Never been done before balance scale experiment.....badaboom ;-)

[BoydAllen]

I'm doing my best to follow along with the discussion in this thread, but one question keeps nagging me: why would you want stronger magnets to increase the dampening effect? Put another way, don't you want the scale to be sensitive, and easily pushed off balance?

In order to understand what takes place, you need to understand how magnetic damping works. When a conductor (the copper blade or plate) is moved through a magnetic field (the space between the damping magnets) eddy currents are created within the conductor, as well as a magnetic force that is in opposition to the field that the conductor is moving through. It is the interaction between these magnetic fields that damps the beam's motion. If there is no motion, no current is generated or any magnetic field, so as the beam slows the eddy currents and magnetic field of the conductor are reduced as well, to the point where when the beam stops, there damping magnets exert no force on it at all. My concern was that if you add weight to a balanced scale, that the damping would be so strong that the amount that the beam would move before being stopped would be less than it would be with weaker magnets. I can do some testing on this when the magnets arrive later today. With the scale beam motionless the magnets have no pull on it, but I was concerned about how quickly the force would generate and how much swing would take place after the magnets are made stronger. We shall see.

 

[Webster]

On he one with the single magnet, how is the sensitivity when trickling? Man that is some serious damping. I take it that the 1/2 square faces of the magnet are its poles. I never thought of using a single magnet. I noticed the piece of foam in the notch....simple and direct. I like that. Thanks for the info, and videos.

Would a single magnet move the beam and knife edge a little crooked. I would use two to play it safe. $3.95 Neodymium Rare-Earth Magnet Discs magnets at Harbour Freight. Don't know if they are as strong as the ones you bought. Depending on size 3-6 per $3 pack. Should be strong enough. I have a few a home they are hard to pull apart.

 

[Brians356]

Without dampening, the scale beam will swing up and down and up and down... forever.

True - in the absence of any friction. Remove the magnets entirely and your scale will eventually come to rest, albeit slowly. The slight friction between knife edges and agate bearings will slowly dampen it. There's also air drag on the beam and pan, small but nevertheless not zero. Slight movement of the surrounding air will induce the beam to start swinging.
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[Brians356]

If you pull the housing off of the M-5 that the copper blade runs in, you can measure the space and then order something the right size.

The OEM M5 magnets are horseshoe type, with a 'V' shaped notch separating the two poles. You had to grind away the center rib that fits in the 'V' notch on each side to narrow the gap between your simple cylinders. I didn't want to grind away any of the M5's original pot metal, so I used smaller neodymium magnets, with a steel tie strap to form my horseshoes:


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[Brians356]

Here's another great source for magnets:

https://www.kjmagnetics.com/

I found it best to arrange each side as a horseshoe magnet. If you have a strong single N pole opposite a single S pole, it is not as "neutral" in the space between as two sides, and it tended to induce oscillation rather than dampen it. You want there to be a relatively neutral region directly between the magnets, without closely spaced parallel force lines, as illustrated by this drawing. Notice there is a N and S pole on each side, i.e. akin to two horseshoe magnets (a variation on the simple parallel magnets shown here):



In this arrangement, maximum damping is induced when the blade swings past center, and encounters the close parallel force lines adjacent to the middle eddy section.
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[Brians356]

The damping blade on my scales seem to be a copper alloy. Now I see why. Observe:

http://digg.com/video/copper-and-magnets
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[M-61]

Sort of a larger version:
https://allaboutmagnets.wikispaces.com/How+does+the+Giant+Drop+use+magnets?

 

[Fotheringill]

Boyd:

Keep them away from your dog, as well. You don't want them trying to attach to the dog's collar ..... from the inside.

 

[JohnKielly]

The scale seems to be of good quality and tuned up OK (within the limits of my skill) but it is apparent that the magnets that are part of the damping system are weaker than my old USA produced scale of the same model.

I recall many years back when forums were group emails, somebody ran experiments on how to get the most accuracy out of shooter type balance scales. One of the conclusions they came to was that the best accuracy was achieved when dampening magnets were removed, the weight being judget correct when the pointer oscillated equally both sides of the zero line.

 

[Brians356]

I recall many years back when forums were group emails, somebody ran experiments on how to get the most accuracy out of shooter type balance scales. One of the conclusions they came to was that the best accuracy was achieved when dampening magnets were removed, the weight being judget correct when the pointer oscillated equally both sides of the zero line.

Good luck estimating that with any precision with human eyeballs. Every swing of the beam is slightly shorter than the preceding swing, so that implied zero is constantly shifting in both directions. And an undampened scale is much more subject to the vagaries of always-present air movement. To prove this, walk away and let the undampened beam eventually stop moving (you may have to switch off any forced-air temperature control system to achieve quiescence!) Simply approaching the scale at normal walking pace, sitting down at the bench, and breathing normally will likely stir the beam and set it moving again.
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[BoydAllen]

I recall many years back when forums were group emails, somebody ran experiments on how to get the most accuracy out of shooter type balance scales. One of the conclusions they came to was that the best accuracy was achieved when dampening magnets were removed, the weight being judget correct when the pointer oscillated equally both sides of the zero line.

