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View Full Version : Request for two small steel rod-esque lathed part!



HankMcSpank
18-06-2009, 01:41 AM
I don't have access to a mill, but really need the following parts made...

Part 1.

A 9mm diameter mild steel rod, about 50mm in length. Milled into the centre at each end, a 5mm circular 'recess'/pocket 2.5mm deep at one end of the rod, & a 5mm circular 'recess'/pocket 1.8mm deep at the other end of the rod. Ideally, on the outside edge perimeter of the 5mm pocket, I would like the smallest hole 'do-able' drilled at say circa 45 degrees through the rod body to pop up at the main rod edge (it's to thread enamelled copper wire through...more on this below!)

Part 2.
A 9mm diameter mild steel rod, 30mm in length. Milled into the centre at one end, a 5mm circular pocket 1.6mm deep ...at the other end of the rod, no pocket, but about 1cm of M8 thread. Once again, ideally, on the outer perimeter of the 5mm pocket, I would like the smallest hole 'do-able' at say circa 45 degrees through the rod body to pop up at the main rod edge


Just for a bit of background..this is to wind small coils.

Part 1 will go into a 'holding/turning' heath robinson chuck - a 5mm diameter magnet will be inserted into the small pocket/recess. Part 2 will be threaded onto an M8 rod, but then used to push up against the other end of the magnet - the idea is to rotate the magnet by a motor while feeding copper wire onto it - essentially making a coil. These parts hold the magnet in place & provide a pseudo bobbin 'edge' for the wire boundary as it traverses left to right. Therefore The above 'recessed' circular pockets need to be razor sharp from an angular perspective - ie a 90 degree corner (I'm using wire that is very thin ...0.1mm diameter & don't want any wire to be able to go into the recess). I could post out the small cylindrical magnet that I'll be using to ensure there's a nice tight fit for it into the recessed pockets.

This is not for a commercial venture...just a little hobby project I've started out on!

Could some kind soul quote me? (or if they don't fancy quoting, at least give me a flavour of what would be a ballpark price (I have some acrylic rod that in theory I could try * mill thos pocket into...but I'd really like this to be steel as the magnets will adhere to them (since the recesses are quite shallow, I need all the help I can get at holding the magnet steady!)

here's a very rough and ready sketch ...

http://img31.imageshack.us/img31/8454/partsy.th.jpg (http://img31.imageshack.us/i/partsy.jpg/)

HankMcSpank
18-06-2009, 02:21 AM
Hall effect pickup coil?

Could the holes simply be drilled/bored on a lathe?

9mm is an odd size...is that to be the guide for the OD of the coil winding?

No nothing as clever as a hall effect... just something I'm toying with in my spare time, but I've had little success getting decent coils ...& I need six of them for each of the pickup I want to knock up. It's got to the point where I've exhausted all other options (sewing machine thread bobbins, etc!)

Re drilling the holes....I need the far endof those end pocket/recesses to be nice & flat flat (the magnet end has a completely flat face & I want it to mate up to those recess perfectly - else when they're turning they'll wobble)...I'd also need the magnet to be a nice tight fit diamter wise( same reason...anti wobble!)...so unless I got lucky with the drill diameter, then I'm not sure it'd be precise enough.

The 9mm is derived from the maximum distance permittable between guitar stings (ie it's about 9.2mm from the centre of one string to the next string). Therefore the coils ought to be 9mm wide (max) - these two parts I'm asking for will hold in the edges of the coil as the copper wire is being wound onto the magnet from side to side.

Back of an envelope (literally), bad drawing here...

http://img200.imageshack.us/img200/8379/illustrationf.th.jpg (http://img200.imageshack.us/i/illustrationf.jpg/)

John S
18-06-2009, 10:40 AM
I make a few bobbins for the rewind industry from time to time and they also have to make non cored coils, not as small as this but similar principle.

What about getting a bar turning part down to 4mm longer than your coil and threaded it M4

The can be any size within reason but the part next to the thread turned down to 9mm as I gather that's just a visual guide on the coil being full ?
This will allow you to wind onto a thin plastic or paper former which can then be removed after.
The ends can have a card washer fitted with a small hole in to locate the wire at the start and then be disposed of after winding. This does away with the tiny drill hole at an angle. not sure why you need two start holes as the end of the wire is going to be on the OD.

Length of coil is controlled by a 9mm diameter 'washer' threaded M4 and held in place by a lock nut to adjust length of coil.

Or am I missing something ?

HankMcSpank
18-06-2009, 11:02 AM
Firstly thanks for the comments.

