Something I learned today..."Minute of Elk". Thanks for that gem!
Put your time in where it counts...for you. This site is sometimes plagued by "competitive shooters that sometimes hunt", as well as "hunters that never compete, but might outshoot those that compete!"
Boomtube clearly has the upper hand on scale mechanics. Listen, learn and fear the knowledge...but I still use a digital!
[QUOTE=montana_native;288370]If I wasn't anal retentive about reloading, I'd have to find a new hobby.
I cleaned the balance and it's a little better now. I will have to see what happens.
There is a reason I want exceptional accuracy out of my gun and it involves a huge mule deer that won't come onto our place. I will need to make a long shot to get him and I want to eliminate as many variables as I can.
Thanks to all who replied.[/QUOTE )
I would have to agree with Montana on this one.
And to prove the point on accuracy I would like to see a poll on accuracy goals for the members
of this website.
Under 1/2 MOA.
Under 3/4 MOA.
Under 1in MOA.
Under 1.5" MOA
And anything over 1.5 MOA to 3 MOA.
I'm just curious just how many of us are anal about everything that it takes to produce
Can one of the moderators do a poll for this. (I am still computer illiterate)
I disagree. Reluctance effects rise from internal eddy currents that occur when a conductive object (that little copper plate on the beam again) passes through a magnetic field.
And... I disagree in turn ;) Reluctance is not an 'effect' from moving through a magnetic field, it is a *property* of the material, whether conductor or non-conductor which represents the opposition of the material to magnetic lines of flux. Mathematically it varies directly with the length of the flux path in centimeters and inversely with the cross-sectional area and permeability of the material (at least according to the electrical primers I have on my shelves).
And, that effect ONLY exists while the beam is moving, it has zero effect on the scale when the beam stops. No non-conductive material (that is, no insulator), including air, can develop such eddy counter currents, so no counter field can occur. Meaning no insulator of any kind can experience any reluctance effect when moving through a magnetic field. ???
And... this gets to the heart of where we disagree, I believe. As I mentioned before... based on my training & past experiences working with reluctance motors (like control rod drive mechanisms for certain flavors of nuclear reactors), granted as a 'tech', not as an engineer... reluctance can be used to provide motive force, albeit at relatively low torque values, or in the case of these scales, to slow down & stop motion. From the manual for a 10-10... "it operates on the principle of a permanent magnetic field resisting the motion of a non-magnetic, copper damper vane attached to the beam." There is no magnetic field being induced in the copper vane, no significant circulating (eddy) currents generated. Just the reluctance of the non-magnetic vane to the magnetic flux of the two sets of magnetic poles in the slot creating some resistance to its motion. Normally the reluctance of copper is very, very high as compared to iron or sheet steel (like the laminations used in xfmr cores and pole pieces for motors or generators) - but compared to air, it is somewhat lower. Given that there are two sets of poles they are probably set up so that they oppose one another - so as to simply encourage the vane to *stop*, rather than push it one way or another.
As for the tendency of the vane to want to 'stick' to one side or another... I agree, it *shouldn't* be capable of building up any residual magnetism (being copper and all that). Likewise it *shouldn't* be capable of generating or retaining static charges, being made primarily of metal - iron, copper, aluminum, etc. In that regard I'm simply reporting on what I've *seen*. But... here's a thought for ya... we have a metal beam, and a metal scale body. What separates the two? Air on the one end, and agate bearings on the other - I'm not entirely sure how conductive agate (member of the quartz family) is? Two conductors separated by an insulator makes a... capacitor, capable of storing static charges. Really going out on a limb on that one, but the usual explanations (debris of some sort in the knife bearing surface areas) don't fit when I've cleaned the heck out those regions and seen the scale start to pull over to one side over time. I don't have that particular scale anymore, and my current 10-10 doesn't seem to have the same 'issues' so who knows?
You've gone where others have feared to tread!
I was wondering about those agate bearings insulating the beam. By comparison, your Redding scale has steel bearings. Would these be more conducive to grounding the beam, or is that scale's body insulated in some way? I'm sure that to some extent the bench on which a grounded scale is sitting has some influence. Any opinions?
Your input is much appreciated. I'm a PE, but my training in this area is limited to sophomore physics, and it sure didn't involve any practical applications. And, that was a long, long time ago. Thanks for the breakthrough.
Last edited by Winchester 69; 06-14-2009 at 03:11 AM.
"reluctance can be used to provide motive force, albeit at relatively low torque values, or in the case of these scales, to slow down & stop motion."
Oh well, we're in this deep....
Final quesition; What makes the copper vane reluctant to move though the magnetic field? There seems to be only two choices - either it's magic or it's the induced currents creating an electical field in opposition to the magnets.
"And to prove the point on accuracy I would like to see a poll on accuracy goals for the members
of this website."
My goal has always been one hole accuracy. I attain it quite often. Only lasts until I fire the second shot. So, I eventually settle for what ever seems the best possible for any particular rifle. Not all have the potential for the 3/16" or so groups many web shooters (quite simular to BS shooters) attain with factory rifles with blister packed BSA scopes while shooting over the hood of their truck at something thought to be about 100 yards.
My formal civilian education is perhaps a bit behind yours... but my 'applied' training was mostly directed towards 'how does this work?'. It's been a while, though. Having to blow out some cob webs and dust off some books. Which is why I take an interest in this sort of thing... whether I'm right or wrong, I want to *know* ;)
You really seem to have a thing for eddy (Foucault) currents ;) I will spot you that there *is* such a thing as an 'eddy current brake' that works much like what we have here: copper plate between two magnets, typically used for slowing down things like mag-lev trains and roller coasters. It does appear that it is relatively weak at low speeds - which is where reluctance seems to have an edge - it is a weak force to begin with. I did not know about those particular applications until I was digging around some more this morning. As for explaining the 'magic' behind reluctance... this is about the best I can provide: The concentration of flux in low-reluctance materials forms strong temporary poles and causes mechanical forces that tend to move the materials towards regions of higher flux so it is always an attractive force(pull). Copper not being a low-reluctance material (in hindsight the reluctance motors I worked with *did* have iron pole pieces)... perhaps it is 'just' eddy currents. Looks like you were right after all. Point to you