Vern juenke machine

Norm's back!

I'll try to explain the eddy current meter made by Juenke.

First, there is nothing wrong with the original design, just that today some of the circuit blocks can be done easier and with more consistency and accuracy.

The basic unit is an electronic oscillator running at, say, 5kHz to 20 kHz. This oscillator frequency is set by an inductor and a capacitor. The inductor is nothing but a bunch of turns of fine copper wire on a form of anything from paper to iron or ferrite. This oscillator is set for an oscillating mode where the waveform is relatively distortion free. Then, the metering system is set for the actual amplitude of oscillation.
When a bullet is put next to the end of the coil, the metal of the bullet looks like a shorted turn of wire which the inductor thinks is the secondary of a transformer and the inductor is the primary. With a shorted secondary turn (the bullet), The oscillator circuit is loaded more than usual and the circuit gain decreases lowering the amplitude of the oscillations. This lower amplitude, or the difference between no load and bullet load is what is displayed on the meter. And, when the bullet is spun, the amount of "wiggle" indicates deformities in the bullet. All things in order, the meter indication could even indicate bullet shell thickness or case neck thickness or continuity between shell and lead core, etc. That is, with very accurate set-up and very stable operating points. These items are quite difficult with the original circuit, but in some cases may be possible.

See, very simple!
 
Oh I knew that , that what I thought to.

Normmatzen
Thank you for you explanation it was great.
What do you think about a upgrade
Kit for the ones out there now .
Would it make a big difference .
 
Juenke...........

Normmatzen said:
Norm's back!

I'll try to explain the eddy current meter made by Juenke.

First, there is nothing wrong with the original design, just that today some of the circuit blocks can be done easier and with more consistency and accuracy.

The basic unit is an electronic oscillator running at, say, 5kHz to 20 kHz. This oscillator frequency is set by an inductor and a capacitor. The inductor is nothing but a bunch of turns of fine copper wire on a form of anything from paper to iron or ferrite. This oscillator is set for an oscillating mode where the waveform is relatively distortion free. Then, the metering system is set for the actual amplitude of oscillation.
When a bullet is put next to the end of the coil, the metal of the bullet looks like a shorted turn of wire which the inductor thinks is the secondary of a transformer and the inductor is the primary. With a shorted secondary turn (the bullet), The oscillator circuit is loaded more than usual and the circuit gain decreases lowering the amplitude of the oscillations. This lower amplitude, or the difference between no load and bullet load is what is displayed on the meter. And, when the bullet is spun, the amount of "wiggle" indicates deformities in the bullet. All things in order, the meter indication could even indicate bullet shell thickness or case neck thickness or continuity between shell and lead core, etc. That is, with very accurate set-up and very stable operating points. These items are quite difficult with the original circuit, but in some cases may be possible.

See, very simple!
Click to expand...

THANK YOU NORM,it`s so nice when someone who actually knows...explains it................
bill larson
 
Normmatzen said:
Norm's back!

I'll try to explain the eddy current meter made by Juenke.

First, there is nothing wrong with the original design, just that today some of the circuit blocks can be done easier and with more consistency and accuracy.

The basic unit is an electronic oscillator running at, say, 5kHz to 20 kHz. This oscillator frequency is set by an inductor and a capacitor. The inductor is nothing but a bunch of turns of fine copper wire on a form of anything from paper to iron or ferrite. This oscillator is set for an oscillating mode where the waveform is relatively distortion free. Then, the metering system is set for the actual amplitude of oscillation.
When a bullet is put next to the end of the coil, the metal of the bullet looks like a shorted turn of wire which the inductor thinks is the secondary of a transformer and the inductor is the primary. With a shorted secondary turn (the bullet), The oscillator circuit is loaded more than usual and the circuit gain decreases lowering the amplitude of the oscillations. This lower amplitude, or the difference between no load and bullet load is what is displayed on the meter. And, when the bullet is spun, the amount of "wiggle" indicates deformities in the bullet. All things in order, the meter indication could even indicate bullet shell thickness or case neck thickness or continuity between shell and lead core, etc. That is, with very accurate set-up and very stable operating points. These items are quite difficult with the original circuit, but in some cases may be possible.

See, very simple!
Click to expand...

Where in this discussion was it determined the Juenke was eddy and not ultrasound as previously believed?

I've missed something?
 
Lou,

I think if I had one of the original Juenke machines, I would not mess with it! I seriously subscribe to the "If it Ain't Broke, Don't Fix It!" The electronics, even tho it is archaic to me, seems to work well, and the motor drive, which I think is un-necessary, also works. So, If I was successful at finding bad bullets and verifying good bullets with my Juenke, it would be a no-brainer. But, to build a machine to sell, I would certainly re-engineer it. In my opinion, what my version of the machine brings to the party, bear in mind I haven't even proven my design yet, is easier assembly, more stable operation and easier set-up. As well as simpler operation as I will be spinning the bullet by running my finger back and forth over a slippery V-Block stand for the bullet. The meter I will be using is a nice little digital read-out that costs a fraction of what an analog meter like the Juenke uses.
But, saying all that, the existing design could be simplified by replacing the electronics and meter by a simple PC board with a couple op-amps and a digital meter and make the costs decrease as well as reliability and stability being increased. The initial set-up would be easier too.
 
IMO the motor drive is important. Very important. I think a Juenke-style machine without a motor drive would be useless.

