Nasir A

The speed ratio will not be constant.

RPM ratio will be proportional to the tangent radius ratio at any given moment.

RPM driven = RPM driver x driver radius / driven radius

Hi Hendrik,

Many thanks for the reply to my question which is in-complete, infortunatly.

What I really need is the mathematical formule that will let me calculate for any given moment in time.

Example, for time T=0 min, to elapsed time T= 10 min.

Start ratio of 1:10. Progressing through to any intermediate ratio. Ending at 10:1

a- the RPM ratio at Time T= 3 min.

b- length of belt, for Time T=3 min

wound on to Spool 'A' (belt thichness t= constant, for a simple case)

c- respective spool dia's (driver-'A', and driven-'B') at Time T=3 min

In other words;

Spool 'B' Dia. as a Function of; Spool 'A' Dia., belt thickness 't'

I will greatly appreciate if this can be provided.

Thanks once again.

Nasir

Hi Nasir

The formula for the length of a spiral is (somewhere between a lot of paper - I have lost the paper war) but it may not be what you need for practical reasons.

The tension on the takeup reel may cause the ratio to change.

When one reels are close to empty the ratio will stay the same for almost one revolution of the empty reel where after it will jump for the next revolution.

I am curious as to your application.

Can you give more detail? (size of drums , belt thickness, belt length etc)