My needs are only to wind copper wire directly onto an Alnico magnet (let's call this magnet the 'core', as essentially that's what it will be - the core of a coil ...essentially a solenoid)....I have no other coil winding requirements (paper /plastic formers etc)

These parts are towards a hobby DIY projectette for a guitar ...therefore I'm constrained to the dimensions of the guitar. So One limiting factor is the core length (ie the magnet you see in my second scribble above), which will be about 8mm max (of 5mm diameter Alnico magnet). This is a very small bit of metal to be turning 150 turns of copper wire onto! Therefore I need all the help I can get at keeping it rigid between those two parts. To help centralize it (since it'll be turning at about 200RPM) & stabilize/rigidize it while turning, I figured I'd need....

1. The parts I'm requesting to be made of steel (bearing in mind I want these parts to 'hold' a magnet...being steel will help them 'click' into & hod in place)

2. The 5mm diameter pocket/recesses at the end of the parts, to be a nice tight fit.

The tiny 'start' holes (I'm thinking 0.5mm!) I mentioned are a 'nice to have', but I can appreciate that it might be a task to get them drilled so small & at an angle. The angle isn't important, but what is important, is that I can thread the wire through the part out of the way - so as I start to wind the coil, the wire isn't a pain to get to start 'biting' (for want of a better word) around the core quickly...to get the coil off to a nice neat start on it's first layer. I need a 'start' hole at both ends, because I anticpate, some coils will be wound starting at the left moving right & other coils wound starting at the right moving left.

The 9mm diameter 'dimension' you picked up on, is both a visual representation (that said, I'm knocking up a PIC based coil winding program which will count the coil turns anyway), but more importantly, to make sure the edges of the coil are nice & perpendicular to the magnet core.

It's all a bit hard to explain in writing,

But in short..the way I'm proposing making the coils perhaps the only way I think it'll be possible to get decent results on a core so small (& I'm sure my mates will probably ask me to make them one too...so I may need to make a good few coils!)

BillTodd
18-06-2009, 01:05 PM
Does Part2 turn with the magnet ? - I'd worry about the run-out of the M8 thread coupling. If it doesn't I suggest you make it turn with the other end, else the coil will drag.

Drilling a 0.5mm hole more than a few mm deep might prove interesting. Presumably you only need the hole to be 0.Xmm near the coil end, so most of the length of the hole could be larger. Actually, a slot might be of more use than a hole (saves that 'threading the needle' problem)

The magnet hole doesn't need to be flat bottomed it just needs a definite stop - have you considered having a set screw at the bottom of the hole, so the depth could be adjusted? (you could probably rely on the grub screw to attract the magnet and make the rest of the piece from Al or plastic)

[edit]

Thinking some more...

Hold the magnet in a brass collet with a smaller collet on the other end as an end stop (that way you'd get a concentric positive drive on the magnet)

HankMcSpank
18-06-2009, 01:38 PM
Does Part2 turn with the magnet ? - I'd worry about the run-out of the M8 thread coupling. If it doesn't I suggest you make it turn with the other end, else the coil will drag.


Yes part 2 will be turning in sympathy with part 1 (which has the motor). I have to admit this is the most troubling bit. Essentially this will be a similar setup to what you see on a lathe tailstock...excepot it';s a right heath robinson cheapsjaket's version. A bit more meat...

Part 2 will connect to a length of m8 threaded rod (I will connect it via one of these ... http://www.tinyurl.com/ny63ds ) One other option is to have part 2 with a tapped M8 hole - & the M8 threaded rod screwed directly into it...I'm not sure what the best option would be?

ok, so now part 2 is affixed to a a length of M8 rod. Along this M8 rod will be some roller skate bearings (yes, you heard me right), these in turn will be held by some SK16 mounts ( http://tinyurl.com/nw8tlp
the outer diameter of the skate bearing is 16mm...the inner dimension is 8mm, so these are ideal). ok, so there you have it...part 2 is now mounterd horizontally into some M8 threaded rod, which turns within some skate bearings held steady by the Sk16 mounts - I told you it was a heath robinson!

Part 2 will then be pressed up agaist the magnet. If everything align (if!!!), then the magnet should turn easily & be held stable & 'true'.



