View Full Version : Gates Polyflex belt stretching/alternative?

01-01-2009, 11:30 AM
I've been using my little 1980's era 8x16 Taiwan made Emco clone steadily since I got it (used) in 2004. I've been using the same 5mm spindle drive belt it came with for the entire time.

It finally started to fray recently and I decided to get a couple spares. I finally found them at KSC direct. They are Gates Polyflex 5M690 and fit perfectly. I installed one a couple weeks ago thinking I'm good to go for another 4 years. HAH!

The belt is installed on the step pulleys in either the (what I refer to as) "direct" drive or indirect position. Direct meaning it's fitted directly between the drive motor pulley and spindle pulley for high speeds with no tensioner. Indirect meaning it goes through a cogged belt driven reduction jackshaft pulley for lower speeds & higher torque. The indirect option has a lever operated spring loaded tensioner pulley.

In the years I've owned it, I've never taken the belt off or flipped the tensioner handle to the slack position between sessions and have had zero problems with belt stretching. The new belt fit the direct position snugly when I 1st installed it 2 weeks ago but this morning when I switched from indirect to direct the stupid belt fit like socks on a rooster!! It's so loose the motor spins up with no drive of the spindle at all!

Is Gates the only supplier of this type of belt? If so, I wonder if there are different quality levels or a heavy duty option. At $26 (shipped) for 2 belts, I'll go broke trying to keep this feller running!:( Anyone have any experience in this area?

ps: Happy New Year everyone!:) I hope 2009 will be a heck of a lot better than 2008!

01-01-2009, 11:40 AM
I love the Gates Polyflex belts. They're reinforced polyurethane belts that are designed to have high modulus of elasticity. So you need to tension them a lot less than an old-school cotton belt. If you look up your belt on the Gates web page (which is excellent), they'll have a recommendation for the correct belt tension. Just use a fish scale to get it in the ballpark.

In answer to your question, Browning and Goodyear also sell high-modulus polyurethane belts in the same sizes, but you're probably going to have the same issue.

01-01-2009, 12:18 PM
Thanks Robert. I'll keep looking. The belt it came with was either undersized and "broke-in" to it's final size or was of different construction that stretched very, very little over it's lifespan.

Sigh, it's ALWAYS freakin' something!