件名 : RE: SCT GeoModel[Thu, 14 Sep 2006 10:34:41 +0100 (BST)] 送信者 : Pat Ward 宛先 : Tricoli, A (Alessandro) Cc : S.Haywood@rl.ac.uk >>> Dear Alessandro, Thanks for all the explanations of the mass differences I highlighted in my mail of 18/8, it looks as if everything is essentially understood. I have added more comments on a couple of points below. One general point: in several cases differences arise because components have been included in one volume by Taka and in a different one by you - either of which is a reasonable model. This makes some of the proposed changes look rather like 'change for the sake of changing', which I think should be avoided - so I wonder if, in a few cases, it would be better for you (if easy) to move a few components to correspond more closely to Taka's model, so the changes to masses and compositions will be smaller? Just a thought - we should clearly use the best arrangement where there is one - but I don't see any point in shuffling things unnecessarily. On Tue, 12 Sep 2006, Tricoli, A (Alessandro) wrote: > Cooling Pipe > ============ > Current Alessandro Drawing > ------- ---------- ------- > Radius/mm 2.0 1571.76 > Length/mm 2.1 1471.6 > Radial position/mm (3) 304.8 306.9 307.1/309.7 > (4) 375.7 377.9 378.0/380.6 > (5) 447.4 449.9 449.7/452.4 > (6) 518.1 520.9 520.4/523.1 > > * Current positions (estimated from entry points of particles) are > 2-3mm inside values suggested by Alessandro and drawings. Propose > to leave them there - moving likely to cause huge problems. > > -A.T.: I don't understand the values in the first two rows under "current" > and the "radius/mm" value under "Alessandro". (?) -CPW: Sorry, I have obviously typed in the numbers the wrong way round: the first two lines should read Current Alessandro ------- ---------- Radius/mm 2.0 2.1 Length/mm 1571.76 1471.6 > > * Length will be updated to 'whatever is convenient'. > I think the radius can be increased, but am not sure it is worth it. > Mass and composition will be updated. > > > Bottom Bracket > ============== > Current Alessandro > ------- ---------- > Thickness/mm (r) 4.0 3.2 > Width/mm (phi) 8.0 7.5 > Length/mm (z) 51.0 54.0 > Volume/cc 1.63 1.30 > Mass/g 4.94496 2.68 > Density/(g/cc) 3.03 2.07 > > * Why the mass difference? Think Taka includes an 'interface PCB' and > Alessandro does not (I think this is in Alessandro's harness). This > needs checking. > > -A.T.: it is true that the "interface PCB" is placed in the harness in my > model, but this accounts for only 1.43g extra, which added to > 2.68 g gives 4.11 g. That means that 0.84g are missing. > I notice that in Taka's excel sheet in > http://atlas.kek.jp/si-soft/geometry.html the "bottom bracket" > is actually 4.36g. The difference wrt my estimate is only 0.25 g in > this case. Going through Taka's calculations I notice that he used > both THIRD MOUNTING POINT UPPER and LOWER, whereas I only used > an average between the two, since (if I understand correctly) either > the lower or upper third mounting point is on each bracket assembly, > depending whether the module is in the upper or lower position. > Furthermore, I have one more screw (M1x4=0.027g) than Taka. In > conlusion the differences between my description and taka's > description are minor, whereas I do not know where the current > value in the simulation (4.945g) comes from. Any idea Pat? > -CPW: The density in the current simulation is the same as Taka's spreadsheet, but the volume dimensions are different. I have no idea why the dimensions are different - the overall volume is bigger (hence the bigger mass), so they have not been reduced to fit in..... Pat