Pulley ratio

[703Y]

Hi all,
Was wondering if anyone could advise me on how to calculate the ratio of the attached pulley set up.
Am trying to set up a stepper motor and am trying to determine the ratio.

Would i be correct in: - ratio = (T1/T2)(T2/T3)
I am not sure if that is correct, due to the two pulleys (T2 and T3) being on the same shaft. Bit confused.
Any help gratefully received.

 

[3DDave]

It would have been nice to label either the pulleys or to give the number of teeth.

Still - for one turn of the top pulley will see 18 teeth go by, so that one turn will see 18/45 of a turn of the second one. Then since that fraction of a turn is applied to 20 teeth then the input is (18/45)*20 to the periphery of the output.

 

[703Y]

Thanks very much for your reply.
Hopefully now i will be able to set up the DRO for my y axis travel.