I have 5 finger drive bullet-checking machines and they all suck, I drive them with things like a pencil with a length of rubber hose over, a small slow-speed drill etc.

I'll barely touch a pool ball with my fingers, let alone a bullet. Heat, grease, inconsistent pressure, inconsistent speed, fingers in the way....... I just don't see it happening.
 
Normmatzen said:
Lou,

I think if I had one of the original Juenke machines, I would not mess with it! I seriously subscribe to the "If it Ain't Broke, Don't Fix It!" The electronics, even tho it is archaic to me, seems to work well, and the motor drive, which I think is un-necessary, also works. So, If I was successful at finding bad bullets and verifying good bullets with my Juenke, it would be a no-brainer. But, to build a machine to sell, I would certainly re-engineer it. In my opinion, what my version of the machine brings to the party, bear in mind I haven't even proven my design yet, is easier assembly, more stable operation and easier set-up. As well as simpler operation as I will be spinning the bullet by running my finger back and forth over a slippery V-Block stand for the bullet. The meter I will be using is a nice little digital read-out that costs a fraction of what an analog meter like the Juenke uses.
But, saying all that, the existing design could be simplified by replacing the electronics and meter by a simple PC board with a couple op-amps and a digital meter and make the costs decrease as well as reliability and stability being increased. The initial set-up would be easier too.
Click to expand...

Digital meters suck for visualizing peaks and valleys. Unless you are processing the data to calculate the amplitudes, an analog meter is better, IMHO. Certainly could be good to modernize everything else.
 
mks said:
Digital meters suck for visualizing peaks and valleys. Unless you are processing the data to calculate the amplitudes, an analog meter is better, IMHO. Certainly could be good to modernize everything else.
Click to expand...

Absolutely right! A digital meter would the worst possible choice for this application.

RWO
 
Digital meters aren't any good for tuning stuff.

But, don't compare apples and oranges. My system uses high quality active filters to filter out the deviation in oscillator amplitude while the bullet is being turned and only indicates the peak to peak amplitude. And, in another mode it will indicate the steady state amplitude level with respect to un-loaded level without a bullet or case and indicate film thickness, either neck thickness or bullet sheath thickness.
 
Yes and No. I have all the parts in hand and the active area where the bullet rides in a plastic V block and its adjusting parts as well as a pedestal for cases to measure neck thickness is prototyped and I am loading the PC board to build the first bread-board.
 
Crooked Bullets

I suspected a
(lot of bullets) were crooked because the bullet maker was crooked. I also drank milk along side 7 new born pigs, and I could see the wind for 6 days.
Wilbur said:
OK, then what's the adjective I can use in place of crooked? I'll be sure to use it next time....rather than crooked.
Click to expand...
 
For those of you shooting 600yd and 1000yd BR, how many D.Us can you use before you start seeing group sizes increase? Either with 6mm or 7mm/30 cal bullets?
 
BulletInspector Kit

Hi

Have been following this discussion.

I have one of the Bullet Inspector Kits and have been examining how it operates.

I have produced a professionally made version of the PCB that I will be testing very soon.

Hoping to assist Bullet Doctor and Bullet Inspector to make these easier to produce and calibrate at least as far as the electronics go.

The other purpose is to reduce manufacturing costs of the parts.

I also am looking at updating the circuitry to Op-Amps.

Normmatzen I would love to see what you have come up with.

The Oscillator runs much higher than 20KHz.

It works off Eddy Currents.

The eddy current effect from the bullet lowers the amplitude of the Oscillator (we are talking millivolts difference here. The Medium and Fine controls are used to center the meter at 25uA with a bullet stationary in the fixture. Changes in the eddy current as the bullet rotates changes the current through the meter. The original circuit is temperature sensitive and needs 10-15 minutes to stabilize.

I still don't have a full understanding of the meter driving part of the circuit. And therefore I am unable to come up with a procedure to set the two trim pots on the board. I know what they were set to on the original machine. Also not sure of the true function of the Germanium diode and how critical it is to use the one Vern used.

It is somewhat sensitive to distance from the sensor coil to the surface of the bullet. Bigger bullet more distance from the coil to the bullet jacket surface.

Having talked with a few people in the Eddy Current sensor field and told them of the frequency of the Oscillator, they tell me that it would be seeing through the copper jacket and a little bit into the core.

Variations in jacket thickness as well as voids and microscopic scratches on the outer or inner surface of the jacket will be sensed.

This one area where Eddy Current sensors are used. Detecting surface defects that are extremely small usually on plated surfaces. Usually at much higher frequencies than this device operates at as all they are interested in is from the surface to a very small depth into the material.

There is definitely room for improvement on this machine, and a better understanding of how the original works and is calibrated will lead to this. I have a call into Vern, will be interested if he responds.

My hope is to help Bullet Doctor and Bullet Inspector be able to produce a cheaper and more reliable machine, that they can definitively state what it is doing. Now cheaper is a relative thing and it may be affected by improvements to the jig where the bullet rests.
 
Last edited by a moderator:
Normmatzen said:
Yes and No. I have all the parts in hand and the active area where the bullet rides in a plastic V block and its adjusting parts as well as a pedestal for cases to measure neck thickness is prototyped and I am loading the PC board to build the first bread-board.
Click to expand...

Normmatzen

Would love to see what you have come up with for the electronics.

Sounds very interesting.

Let me know if you need a circuit board done for your circuit.
 
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