Vibration Free Link Belts

Copyright 2004 by Jim Wilson
(Click images to enlarge)

PowerTwist (red) and Accu-Link (green)

What are they?

Vibration can be more than a mere annoyance for many tools. It can reduce accuracy, roughen cut surfaces, and increase noise levels. "Vibration free" link belts are formed from interlocking segments that twist together. Their link structure can dampen vibration from other sources, such as unbalanced pulleys. They are more durable than standard v-belts and they are easier to install and remove.

When to use them

I have the twist-lock link belts on much of my machinery, including my cabinet saw, which takes three matched belts. Everything works just fine; my cabinet saw easily passes the "nickel test."

Nonetheless, I have found by experimentation that the link belts are no better than cogged v-belts in some applications, and no better than top quality ordinary v-belts in others. Cogged belts share many of the advantages of link belts: excellent vibration dampening characteristics, reduced slippage, higher energy efficiency, longer life, and resistance to taking a set.

Additionally, there is no waste, as occurs with a link belt when there is a leftover, unused portion, and which drives the already high cost of link belts up even more. On the down side, cogged belts are not adjustable and when they break (exceedingly rare) the entire belt is lost, as opposed to one or a few links. Personally, I'm willing to give up these latter two advantages in exchange for the cost savings when the link belts don't perform noticeably better on a given machine.

The unchallenged advantages of the link belts are (1) the ease of replacement, especially in cases where machinery must ordinarily be disassembled for it, and (2) the ease of maintaining spare inventory.

While both the link belts and the cogged v-belts dampen vibration, the link belts are a little better with lower frequency vibrations such as are caused by pulley or load imbalances. However, both types of belt also introduce some higher frequency noise owing to their "teeth." In this respect the link belts are noticeably worse (louder in the higher frequencies), and they also squeak a bit from the links rubbing against one another and the pulleys or sheaves.

Because of this, a machine may sound quieter or louder with the link belt than with a cogged or regular v-belt. On all my machines that run them, save one, the link belts are as quiet or quieter than regular or cogged v-belts. The oddball is an old Delta 14" bandsaw whose sheet metal stand apparently oscillates in harmony with the higher pitch of the link belt links. That saw runs about 3 dBA quieter with a cogged v-belt and 2 dBA quieter with a regular v-belt. On a very smooth running machine, like a top-quality metalworking lathe or mill, a premium classic v-belt runs the quietest and with the least vibration.

Ultimately, it's a price/performance decision. Here is some quite dated (2004)pricing information I collected from MSC (www.mscdirect.com), one of my favorite industrial suppliers. Prices for 36", 48", and 60" classic v-belts are $6.80, $8.16, and $9.35, respectively. Cogged belts in the same sizes run $8.43, $10.14, and $11.47. Assuming no waste, the same link belts would cost about $12, $16, and $20 each at Harbor Freight pricing. Something to think about.

Where to get them

There are at least two brands currently on the market:
    PowerTwist belts, manufactured by Fenner Drives, are red.
    Accu-Link belts, from Jason Industrial, are green.

  Links - side view

When this article was written (in 2004) Harbor Freight had the best price ($20 for 5 feet) that I had seen. [By 2012, HF's price had reached to $25 per 5-ft length.]

I believe Fenner Drives invented this style of link belt. I have been using the PowerTwist brand for years, and am very happy with them. I currently have them installed on my vertical mill, metal lathe, wood lathe, and metal bandsaw.

The best price I have seen on the PowerTwist brand is $24 for 5 feet at McMaster-Carr. Double check with them before you order, though, to be sure they are still shipping the PowerTwist brand. They often do not publish brand names, and have been known to substitute.

In October 2001, I needed belts for some new additions to my wood shop. I ordered from Harbor Freight and received the Accu-Links. I had previously gotten the PowerTwist brand from them. The Accu-Links are installed on a Rockwell 10" Unisaw, 14" bandsaw, and shaper, an 8" jointer, and a 20" drill press.

Which brand is better?

Links - outside view

So far, there is no noticeable difference in performance between the two brands, although the PowerTwist appear to be slightly better quality all around, perhaps by as much as the price difference.

Both brands are made of a urethane elastomer reinforced with woven polyester fabric. The Accu-Link urethane does not appear as though it will be as durable.

Accu-Link flaking

Twisting the links apart and together causes little bits to flake off. They flakes have a waxy consistency. The amount of flaking is small, and may well be negligible over the life of the belt. I mention it only because I have never noticed it with the PowerTwist brand. Flakes are shed during use also, as can be seen in this photo of my drill press. The flakes are dusty and usually dispersed by the turbulent air around the moving belt, but they do stick to nearby oily areas.

Links - side view

Overall, the PowerTwist links are neater. They are cut more cleanly. The surface of the belt material is smoother. The weave looks tighter.

Links - inside view

The PowerTwist also has a smaller size increment, owing to a slightly smaller link size. Each PowerTwist link adds 3/4" to the belt length. The Accu-Links are 7/8". Both of these measurements are for new belts. They do tend to stretch some during the first few hours of use, so the true long-term increment will be a bit higher.

The 1/2" Accu-Links are a little wider than the 1/2" PowerTwist. I thought they seemed a tad too wide for the Unisaw pulleys, and I was concerned about them rubbing on each other. So far, though, the fear has proved unfounded. The saw runs fine, and there's no evidence of excessive wear, etc. By the way, some users have reported that using link belts on their cabinet saws helps to reduce startup "thump," which is apparently caused by high motor torque. My own Unisaw has never thumped, but then again, I've never used classic v-belts on it.

The differences may be inconsequential with respect to function, performance, and durability. There's no way to tell in the short term. Since they were installed, though, the green belts have turned my machinery as well as the red ones.

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