(09-27-2017, 08:35 AM)Pirate Wrote: Question
Is it supposed to have a 2 hp 1800 rpm motor? seems like it would loose a lot of torque, stepping up to 3500 rpm blade speed or so.
Remember that an 1800 rpm motor with 2 rated hp will output twice the torque of a 3600 rpm motor with the same 2 hp rating (70 in-lb vs 35 in-lb).
Using the belt drive to double the arbor speed (for example) to 3600 rpm will, of course, halve the torque at the arbor, but you're starting with twice the available torque, so in the end, you get the same thing.
Mechanical shaft power is the product of torque and speed, so for the same power, as speed goes down, torque goes up and vice-versa.
So 1800 rpm motors are not unusual for older design saws and other wood machines, like the original Unisaw. And you're not losing anything with an 1800 rpm motor.
Edit: I should add that, as a general rule, 1800 rpm motors cost more than 3600 rpm motors of the same output rating, and 1200 rpm cost more yet, but not as much as 900 rpm, and so on. Torque equals dollars in almost everything mechanical (speed isn't as expensive), and a 2 hp 1200 rpm motor will have a larger frame size than a 2 hp 3600 rpm motor. So a good reason for high-speed motors on high-speed machinery is lower motor cost as well as smaller drive parts, specifically the motor sheave since it can be smaller.
![[Image: 233-A.jpg]](http://vintagemachinery.org/photoindex/images/233-A.jpg)
