Official Luthiers Forum!

Hi folks,

I just picked-up a used StewMac arbor, I am setting up the motor/arbor, but have run into a question. The arbor has 3 pulley sizes, and I was not sure which one to align the belt with. Large, medium or small?

Thanks up front for the help,

Dave

_________________
Dave

Remember, to always plant trees under which you may never sit.

I'd get a similar pulley for the motor & install in reverse for full speed range. Depends on finish / wheel dia which speed is best.

_________________
Dave
Milton, ON

Hi Dave,

Thanks for the response. I actually bought the StewMac Motor, 1/2 hp, 1725 rpm, and the wheels are 14", total shaft length 36". I am trying to line up the motor and belt w/ the correct pulley to give it straighter alignment, rather than having it running at too sharp an angle between motor and arbor.

Any thoughts on that?

Thanks,

Dave

_________________
Dave

Remember, to always plant trees under which you may never sit.

It's easy enough to mount the motor on a base that can shifted side to side, so you can experiment with different speeds. Get the longest belt you can. having the motor set well back from the buffing assembly will make things easier when buffing a guitar with the neck on. The longer belt will also make side to side alignment less critical. Start with the slowest speed available (the biggest wheel on the arbor). This will be less exciting while you're becoming familiar with your machine. If that isn't aggressive enough, try a little more speed. If the finish starts to ripple, or pick up a lot of marks from the buffing wheel, you've probably got more speed than you need.

The number you are shooting for is in the range of 900-1200 sfm (Surface Feet per Minuter) for most lacquer, and that is sort of the high end, you can go slower if you want. So you need to do your basic math and figure the circumfrence of each of your various pulleys and the buffs. In case you have forgotten what Mrs. RulerAcrossTheKnuckels , your math teacher, tried to get you to understand in 5th grade, C=Pi*D where D is the diameter and pi is 3.14159...etc... and * means multiply. If your pulleys are opposite pairs of triple sheaves then you can just figure the ratio for each position, the middle one of course being 1:1. Then you don't have to figure the sfm for the pulleys, just the buffs. But wait! your motor is running 1700 so 1:1 is going to be way high. Figure it backward from the buffs and calculate what RPM you need on that shaft to get into the 1000 RPM range, then get your pulleys for the proper step down.

FWIW,
Alan D.

Eric and Alan,

Thanks for the comments back. I just ordered a longer belt from Grainger, so I will start there and work my way around to the solution.

Cheers,

Dave

_________________
Dave

Remember, to always plant trees under which you may never sit.