Drilling a 0.5mm hole more than a few mm deep might prove interesting. Presumably you only need the hole to be 0.Xmm near the coil end, so most of the length of the hole could be larger. Actually, a slot might be of more use than a hole (saves that 'threading the needle' problem)


That's a great point ...you are right, it would only be the last bit that would need to be 0.5mm....the rest of the hole could be larger. The slot is another good option, but I'm not sure what the optimum wire size is yet (to determine the slot). I do know from the few times I've tried to wind these coils that the 'loose' threaded end, ideally needs to exit the edge (ie part 1 'small hole') at the actual perimeter of the magnet core ....else it interferes with the coil 'neatness' (& I'd like this to look neat, since it's going on my guitar!)

Some great points though....thanks!

Since posting, I'm now seriously considering using the fact I need these parts as an excuse to buy a hobby desktop lathe ...her indoors won't be happy, but hey "McSpank-ess, shut it!"

HankMcSpank
18-06-2009, 01:41 PM
Hello Hank,

How big a hurry are you in!! . . . . . . . . If no rush IE: next week will do then i will "try" to make you this part, TRY being the word. probably take be a few go,s being so small.
Dont want anything for doing it just cover the postage thats all.
Will need you to send me the magnets for test fit.
Q: how are you going to wind these coils. . . .IE do they fasten to winding machine or some device you made?

IF you want it doing send me a PM with ya details and well av a natter.
Cheers
Dean.

Wow Dean...thanks! Certainly the internet working at its finest!

I'll PM you, but keep this thread running as there are some good points being made (I'm not really an engineering type...just a part time kludger - my area is more electronics), re your question...


Hello Hank,

Q: how are you going to wind these coils. . . .IE do they fasten to winding machine or some device you made?




you'll not believe this but here goes anyway (& no laughing at the back!)...

I have a reasonably powerful 48V DC fan ...in the middle of this fan I hot glued (yes, you heard right!) a 13mm drill chuck. It took a bit of effort, but I eventually I got the chuck centred pretty much perfectly in the middle of the fan (hot glue is excellent for this as you can keep reheating it until you get it right - also there's not a lot of load going top be placed on this setup, so no worries about it falling off) . Ok, so now I have a turning mechanism capable of holding 'rod'. The problem was that at 48V it turned *way* too fast, so I knocked up a PWM DC motor speed controller. I can now start the fan from static up to any speed I care to nominate. So in short, part 1 will be held in place by 13mm drill chuck jaws.

Not realted to my needs, but just for some background info, to get really slick I made an encoder wheel (a circle with 192 black on white stripes radiating out from the centre)....this is attached to a CD and stuck to the fan blades. I then knocked up an electronic circuit to count the black stipes as they pass an optical pickup. This give me two things...

1. The RPM.

2. the distance travelled - this bit allows me to 'synchronize' a stepper motor to move back & forward as the main motor turns - this stepper has a bit of plastic M8 threaded rod inserted over the stepper shaft. I then feed the copper wire over this plastic M8 threaded plastic onto the rod held by the drill chuck & it traverses left to right in perfect syncronism. To get an idea of this last bit, look here - [http://www.tinyurl.com/m4mmfl (from about 27 secons, in - that's not my video, but I've got a similar setup except the wire I'm using is hair thin!)

Convoluted, but like I say, there's not a whole lot of budget...& you can't exactly buy such coil winding machines at the local MachinMart! Therfore I've had to get creative!

I'll try & get a photo posted up tonight.

John S
18-06-2009, 02:08 PM
Firstly thanks for the comments.


I need a 'start' hole at both ends, because I anticpate, some coils will be wound starting at the left moving right & other coils wound starting at the right moving left.



No just one hole, left to right, right to left can be obtained by reversing the bobbin direction.


.

HankMcSpank
18-06-2009, 02:16 PM
:clap: MR Creative.

Will you have to sync the stepper and the motor so they turn together at the same speed?

Yes, but this bit has been sorted...ie no matter what speed the main motor turns at, the stepper adjust its traversal speed accordingly.

A bit nerdy but here we go...

If the copper wire width is 0.2mm in diameter, then I know for every turn of the main motor, the stepper motor has to rotate the plastic M8 threaded rod on its shaft sufficiently to move the wire exactly 0.2mm to the left (or right). M8 threaded rod has a 1.25mm pitch, therefore all I need is a simple PIC program to count/map 'black stripe incoming pulses' from the main motor, to stepper pulses out.

For example, the program is typically doing this "For every 10 black stripes received , send a pulse to the stepper" ...it took a while to sort, but it works perfectly. You might think this is a lot of work for a simple guitar part, but I wanted to learn about steppers anyway (I was about to build my own CNC mill) & I also wanted to learn about PIC proramming - I'm the type that needs an end goal to motivate myself enough to do it!


I hope i'm not clouding the issue here...wrt the parts I need, this stepper traversal bit isn't a factor!

