Standard Belt Tensioning

In my experience, no. The correct tension is what the manufacturer of your equipment says it is. A general rule of thumb would be that there should be no slippage or screeching sound when running, yet will depress slightly when idle up of belt is pressed down. Note that only half of the belt is actually doing work when the machine is running; the other half is just returning.

Depends on the belt and application. Most say that the belt tension should only be what is required to move the load without slippage - round belts, v-belts, flat belts. Anything more than that would be unnecessary strain on the belt. If it is a gates power max GT belt (cog belt), you only need to tighten to the point where its not slipping.

Hope this helps

Remember also that you are pulling the pulley off center too, you may need to make sure that the pulley is simultaneously pulled in the opposite direction to reduce side loads....

Big side loads + small bearings = bad problems.....

There are various ways to do this properly that a search on the web should help out.

Its the motor bearings that you need to be sure will take a side load, not the belts example: a rotating pump is horizontal/vertical so the bearings on motor an pump will have more of an axial load, the motors designed for belt drive systems are side loaded so the bearings will be designed for side load (usually they will have more surface contact to handle this side load)

To calculate tensioning : YOU HAVE TO KNOW THE DEFLECTION

after the sheaves have been aligned and the belts installed

measure the span of the sheaves....the distance in inches from the center of the drive shaft to the center of the driven shaft

the deflection height general rule is 1/64" of deflection per inch of span (for a system utilizing 16" of span the deflection would be 16/64" or 1/4"...... but at what TENSION (force) you have to know what the manufacturers recommendation is from their charts for your belts

When this is known you put a striaght edge of some kind resting on across the top edges of both pulleys and using a belt tensioner gage, you set the tension force needed and then you press down with your hand till the mark on your gage reads the 1/4" deflection against the straight edge, then you look at the plunger on gage to see how much the tension was and make necessary adjustments.

You have to know the deflection to be able to get your tension also this is applied for all belts regardless of type............You should also maintain a minimum percentage of belt wrap on pulleys of at least 35%.....................also if you have a system that calls for 2 belts and you decide to add another because of slippage or other reasoning, you will have to reduce the tension of the 3 belts (regardless of the recommendation from manufacturer--remember it's their recommendation and they are in business to sell belts)

example: 100 h.p system designed for 3 belts

@33 1/3 h.p per belt at 20lbs. tension

Your engineer wants to add another belt ????

100 h.p system now has 4 belts at 33 1/3 h.p per belt at the 20 lbs.

So what should the correct tension be for the 4 belts ?

20lbs. X 3belts = 60 / 4 belts = 15lbs. is what you would set the tension

or you will overload the system(over tension)and wear out bearings , pulleys, and posibly bend the shafts.

It has been my experience the rule of thumb is to tension the belt until slack just allows you to push in on the belt at it's center between the two pulleys a 1/4 inch.

Machinery' handbook,p1074 for v belts; 1073for use of idlers, 1067 for installation and take up allowance.

my copy is 20th edition

milo

Hey guys, engineering is pretty specific and details are important. The proper term for the "pulley" in a power transfer situation is sheave. A pulley re directs motion.