Buying Pulleys & Belts

[herbhighstone]

Hello to all the folks --

What do pulleys and belts have to do with ATM activities? Okay, when it's time for you to make your first mirror grinding machine, you'll probably want to run your turntable and stroke arm with pulleys and belts. This is a very nice way to transmit your rotation and select various RPM's, and for that reason, mirror grinding machines have been made in this way for a very long time.

However, I was surprised last week when I went into our largest local hardware store to look for a new belt. Only a few years ago, this store had an entire aisle full of various belts and pulleys. But now they're all gone, and when I inquired, I was told that these items don't sell in large quantity anymore, so they aren't stocked locally.

Expletive deleted and play swearing galore! How dare they do this to us? And where can we go to get our belts, pulleys, sheaves, and idlers? I'd suggest two places. The first is a large organization such as Grainger that sells all kinds of equipment and accessories. Just go to Grainger.com, select motors & power transmissions, and look up " belts " or " pulleys and sheaves " . Or get hold of the giant Grainger catalog if anyone you know owns one. Graingers will certainly stock the belts and pulleys that you want. And no doubt, Google will also find you other sources for " motors and power transmission " components.

But there may be cost problems when you try to buy these items at full bore retail. Suppose that you're looking for an idler pulley so you can adjust the tension on your turntable belt, but the idler pulleys from Grainger cost upwards of $65. So costly! What to do now? Run to Ebay, hit "Business and Industrial" and search for "idler." And what did I find this morning when I did that? I found a very nice flanged idler pulley, 1/2" bore, 1 3/4" diameter, with needle bearings, for ----- the vast sum of TWO DOLLARS plus shipping. Wow! I can actually afford that!

Why so cheap? The same reason that my local hardware store isn't stocking these items any longer. Obsolescence is a two-edged sword in this situation. First, pulleys and belts are no longer stocked at your local stores, BUT this same obsolescence also makes these items extremely cheap on Ebay, because very few people want them in today's digital world.

Happy belt & pulley shopping, everybody ---

Best wishes from Herbert Highstone

[doginstine]

You could check with an auto store for belts, the V type that is. Trouble is, more and more cars are going to the large single type of belt. So in a few years the V groves will be harder and harder to find.
Another place to check is a lawn mower repair shop, they should have V tpe belts for riding lawn mowers decks.

[herbhighstone]

Hello to all the folks ---

Ebay is not such a bad place for finding belts and especially the larger pulleys that cost a great deal if/when you can find them new. Why a large pulley? A friend tells me that you'll want your turntable's driving pulley to be no smaller than the diameter of the mirror that you're grinding or polishing. How come? Because a big pulley will reduce the bad effects of the inevitable slight looseness of the belt drive.

Let's say that you're polishing a 24 inch mirror and you're using a 6 inch pulley on your turntable shaft (yes, this is an exaggerated example). Even a small "give" in the belt will allow the turntable to flip back and forth as the strokes are completed and the forces on the mirror abruptly change. In the old days, the polishing defects that these rapid, jerky movements caused were known as "scrubs."

On Ebay I've seen pulleys or "sheaves" as large as 24 inches available for rather small prices. The big ones are heavy, so shipping may cost more than the price of the item! Pulleys and belts will largely be found under Motors and Transmissions, but sometimes people list stuff in the strangest categories. So be creative in your searches to get the best bargains.

Gearmotors are another thing that you'll want for your grinding/polishing machine. What's a gearmotor? It's an electric motor with a worm gear speed reduction "built in" via an attached housing. The result is a large step down in speed from the 1700 or 3400 RPM of a standard motor to 150 or even 50 RPM. This will save you an extra belt and pulley at the very least so you can have a more compact setup.

Best wishes from Herbert Highstone

[JACK]

Herbert,
I'm new as of today on this site. I'm looking for a clock drive gear motor for my custom built 12 1/2" Newtonian. The clock drive that offered by Clestron, Orion, etc. are for exsiting scopes. I'm looking for a gear motor
with a .250RPM output on the shaft with .250 diameter. I'm new at motors, if I buy an AC gear motor all I have to do just plug it in, but a DC gear motor, can I do the same. What do I have to buy to use a stepper motor? A friend built a 12 1/2" scope and bought a Gear motor from Hurst Mfg. model # (CA) synchronous 250 in.oz torque. I called them and they don't mfg it anymore. I would appreciate any info you can give me in my search.