Unisaw (3HP) belt replacement

[andrew whicker]

Hi,

After doing some searching.. it looks like I can go with one AX style belt to replace all three L type belts on my unisaw.

I saw someone used a single 3VX or 5VX belt, but those fit differently in the pulley (https://blog.micrometl.com/hvac-the-basics-of-v-belts/). His real life experience says this works too, regardless what the article says. Anyway, I think I'll go with a single AX considering the HVAC site cited above states that the VX belts aren't needed until you get into the 10 HP range.

Wondering if anyone has done something similar.

cheers,

[Jerry Bruette]

I would replace belts with those that the manufacturer specifies. The company that built the machine no doubt has an engineering department that designed the machine and figured out what size and quality components are needed to make the machine operate properly without "over building" it or "under building" it.

The article you referred to has a few mistakes and misunderstandings in it.
1. Belts with a X designation aren't cogged, they're notched. The purpose of the notches is to give the proper contact in the sheave groove. If you take a belt that's not notched and bend it in a tight radius the sides bulge. This bulge will interfere with the belt contact in the groove. The notches eliminate the bulging. A side benefit of the notches is that the belt doesn't take on a "memory" as easily.

2. A belt should never touch the bottom of the groove. If the belt touches the bottom of the groove it can't have the proper contact with the sides of the groove. If your belt touches the bottom of the groove the belt and sheave aren't the same size or you have wear on the belt or the groove.

3. Belts that have a V designation should never be run in sheaves that have the A,B,C, or D designation. The angle of the grooves are different. The V belts have a steeper angle and were developed to transfer higher torque loads. The difference in angles would mean that only a portion of the belt is in contact with the side of the groove, which could in turn cause premature wear of the belt or sheave or possibly both.

4. I've never seen and don't believe that there is such a thing as AV BV CV belts. All the belts with V designation have a number in front of the V. 3V 5V etc.

5. I've never seen belts sized using the inside circumference. They use the pitch diameter. I won't go into explaining what the pitch diameter is.

If you'd like to learn anything that's worth learning about belts I'd recommend going to a belt manufacturers website and reading what they have to say about belts. You could bore yourself to sleep with some of what they have to say but with a little attention you could learn how to separate truth from fiction.

[andrew whicker]

I don't see what the argument is against a notched V belt of the same profile? I.e. an AX24 or AX23 vs the old style of V belt? The notched is better so I shouldn't do it?

"A notched belt has grooves or notches that run perpendicular to the belt’s length, whichreduces the bending resistance of the belt. Notched belts can use the same pulleys ascross-section standard V-belts. They run cooler, last longer, and are about 2% moreefficient than standard V-belts." - US Dept of Energy

I'm wondering if the three belts can be replaced by one, to help the machine run smoother. When I was looking this morning, I found there are some calculations, but I had other things to attend to. I'll keep searching for those.

I know what pitch diameter is on threads and gear teeth. I'll google around if it is required for calculations, but I see all these belts defined by outside circumference as far as purchasing. The original belts are 26" outside circumference, from what I can tell.

[andrew whicker]

I ran the calculations (using the Machinist Handbook) with the following variables:

Pulleys: 3.575" and 3.0"
Center distance: 8.0"
Belt: classic (no grooves) and AX (with grooves)
Belt length: 26"

My results (after speed ratio, belt length and wrap angle corrections):

HP, classic: 2.7 HP
HP, AX belt: 3.2 HP

[Eric Arnsdorff]

I'll start with my disclaimers: It's been a long time since I've specified a belt professionally. I also haven't studied the application for table saws and other woodworking equipment.

I do know in design you first look at things as you indicated for belt horsepower. Then you have to also look at the starting loads. I know my 5 hp unisaw starts fast and the rotational inertia effects make it tough for my belts to not squeak/slip some. I haven't done this but have thought that it would be worth getting the grooved belt to reduce this effect (note that this puts extra starting torque on the motor with likely increased inrush current).
The next aspect is designing for mitigations to potential hazards (equipment damage as well as personnel harm hazards). I have no idea what mitigations they have in the power transmission design but it is certainly plausible that they would design it such that slip would occur to help provide a mitigation. This may be a reason why the belt would not have the highest friction or power transmission possible.

And of course cost comes into the design mix.

Throwing all that in, it is very difficult to say why the manufacturer chose the exact belt spec. on your saw.

In the end - I've replaced standard v-belts with notched and they always seem to work better for the reasons that have been identified. I put one on my DJ20 jointer and it starts up so much better than the standard smooth v-belt it had on it when I got it.

One day I'll change my 5 hp unisaw belts out to notched belts. Both of them. I try to tighten them without over-tightening but still will get some startup slip/squeal on occasion with full kerf blades. Thin kerf blades never squeal the belts.

There's probably nothing wrong with using 1 notched belt but if you have any issue with startup slip/squeal then you may want to put both belts on.

In the end - go with what works for a belt. You may find out why they have 2 instaed of one. Or your one may work just fine.

[Jerry Bruette]

I don't see what the argument is against a notched V belt of the same profile? I.e. an AX24 or AX23 vs the old style of V belt? The notched is better so I shouldn't do it?

"A notched belt has grooves or notches that run perpendicular to the belt’s length, whichreduces the bending resistance of the belt. Notched belts can use the same pulleys ascross-section standard V-belts. They run cooler, last longer, and are about 2% moreefficient than standard V-belts." - US Dept of Energy

I'm wondering if the three belts can be replaced by one, to help the machine run smoother. When I was looking this morning, I found there are some calculations, but I had other things to attend to. I'll keep searching for those.

I know what pitch diameter is on threads and gear teeth. I'll google around if it is required for calculations, but I see all these belts defined by outside circumference as far as purchasing. The original belts are 26" outside circumference, from what I can tell.

There is no argument against a notched belt. As long as you keep the same profile, A24 vs AX24 but you don't want to swap a 3V or 3VX for a A sized belt.

I didn't know that you had knowledge of pitch diameters. Not everyone understands what P.D. is. Fractional horsepower belts are measured on their O.D. and other belts are measured on their P.D.

Here's a link to a Gates manual about belts. https://www.bearingsandindustrialsup...tes-belts.html When you look at the profile of the different types of belts you can see how the dimensions are different and can understand how the different belts aren't interchangeable from industrial belts to V profile belts.

Are you having some vibration issues with your saw? How old are your belts?

[fritz eng]

Recently replaced three belts on my Delta 3 HP 10" with Gates AX24 purchased from Biedlers....................see link below. They were very helpful on the phone.

https://www.biedlers-belts.com/

[andrew whicker]

Thanks much everyone.

I looked at my belts the other day and was embarrassed at how badly they are out of shape. I thought I checked them not too long ago. Guess not. I figure vibration is something creeps up so slowly you don't notice it until you fix it or it's something that you just think is normal until you make it better.

My theory is fewer belts would equal less vibration.

Also, for what it's worth: in my Machinist Handbook the minimum pulley size for a non-notched V belt is ~3" and the smaller pulley on my machine is 3". I'm guessing Delta decided to save money on the belts they shipped w/ the machine. I doubt engineering got much of a say.

[Richard Coers]

Do you have a vibration issue right now? Modern V belts are far superior to ones made just 10 years ago. We used to have to buy matched sets, now the recommendation is that manufacturing tolerance are good enough to forgo that. I was an engineer before retirement, I figure people trusted my work, I trust the engineers that designed that system in 1939. Hard to improve on 82 years of experience.