Tractor PTO pressure washer

[Karl_T]

I need to power a large pressure washer with my tractor 540 PTO...

Its a CAT 1050 pump. Takes 15Hp at 1000 RPM.

https://www.catpumps.com/sites/default/files/2020-09/1050_L.pdf

So I need to step up the RPM and I'd like to run the tractor at a bit less than wide open.

Picked out these two pulleys at surplus center. One is 18.75" and the other is 8.75 ". My main question, will this easily transmit 15HP? Can I get away with a slightly smaller samll pulley to step up the RPM a bit more?

Put another way, how does one calculate the HP rating of a pulley system?

 

[Reddinr]

If you double the RPM with a pully system you half the available torque (roughly). HP should be roughly the same except for any frictional losses of the pulleys/belts. Power = Torque x RPM.

 

[Karl_T]

sure. My question is how much can you push through a double belt 8.75" pulley before it just slips and wears out right away? The smaller the pulley, the lower the rating here. These pulleys use the 5/8 type "B" belt. There are far more expensive larger belts and matching pulleys if this design is not robust enough.

I found some HORRIBLY complex calculations for this, above my pay grade. There must be some rules of thumb here.

 

[Karl_T]

OK, I am NOT sure this is even the right chart. This is a design manual:

https://www.bandousa.com/media/uploads/0/1352_bu-143-V-belt-design-manual_updated-2018.pdf

page 24 has a B design page. IF I am looking right, the red and orange circles are the Hp ratings for"B" size belt by pulley size. Am I even on the right page here??

 

[Karl_T]

There is another chart on page 34 that "I THINK" is for the slightly better Bx belt. If i read it right, one can go down to about a 6.5" pulley. Anyone care to see if this is right??

 

[Eddyde]

It appears the 8.75" pulley will work, I wouldn't cut it so close with the 6.5".