<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Sustain pedal lift ratio</title></head><body> <div>Hi all,</div> <div><br></div> <div>At 10:48 AM +0100 10/11/06, RicB wrote:</div> <div><br></div> <blockquote type="cite" cite>... I'd like to hear more about how you go about designing a change in the lever systems.  I remember my brother Joe doing this to accommodate pianodisk systems... tho I dont think he was concerned directly with the lifting ratio... more a matter of making everything fit.</blockquote> <blockquote type="cite" cite>Still.. this might be a nice addition to ones technical toolbox as it were....</blockquote> <div><br></div> <div>At 5:01 AM -0600 10/11/06, Conrad Hoffsommer wrote:</div> <div><br></div> <blockquote type="cite" cite>I second this. The difference in feel, usually expressed as "heavy"/"light", has been noted more lately by both students and faculty.</blockquote> <div><br></div> <div>The lift ratio and the resistance of the pedal system are two separate issues, regarding the performance of the sustain pedal. Most manufacturers fit a return spring to the damper lift tray, the sustain lever directly under the keybed, or both. The return spring on the damper lift tray can create problems over the longer term, since its not usually possible to position the spring directly over the push rod. When the return spring is offset from the push rod, the damper lift tray can develop a compression-set warp over a number of decades. This is a long term problem which won't usually occur while those who built the piano are alive. Eventually, once the builders are lying quietly in a box on a hillside somewhere, some repair tech in a workshop might be found whining about another case of poor design staring them in the face, as they deal with a warped damper lift tray.</div> <div><br></div> <div>I prefer not to fit a return spring on the damper lift tray for the reasons above mentioned. For those damper systems where the push rod is located via a bushed guide hole in the keybed, it is best to convert these by drilling a larger clearance hole in the keybed and fitting a push rod with a guide pin in each end. This will be quieter, creating less friction and noise. Its a good policy to make and fit a new pin-guided push rod when rebuilding pianos with the older style bushed push rod.</div> <div><br></div> <div>As mentioned in my previous post, most pianists seem to prefer a pedal/damper lift ratio of between 2.5 to 3.25 to 1. When making an adjustment to the ratio, I prefer to set it between 2.5 to 3.0. But for some pedal systems 3.25 is about as high a ratio as can be achieved using a single lever under the keybed. So, in these cases I'll go as low as 3.25 because the double lever design, as used in the Grotrian 275 conversion image I posted yesterday, is a whole lot more trouble.</div> <div><br></div> <div>I check an existing damper lift ratio by measuring the damper-head lift, and measuring the damper pedal travel from the end of the lost motion to full lift. The pedal travel is divided by the damper-head lift to arrive at an overall ratio.</div> <div><br></div> <div>If I need to revise the ratio, the formula for calculating the lever lengths is similar to the formula I use for calculating action ratios. Each pair of lever lengths is divided one into the other, with the three results being multiplied together to arrive at an overall ratio.</div> <div><br></div> <div>The three lever lengths are the pedal pair, the lever under the keybed pair, and the damper tray pair. Here's a graphic to show the various lever lengths A - F.</div> <div><br></div> <div><br></div> <div align="center"><img src="cid:a06240817c17a871f4d21@[192.168.0.7].1.0"></div> <div><br></div> <div>The pedal/damper lift ratio is calculated using the following formula.</div> <div><br></div> <div align="center">(A/B) X (C/D) X (E/F)</div> <div><br></div> <div>For many damper systems, the push rod will come through the keybed to contact the damper tray almost directly under the damper wire flange. In these instances you can disregard the lever lengths F and E, giving them a value of 1. There will be some small variation in the actual ratio due to variations in the lever angles from piano to piano. However, the variation is too small to worry about in practice with respect to the ratio, but the lever angles are critical with regard to friction.</div> <div><br></div> <div>If the push rod is fitted with guide pins the angle of the push rod, with respect to the damper tray and damper lever, won't be of much consequence, since it will contribute very little friction. The damper lever under the keybed is a different matter. I prefer to set this lever so that it is horizontal at half damper lift. This arrangement will minimise friction between the lever and the lyre push rod. For our own 225 piano, we machine away the lower-half of the damper lever thickness where it meets the push-rod capstan, and lengthen the lyre push-rod so that the lever is horizontal at half damper lift. This results in less friction and less likelihood of squeaks developing between the lyre push-rod capstan and the lever bearing-felt.</div> <div><br></div> <div>I hope you have found the above mini-doc to be useful, since this is the first time I've written-up the procedure onto something more substantial than a piece of scrap of paper around the workshop. However, its been good for me to document the procedure.</div> <div><br></div> <div>For those of you who would like to know how I produced the graphic and imported it into the Eudora programme, here is the procedure.</div> <div><br></div> <div>1) Draw the graphic using my old 2D CAD programme.</div> <div>2) Capture a screen image of the drawing and save it to the desktop as a TIFF file.</div> <div>3) Open the TIFF file in Photoshop, resample, reduce in size and save as a jpg file.</div> <div>4) Drag the jpg file into the Eudora email document.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>