Need some help building a grinder

[PegLegPeat]

I am pretty new to knife making and have made several. Although nothing really to look at. I have been reading here for a while and decided to make myself a 2 x 72 grinder. I have most of it planned out except I need a little advice. The motor my brother-in-law gave me is a 1725rpm 1 hp but I don't know how fast the belt actually needs to turn. If I could get someones motor rpm's + drive wheel size + pulley ratio I could do this math myself but I have no grinders handy to look at. I also need some way to quantify how much tension needs to be on the belt. Any help would be really appreciated!

Thanks in advace

---Peat

 

[silver_pilate]

This page has a handy formula for figuring out what size pulleys will give you what rpm's at the drive shaft:

http://www.temecularodrun.com/ref/rpm_calc.asp

Then this calculator can use that rpm and your known drive wheel siameter the grinder to calculate belt speed in SFPM:

http://i-logic.com/utilities/sfm.asp


For instance, using your 1725 rpm motor, if you run a 4" sheave on the motor to a 2" sheave on the drive shaft, you will spin your shaft at 3450 rpm. If you have a 6" drive wheel mounted to the other side of the shaft spinning at 3450 rpm, you will develop 5419 surface feet per minute.

Hope that helps. As far as tension, I know many use springs that deliver from 15-30 pounds of pressure against the tension arm. You could always try a spring and see how it works. They're not too expensive to change out.

--nathan