HankMcSpank
18-06-2009, 02:21 PM
No just one hole, left to right, right to left can be obtained by reversing the bobbin direction.


.

i'm not sure I'm following?

I can't change the parts around from side to side as they have different 'pocket' depths milled into their end bits (this is becuase I need different amounts of magnet core to protrude outside the copper coil at each end). Also each part is held in a different manner ... ie part 1 is held by a drill chuck, whereas part 2 is threaded onto some M8 rod. Therefore if I need to start the coil winding at a different end, then they both need the 'start' holes drilled.

But as Bill helpfully mentioned...the 0.5mm hole wouldn't need to go the whole way, just the last say 0.3mm if drillling from the main rod perimeter down towards the part 1 end surface.

John S
18-06-2009, 03:06 PM
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....................

.

HankMcSpank
18-06-2009, 03:12 PM
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
18-06-2009, 05:12 PM
Interesting coil winding thread on the 'zone
CNC Coil Winding Machine - CNCzone.com-The Ultimate Machinist Community

HankMcSpank
19-06-2009, 12:27 AM
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!)

http://img195.imageshack.us/img195/8435/62907644.th.jpg (http://img195.imageshack.us/i/62907644.jpg/)

http://img195.imageshack.us/img195/737/82984009.th.jpg (http://img195.imageshack.us/i/82984009.jpg/)

http://img195.imageshack.us/img195/9404/34935024.th.jpg (http://img195.imageshack.us/i/34935024.jpg/)

http://img195.imageshack.us/img195/2064/92969580.th.jpg (http://img195.imageshack.us/i/92969580.jpg/)

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
19-06-2009, 11:07 AM
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
19-06-2009, 02:14 PM
small lathe required:naughty:. . . . much easier. . . . . and cheaper:whistle:

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 :biggrin: )

HankMcSpank
19-06-2009, 10:34 PM
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....

http://img32.imageshack.us/img32/8057/70199723.th.jpg (http://img32.imageshack.us/i/70199723.jpg/)

& here's a recent coil prototype...

http://img200.imageshack.us/img200/1626/80207593.th.jpg (http://img200.imageshack.us/i/80207593.jpg/)

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!

HankMcSpank
20-06-2009, 12:18 AM
Cool - that rig actually looks very good (see what you mean about the 9mm diameter - that'd be fine)

When you mount the larger holder in a chuck, how does it turn overall? In my simplistic head, I just can't imagine that it'd turn 'true' ....as it looks like the opposite part would potentially cause wobble, (ie if it was out of alignment slightly?)

Like I say, I could be wrong!

re measuring those magnets I have...I only own one of those ubiquitous simple digital micrometers (allegedly measuring to 0.01mm accuracy)...it's not the best thing in the world (that said, in the main it suits my simple needs), but they all seem to be coming in at 4.96 - 4.99mm (that variance is more likey to be the inconsistent pressure I'm applying on the micrometer thumbwheel!)...I doubt any would come in over 5mm (on the basis it's cheaper for them to make smaller than larger!) ...& I reckon this simple coil making rig could withstand error of up to .2mm 9ie that's just 0.1mm slack either side of the magnet)

HankMcSpank
20-06-2009, 11:19 AM
For once on a forum I'm chuffed to be wrong - Dean that's brilliant.

If you say the runout wasn't bad & can be (essentially) adjusted away, then that's good enough for me.

I'll drop you a PM.

Ross77
23-06-2009, 12:31 AM
How dose that pick up work? if I may ask. coil winding is next on the list of machines to build. after mill, router, raduis machine and inlay cutter....

Are each of the coils feed back to amp/processor individualy or are they conected in series for better string balance?

Sorry to interupt the thead..

HankMcSpank
23-06-2009, 12:40 AM
How dose that pick up work? if I may ask. coil winding is next on the list of machines to build. after mill, router, raduis machine and inlay cutter....

Are each of the coils feed back to amp/processor individualy or are they conected in series for better string balance?

Sorry to interupt the thead..

No probs...I've been scant with the details because after all, this is more of a mechanical-centric forum than an electronics forum. The small coils I intend winding aren't actually pickups (I used the term as it was simpler!).

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.

the coil is the easy bit...the tricky/creative bit is coming up with a good circuit to drive the coils!

re the pickup winder...it really is a heath robinson, but essentially it's a main motor, with an encoder disk mounted on iT (a CD label containing a lot of black/white stripes). I created an electronic circuit to synch the main motor with a stepper motor (buy counting the black stripes). It's via the shaft of the 'synchronized' stepper that the enamelled copper wire feeds onto the coil core.

