V Belt Pulley Bore Diameter
V Belt Pulley Bore Diameter
(OP)
I received a 250 HP motor with some "noise" problem. On examination, I found that the noise was coming from the 8 groove, V belt pulley of the motor.
The motor shaft dia is 109.92 mm and the pulley bore is 110.20 mm i.e. 0.28 mm loose fit. The key was also loose both in the shaft and the pulley.
The motor runs smoothly without the coupling.
I would appreciate if any one can point out the kind of fit of V belt pulleys (loose fit, mallet fit or interference fit) require.
Any pointers to web references would be nice.
(I did google v belt pulleys but got 43,800 hits and the few sites I saw did not have this fit information).
Thanks
The motor shaft dia is 109.92 mm and the pulley bore is 110.20 mm i.e. 0.28 mm loose fit. The key was also loose both in the shaft and the pulley.
The motor runs smoothly without the coupling.
I would appreciate if any one can point out the kind of fit of V belt pulleys (loose fit, mallet fit or interference fit) require.
Any pointers to web references would be nice.
(I did google v belt pulleys but got 43,800 hits and the few sites I saw did not have this fit information).
Thanks





RE: V Belt Pulley Bore Diameter
RE: V Belt Pulley Bore Diameter
It is either a pulley with a taper hub & sleeve or reshaft the motor. It is a no-brainer.
My client has been running this motor with this issue (production pressure) for over six months. The end result was the damaged motor bearings due to all the knocking.
RE: V Belt Pulley Bore Diameter
ht
RE: V Belt Pulley Bore Diameter
Have seen several split over the years.
RE: V Belt Pulley Bore Diameter
Mike Halloran
Pembroke Pines, FL, USA
RE: V Belt Pulley Bore Diameter
Mike
Will loctite work for such a clearance (0.28 mm) ?
RE: V Belt Pulley Bore Diameter
Another alternative is a wrap of .005" shim stock, and regular Loctite.
Again, temporarily, until you get the correct part.
Mike Halloran
Pembroke Pines, FL, USA
RE: V Belt Pulley Bore Diameter
RE: V Belt Pulley Bore Diameter
RE: V Belt Pulley Bore Diameter
I have two questions.
1. The existing pulley is cast iron. Should I go for cast steel in case of taper lock ?
2. The existing pulley has 4 holes of 2 inches dia centrally in the thin stem area above the central hub. What is the purpose of these holes ?
(One theory is weight reduction, but given the total weight of the pulley, these holes on the thin stem do not save much in weight.)
RE: V Belt Pulley Bore Diameter
2. My guess is that the holes are intended to provide relief of shrinkage stresses and prevent cracking as the casting cools. In a much older casting, you'd see curved spokes instead.
Mike Halloran
Pembroke Pines, FL, USA
RE: V Belt Pulley Bore Diameter
Russell Giuliano
RE: V Belt Pulley Bore Diameter
I have a 1300 dollar quote for cast steel and a 1000 dollar quote for cast iron pulley.
Is spending additional 300 dollars for cast steel pulley worth it (in terms of better strength, less brittle, durability etc.) ?
Also, are the v-belts different for cast steel and cast iron pulleys ?
RE: V Belt Pulley Bore Diameter
I'm not aware of a preference on the part of the belts.
Mike Halloran
Pembroke Pines, FL, USA
RE: V Belt Pulley Bore Diameter
Steve
RE: V Belt Pulley Bore Diameter
Motor fitted with cast iron, taperlock pulley. Working fine for the past 3 days.
I thank you all for your valuable tips.
*Nothing exists except atoms and empty space; everything else is just an opinion*
RE: V Belt Pulley Bore Diameter
Otherwise, it is a good suggestion and decision as well.
RE: V Belt Pulley Bore Diameter
What type of bearing is at the drive end of the motor? Some bigger motors headed for belt drive service have roller bearings at the drive end to handle the radial belt loads. I'd be sure the replacement motor (or the rebuild, assuming the worn shaft can be replaced economically) is meant for belt driven application. I think if the motor bearing that failed was a ball bearing, its failure is more likely from mis-application than the impact of a loose pulley whacking around on the shaft.
The design of the belt drive should be evaluated. What was the outside or pitch diameter of the drive pulley? The largest diameter pulleys should be used to reduce the belt tension (installation AND operation) Larger diameter pulleys cost more, but may require fewer belts, and regardless have lower tension requirement. Some motor specs include a minimum pulley diameter, and I believe that is an attempt to prevent subjecting the motor to unnecessarily cruel belt loads.