HP rating for pulleys

[stuckmotor]

I'll need two pulleys for a project that I plan to drive with a 13 hp engine. The specs for pulleys of the right diameter that I've found at Surplus Center say they are for fractional hp applications. I can't even find hp specifications on pullies from most other companies. What I can sometimes find, is an industry number. I suspect there's something in that number that specifies hp rating. Can anyone tell me if my guess is right or how to determine what horse power a pulley will carry.
Thanks,
Stuck

 

[CalG]

Simply, ...It's not that simple.

Horse Power is a function of speed as well as torque. That means that a power transmission system that is designed around high speeds in it's shafts, gears, belts, or chains can make use of smaller components and still transmitt equal HP as it's bulky, slower moving counterpart.

Use the pulley hole size as an indication of it's possible capacity. Construction can be a tip off as well. Spot welded, stamped steel "halves" won't last long in hard service.

But, 13 hp isn't much. That's whats on the walk behind lawn mower I've got. That unit is fitted with cast iron pulleys with engine shaft diameter bores for power transmission, and stamped steel for idlers and guide pullys.

Big reason for pully failure? Over tensioning the belt because of undersizing the requirement. An "A" belt won't carry much hp. B belts carry more, and doubles or triples do weally well.
(triple "B" belts transmit the 23 hp to the pto on the Bolens HT)

'hope it helps

 

[Baby Grand]

Here's a reference with lots of interesting reading:

http://www.bandousa.com/html/pdfs/bu-143manual.pdf

 

[SPYDERLK]

I'll need two pulleys for a project that I plan to drive with a 13 hp engine. The specs for pulleys of the right diameter that I've found at Surplus Center say they are for fractional hp applications. I can't even find hp specifications on pullies from most other companies. What I can sometimes find, is an industry number. I suspect there's something in that number that specifies hp rating. Can anyone tell me if my guess is right or how to determine what horse power a pulley will carry.
Thanks,
Stuck

Well, Whats your guess? ... I can tell you from experience that a 4.5" cast iron "A" pulley at 3600RPM will transmit 13HP durably to another pulley at least as large. Go up an inch on both ends for a good safety factor if you have room. Avoid multi belts. Youll do better replacing one belt twice as often.
larry

 

[BHD]

belts are usually what is rated, but diameter of the pulley is also important. for example one could use a 2 inch diameter pulley and would not transmit very much HP, but if one used say 5 inch diameter pulleys the power that would be able to be transmitted, would be more than double and possibly up to 4 times more,

on v belts the V sides are the griping part, the belt should not be touching the bottom of the pulley, and with tension the belt grips the sides, on a small pulley first there is not much surface area, and the tight bend is not working in your favor, or the belts, on the larger pulley much more surface area, and longer V section to grip into,

both set up would be turning the shafts the same speed,

here is some info from gates, the design info is about page 20 -34 or so, http://industrialbeltdrives.com/wp-content/uploads/2012/05/20070_V-BELT_DDMANUAL_ENGISH.pdf

when you get done reading and understanding it, you will know more about V belts than you thought was out there,

 

[stuckmotor]

Thanks to everyone for your wisdom. I especially like CalG's opening statement, "Simply, ...It's not that simple" and, I'm afraid he's right.
It'll take me a while to digest the information you've all given me, then, maybe I'll know what to look for.
Stuck

 

[Baby Grand]

You could always use the size of the pulleys on a professional grade 4 or 5 foot finish mower deck as a start ... they should handle 13 HP, all day, without breaking a sweat.

 

[LD1]

Perhaps tell us what this project is and we may be able to offer some more insight? Are you trying to change speeds? or just simply transfer power?

And yes, it isnt simple. While size is certainly important, thats the easy part. Without trying to decode every manufactures number, construction type is the hardest to figure out. Take a simple 4" A-section pulley. There are many styles and likely ranging from a few bucks to $50+ Some are the stamped halves. Some have welded in hubs, some are a "pot metal", and some are quite stout or even a solid piece.

 

[Brad_Blazer]

This reference from Grainger looks easy enough to follow. http://static.grainger.com/tps/powe...nce.pdf?cm_sp=TPS-_-VBeltReferenceGuide-_-Top

McMaster-Carr USA Bearings and Belts www.vbeltsforless.com are vendors I have had good luck with.

 

[BHD]

also most gasoline small engines are over rated in the Hp they produce, (if you noticed many no longer rate the power in horse power),

(it is my understanding the way the old system worked was to use a brake and to get the max HP, that meant to kill the engine, by over load),

in the past, one could usually safely replace a gasoline engine with an electric motor in the 1/2 to 2/3 range and usually no have any problems,

or if one was replacing an eclectic motor it was normally suggest you double the gas engines HP,

so I really doubt if you engine can continue to run and produce the 13 HP, most likely it really only has the ability to produce about 6 to 8 true horse power,

(one quick example is a generator, say a 13 HP engine is used to run a generator, most are only about 5500 watt normal out put generators (alternators actually), a horse power is said to be, 745 watts, take that 5500 and divide by is 7.3 (horse power), yes I know there is some losses, but 5.7 HP in losses, I doubt it,

https://www.google.com/search?num=1...-1.1.0....0...1c.1.42.serp..1.0.0.rYnzlbsZI1s