Watch gear gearboxes - Page 6 - RC Groups
 Jun 27, 2006, 02:48 PM Registered User Jon, you have to count. The "working diameter" (as I called it) is not the outer diameter but the diameter at about (not exactly) half of the height of the teeth. For getting the count of the teeth by measuring the diameter of the gear you need special mathematics or special tables and exact micrometer calipers. In the case of watch gears you also need a loupe. And you might fail anyway because you don't know to which standard the gear is manufactured. A watch gear can easily be based on cycloidic curves or on involute curves, both are difficult to calculate, and you don't know which amount of addendum modification was applied. At the end of the day counting is the easiest way. The exact dimensions of gears and the shape of the teeth are a complex matter, as you can easily see on that page MegaTesla pointed to. And, I wrote "(50+10)/2*0.2 = 6mm", you interpreted it as "(50+10)/(2*0.2) = 150", which is, I'm sorry, something different. Regards, Jochen (mechanical engineer) Last edited by jberg; Jun 27, 2006 at 02:55 PM.
 Jun 27, 2006, 05:55 PM Registered User Jonathon You can use my gear center calculator to calculate the gear centers and mod. It is pretty close or close enough for our purposes to use the following formulas Mod = module = the lenght in mm, of the pitch circle diameter per tooth PCD = Pitch Circle Diameter PCD(s) = PCD of spur PCD(p) = PCD of pinion C = Center Distance, this is the calculated value of the center to center distance MA = Mesh Allow Distance, this is how much you want to add to C to allow the gears to run smoothly Didel recomends 0.02mm for 6.67:1 and lower ratio 0.3mod gears For the 0.2 module gears the mesh allow distance is 0.01mm Formulas: Mod = OD /(N+2) PCD = N x Mod C = (PCD(s) + PCD(p)) / 2 http://geocities.com/billy_stiltner/gearboxes.html There was a problem with the javascript that caused errors in the calculator results on my site but it is fixed now. Billy
 Jun 27, 2006, 05:57 PM Registered User Wow, thanks Billy. that will make it much easier. For some reason, I didnt see that on your site. thanks though. It kind of sucks that i will have to count the teeth by eye to find the mod. oh well
 Jun 27, 2006, 06:08 PM Registered User Jonathon your PM box is full. Billy
 Jun 27, 2006, 07:22 PM Registered User Jon, you have to count the teeth with your naked eye. Using any kind of magnification is cheating Robert
 Jun 27, 2006, 08:25 PM Registered User It really is cheating just like using your prop instead of carving my own. Billy
 Oct 08, 2006, 09:04 PM Registered User Hey I looked for the 1/4 bag of watch part soup at clockworks.com and cant find it. Does anyone know if you can still get a 1/4 lb bag of assorted watch parts? Billy
 Oct 09, 2006, 12:37 AM Registered User billy, try www.scotchwatch.com for gears, etc. steveh
 Oct 09, 2006, 09:33 PM Registered User great site...no gears??? EDIT: sorry just saw the gears
 Oct 09, 2006, 10:04 PM Registered User they call them train wheels (spur gears) , clutch wheels ( crown gear...) , cannon pinions (pinions...)
 Oct 10, 2006, 05:07 PM Registered User Steve Thanks for the link. The bulk watch parts are no longer available from clockworks or slarose. clockworks supplier was slarose and they are out of business it seems. The phone message at slarose says closded for inventory for 2 weeks. Robert Check out page 2 of there bulk items. They have the ruby bushings 70 for \$40.00. Billy