Yeah. My approach has been to
- Calculate the high end speed/gearing first, knowing that approximately 10-15% of the available power may be lost in the CVT. (In other words, knowing that you won't be able to achieve the same max top end that you could without the CVT)
- Then, back off to the 5500 RPM range, to determine the cruising speed, when the CVT pulleys get to a 1:1 state.
- Finally, calculate the max torque situation (at 5500 PM,) as if you're climbing a steep hill. (You divide the 'cruise' speed, from step 2, by the pulley ratio of 2.2)
With this approach, if you wanted to hit 30 as a top end, then you wound need 18:1 total reduction, cruise would be at 23.6+ MPH, and max torque at 10.7 mph.
Now, if there are lots of hills, and your main objective would be to have hill climbing ability, then you could work 'backwards.' Suppose that you needed to have max torque at 9 MPH. because of steep hills. Multiply by 2.2 to get the minimum 'cruise' speed of 19.8 at 5500 RPM. The gear ratio could be calculated to be 21.5, meaning that you would need an additional 6.7 gear reduction after the gearbox on the CVT. and, with a 12T sprocket, you would need a 81T hub sprocket, or, a jack-shaft. The top end would then be about 25 MPH.
I think the key thing to remember is that the CVT isn't the cure-all. Yes, it can increase acceleration (and hill climbing torque,) but it can't do this AND maintain the same top end that you could without a CVT. There are some losses in the CVT (on average, over the life of the CVT belt, about 10%) that will reduce the top end that can be achieved.
And, I think that you need to get the system gearing right, before you start playing with the variator weights.
Possibly, the chart below will help in understanding what the CVT does for you, when the bike is geared for climbing, per above.
Assuming that you peddle up to 5 MPH, then gun the engine. Assuming the clutch pulls in at 2000 RPM, engine RPMs will quickly rise to the 5500 RPM level, and will then level off until the bike's speed reaches the minimum 'cruise' speed breakpoint, and then, since the CVT has no further pulley ratio changes to make, the engine RPM then starts rising as the speed increases.
Adjusting the pulley weights has the effect of lowering or raising the 'flat' portion of this rpm-speed curve. Adjusting the system gear ratio has the effect of shifting the curve to the right or left (shifting the the first two 'breakpoints and the top speed to the right or left.)