Because there is so little room to fit my sustainer device (I don't want to route the guitar body), I reckonedthat the only way forward for these coils was to go bobbinless (coils/pickups are normally have a bobbin, upon which the copper wire is fed onto...but the bobbin itself takes space). That's when I had to throw open my plight to this forum...Dean kindly offered to get involved & help out.

Ross77
23-06-2009, 01:05 AM
Sounds good, at last a fellow guitarist.......
Maybe Lee will open a musical instument section so we dont bore the rest.....Building guitars and related parts is is main reason for getting in to cnc.

Not able to help yet tho as not properly setup. :thumbdown:

So is this basiclly causing the strings to vibrate like feedback?

BTW always found that a Marshall on full tilt driving a 4X12 is good for sustain.....:dance:

HankMcSpank
23-06-2009, 01:07 AM
So is this basiclly causing the strings to vibrate like feedback?

BTW always found that a Marshall on full tilt driving a 4X12 is good for sustain.....:dance:

Yes...that's right, but this is somewhat more neighbour friendly (with no ASBOS received ...except maybe for the incessiant whine of my clunky DIY CNC milling me some guitar bits & bobs!)

Ross77
23-06-2009, 01:15 AM
Yes...that's right, but this is somewhat more neighbour friendly (with no ASBOS received ...except maybe for the incessiant whine of my clunky DIY CNC milling me some guitar bits & bobs!)


Dont have that problem, nearest neighbour is a quater of a mile away :biggrin:
Thats probably why I'm deaf..:surprised:

Wot geetarrs have you got?

BillTodd
23-06-2009, 05:14 PM
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
23-06-2009, 05:22 PM
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
23-06-2009, 05:40 PM
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.

Ross77
23-06-2009, 07:11 PM
you can then have a slight quiescent pull on the string


Isnt that going to give you tuning and intonation problems like when a Pup is set to high? :surprised:

Where dose this go then? since it looks like a single coil are u lossing a pickup to use it?

HankMcSpank
23-06-2009, 07:34 PM
Isnt that going to give you tuning and intonation problems like when a Pup is set to high? :surprised:

Where dose this go then? since it looks like a single coil are u lossing a pickup to use it?

Well this is how the commercial ones work too!

in practise I don't see how it could it would cause much in the way of problems (if your guitar's intonation is setup up right, then it'll cause no impact whatsoever. After all, that's what setting up intonation is about....so the tuning isn't knocked out of whack no matter where you fret the string) ...& we're talking minimal quiescent pull. Where you have to be careful is on the guitar's natural sustain (ie no sustainer active)...if the sustianer coil magnets have too strong a pull on the string when inactive, it actually kills the guitar's natural sustain.

re mounting....well, the commerical ones, you have to sacrifice a pickup...but I'm trying to get a surface mount one to work (hence the low height). These sustainers aren't suitable for all guitars as normally they do radiate a lot of magnetic interference, which alas is the very thing a guitar pickup senses! Therefore it certainly needs some physical distance from the next nearest nearest pickup.

Ross77
23-06-2009, 10:08 PM
Ah. I see. sounds like a good project.

Is it the no.of turns and length of wire that makes it work? If so you could use a small square bobbin to reduce the wasted space between the coils and then you can drill them to suit the size of the magnet. no need for a fancy holder and hopfully reduce the height.

Just my 2 peneth :biggrin:

HankMcSpank
23-06-2009, 10:22 PM
It's a combination of the current through the coils, coupled with the number of turns (ampere turns in fact). It's a fine balancing act at that too.

Too many coil windings = too high an inductance, which means the coil presents resistance to higher frequencies feeding into it. The higher frequencies are the thinner strings, less ferrous material in them, so they actually need more drive

Too few windings = not enough magnetic force presented at the strings...only way to compensate is to cranck the current up, but that saps the battery.

Re round vs square coils. Square would be better (as it goes, I'd already considered them...in fact, you wouldn't believe the amount of McSpank Grey Matter processor 'cycles' I've dedicated to this little project!), but my simple coil winder (a drill chuck) cant cater for winding anything other than circular shapes! In fact longer rectangular coils would be better still...slightly overlapping one another so no dead spots when bending strings etc.


Ah. I see. sounds like a good project.
Is it the no.of turns and length of wire that makes it work? If so you could use a small square bobbin to reduce the wasted space between the coils and then you can drill them to suit the size of the magnet. no need for a fancy holder and hopfully reduce the height.



