Request for two small steel rod-esque lathed part!

[John S]

In the latest Digital Machinists magazine there is an article on a small coil winder by Weston Bye.

If you want I'll scan it later tonight [ got 102 winch levers to keyway this afternoon - aahhgg - crap job as they are a blind bore ] and can't play....................

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[HankMcSpank]

In the latest Digital Machinists magazine there is an article on a small coil winder by Weston Bye.

If you want I'll scan it later tonight [ got 102 winch levers to keyway this afternoon - aahhgg - crap job as they are a blind bore ] and can't play....................

.

hi John,

that'd be interesting, but only do it if you're at a loose end....my coil winder is done (could have done with the article 4 months ago!) ...but I'm always interested in stuff like this (it'd probably draw in a few people onto this site if Google steers them this way too)

[BillTodd]

Interesting coil winding thread on the 'zone
[ame="http://www.cnczone.com/forums/showthread.php?t=2497"]CNC Coil Winding Machine - CNCzone.com-The Ultimate Machinist Community[/ame]

[HankMcSpank]

This might help you visualize it...note though, that it's just been lashed up temporarily to photograph for that purpose! (especially the M8 threaded rod aspect!)









Just for illustration (& give some sense of scale), I've placed the magnet in the drill chuck jaw...presently the magnet is 20mm long, but it will need to be cut down in length to be 7 or 8mm.

After I've got the bits needed ...part 1 (as per my sketch further up), will be held by the drill chuck, the 5mm dia magnet will then be placed into part 1's end pocket/recess & part 2 will be forced up against the other end of the magnet (forming a a 'virtual bobbin for the copper to wind back/forward in between)....part 2 will rotate with the M8 threaded rod supported in turn by the bearings you can see in the photo.

I originally thought to use the M8 hex coupler you see in the photo to join part 2 onto the threaded rod, but I guess part 2 itself could have an M8 threaded hole in that end, which would eliminate the need for the coupler - not sure what's easier from a 'making' aspect? (a tapped whole or a 8m rod with an M8 thread cut into it)

[HankMcSpank]

Do you buy the magnets in 20mm lengths or as a bar and cut it to required size?

that's my next challenge...yes, i bought them as 20mm lengths (this is the only length I can find in 5mm dia) - i've bought some diamond cutter discs for my dremel...& intend using my cnc mill to cut them as they stand vertically while spraying the magnet with water mist! (from an airbrush!)

[HankMcSpank]

small lathe required:naughty:. . . . much easier. . . . . and cheaper

Yes, that's beginning to dawn on me. You'll gather that I'm the kind of guy that'll try & knock something he needs ala scrapheap challenge, but I think a lathe is beyond my ability! I'm now scratching around wondering what I can sell to placate my wife if I do utter the unmentionable under my breath "I think I need a lathe honey" ...it's likely to be a kidney. It'll then likely cost me double as she goes out to spend the equivalent (shoes, clothes, food - other unecessary stuff )

[HankMcSpank]

Ok, I said they'd be bad - it's about the only commitment I can meet!

Hopefully, this will help visualize what I'm aiming for....



& here's a recent coil prototype...



It quickly became apparent, I need a better bobbin (those are sewing machine Bobbins bought from Boyes, Whitby @15p each! The diameter is (ar too wide & the centre hole is just over 6mm ...but then I'm into the domain of specialist bobbins (min order 1000s!). Then I thought, actually because space is so tight (the pickup from top to bottom must come in at less than 9mm in height - see cross section sketch immediately above), then I really ought to dispense with the bobbine completely - this is when my probelms started ultimately ending up here throwing myself at the mercy of the forum!

[BillTodd]

These coils will actually be sustainer coils. The intention being to keep the guitar strings sustaining as long as the player wants them to. It does this by tapping off the guitar's standard pickup output signal, amplifying it & feeding the signal into these coils...this creates a varying magnetic field...& the guitar strings are ferrous so react to the mahgnetic field.

Do you even need a magnet?

A magnet is required in the pick-up (the pick-up is actually a reluctance sensor) since the strings are not magnetic (i.e. they don't produce a flux). However, to vibrate the string surely only requires a varying magnetic field which could be produced with just a coil and a suitable pole piece. The effect of your magnet is to produce a strongly biased field - I can't see how that helps to produce the drive you require.

[HankMcSpank]

Do you even need a magnet?

A magnet is required in the pick-up (the pick-up is actually a variable reluctance) since the strings are not magnetic (i.e. they don't produce a flux). However, to vibrate the string surely only requires a varying magnetic field which could be produced with just a coil and a suitable pole piece. The effect of your magnet is to produce a strongly biased field - I can't see how that helps to produce the drive you require.

Yes, I thought the same when i started out on this journey, but you do need a magnet (& believe me I've tried just about every permutation).

You can think of the magnet along the lines of DC biasing in electronics terms (best comparison I can make). The guitar strings aren't 'magnets' ...just ferrous material, so the sustainer coil can only pull on them (& release)....that is, the sustainer can't "push" the string away from the coil. By having a permanent magnet, you can then have a slight quiescent pull on the string & then when the AC guitar (drive) signal is added into the mix, you're effectively getting a pseudo pull/push effect (on one half of the AC signal the permanent magnet's quiescent 'grip' on the string is relenquished which is like a pseudo-push...& then the other half of the AC signal the permanent magnet is given a boost, forcing it to pull stronger than in its quiescent state) ...it's difficult to explain in the written word, but yes, you really do need a magnet.

The other option would be to apply a DC biasing current through the coils (ie dispense with the permanent magnet - just a pure solenoid) .....the problem with this method is it'd draw too much current....& power is scarce on a guitar (such guitar circuits normally being driven by 9V PP3s, which are only 500mAH at best)

[BillTodd]

You can think of the magnet along the lines of DC biasing in electronics terms (best comparison I can make)...<snip>

Ah yes, that makes sense. And, thinking about it some more, is why old type telephone speakers, that were a spring-steel plate suspended above a coil & magnet arrangement, had magnets in them.