Recent content by rglassburn

cswilson, sreid, I do not see any error in your calculation and it does square with where I am now in my calculations. During the course of this discussion, I have been reducing my table size and increasing the speed required. Currently I have reduced the inertia down to 2.7 lb-ft^2 (without...

We are using the mass moment of inertia (I: I = m x r^2) and not the polar mass moment of inertia (J). 'J' deals with torsion, 'I' with angular motion. Easily confused. There is even another inertia that is also called 'I'(second moment of inertia). Wikipedia does a pretty good job of...

sreid, The units are lbm-ft^2. So they are pound mass units [no-one likes slugs anymore :-( ] Typically called WR^2 or WK^2. Simply the weight times the radius of gyration squared. The time in seconds to change speed is given as follows: t = (WR^2)*(change in RPM speed)/[308*(avg. accel...

itsmoked, Unfortunately, that is covered in the NDA with our end client. Thanks, Rob

itsmoked, I thought that was what you had meant :-) Thanks, Rob

Jraef, That makes sense to me. In order to accelerate my load up in the time that I need, I need a 1.7 lb-ft of torque on average. The motors full load torque rating is 15.0 lb-ft of torque. Which of course seems like way too much for the need. Unless this diminishing HP with increasing...

The table is connected to the machine frame thru 2 bearings located on a shaft connected to the table. The motor is vertically mounted and connected to the frame. The frame will be welded together. I am allowing adjustment room in the bearings and the motor for alignment. I am going to...

Thank you all! Very useful and helpful information. The flexible coupling is indeed like a "lovejoy" flexible coupling. I will make sure that the drive and load are well aligned even without the flex coupling - as well. I have chosen a 5HP TEBC(Totally Enclosed Blower Cooled) motor. It is a...

Electricpete, Thanks for the reply! I was going to let the VFD control the deceleration. For your other VFD question - I do not have an answer. I am being led toward a 3HP (8.9 lb-ft full load torque) or a 5HP (15 lb-ft full load torque) 4 phase(1750rpm) inverter duty motor by a...

Very interesting comments all. Thank you! So using the equation relating inertia, speed change, time I get an average torque required of 3.5 lb-ft. This should allow me to accelerate my inertia to my speed in the time frame I need. The way I understand this is that as long as my motor has...

Hello All, I have been asked to specify a motor for a new centrifuge. It needs to be able to handle 9.4 lb-ft^2 of inertia and spin at 3425 rpm. In order to cycle the number of parts that I need, I will need to be capable of cycling the centrifuge from 0 to 3425 rpm up to 30 times per hour...