V Belt or Roller Chain?

Belt

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Laurie, I would go to an ag equipment graveyard and look for a set of two- or three-V pulleys no smaller than 10" and 4". If you are careful with alignment and tension, your setup will last longer than the bearings and run quietly. No lubrication requirements, great freedom from dust/dirt problems, cheap parts available everywhere.

Your 5kw converts to 6.7 hp, so a single "V" belt should work. I think the rule is 10hp per "V" belt. As others have pointed out a belt needs no lube, where any chain drive will need it. Have you looked at the PTO gear drives available to mate generators to tractor PTOs?

Paul

Laurie Forbes wrote:

As others sayed: Belt! A roller chain is loud, costy and needs lubrification. If you look a v-belt manufacturers site, you will find some formula to calculate the necessary size (depending on kind of load, rpm, ratio and power). A roller chain is OK if you require defined phase between the two shafts. Somehow roller chains are getting out of style ...

Nick

Belts are more forgiving to misalignment of the two shafts and have the advantage that no lubrication is required. More importantly, if the load suddenly increases ( a jam in the generator or similar failure) the belts will (usually) slip before damaging the prime mover. On the other hand, belts often slip when you don't want them to so they need to be adjusted or an automatic tensioner installed.

Chains will deliver more horsepower per pound, but require relatively close alignment of the two shafts and periodic maintenance (lubrication). Sprockets for chain drives are marginally more difficult to come by than pulleys, but not impossible. Chain drives are usually more noisy than belts and are less tolerant of dirt and dust. Chains are usually used where positive motion is required (no slip) and tend to be more expensive.

Hope this helps.

Kelly Jones PE

A couple votes against roller chain:

1. They're loud.
2. They need lubrication.
3. For relatively high speed applications like what you're doing, I consider roller chain more dangerous than belting. Low speed apps (e.g. forklift masts) are fine, but I don't like chain when it's moving fast because the stuff magnetically attracts human flesh.
4. On a toothed cog, a chain cannot slip. You must have a clutch elsewhere in the system.
5. Roller chain is more expensive than belting.

Generator sets tend to be so loud that it won't matter, but if you want to quiet down a belt system further, there's something called a link belt that runs on most sizes of v-belt pulleys. It is noticably quieter than v-belts, which are quieter than chains. Here's a reference to one manufacturer, mostly just to show a picture:

Mulitple belts, preferably matched...DO NOT DO CHAIN!!!

Thank you everyone who replied to my query. It looks like belt(s) are the way to go (minimum 4" sheave on the gen end?). That being the case, for a 5 KW gen, would a single B belt be sufficient or would a double be requried (the only possible downside I see to belt(s) would be slippage or breakage)? It seems that a single B might do it as the tractor 3PH mower has single internal drive belt and has worked for years w/o slippage or breaking all the while absorbing the full engine output (15 HP) from time to time.

Thanks again for the help............

Laurie Forbes

To transmit 6kW at 3600 rpm a v-belt with the profile SPZ is good enough as long as the diameter of the small pulley is bigger than about 150mm.

At 180mm diameter and 2800 rpm, you can transmit 8.2 kW. As your rpm is higher, the power that can be transmitted is higher too.

SPZ-profile is: height 8mm, big width: 9.7mm, angle is 38°

Nick

Laurie, A single belt would carry the load just fine. I suggested a double just to add V-suspenders to the V-belt, keeping you running in case one breaks. They are very commonly used in machinery like combines, so you can save some money by scavenging the pulleys, otherwise rather pricey. Single pulleys are available in hardware stores and are inexpensive. Really cheap ones are to be avoided as they will likely be unbalanced or not actually round.

BTW - slippage capability is *good* for protecting more expensive parts if something jams, plus the copious smoke makes a marvelous multisensory warning signal!

Greetings Laurie, What a coincidence. I was just reading an engineering kinetics book. Especially the parts about chains and belts. From what I read it appears that toothed belt drive is the best. Next, for quietness is vee belts. But best for effiency would be chain. If I did it the toothed belt drive would be my choice followed by vee belts. ERS

Fred, I think I'll go without the suspenders as it doesn't matter a whole lot whether or not the pants fall down. I have looked a cast iron pulleys and they *are* rather pricey (and I don't suppose the Al variety would hold up long).