Not sure I fully grasp what you're getting at when you say (re square bobbins) "drill them to suit the size of the magnet" nor how could this proposale "reduce the height" .....I'm all ears, could you put more meat on the bone?

Ross77
23-06-2009, 10:49 PM
Not sure I fully grasp what you're getting at when you say (re square bobbins) "drill them to suit the size of the magnet" nor how could this proposale "reduce the height" .....I'm all ears, could you put more meat on the bone?


I may have misunderstood, but I thought you said that the magnets were different sizes which was causing problems with holding them? If you use a square bobbin then it could easily be shaped to suit the magnet size (or epoxy the smaller ones)

I was thinking of the small plastic box section that you get from model shops, if you cut to size and put a small bolt through with a washer on each end then you would have a former and be able to hold it in jacobs chuck......

With regards to reducing height I meant that if the square section utilised the availble space better then it wouldnt have to be as tall...

Is that better? :smile:

HankMcSpank
23-06-2009, 11:29 PM
All the magnets are the same size 5mm rod (which will be the core of the coil), this bad sketch i did for Dean helps visualize...


http://img221.imageshack.us/img221/377/58284658.th.jpg (http://img221.imageshack.us/i/58284658.jpg/)

(it's probably worth pointing out, that the above sketch was a simplified version of how it'll look....and only used for testing. The coils will not eventually be visible ...as I intend mounting them into some CNC milled perspex. The only bits you'll see arethe tips of the magnets protruding above the perspex holder)

Ross77
24-06-2009, 11:23 PM
Did Dean sort you out?

Will you be selling any of them? Im always keen to try new ideas, but havent got the time to make my own yet. Can you wind inductors for Wha's with that machine? Just replaced the inductor in my cheap wha with a halo and totally transfromed it.......

Ive got a bit side tracked with this thread and just spent the last hour on Utube looking at pickup winding... :beer:

HankMcSpank
24-06-2009, 11:32 PM
Did Dean sort you out?

Will you be selling any of them? Im always keen to try new ideas, but havent got the time to make my own yet. Can you wind inductors for Wha's with that machine? Just replaced the inductor in my cheap wha with a halo and totally transfromed it.......

Ive got a bit side tracked with this thread and just spent the last hour on Utube looking at pickup winding... :beer:

What's a Wha?!!

Dean is up to his eyeballs - when he offered to help it was conditional that I wasn't in a hurry. I'm not (& remember he's doing this for free!).

re selling them...this isn't a commercial venture...& to be honest, even if I wanted to sell them (which I can't imagine it being worthwhile!), there's still an awful lot of further experimentation done wrt the coils themselves (number of of turns, wire gauge, type of core material etc)....the final coil design is still some way off.

I have no real proper coil winding facilities...just something I've put together myself "Blue Peter-esque! ....a 48V DC cooling fan, an encoder wheel striped disk (the pattern which I downloaded off the net, then printed onto a CD label & attached to a CD...I then cut out the middle of the CD & mounted on the fan!), a DC motor PWM speed control circuit (based on t he good old 555 timer!)....an optical pickup cct (to read the encoder disk) and most importantly a little bespoke PIC program that I wrote (which took me yonks as I hadn't a clue about PIC programming!). Previously I've been winding the coils onto small sewiing machine bobbins...but they're too big...hence the need for wanting to wind straight onto the magnets.

Ross77
24-06-2009, 11:54 PM
What's a Wha?!!


Wha wha pedal....(Wah Wah if your fussy)..........AKA voodoo chile intro
Dont want to interfer, but if Dean gets mega busy then I could have a go.
Just re-read the thread, sorry about the previous posts.

Is this Idea limited to just sustain? if the coils where energised from a PIC then could some strange new effect be created? Ie just sustaining certain strings for a preset time.............:dance:

HankMcSpank
25-06-2009, 12:13 AM
Wha wha pedal....(Wah Wah if your fussy)..........AKA voodoo chile intro
Dont want to interfer, but if Dean gets mega busy then I could have a go.
Just re-read the thread, sorry about the previous posts.

Is this Idea limited to just sustain? if the coils where energised from a PIC then could some strange new effect be created? Ie just sustaining certain strings for a preset time.............:dance:

Yep Wah Wah is better (I'm fussy!).

Do you know the spec of the inductors in the Wah Wah? In therory, I could probably wind such an inductor...but why? (are they hard to get or something unique about them?)

I'm using a PIC in two places...

