The discussion revolves around selecting an appropriate motor for a potter's wheel, focusing on specifications such as RPM, load capacity, reversibility, and controllability. Participants explore various motor types, their characteristics, and practical considerations for implementation.
Participants express a range of opinions on motor selection and design considerations, with no clear consensus on the best approach or motor type. Multiple competing views on the necessity of speed control and the implications of inertia remain unresolved.
Some discussions involve assumptions about motor performance characteristics, such as torque and RPM relationships, which may depend on specific motor types and configurations. The impact of inertia on motor behavior is also noted but not fully resolved.
sophiecentaur said:Power is torque times angular speed - as you say.
Also, just as Force equals Mass times Acceleration (Newton's Laws), you also have Torque equals Moment of Inertia times Angular Acceleration - which you also described.
Those are the basic definitions. That means that, a given power of motor / transmission system will produce high torque at low speed or low torque at high speed (basic principle of car gears etc.) Also, for a given torque, the acceleration for a high MI will be less than for a low MI (Obvious really)
Things are not quite the same for Induction Motors but the following applies to most electric motors.
An electric motor tends to produce higher torque at low speed (max when stalled, in many cases) because the current is highest. Eventually, a motor will reach a speed where the power it's delivering is limited by the torque. Because the rotation will produce a 'back emf', the current will drop off to near zero and the motor may go at high speed with very low power, only limited by the friction in the system.
The problem is that, because there isn't just one value of torque to consider - it changes as the thing accelerates - there isn't a simple answer to any of these questions.
There are two aspects to most motor applications. You need to know how quickly you want it to reach operating speed and also you need to know how much mechanical power is needed when it's running (rate of cutting / grinding etc.).
In your case, no significant work is done, once it is up to speed, - just the energy needed to re-arrange the gloop in the drum. You don't even want the acceleration to be too high. The motor requirements are not great (less than for a Potter, in fact). You will need some facility for speed control though. Almost any fractional hp motor would do, I suggest. You would just need an appropriate transmission (belt /pulley) system to get the speed range right and motors have their normal running speed marked on them, usually.
"what torque is calculated by formula hp=(torque(rpm))/5252? is it full load torque, accelerating torque, locked rotor torque or what? "
The formula applies for all speeds (except zero - when there is NO Power delivered, just wasted as the thing frazzles). Torque and Power would be specified for normal running revs, I should imagine)
You need to specify two of the three quantities in that formula in order to find the third - which is a bit confusing because the torque from any motor is not constant with speed.
I am still concerned about your ideas for suspension. I think you need to reconsider why you think hanging the drum is preferable. I think you may be thinking too subjectively. Look around you at other spinning machinery. How many examples are there of hanging systems? There must be a good reason for it. Consider washing machines - the best ones for water extraction are top loaders, with the drum supported at the bottom. Imagine the problems involved in doing the same thing with the drum hanging. You'd need all that stabilising concrete to be fixed to the ceiling! And you DO need an (ideally) infinitely massive support for stability and to counter any possible imbalance effects. I seriously cannot imagine it somehow automatically centring itself up, just by hanging there.