Playing with a photo switch and powder measure

[jmorris]

I rigged a photo electric switch above the beam of my old 10-10 powder scale to see how sensitive it was.

After this video


https://www.youtube.com/watch?v=dLp9M6VI3gM

I weighed a gn of powder and counted the kernels, a calculated resoultion of .02083 grains.

[DaveInFloweryBranchGA]

So the beam on the powder scale deflected enough with a single kernel of IMR3031 to activate the photo electric switch. That would seem pretty sensitive and certainly enough for most handloading applications without being too sensitive.

Weighing a grain of powder resulted in a calculated resolution of .02083 grains. What was your standard of measurement? By standard I mean a set of check weights such as the ones RCBS sells to check the scales.

I remember you had asked for information on Scott Parker. This old thread from another forum contains his contact information:

http://6mmbr.websitetoolbox.com/post?id=1219130

[DaveInFloweryBranchGA]

Here's some interesting information in this quote from Scott Parker:

“I have tuned several 10-10s. They all have turned out very sensitive, consistent and hold linearity like a dream. If only they came that way from the factory. The sensitivity after tuning is such that one kernel of powder registers a poise beam deflection.

For repeatability, I remove the pan and replace it for the zero 10 times. The zero line and the poise beam balance line must coincide for each of those 10 tries.

I then set the poises to read 250.0 grains. I remove and replace the pan 10 times with the calibration weight. For linearity, the poise beam balance line and the zero line should coincide within the line width. This is roughly one half a kernel of powder.

For repeatability, the poise beam balance line must return to that same balance point ten times. I then adjust the poises back to zero and recheck the zero.

I have a master’s degree in chemistry, thus I am very familiar with laboratory balances. Email me at vld223 [at] yahoo.com or give me a call at (661) 364-1199.”

Unless I memory fails me, most of his tuning work involves something like the following from Boyd Allen:

"Step one: level the main frame with a good combination square or torpedo level, then adjust the weights in the pan holder so that the scale is perfectly zeroed. This will take some little bits. I used a plastic collar stay. I pulled out a piece of shot, reassembled the holder, set the pan on it, and put plastic pieces in the pan till it was perfectly balanced. Then I transferred the pieces into the cavity in the pan holder with the rest of the shot.

Step two: Use an inexpensive diamond hone (Mine is a worn coarse.) to sharpen (maintaining the angles by eye) the beam knife edges, till they show no shiny spots when looking at the edges straight on, then deburr with the side of a hard pencil lead. About the same time, remove the agate bearings and clean them and the spaces that they sit in with alcohol and Q tips. Reassemble.

Play with the wire hanger that rests on the other set of knife edges so that it is spread wide enough so that while not rubbing on its sides at the outside ends of the knife edges, it is prevented from shifting from side to side. When using the scale, make sure that main knife edges ( on the agates) do not make contact on their ends. Also, pick up the whole pan and holder assembly off of the pan knife edges by holding the loop that the pan holder passes through, between your thumb and finger, and then set it back down on its knife edges so that they are at the very top center of the loops that rest on them.

Weigh the brass weight that is in the leveling screw, you may need to tune the sliding weight, that is used to make 10 gr. adjustments. Weigh other things, like test weights, or ordinary objects like various coins that have been weighed using a more accurate scale, preferably one that is good to .002 grain.

Do this a little at a time, so that you have time to think over what you are doing. To stop the pan from swinging, you can place your right finger tip on the table, so that the swinging pan just touches the side of your finger."

[catgunguy]

I rigged a photo electric switch above the beam of my old 10-10 powder scale to see how sensitive it was.

After this video


https://www.youtube.com/watch?v=dLp9M6VI3gM

I weighed a gn of powder and counted the kernels, a calculated resoultion of .02083 grains.

That is really nice. Thanks for sharing it.

[catgunguy]

Here's some interesting information in this quote from Scott Parker:

“I have tuned several 10-10s. They all have turned out very sensitive, consistent and hold linearity like a dream. If only they came that way from the factory. The sensitivity after tuning is such that one kernel of powder registers a poise beam deflection.

For repeatability, I remove the pan and replace it for the zero 10 times. The zero line and the poise beam balance line must coincide for each of those 10 tries.

I then set the poises to read 250.0 grains. I remove and replace the pan 10 times with the calibration weight. For linearity, the poise beam balance line and the zero line should coincide within the line width. This is roughly one half a kernel of powder.

For repeatability, the poise beam balance line must return to that same balance point ten times. I then adjust the poises back to zero and recheck the zero.

I have a master’s degree in chemistry, thus I am very familiar with laboratory balances. Email me at vld223 [at] yahoo.com or give me a call at (661) 364-1199.”

Unless I memory fails me, most of his tuning work involves something like the following from Boyd Allen:

"Step one: level the main frame with a good combination square or torpedo level, then adjust the weights in the pan holder so that the scale is perfectly zeroed. This will take some little bits. I used a plastic collar stay. I pulled out a piece of shot, reassembled the holder, set the pan on it, and put plastic pieces in the pan till it was perfectly balanced. Then I transferred the pieces into the cavity in the pan holder with the rest of the shot.

Step two: Use an inexpensive diamond hone (Mine is a worn coarse.) to sharpen (maintaining the angles by eye) the beam knife edges, till they show no shiny spots when looking at the edges straight on, then deburr with the side of a hard pencil lead. About the same time, remove the agate bearings and clean them and the spaces that they sit in with alcohol and Q tips. Reassemble.

Play with the wire hanger that rests on the other set of knife edges so that it is spread wide enough so that while not rubbing on its sides at the outside ends of the knife edges, it is prevented from shifting from side to side. When using the scale, make sure that main knife edges ( on the agates) do not make contact on their ends. Also, pick up the whole pan and holder assembly off of the pan knife edges by holding the loop that the pan holder passes through, between your thumb and finger, and then set it back down on its knife edges so that they are at the very top center of the loops that rest on them.

Weigh the brass weight that is in the leveling screw, you may need to tune the sliding weight, that is used to make 10 gr. adjustments. Weigh other things, like test weights, or ordinary objects like various coins that have been weighed using a more accurate scale, preferably one that is good to .002 grain.

Do this a little at a time, so that you have time to think over what you are doing. To stop the pan from swinging, you can place your right finger tip on the table, so that the swinging pan just touches the side of your finger."

Thank you for the info. I have been searching for how to do that and had not found that much info. Thank you again.

[rbertalotto]

Why are you weighing powder. ALL the accuracy benchrest folks load by volume. Weight is only used as a standard mesure to get you in the ballpark. From that point on it is all about volume.

But then again, we all know this but some of us simply like weighing powder......:bigsmyl2:

By the way....very nice addition to your scale.

[jmorris]

Why are you weighing powder. ALL the accuracy benchrest folks load by volume.

To be honest I don't weigh except for setting up my measures. However, I always wondered why folks like David Tubb would load on a 550 but felt the need to use a powder measure/dropper accurate to a single kernel. Like the promethous and others use the likes of gem pro, Denver instruments and such.

While dropping charges has always done what I have needed it to (MOA or better) I am in the parts gathering stage of building a railgun, might be able to see a difference under 1/2 MOA, don't know yet.

I am either going to learn something new or reenforce the way I have always done it.

[deepwater]

There is a current thread over on 6mmBR about guys using electronic scales in the $500 to $1,200 range. Seems weighing each charge is back in vogue. Also discussed is truing ("blueprinting") balance beam scales and getting near the same accuracy but not the same speed.

deepwater