I think that the reason that this may have been true is that in my experience unmodified balance reloading scales have issues with reliably returning to the same exact zero. Proper knife edge work solves that problem. The last scale that I worked on, before the Chinese one, will show slight additional deflection with each added granule of Varget. The best way to reliably observe these small differences is to use a web cam, phone, or tablet camera to eliminate parallax and magnify.

 

[danny]

By Thursday we should know. I have been playing with a new old stock Chinese made RCBS 10-10 balance reloading scale that I wrote about in another thread. The scale seems to be of good quality and tuned up OK (within the limits of my skill) but it is apparent that the magnets that are part of the damping system are weaker than my old USA produced scale of the same model. Sooo I ordered some little but powerful cylindrical neodymium magnets that I plan on putting on the bottom of each of the scale's magnets, held there by magnetic attraction, opposite poles facing each other. Just now (early Monday afternoon) after checking on my order with the magnet company, I spent a couple of minutes with one of their engineers to find out if my plan has a chance of working, that is strengthening the magnet field of the damping system. He said that it should. If this works, I believe that it will be the first time that it has been done. On the other hand, if it does not, I will be out ten dollars for some very powerful little refrigerator magnets. I was also going to mention that I would have to remember to keep them away from my flash drives, but taking the precaution of looking that up first, I learned that that is not true, so it is only my hard drives that I need to be concerned about, because I know that they are vulnerable, and verifying that, something that I had not thought of, my credit cards. I will let you know if this works.

I have a Chinese, or possibly Mexican 5•0•5 (can you discern the difference between them without the box?). This is one of, if not the best scales I have, so, evidently, some of the non American ones can be very excellent, on a case by case basis.

Danny

 

[6MMsteve]

I put 2 50 neos in my 5-10 they are .100 thick .200 wide and 1.0 inch long work great stops quick and perty reliable

 

[Rsadams]

I have a Chinese, or possibly Mexican 5•0•5 (can you discern the difference between them without the box?). This is one of, if not the best scales I have, so, evidently, some of the non American ones can be very excellent, on a case by case basis.

Danny

Mine works very well , stays zeroed and very sensitive... As border said, a little touch up on the knife edges does wonders....

 

[alinwa]

The dampening blade on my scales seem to be a copper alloy. Now I see why. Observe:

http://digg.com/video/copper-and-magnets
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Not to be a wet towel but,


you gonna' use terms like "eddy currents" then...... it's DAMPING.



jus' sayin'

 

[JimSC]

I had some small magnets left over from another project and experimented on my M5 this morning and found them too strong. I found a sweet spot by replacing only one of the original magnets and leaving the other original

 

[oley55]

Mine works very well , stays zeroed and very sensitive... As border said, a little touch up on the knife edges does wonders....

I am having trouble visualizing how to go about accurately touching up those knife edges. I can see myself ending up with an off angle or off axis edge, resulting in more friction and/or increased wear to pivot cradles. I use an older Redding #2 and recently noticed it was not reliably responding to dropping a kernel or two of Varget in the pan. If I very lightly tap the pivot column down near the bottom base, the slight vibration will let it register the increased weight. So in my mind that means I have a tiny bit of friction in the pivots. Although my edges appear reasonably sharp, catching the light just right, I can see where portions of each knife appear shiny.

I would hate to ruin a nice scale which I am comfortable. I have a new RCBS 500, but find it flimsy and no more accurate than my ole Redding. So it is only used for accuracy comparison checks.

 

[Rsadams]

I am having trouble visualizing how to go about accurately touching up those knife edges. I can see myself ending up with an off angle or off axis edge, resulting in more friction and/or increased wear to pivot cradles. I use an older Redding #2 and recently noticed it was not reliably responding to dropping a kernel or two of Varget in the pan. If I very lightly tap the pivot column down near the bottom base, the slight vibration will let it register the increased weight. So in my mind that means I have a tiny bit of friction in the pivots. Although my edges appear reasonably sharp, catching the light just right, I can see where portions of each knife appear shiny.

I would hate to ruin a nice scale which I am comfortable. I have a new RCBS 500, but find it flimsy and no more accurate than my ole Redding. So it is only used for accuracy comparison checks.

Please contact Boyd Allen here by PM he helped me and has done a bunch of stuff on these scales , he can head you in the right direction.... He has a reply at the top of this page...

 

[dave@aDave]

I believe Redding has a life-time warranty. I sent a early 1970's oil-damped scale back to them and they cleaned, repaired, and calibrated with no cost.
Great people.

 

[Brians356]

Not to be a wet towel but,


you gonna' use terms like "eddy currents" then...... it's DAMPING.



jus' sayin'

I once caught a six-foot sturgeon in Buffalo Eddy in the Snake River. Strong eddy current. Upon landing the sturgeon was well dampened. I know not what else I can say. It's a deep subject.
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