1. For the coil winder itself (nothing to do with the sustainer!)...to count things like number of turns, traversal count etc (when to reverse the motor feeding the coppoer onto the coil)

2. In the sustainer circuitry. A lot of folks use an analogue AGC (and a good AGC is what a sustainer needs), but that's a failry lo-tech inflexible approach & since I've just learned how to program PICS (that makes m an expert!), I'll be using the PIC for the AGC. Basically, it'll take sample of the dc rectified incoming guitarl (ie into the sustainer circuit rom the pickup)...based on the sampled incoming level it'll ether increase or decrease the signal at the power amp stage (feeding the sustainer coil). The PIC could also be used for clever switching (mainly powering stuff off when not in use as battery life is key), but I can't envisage actually adding an effect itself....PICs are actaully pretty feeble things processing wise.

Ross77
25-06-2009, 12:34 AM
PICs are actaully pretty feeble things processing wise.

And I thougth they were the answer to all processing problems, is the clock speed to slow?



Do you know the spec of the inductors in the Wah Wah? In therory, I could probably wind such an inductor...but why? (are they hard to get or something unique about them?)



No not hard to get but at 20 from the gud ol US its a bit pricey. 520mh is the magic value apparently. Read an article on old vintage Wah's and it seems that the sound is due to the magnetic build up of the pot core and suggested that an additional second winding could provide this varible magnatism (if that sounds correct) to recreate the sound?

I know lots about guitars but electronics to that level is beond me...:heehee:

HankMcSpank
25-06-2009, 12:51 AM
And I thougth they were the answer to all processing problems, is the clock speed to slow?


Yes...I think they go up to 20Mhz (though I just run mine at 4Mhz ....I'm placing modest processing requirements & higher clocks just results in more heat/consumption)



No not hard to get but at 20 from the gud ol US its a bit pricey. 520mh is the magic value apparently. Read an article on old vintage Wah's and it seems that the sound is due to the magnetic build up of the pot core and suggested that an additional second winding could provide this varible magnatism (if that sounds correct) to recreate the sound?


Well, i know a little about electronics...but inductance & the associated magnetism is something I've never had to apply a lot of thought too. (& is a specialist field in itself). i know the basics.

As it goes, the single string sustainer coils I've wound are about 1mH ...520mH seems like a whacking big inductance (you sure you don't mean 520uH?) , but then there's the question of what type of core, wire gauge used blah blah (things get really esoteric when it comes to old vintage components!). Have you a link to the coils in question?

Ross77
25-06-2009, 01:18 AM
As it goes, the single string sustainer coils I've wound are about 1mH ...520mH seems like a whacking big inductance (you sure you don't mean 520uH?) , but then there's the question of what type of core, wire gauge used blah blah (things get really esoteric when it comes to old vintage components!). Have you a link to the coils in question?

Definatly 520mh

http://geofex.com/Article_Folders/wahpedl/wahped.htm

Its a few scrolls down. and easyier reading on the site....



The best explanation I could come up with is this. The inductor in the classic wah setups carries the DC bias current for the first transistor. While this is only microamps, long exposure to this unidirectional bias could result in a remanent magnetization of the inductor core if the core material was not very good in the classical, linear EE sense. It's possible that Vox merely specified the circuit, the maker (Jen, I think, in Italy) made the early wahs from as inexpensive a material as they could, and the slight deviation from linearity resulted in a sound that the folks at Vox liked. That is - it was a happy accident resulting from being cheap. I've never heard another explanation that accounts for the differences. There are differences, and measurable ones, and ones that square with reasonable explanations for how the thing works and sounds. This legend's true.
I have not seen or heard any of the supposed "next generation" Fasel style inductors, so I can't say whether they are true to the originals.
One thing that became obvious is that you could artificially get a more linear core material to have an offset, and in the easiest way. If we're always pumping current through the inductor, we can get any offset we like by just pumping more. If we were to put a second winding on a wah inductor, we could force DC through it from a current source circuit, which would force the "center" of the magnetic operation toward one or the other saturation points. Of course, this is not possible with a pre-wound and potted wah inductor, but is emminently feasible if you happen to wind your own. It's even more feasible if the inductor you use happens to have a second winding, like the Radio Shack transformer that is mentioned later. This secondary can just be hooked up and current fed through it. I intend to do this as as soon as I get some bench time. Note that I've been saying "current source". You can't just use a resistor, because transformer action would reflect this resistance into the inductance winding as a load and damp the resonant action of the inductor. The minimum you need is a transistor connected as a current source to keep from doing this.


Any help would be most appeciated.

