I think the desired speed is close to 5,000 ft. per minute.
The 4 inch pulley will have 2.5 times the rotational speed of the 10 inch pulley. The pulley diameter times the RPM rate will be constant. So, as the pulley size gets larger, the pulley speed gets lower.
From contributor R:
I'm sure that the above post meant that as the driven pulley gets larger the RPM gets slower. I just wanted to clarify to make sure no one got confused. If the drive pulley got bigger the driven pulley would get proportionally faster. Let us know when your mill is making sawdust. Boards may be a couple of days after that. Endeavor to persevere!
I just found the info that you need. It is for the Suffolk low tension blade. Here is the formula for finding pulley size for you particular engine. You are shooting for a *minimum* of 4500 surface feet per minute up to 5800 for a maximum. This is for Timberwolf blades from Suffolk Machinery.
Motor RPM X motor pulley diameter divided by driven pulley diameter X band wheel diameter X 3.1416 divided by 12 = SFPM
Before any calculation is made, you need to know what the motor RPM is at the shaft (either stated on the motor label or taken with a tacho or whatever other means). Once you get that, multiply this RPM by 4 and divide the result by 10 to get the bandwheel RPM (I presume the bandwheel and the 10 inch pulley are on the same shaft). Next, find the circumference of the bandwheel in feet and multiply this by the bandwheel RPM. There you have what you're looking for - the number of feet (blade) per minute, or what you call "band speed".
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From contributor A:
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