This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment Hi Terry, OK, here's a more user-friendly method for you that will give you the = correct position of the rib anywhere along its length. (You can also = use this method to plot out points on a template. Compute numerous = points and connect the dots. :-) Clamp any part of the rib against a flat surface, concave side up = (soundboard side down). With this arrangement, let: h =3D the height of the rib above the flat surface r =3D radius of the rib d =3D the distance along the rib you are measuring, with respect to the = clamp point. For instance, if you clamp in at the middle of a 4 ft rib = and measure at the end, d would be 2. Of course this is approximate. = More accurately, d would be the distance from the clamp point to the = position on the flat surface, directly underlying the measurement point. = (Think right triangles.) Then: h =3D r - Sqrt ( r^2 - d^2)=20 So for a rib of 60 ft radius (720 in radius), these would be some of the = elevations, h, as a function of distance, d, from the clamp point: d (in) h (in) =20 =20 =20 1 0.001 =20 2 0.003 =20 3 0.006 =20 4 0.011 =20 5 0.017 =20 6 0.025 =20 7 0.034 =20 8 0.044 =20 9 0.056 =20 10 0.069 =20 11 0.084 =20 12 0.100 =20 13 0.117 =20 14 0.136 =20 15 0.156 =20 16 0.178 =20 17 0.201 =20 18 0.225 =20 19 0.251 =20 20 0.278 =20 21 0.306 =20 22 0.336 =20 23 0.367 =20 24 0.400 =20 25 0.434 =20 26 0.470 =20 27 0.506 =20 28 0.545 =20 29 0.584 =20 30 0.625 =20 31 0.668 =20 32 0.711 =20 33 0.757 =20 34 0.803 =20 35 0.851 =20 36 0.901 =20 37 0.951 =20 38 1.003 =20 39 1.057 =20 40 1.112 =20 41 1.168 =20 42 1.226 =20 43 1.285 =20 44 1.346 =20 45 1.408 =20 46 1.471 =20 47 1.536 =20 48 1.602 =20 49 1.669 =20 50 1.738 =20 51 1.809 =20 52 1.880 =20 53 1.953 =20 54 2.028 =20 55 2.104 =20 56 2.181 =20 57 2.260 =20 58 2.340 =20 59 2.421 =20 60 2.504 =20 61 2.589 =20 62 2.674 =20 63 2.762 =20 64 2.850 =20 65 2.940 =20 66 3.031 =20 67 3.124 =20 68 3.218 =20 69 3.314 =20 70 3.411 =20 71 3.509 =20 72 3.609 =20 Hope that helps! Peace, Sarah ----- Original Message -----=20 From: Farrell=20 To: Pianotech=20 Sent: Thursday, December 11, 2003 7:00 AM Subject: Re: Rib dimensions Lots of good methods for calculating the radius of an arc have been = provided. But there is also the question of whether the curve is a true = arc or some other shape (this assumes you have a specific shape as a = target). Most of the provided methods do not address that concern - in = fact you could have an obtuse angle with two straight sides rather than = an arc. That's why I suggested making a number of measurements along the = curve - offsets from a straight line. Terry Farrell ----- Original Message -----=20 From: Absolute Piano=20 To: pianotech@ptg.org=20 Sent: Wednesday, December 10, 2003 4:40 PM Subject: Rib dimensions Hello, I'm trying to apply some science to my soundboard rib making and I = am looking for "tables of static values for the Resisting Moment (W) = and the Moment of Inertia (I) for all the possible cross sections of = sugarpine and spruce (DIN 1052 Class I will suffice). What is the formula for converting pounds/inch squared to kg/cm = squared? Given a right angle connected to the outside of an arc of a circle, = how do you prove the circle is 60'? (I made a jig for crowning ribs that is adjustable and I want to calibrate it. Thanks, Jude Reveley, RPT ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/63/01/0f/9d/attachment.htm ---------------------- multipart/alternative attachment--
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