Australian/New Zealand Luthiers Forum

EricDownunder wrote:I like that thing; do you mind if I copy your idea and build one for myself?

Go fer it, any improvements should be posted back but..

John, If you tell us that you've both tapered the rails, and adjusted each side of the bearing form to allow for a tapered fretboard radius--compound--I, for one, will never read another of your posts. You clever fellas just piss me off! :lol: Not smart enough to solve that one but happy to rip off...

Ah sorry Henk, just realised that you're in Holland and the dude in SA only ships to Oz. I just did a search on Ebay and found this in the US which looks like much the same sort of jigger: http://www.ebay.com.au/itm/24-Digital-Readout-Read-Out-DRO-w-remote-LCD-display-fits-Bridgeport-Mills-/14083920...

Looks really good. I must say, I didn't invent the concept, just copied someone else's idea but glad it is cutting down time. It certainly has for me. Even so it's a great idea and major time saver bonus that I can add it to the slotting jig without too much hassle. Always nice to have a multipurpo...

Thanks guys, I was sure I'd get a bollocking for using a sledgehammer on a walnut! Makes my jig look prehistoric! Would love to see how the saw is mounted. The saw is held vertical by the RE magnets. I had to spend a bit of time getting it squared up and it's not too hard if you go easy with the pul...

Probably over kill but.... I tried using a rule and marking knife for fretboards but couldn't seem to get them accurately marked/cut so I resorted to preslotted and radiused fretboards for my first two guitars. The two I'm currently building have 'non standard' scale lengths so I'm obliged to make m...

Thanks Trevor, I have started reading Wright's thesis and already picked up a few things that needed clarifying. Given that K has such a dramatic roll in moving and shaping the T(1,1) peaks, I was hoping to use the model to trim the peaks into position for various timber varieties. It seemed to me t...

Another quick question for you Trevor. Where do you get the stiffness and damping factor for the 4DOF parameters? I figured that K could be calculated from the Young's modulus of a measured plate using (4EBD^3)/L^3 but this comes out tiny compared to your 68000. I used the long grain E, body length,...

" I'll try it at work tomorrow on the machines we use to run the economy. Keep your fingers crossed, for all our sakes." Is that appropriate? No wonder the expected budgetary deficit is now in doubt! :lol: Treasury computers should work fine, they should be familiar with working in i maginary numbe...

Thanks John. Are you happy to declare victory over this lot? I think it's probably going to take someone programming it up in Matlab or something, working in 64 bit double precision to shake out the rest of it. I hope Microsoft are watching this one! I'm happy :D :D :D with the results. I might hav...

Your plot looks pretty close now, but the first peak is about 10 dB down compared to what I got, but the overall shape and the other peak heights are about the same. Given what we're finding out, it's hard to say which is the more accurate. A lot of the calc results are stored in textboxes which I ...

Well, I cracked it with Excel after checking the calcs several (dozen!) times over and not finding anything wrong. I decided to try a different approach and wrote an app to do it. Eureka, worked first up. I still have to sort out a few issues with the plot output format but the shape and amplitude m...

Anyone tried the calculations on a Mac? :mrgreen: No, don't got one of them but if I thought it'd work I'd get one!! I checked the Dbar calc (yet again) and I have it coded exactly as per the book. So, Yeah, I'm absolutely positive It's us. Ive even gone through and checked your matrices and worked...

Don't worry Os, I'll track down the problem. Cheers Dom Yeah well I think the balls in your court, I'm running out of ideas. I've even spent 2 hours working out the determinants just in case there was a misprint in there somewhere (a couple more zeros in the Dbar matrix would have been nice Trevor!...

You're right Martin. This is all your fault from memory after I asked a simple question about a hybrid classical build for SWMBO on the woodwork forum. wasn't it you that suggested getting into the books? Quote from the WWF: "You're playing around with the design of the guitar. Rather than make it a...

Tonight I will plug the calculated values for Yi back into Eq AII 2-25 through 2-28. I figure that once the solution to AII 2-25 equals AII 2-40, etc. then the maths must be correct. Done this and found that there are about 12 orders of magnitude difference between yt at Eq AII 2-40 and plugging in...

trevtheshed wrote:Yes, the Dbar calc is massive. I did it with IMPRODUCT over 11 columns and then used IMSUM.

You're not wrong!

I broke it down to 21 rows and annotated it as I kept losing track. Plenty of scope for errors though. Hopefully Dom will pick up my blunder as I am going bleary eyed looking at it.

I went through the Dbar calcs last night and I couldn't find anything that stood out. I then calculated (at least using Excel but without the IM functions) a couple each of the products and then sum and subtract terms and got the same answers as with the IM functions so think I am using them ok. I'm...

Dt 57535.9078102831+1884.95559215388i Ds -117827.340834859+6283.18530717959i Db 107748.740785237+4398.22971502571i Da 134.116591266459+8.79645943005142i Dbar 2.31298863526292E+015-3.13890440436301E+016i Yup, problem starts as soon as I hit the IM functions. I think there must be something about the...

John, the D's are all a function of ω, so how are you handling that? In your last post you must have them evaluated at a particular frequency? ω (2piF) - in fact all the values on the screenshot - is the result of the 100Hz entered in the input box. The table (off screen) auto inserts all the value...

Well, John, I think you're there, or very, very nearly. Well done! Sorry about that last bit. Not sure why that didn't get into the book! It was probably not required for those less mathematically challenged. I'm sure there's whole bunch of people out there that have already got it up and running w...

That's what I did, calculate the magnitude (plot in the post above). It can't be too far wrong as it does exactly what you'd expect (well as near as I can tell). Changing the parameters changes the modes/levels, if it wasn't for the fact that the overall shape doesn't match yours on P2-37 I'd almost...

I was just reading up on imaginary numbers and this site did not say j = sqrt(-1). But it did say the j is the answer to sqrt(-1). Credible? This stuff is hard enough without learning the wrong stuff at the same time. Its still cool though. Cheers Dom As I was taught j is the square root of a negat...

I just nested the imsums and imsubs because I was trying save space to keep everything on the same page so that I could try to keep up with it. I broke it down today and broke them up into logical groups and put them on separate sheets. Found 3 or 4 oopsies in the process and it moves closer to reso...

I think the penny finally dropped last night Trevor. I had assumed that the denominator issue was related to producing a real solution for Di and then plug that into the displacement calculations. I then gathered from what you were saying that the denominator stays in complex form and then each of t...