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+--- Thread: belt grinder torque question (/showthread.php?tid=179)
belt grinder torque question - Ken S - 10-03-2017
I recently rebuilt my Viel grinder with a smaller (3 1/2” instead of 6”pulley). The driven, top pulley is the original 3 1/2”.
Many years ago I purchased a right angle adaptor for my electric drill. The adaptor could be installed two different ways: one gave higher speed and lower torque; the other gave lower speed and higher torque.
For ease of calculation, let's round the pulley diameters to three and six inch diameters and use 1000RPM. My gut feeling is that the smaller pulley, with lower surface feet per minute will produce more torque, however, my gut feelings are not always very scientific. Once again, my high school math background from fifty yeats ago is not up to the task.
Help will be most appreviated. What is the effect on torque from using the smaller pulley?
Thanks,
Ken
RE: belt grinder torque question - Ken S - 10-03-2017
I'm just taking a guess at my own question. I believe the Penn State Industries variable speed motor is variable speed because of using DC power. If the power to the motor increases with higher speed; and if the surface feet per minute with the smaller pulley is approximately 60% of the larger pulley; to achieve the same surface feet per minute would require a higher motor speed, and, thus, more power. I would translate that into more torque.
Thoughts?
Ken
RE: belt grinder torque question - Rupert Lucius - 10-03-2017
(10-03-2017, 08:45 AM)Ken S Wrote: I'm just taking a guess at my own question. I believe the Penn State Industries variable speed motor is variable speed because of using DC power. If the power to the motor increases with higher speed; and if the surface feet per minute with the smaller pulley is approximately 60% of the larger pulley; to achieve the same surface feet per minute would require a higher motor speed, and, thus, more power. I would translate that into more torque.
Thoughts?
Ken
My guess is that the torque is more than doubled.
Rupert
RE: belt grinder torque question - Jan - 10-03-2017
Mr. Rupert is correct!
Mr. Ken, you are asking a complex question. I can answer it only partially.
When you fix the power to the motor and then replace the original 6" driver pulley with 3" driver pulley than the torque on the driven top 3" pulley will be two times larger.
It is because the torque on the driven pulley is inversely proportional to the driver pulley diameter.
Jan
RE: belt grinder torque question - Ken S - 10-03-2017
Jan,
If you gave me a complete answer, it might take a century and a Nobel Prize to verify it.
Actually, your partial answer is exactly what I was looking for. Double the torque will let me use the slower speeds I like and control the cutting speed by touch. My work is mostly with a light touch, with some heavy artillery in reserve when needed.
Thanks.
Ken
Rupert,
I really like the smaller Gen III pulley, and the washers work well!
Thanks,
Ken
RE: belt grinder torque question - Rupert Lucius - 10-03-2017
(10-03-2017, 04:59 PM)Ken S Wrote: Jan,
If you gave me a complete answer, it might take a century and a Nobel Prize to verify it.
Actually, your partial answer is exactly what I was looking for. Double the torque will let me use the slower speeds I like and control the cutting speed by touch. My work is mostly with a light touch, with some heavy artillery in reserve when needed.
Thanks.
Ken
Rupert,
I really like the smaller Gen III pulley, and the washers work well!
Thanks,
Ken
You are most welcome - as you get more time operating the Gen III you will be using it like a pair pliers, screw driver, crescent wrench.
It will become a tool that you will not be without.
A local professional machinist keeps one on the table that holds his wooden tool chest at his lathe station. Uses it to keep from having to fixture items at his milling machine station - the belt is so versatile and handy.
RE: belt grinder torque question - Ken S - 10-04-2017
Rupert,
Excellent comment about the local machinist keeping his Viel nearby. I find it is a very handy "go to" tool for many jobs. (The plastic Melitta filter holder cup I have used daily for over twenty five years has some rough spots where the two parts of the mold met. Gen III with a worn belt used at slow speed will soon make quick work of the rough spots!)
Ken