Pulleys and Sheaves

I didn't know what a 'bushed' pulley was till I started having trouble with my DIY projects.

This is a living document and will grow as we learn more about the pros and cons of pulley types.

They come in all sizes and grades, we've covered the pros and cons of pulleys versus direct Drive elsewhere, so this will be about pulleys only.

Vee belts have been around for a long time, because they are typical, many DIYers are comfortable using them. Following are common mistakes DIYers make, sometimes they have to scrap the first set of pulleys and belts and start over. This can generate a considerable expense for your DIY project.

If you are going to build a generator using VEE pulleys, invest in larger diameter pulleys, a 3" set of pulleys offers the same ratio as a set of 6" pulleys, but the larger set will transfer far more torque, and usually last longer under load. Use the larger pulleys or live with the results of your decision to save a few dollars, it'll often cost you more in the long run, the smell of smoke under heavy load, black deposits in and around your gen set will be signs you under engineered your drive, the cooler your pulleys and belts feel right after pulling a big load, the better.  

I once destroyed a 220 volt AC deep well submersible pump when a belt slipped during the attempt to start it. It took me a while to figure out what had happened, but there in the manufacturer's notes was a warning that erratic power could destroy the coupling between the electric motor and pump! This was an expensive lesson, and I had plenty of time to burn it into my memory as I was pulling the pump; and coming to grips with the replacement costs. This experience is shared on the utterpower CD, and it is a constant reminder that I have learned too many things the hard way :-)     

Above: Here's an example of a 'real' pulley, the center accepts a bushing; the bushing is an off the shelf piece that is purchased to match the shaft of the equipment you will install the pulley on. This example is 20 inches wide and was designed to take a double Vee common back belt.

Above is a typical split tapered bushing. This 'bushing' is bolted to the pulley, once the pulley and bushing is positioned, the bolts are turned in and the bushing follows the taper into the pulley to 'lock' it on the shaft. In my opinion, this is a proper pulley for a generator you wish to rely on, if it's not a bushed pulley, you won't find it on the stuff I build, I've had my share of  loose pulleys, lost Allen screws, smoking belts, shaking and rattling noises in the middle of the night followed by darkness. The drive system is NOT a place to take short cuts, and the majority of the problems I've had with home built pulley driven gen sets are found in the drive system. 

Note the threaded holes, these are jacking holes, when you wish to remove the pulley, simply move the bolts out of the fastening holes into the jacking  holes to extract the pulley. Your Grandmother can remove a bushed pulley in 60 below weather, and you will appreciate this feature when it's time for maintenance, or when you wish to move the pulley to another shaft, you keep the pulley, and buy the proper sized bushing. These are commercial grade, and they can be purchased from any good supplier. If it's not a bushed pulley, it's likely to cause you trouble, I've seen a number of gen shafts tore up when one of those cheap hardware store sheaves came loose, if this happens to you, it will be at the worst possible time, and if you are married; your wife is likely to make a comment about how much money you spent, and for what? Then she'll light a candle, and go off to read the brochure on the new kitchen appliances she could have bought with the money...  

9/19/05

I was reading an article written by Richard Perez (Build your own 12 VDC engine Generator, Home Power #42 Aug/Sept 1994). You can find these articles on line at home power, and I encourage you to read this one! There is personal experience shared in this article that validates my findings, and it provides sage advice as to how you can build something that won't rattle apart. There's a few notes about gas engine experience, and this alone is valuable; this is the kind of information I crave; for it comes first hand from an experienced DIYer, not from some Joker Salesmen trying to convince you his stuff is best. One of the mentions is his experience with aluminum pulleys, and finding them totally unsuitable for even small home built  battery charging units. If you attempt to build with cheap pulleys, you will be buying pulleys twice.

Richard, thank you; this article is loaded with valuable information!

8/5/2010 added note:

It's been six years since I added to this page. I've since worked with several companies who noted that the biggest problem they had with their commercial product was the VEE belt drive system. Several have bought pulleys here and field tested their units, one a commercial gasoline driven pressure washer. some will ask, why not direct drive instead? My answer to the question after studying this for years? An efficient drive system allows you to tune the system, in the case of a generator, there can be a shocking difference in fuel/kwh conversion depending on how well the engine is loaded. you can increase the loading by doing the work with a few less power strokes per minute.

Here's an example: http://www.youtube.com/watch?v=ZYwlyng01cY

Before I get too far down the road with this conversation, this Site is all about >OUR< needs, we are one percent of the population, and we know that the Hardware Store Generators will serve the needs of the other 99%. For us? We want a generator we can afford to run longer periods to cover storm outages, others in our group use these power plants off grid where failures ARE far more inconvenient. Yes, we prefer diesel as a fuel, we know it stores longer, it's a far more efficient engine and usually has a longer life in service with proper care. We know our gasoline is now pretty much crap if we buy it in winter months. We expect 5% less work from it when there's 10% ethanol in it, and we know the shelf life is far less. Rotate your gasoline fuel stocks often. If our power plants do stop running, we want a fair chance to diagnose the problem and fix it in the field. Yesterday I received an email from a contractor, he was looking at a Honda OHV 11 hp engine on ebay and asked how it would work with the PMG  ? I told him that most of the gen sets I hear about with this engine fail because of the generator head or electrical problems, and that reducing engine speed from 3600 to 3000 and driving a head like the PMG via serpentine drive would likely increase longevity of the engine, ...maybe double it. Some real off gridders have seen an amazing 10,000 hours of service out of Honda OHV engines, this is amazing. The OHC models are often build for the throw away market, I have torn a few apart to find plastic cams, really good plastic mind you, but there are now engines that were never designed to be repaired, you simply toss them if there's a problem and Honda realized they must serve the throw away society in order to stay in business. what I think is interesting is this type of equipment is exactly what the average mechanically challenged Sierra Club Member would buy. Designed to throw away.... the EPA and the Political appointees who run CARB guarantees a short service life by forcing the manufacturer to fit a carburetor with no adjustment and no way to compensate for coated jets and other problems caused by crap for fuel. No, there's no sure way to clean them either, so do use a high detergent gasoline, or add one to your lawn mower fuel and small engine fuel. Now where were we? OH yes, I just checked ebay, there's two 11HP Honda powered direct drive generators up for sale right now, both direct drive, one with a broken crank shaft, one with an unknown electrical problem.

The serpentine drive makes trouble shooting easy, got a noise you can't find? remove the Belt to trouble shoot. Some people make the big mistake of connecting generator power with grid power. When you do it 180 degress out of phase, it's much the same as a train wreck, the serpentine will often save you, a direct drive unit might be in pieces depending on coupling type.     

All the best,

George B.

Want something  far superior to VEE belts? see the Utterpower Drive for the Big Flywheel engines.