--- In [EMAIL PROTECTED], "Leslie Watts" <[EMAIL PROTECTED]> wrote: > Dave, > Power is just torque times rpm. The motioneering software selected motors > and displayed a torque curve showing the operating point was in the > safe region. > > Although I did not list it, the optimum motors were in the range of > 600W or so rated cont power. This occurs at max cont torque and max > rpm. > > At the 3 to 5 reduction the motor will only be going a few hundred rpm > for the gantry speed I used. The power actually delivered will be > only perhaps a tenth of what the selected motor is capable of. The > voltage will similarly be much lower than rated. > > I know this may seem really sub optimal to use the motor this way, but > we are trying to optimise cost- not motor power utilization or efficiency. > > The only mechanical load that really consumes real power is friction. That > is > very low in your proposed machine. What we need is FORCE to accelerate the > moving > mass... and in a regenrative servo system you actually get that back when > you > deccelerate....it pumps up the supply cap voltage. > > So it turns out that the software selected motors capable of the torque > required > can generate much more power if they were run at a high rpm. > > The smaller motors at the high ratios run at higher rpm, but they have to > use > more torque to fight their own rotor inertia. As you can see the software > found > NO practical motor that would give the selected machine performance above > 20:1. > > Let's say you had a car that you wanted to be fast off the line. You can use > smaller and smaller motors with more and more gearing to get the same > torque. > At some point the time to wind up the smaller motors to high rpm would > actually > be the limiting factor rather than the car's mass. > > > Les > Leslie M.Watts > http://www.lmwatts.com
Sorry for being so dense. But, it seems one of your earlier posts mentioned flat and large diameter motors are bad and long skinny ones are good. That makes sense as the flywheel effect from the large motor would get in the way of quick response. Ditto cast iron timing pullies vs. plastic ones. I do have the idea that a DC motor is rated on a somewhat linear curve. and that generally speaking, a 100 volt, 10hp 4,000 RPM motor is also a 50volt, 5hp 2,000 RPM or 25 volt, 2.5hp 1,000 RPM motor. so, generally speaking, I can make a prototype axis a few feet long and test the motors I have with different gear ratios to see the acceleration. Dave Dave Addresses: FAQ: http://www.ktmarketing.com/faq.html FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/ Post Messages: [EMAIL PROTECTED] Subscribe: [EMAIL PROTECTED] Unsubscribe: [EMAIL PROTECTED] List owner: [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL PROTECTED] Moderator: [EMAIL PROTECTED] [EMAIL PROTECTED] [EMAIL PROTECTED] [Moderators] URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO OFF Topic POSTS: General Machining If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble. http://www.metalworking.com/news_servers.html http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list. NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........ bill List Mom List Owner Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
