Fixed speed single phase AC setup

[Jarlberg]

Do any of you use a fixed speed AC setup on your 2x72's?  As everyone predicted, I've run into motor problems with my DC treadmill build.  I'm not exactly sure why the motor failed but it's likely do it being open and metal particles being introduced.   I can see this happening over and over again and have begun to look into replacing with an sealed AC motor.  I'm honestly thinking about going with a single phase 2hp motor and no VFD and keeping it single speed.  I have a 4" drive wheel and would need to find the ideal sealed motor.  Honestly I just can't afford to drop $650 on a VFD/motor setup.  And I've found that I really don't vary the speed on the grinder much.  

Anyone use a fixed speed setup?  Any suggestions on a economical sealed motor with a 5/8" arbor and an ideal time for a 4" drive wheel?

[JHCC]

Here is my single-speed 2x90 grinder:

This came with a 1 HP TEFC motor running at 3450 rpm. The drive wheel is 2-1/2" in diameter and mounted directly on the motor shaft, so that gives me a belt speed of about 2250 sfm. That's perfectly adequate for most tasks, although I do sometimes wish I could slow the belt down for the finer grits. While the 1 HP motor is technically a little weak for this application, I have found it to be up to almost everything I've thrown at it so far, with only the occasional bogging down when I've gotten overenthusiastic.

If you did a direct-drive with your 4" drive wheel, a 1725 rpm motor would give you about 1832 sfm. While that's not quite as good for the heavy hogging, the lower speed would be to your advantage for the finer grits -- definitely a plus for knifemaking. However, you could always use step pulleys to get yourself a range of speeds.

 

[Jarlberg]

That's for the info.  I appreciate it.  What would be the ideal sfm for fixed speed.  Sort of a best compromise for both course grit and finer grit work?  Around 2,000?

[JHCC]

I'm happy with 2250; I'm sure I'd be equally happy with 1800. A lot depends on the work you're doing: I'm primarily a hobby blacksmith who uses the grinder for a lot of different tasks, so I like the faster material removal of the higher speeds. If I were doing more knifemaking, I'd probably appreciate the slower speed for a finer finish and would be okay with sacrificing the faster hogging. On the other hand, if my existing grinder were a slower speed already, maybe I'd be more inclined to do more blade work!

Regardless, going for a higher HP in your grinder is almost never a bad idea.

[Marcus_Aurelius]

I am one of the lucky guys and I have a VFD on my Bader grinder. While it is not necessary to use a grinder effectively, it sure can be a real help. When I am using ceramic belts on hardened steel or really need to throw some sparks I'll crank up the speed. From my own experience higher RPM make tasks such as shaping wood handles for knifes/hammers, finer polishing on blades, and precision work harder. So I tend to tune down the RPM on those tasks. Regardless, with enough skill and patience all of these tasks can be done efficiently on a fixed speed grinder.

-Mark

[JHCC]

True that.

[Stash]

My Bader is a single speed, it suits MY needs fine. I have 2 sizes of drive wheels in case I wanted to change things a bit.

Steve

[Irondragon Forge ClayWorks]

Same as our KMG, a three size pulley setup on both the motor and driven wheel allows for rapid speed changes. Drop the belt to the small motor pulley and large driven pulley to slow the belt speed, reverse to speed it up, sorta like a drill press.

[Frosty]

I"m setting mine up with step pullies. 

Frosty The Lucky.

[BeaverNZ]

My large linisher is fixed speed and has a 220mm Dia drive wheel with 50Hz gives 2750 rpm with a 2 pole motor that gives 1900 meters per Min so it really fizzs around and with 60 grit Zirconated belts can really remove lots of material. But my smaller knife making linisher is on a VSD and goes from 270 to 5000 rpm with a 100mm Dia drive wheel which gives 84 to 1570 meters per min so that gives a range of speeds So as others have suggested you could set up a couple of cone pulleys to give you a better surface speed for light or heavy work