HankMcSpank
25-06-2009, 02:15 AM
I'm sure you've grasped it all, but from my (quick) understanding the much cherished old VOX wah were analysed under lab conditions & ultimately acted in a way that wasn't expected. It would appear the inductor core (which is made of ferrite not meant to have to hold any permanent magnetic qualities) had become in part magnetized (he'd guessing the DC current the wah circuit has permanently running through the industor may have led up to this). The end result is that when you feed an AC signal into the inductor, the inductor core will saturate faster in one half of the signal waveform than the other...apparently this sounds good in a wah circuit! (I can't say...this is all news to me!)

Therefore he goes on to hypothesize that this could be 'frigged' using a modern bespoke wound inductor, buy adding a second winding and then pumping some DC current through it. This would generate a magnetic field, utlimately turning the ferrite core into a pseudo magnet...you then have the aformentioned non linearity that is sought.

he doesn't give any figures for the amount of turn the second core should have...so you'd be very much into trial & error territory. And without having access to his data (scope traces at set frequencies for the original VOX inductor etc), it'd likely be a futile (& long drawn out) affair!

But by the looks of it, the inductor used in the Wah circuit has a ferrite core, an inductance of 500mH and about 50-70 ohms of DC resistance. I'm not sure how physically big those inductors are, but that surely amounts to a lot of windings (so I'm guessing they use very thin copper wire)

Ross77
25-06-2009, 09:27 PM
Thanks Hank. yeah I got the basics, although I understood your explanation better. I was looking for a starting point for the magnatising coil, as you said there are no values given.

The main inductor bit is easy, its about 550 turns of 38AWG wire on a pot core. finished size is about the same as a stack of 3 1 coins.....

As I said I planned to look into this later (too many projects) but Ive got side tracked when I saw this thread about coil winding..

May have to pick your brains when I get round to it. :biggrin:

HankMcSpank
29-06-2009, 03:32 PM
Over the weekend I had a bit of a play with my homemade CNC - I made a lot of simple mistakes, like forgetting to zero the tool after a tool change, only to watch the drill bit plunge right down through my material & a little into the table- eeek!), here's what I've been on with (rather than six little coils - one per string - becuase I don't have those parts I need, I had a opo at a larger coil.....

http://img269.imageshack.us/img269/3002/61632909.th.jpg (http://img269.imageshack.us/i/61632909.jpg/)

(I'm not sure if you'll notice, the bit marked 'bottom' part has a slight chip at the top left corner, this is because when changed cutting bits ,I had the feed rate too high, the machine went ballistic & gouged into the part a little! But since this is just a protoype, I couldn't be bothered to re-run the cut! The other two parts turned out well though...particularly happy with that middle bit - that's just 1mm between the edge holes & the bobbin edge at each end - remember my leadscrews are just M8 rod, & my drive nuts are badly homemade delrin ones!

The colour scheme(!) wouldn't be of my choosing, but I was limited to those colours because of the thickness of the acrylic (I needed 2mm thickness which I only had as clear acrylic & also 4.5mm which I only had in translucent royal blue!). Here it is as a temporary 'push fit'

http://img141.imageshack.us/img141/7669/77773538.th.jpg (http://img141.imageshack.us/i/77773538.jpg/)

those poles sticking up are actually 20mm lengths of Alnico magnets ...they obviously need trimming...they were an *extremely* tight fit. I screwed up with the middle part too! Basically, I read somewhere to get rid of the cutter marks that acrylic can be flame polished along the edge ...apparently, all you need to do is run a butane torch gas flame along the edge - I'm sure it normally works well, but not when the part so small....the acrylic heated the small part up & distorted the acrylic! (shrunk it a fraction...hence a couple of the poles not being bolt upright)

Here it is ready to be wound (I've not glued the top to the middle, because, after the coil is potted, I'd like to see how it looks without the top, hence the large washers clamping the top to the middle for while it's being wound)...

http://img524.imageshack.us/img524/9103/50958806.th.jpg (http://img524.imageshack.us/i/50958806.jpg/)

(the square edging makes it look somewhat utlitarian & of "East European circa 1970!" design ...but it's just a prototype so I have expended much effort giving it bevelled/rounded edges!

So then, next I wound 150 turns of 0.235mm wire (which is actually 0.27mm if you include the enamel coating!), this gauge is much thicker than I'm used to & is quite a bugger to 'control' while winding on to the bobbin....

http://img291.imageshack.us/img291/7845/48131539.th.jpg (http://img291.imageshack.us/i/48131539.jpg/) ....those two large screws atop are simply holding the top part to the remainder (pending potting - after which, the screws will come out & the magnets will go in)