How much of a rush are you in, I'm sure I could make you batch of 10 or 20 next weekend. Ive just drawn the 240mm radius over 55mm width and its only 2mm. So with the band saw I can cut the rectangular blanks and then I'm thinking that with a radius jig mounted on the bench grinder the raduis can be ground, which would also give a nice finish as this will be the visible bit.
I really appreciate your offer of help - but I wouldn't dream of putting anyone to that trouble!
As I explained to John via PM, I'm trying to stay one step ahead (so that when I arrive at a given point I already have the info I need!), so wrt pursuing the blade idea, I realised I'd need a quote to get them made properly. I don't actually need them made immenently, as I'm still very much in the 'proving' phase.
As it goes, after further (heavy) testing over the past 4-5 nights (using a rough 1/8" thick rectangular bit of mild steel) I've found that a 'blade' in a sustainer driver bobbin is sub par vs inividual guitar string 'pole' pieces. This is worrying ...I was just about to place an order for a few hundred blade bobbins from Korea! (presently I cut every bobbin I make on my CNC from acrylic - pain in th @rse!) ...I'm hoping it's just the variant of steel I bought (I wanted black steel ...but couldn't find any in a suitable 'hacksawable' size ....so I bought bright steel, which apparently - and I'm no steel expert - has more carbon in it?). If I place magnets at the bottom of the blade & then touch the other side (top) with a screwdriver, there isn't much magnetic pull - whereas when I do the same using pole pieces (mild steel grub screws) the top of each pole piece has a decent magnetic pull.
Two possible solutions...
1. Try a different grade of steel for the blade.
2. Crank up the strength of the magnets I'm attaching to the bottom of the blade (this would mean putting physically bigger magnet on there...and I don't have much room to do so)
So for now, I'm still, stuck in 'uncertain' land wrt blade type drivers.
I appreciate the offer of help though - many thanks.
Last edited by HankMcSpank; 08-02-2010 at 10:59 AM.
Not sure what you are ultimately trying to accomplish but putting a magnet one side of a steel bar will effectively short out the magnet, so I would not expect to get an awful lot of magnetism on the other side.
If you want the magnetism to pass through as it were they would need to be isolated a bit to channel the effect as in transformer laminations which are effectively insulated on one side such that the magnetic effect is channeled around the laminations and not leaking out the sides.
I think you need more design input.
I think Peter has beaten me too it but I was going to suggest using a thinner piece of steel, I dont know much about magnets but maybe a lower mass is required, as I said before the hot rails type of pick up use two thin strips, maybe this isnt a coincedence
Maybe you can create a sandwich of plastic and steel to make up the 3mm width?
Why do you need a blade anyway? is it cosmetic or are there dead spots between the poles?
Anyway good luck
Magnetism....it's well esoteric! (likewise Ross, I actually know very little about the science of magnetism...hence the trial & error aspect of making a good driver is my only option! I did find one magnetism forum, but didn't get much help there!)
OK, at the risk of straying well off all things CNC/Metalworking etc, for those that might not know, a guitar pickup typically has 'slugs' (mild steel 'cylinders') directly underneath each string with a ceramic magnet attached to the bottom. My (good) sustainer, emulates such a setup...the magnetism travels from the magnet attached to the bottom of the slug through the 'slug' & makes an appearance at the top (I don't yet have a gauss meter to measure the strength, but intend making my own gaussmeter with a PIC & a hall effect transistor soon).
The problem with a 'slug' design of sustainer is that a lot of guitars have different string spacings ....so for all this style performs well, if selling these eventually it's going to be a complete hassle establishing the guitar's string spacing & then having to make a custom bobbin to suit. (& Ross, since you ask....sting fade is not a problem when the string is bent between 'slugs')
The reason for wanting to now pursue a blade design is that it circumvents having to worry about the string spacing!
I see your logic Hank, but the blade wont generate the same magnetic field as a slug unless it was treated to localise the magnetic permeability. Otherwise the field lines from the magentic poles will travel horziontally through the steel and back round to the free pole. None of the field will escape the steel vertically and around the string other then a relatively small feild from the coil itself. The main purpose of the coil as I see it is to modulate the magnetic field from the slug/magnet to return energy to the string. But this can't happen if the field never leaves the blade. I'm no expert, but I did do some transformer design in the very distant past...
Only a suggestion, but how about glueing a load of 1/8" x 1/16" iron bars side by side and then cutting the part as slices off that. A sort of large format zebra strip.
The strings might not line up with any particular bar, but they will line up with some of them :naughty:
Edit: Typo :whistling:
Edit: So why isn't it showing the post as edited
Edit: How many goes do I get? Need answers .
Robin - it only shows as edited if it has been viewed before you changed it... back on topic now...
Or ultimatly you could just follow the pickup trend and offer only two sizes; Gibson (ish) spacing/raduis and a Fender (ish) spacing/radius, if there is no loss between the poles then I can see it matters.
I 've just looked at a few of my guitars and there dosnt seem to be a difference in pole spacing from bridge to neck pickup so its not an exact science anyway (I think they are only sold as neck or bridge based on the resistance/power output)
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