Well stringing them on a guitar works great if you have one but hanging a weight off the end will do fine. I let mine stretch for a week or so.
On Jul 25, 2011 4:37 PM, "John Kagan" <john_kagan_at_hotmail.com> wrote:
> --- In Indoor_Construction_at_yahoogroups.com, Tapio Linkosalo <tapio.linkosalo_at_...> wrote:
>>
>> Looking at Treger's drawing (in INAV 125) I find that he uses 0.35mm
>> (0.0138") wire for the axis. Mine is 0.30 (0.0118"), as that size is
>> readily available, but maybe that is too thin and bends in an
>> uncontrolled manner? What size are other D fliers using?
>>
>
> If you are talking about the prop shaft (the part the rubber connects to), I'd say .0118" is too small. I use .013" marked, which measures more like .0135"
>
> The material will also make a difference. Guitar strings work for me - and are cheap and readily available. I tried some stainless steel wire from Small Parts once that didn't work well.
>
Received on Tue Jul 26 2011 - 01:51:40 CEST
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