Woodland Mills HM126 vs HM122

[dgdrls]

Well,.. by observation using the photos posted on their website,
it looks like they use a different size drive pulley,

If you can, go with the bigger wheels, its easier on the blades,

D

[ljohnsaw]

When you really think about it (with the drive belt also being the band belt), it is ONLY the size of the pulley on the engine clutch that matters.  Most engines have their sweet spot of torque at a certain RPM.  When you are looking at 7.5 up to 16 or so, pretty much the same rpm for the max torque.  Since that pulley determines the FPM belt speed, that is also the blade speed. 

So, it doesn't make any difference what the wheel diameter is.  What you will see is a larger wheel will have a slower RPM than a smaller wheel.  But, since it is a larger diameter, the FPM will be higher than a small wheel with the same RPM.  But a smaller wheel driven by the same engine will have a higher RPM - enough that it will have the same FPM.

However, a larger wheel is easier on the blade (less bending).

[Hilltop366]

When you really think about it (with the drive belt also being the band belt), it is ONLY the size of the pulley on the engine clutch that matters.

That is true, when using the driven pulley as the band wheel changing the band wheel size also changes the driven wheel size.