BTW, I've just finished perusing the Voltage Master gen user manual and it has an interesting caution which I don't quite understand. If the gen is to be powered by a 1 or 2 cylinder diesel, because of the high compression ration it is recommended that the diesel be run at or close to rated RPM otherwise there will be some unspecified effect on the gen. I can only thing this must be due to slight crankshaft speed variation as a piston goes through the compression stroke but I cannot think why this would be detrimental. I was planning to run about 1600 to 1800 RPM vs 2450 rated so I guess I will have to call them tomorrow to see what the tolerance is.

Laurie Forbes

Laurie I'm speculating here but it could very well be the speed variations. More specifically it could be the torque impulses due to compression and detonation. If so, you could smooth them by adding more flywheel mass to the generator and let the belt provide some compliance so the generator gets a nice cushy ride.

I do like to slow engines down a bit in general, although diesels seem to thrive on just sitting at full power forever.

Thanks Fred - I'll ask them about that.

Yes - I would be more concerned with gas engine wear & tear than a diesel. For all the time I will be using it as a gen, maybe it's not worth worrying about (unless we have an ice storm or hurricane up here where the power could be out for weeks :). Less noise (this Yanmar 2 cylinder is a real head banger) and fuel consumption would be nice however......

Laurie Forbes

another idea to do too is use the toothed belt and actually and run it off an old VW air cooled engine ,I have seen a few of these setups in different places over the years ,the nicest thing about is the fact that when maintained the engine will last for years and parts are always avaible and they use 4 pints of oil and they are designed to run at higher rpms ,actually I did see one guy who set his up with the transaxle that way he just needed to run his belt 1:1 and just shift into the necessary ratio ,pretty smart and this setup was pretty light ,he could pull it around his property with a simple lawn tractor sorry if it got off topic a lil bit but thought this might be interesting to know in case you need a second unit or something to transport easily with almost any vehicle ,an alternative engine would be the VW rabbit diesel ,they are all over the place and pretty affordable to pick up good luck

Just spoke to a rep at Volt Master re powering their gen by a two cylinder diesel. While he wasn't terribly helpful and in fact seemed annoyed at my questions, I did find out that the concern with running a one or two cylinder diesel at less than rated RPM is vibration transmission to the gen (he says they get then back on warranty and find they have been "shaken apart" in some instances). Now, apart from whatever that says about their construction quality, he said the engine and gen should be mounted solidly to the *same* platform to prevent belt slippage caused by vibration. You then must install the platform on vibration absorbing mounts to keep the thing from shaking. How then you power the thing from a tractor remains the question and all he had to say about that was to use their tractor rear PTO mount units.

I'm thinking then I could possibly mount the gen on the floor (not attached to the tractor frame), connected only by the drive belt with maybe an idler to maintain belt tension and smooth out any belt flopping around. I wonder however how much belt slippage would actually occur in any case if the proper tension is maintained and maybe belt dressing is used.

As to vibration, I once had an aircraft generator bolted to the front end of the same tractor (using it as a welding gen) using a direct shaft drive (with a Lovejoy coupling) and did not have or notice any particular vibration problems. I wonder if these Volt Masters are of crappy construction and won't stand up to much or if they simply are making their recommendations out of an abundance of caution.

Any further advice appreciated...........

Laurie Forbes

ok, you want something SIMPLE, yet works.

have a platform for the generator to sit on. Make that platform HEAVY. For my purposes, it does not need to be rubber mounted. Weld a plate off the platform that goes sideways, and is at ground level.

drive the tractor so one front tire is on the plate. Hook the V-belt up. Drive tractor forwards and backwards until it is lined up. Turn the steering wheel to cure the skew. Eventually, you can weld a stop on the generator to set the "depth" of the tractor by stopping the front tire of the tractor. Have a spring loaded tensioner on the slack side of the belt. Do not be afraid to make this tensioner really stout, with a really strong spring.

Now you have a rubber isolated (front tire) damperner, and it is easy to hook and unhook.

Make sure your PTO can take moderate side thrusts.