Question pertaining to pitch diameter and teeth on timing pulley
Question pertaining to pitch diameter and teeth on timing pulley
(OP)
Guys
I need some help over here. I have a timing pulley system driven by a timing belt with 2 pulleys with a teeth ratio of 2: 1 [Large pulley = 38T, small pulley = 19T].
I wonder whether in timing belt design, the ratio is dependent on the number of teeth on both pulley or the PD of both pulley.
For example, if the large pulley is 38t and the smaller one is 19t, the ratio is 2:1
However, the pitch diameter of both pulleys may not be exactly 2:1 based on the tolerance, does the pitch diameter or other dimensions affects the pulley ratio?
I need some help over here. I have a timing pulley system driven by a timing belt with 2 pulleys with a teeth ratio of 2: 1 [Large pulley = 38T, small pulley = 19T].
I wonder whether in timing belt design, the ratio is dependent on the number of teeth on both pulley or the PD of both pulley.
For example, if the large pulley is 38t and the smaller one is 19t, the ratio is 2:1
However, the pitch diameter of both pulleys may not be exactly 2:1 based on the tolerance, does the pitch diameter or other dimensions affects the pulley ratio?





RE: Question pertaining to pitch diameter and teeth on timing pulley
Bill
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"Why not the best?"
Jimmy Carter
RE: Question pertaining to pitch diameter and teeth on timing pulley
The pitch surface is not within the pulley's envelope; it's at the effective center of the cord ply, somewhere within the belt.
Mike Halloran
Pembroke Pines, FL, USA
RE: Question pertaining to pitch diameter and teeth on timing pulley
I did an experiment to run the small pulley 40 times at 720deg interval then measure the output angle with a rotary encoder on the big pulley. My observation: -
Rev1) Small pulley = 720deg [Input], big pulley = 360.01deg
Rev2) Small pulley = 720 x 2deg [Input], big pulley = 360.02deg.
It seems like there are some cummulative error.
In theory, if the ratio is 2: 1, we suppose to get 360 deg each time.
RE: Question pertaining to pitch diameter and teeth on timing pulley
Mike Halloran
Pembroke Pines, FL, USA
RE: Question pertaining to pitch diameter and teeth on timing pulley
RE: Question pertaining to pitch diameter and teeth on timing pulley
Revolutions?
Degrees?
Radians?
Mike Halloran
Pembroke Pines, FL, USA
RE: Question pertaining to pitch diameter and teeth on timing pulley
RE: Question pertaining to pitch diameter and teeth on timing pulley
Sorry, I am using an incremental rotary encoder with a resolution of 0.001 deg.
I am using a timing belt system.
RE: Question pertaining to pitch diameter and teeth on timing pulley
RE: Question pertaining to pitch diameter and teeth on timing pulley
That is based on firmware control
RE: Question pertaining to pitch diameter and teeth on timing pulley
As long as the teeth don't skip, it can't go wrong...
RE: Question pertaining to pitch diameter and teeth on timing pulley
Mike Halloran
Pembroke Pines, FL, USA
RE: Question pertaining to pitch diameter and teeth on timing pulley
The difference might have been backlash in the system not being tight when you started or you have gross errors on the flanks or loose centerlines.
RE: Question pertaining to pitch diameter and teeth on timing pulley
For timing belts like Gates GT3 series, I realise there is some wear/ drift after running the reliability test. I wonder how durable are these belts as I cannot find any information pertaining to belt life or wear.