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Flat rubber belts and pulleys

N

N Cook

Jan 1, 1970
0
Can someone explain to me how bulbous/baluster pulleys centralise a belt.
And why the belt does not slip off parallel sided , ie non bulbous flywheels
with usually no flange on one side. The chances of grime or shine on one
side or the other of belt or pulley should easily lead to a belt comming off
such flywheels , shouldn't it ?
 
T

Tim

Jan 1, 1970
0
Can someone explain to me how bulbous/baluster pulleys centralise a belt.
And why the belt does not slip off parallel sided , ie non bulbous flywheels
with usually no flange on one side. The chances of grime or shine on one
side or the other of belt or pulley should easily lead to a belt comming off
such flywheels , shouldn't it ?
It's the crown that is on the pulley. The belt will always climb to the
highest point and stay there. It's the same concept that kept those big
flapping belts on old equipment like you see on the Walton's saw mill.

- Tim -
 
D

davidlaska

Jan 1, 1970
0
When Mercedez change to a new body style in 1981, we were in a 380sel
and popped off a couple v belts on a dirt road.
 
Can someone explain to me how bulbous/baluster pulleys centralise a belt.

The centre fattest part of the bulbousness travels faster, because its
wider, thus pulls the belt more than at the ouer edges of the drive
wheel. Hence the belt is pulled towards the fatter wider centre.

As for whats-it-called wheels, the slave ones, the belt position on
them depends on the driving wheel, which feeds the relatively slack
belt to the secondary wheel.

And why the belt does not slip off parallel sided , ie non bulbous flywheels
with usually no flange on one side. The chances of grime or shine on one
side or the other of belt or pulley should easily lead to a belt comming off
such flywheels , shouldn't it ?

grime is distributed fairly evenly in practice. But there is normally
no slippage occurring between belt and drivewheel, so friction level
has no effect. You'd need a very dirty and very slack belt for this to
occur.


NT
 
N

N Cook

Jan 1, 1970
0
belt.

The centre fattest part of the bulbousness travels faster, because its
wider, thus pulls the belt more than at the ouer edges of the drive
wheel. Hence the belt is pulled towards the fatter wider centre.

As for whats-it-called wheels, the slave ones, the belt position on
them depends on the driving wheel, which feeds the relatively slack
belt to the secondary wheel.



grime is distributed fairly evenly in practice. But there is normally
no slippage occurring between belt and drivewheel, so friction level
has no effect. You'd need a very dirty and very slack belt for this to
occur.


NT

I'm surprised they only seem to fall off if the belt is perished or someone
meddling inside the mechanism or as a result of some fault or jam.
 
L

Lionel Wagner

Jan 1, 1970
0
Tim said:
It's the crown that is on the pulley. The belt will always climb to the
highest point and stay there. It's the same concept that kept those big
flapping belts on old equipment like you see on the Walton's saw mill.

- Tim -
I worked on old belt driven VTR's. The speed of the
heads was controlled by a magnetic brake. As the brake
acted, the belt would creep off center of the pulleys
to maintain the correct size ratio for the new speed.
 
S

Sofie

Jan 1, 1970
0
The belt will go to the highest point is where the most tension is.... and
the most grip.... the belt will not go where there is no tension or little
grip.
 
L

Lionel Wagner

Jan 1, 1970
0
Sofie said:
The belt will go to the highest point is where the most tension is.... and the most grip.... the belt will not go where there is no tension or little grip.
Why then not simply have two flat pulleys
the correct distance apart for optimum tension.
Edges would prevent the belt from slipping off.
I've seen this in some audio tape decks that are
fixed speed.
 
H

Homer J Simpson

Jan 1, 1970
0
Why then not simply have two flat pulleys
the correct distance apart for optimum tension.
Edges would prevent the belt from slipping off.
I've seen this in some audio tape decks that are
fixed speed.

Edges would cause wear.
 
Lionel:
If they were truely FLAT pullys with EDGES, the belt would bump the
edges and immediately climb off the pully.
If you look closely at the FLAT pully with EDGES on your audio tape
deck that you mentioned, the motor pully surface that the belt rides
on is CONVEX so the belt stays "high" centered and does not bump the
edges.....
I hope that this clarifies things for you.

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