Question about pulleys & v-belts

[JHCC]

I've recently acquired a large chop saw (discussed HERE) to which I will be mounting a motor I've got kicking around. The problem is that the existing pulley wheel on the arbor takes two 3VX-series belts (of which three came with the machine), but the only wheel I can find to go on the new motor is going to be pretty expensive.

I can get a more reasonably priced double pulley that will fit the motor's 7/8" arbor, but it's designed for A-series belts. I've been looking at some online resources about belt standards, but I haven't been able to get a good answer to my basic question: would a 3VX-series belt run okay in an A-series pulley?

[Randy Griffin]

In a light duty application it should run for a while as long as you can get enough tension on the belt. The angled sides of the belt is actually what grips the pulley and A and 3VX have different angles and widths. You really need to change both pulleys to A-series. What diameter are you looking for?

[JHCC]

The existing arbor pulley has a 3" outside diameter. I suppose that if I replace both pulleys, the diameter doesn't really matter, so long as they're both the same.

[Randy Griffin]

How was the original pulley on the old motor configured? Was it two pieces?

[JHCC]

The old motor was missing when I bought it (probably the main reason that it was so incredibly cheap).

Here’s a shot of the arbor, showing its pulley:

[Randy Griffin]

A single 3vx belt running on 3" pulleys is good for 2.75 HP. Look for a 1/3v3.00 pulley and a JAx7/8" bushing. If you have a power transmission  store in your area they should have what you need for less than $50. Motion Industries or Applied Industrial Technologies is two but there are others.

[JHCC]

Thanks; I will. I might also check with the local agricultural equipment place.

[Judson Yaggy]

Swaping out both pulleys for A belts could be cheaper than mixing and matching vx pulleys and bushings.  No need to keep original diameters as long as drive and driven diameters yeild your desired RPM (as long as they fit in the frame and guards and the motor can handle it).  Some pulley bores and diameters are cheaper than others.  YMMV, good luck John.  

[Randy Griffin]

Another thing, have you done any research on how many rpm's you should have at the cutoff wheel? You can speed it up with a larger pulley on the motor. Of coarse you will loose some torque.

[JHCC]

Yes, that’s discussed on the page linked above. 

[Randy Griffin]

Sorry, I looked but didn't read.

There are some very knowledgeable people here. I think you will be fine at 1750rpm. If you have plenty of torque and want to speed it up, you can do that later.

I looked at prices yesterday and the pulley I suggested above is the least expensive way to go.

[JHCC]

Okay, things are starting to get weird. I went to measure the existing belts to get an idea of what length I'll need, and realized that only one of the three belts that was hanging off the saw when I got it is a 3VX -- and that one doesn't fit the pulley as well as the other two! Those are slightly narrower, being 7/16" in both width and depth -- and that doesn't appear to match any standard size I can find, either English or metric.

[Randy Griffin]

Have you looked at the existing pulley good? Most pulleys have the part number on them somewhere. It may be hard to see. Clean it good with a wire brush and use a good flashlight.

[Charles R. Stevens]

Belt angle, with and size are all important tho most often belts share angles. A too wide belt is better than too narrow. To narrow and the belt can end up touching bottom and no mater what you do it will slip (autozone alternator belts are notorious for this) being rubber a bit of difference in angle will be  ok if the pulley is steeper than the belt. Belts can ride just a bit proud of the pulleys (best fit) as it is the wedge effect providing friction on the sides of the V that is important. Belts are relatively forgiving as long as they don’t bottom out. 

If you can get the existing pulley off and take it with you, getting the right one will be much easier.

 

[JHCC]

8 hours ago, Randy Griffin said:

Have you looked at the existing pulley good? Most pulleys have the part number on them somewhere. It may be hard to see. Clean it good with a wire brush and use a good flashlight.

Yes, it says 3V. Grumble, grumble.

[JHCC]

Long overdue update: having decided to use a 3hp/3450rpm motor that came off another machine, I further decided to go with putting a 3V double pulley (3" x 5/8" bore) on the motor and leaving the existing pulley on the spindle. That's a little less expensive than putting new single pulleys on both motor and spindle, and I get to keep the double belt arrangement (plus use the belts that came with the saw).

Thanks to all for your help.