Not needed IMHO. I have machines with and without the washer and to me there's ZERO difference. As you use your machine the shroud begins to wear down anyways and spins freely without the washer mod.
I believe Rupes tested this washer mod theory and didn't find it to make any improvement. Todd just actually commented on this in another thread.
I wouldn't say it makes zero difference, but the difference on pad rotation and correctional ability when applied to the surface is very minimal.
I think the most important thing to remember is that RUPES designed and engineered - in house - the large diameter orbital polisher revolution. It took nearly 3 years of development, as there weren't any other designs to copy or mimic.
The idea of the anti-spin shroud was built into the design for a number of reasons. Keep in mind, it would have been cheaper and less complicated to design the tool without such a feature.
The BigFoot "System" was designed from the ground up. Part of this was creating specific foam types that will withstand the stress and movement of the large diameter orbit, part of it was developing a counter weight system to match the weight of the Rupes pads, part of this was engineering compounds that will will not absorb into the pad and destroy the delicate balance, part of this was venting backing pad and using open-celled foam for heat control, part of this was using a velcro system with enough shear strength to limit wasted movement, and part of this was the Anti Spin Shroud.
Without the Anti Spin Shroud in place (or disengaged), the pads will be allowed to spin up to a very high rate of speed when the machine is operated in free air, almost matching the orbital speed (in the 21's case, about 4200 RPM). A pad spinning that fast is not only subject to flying off at a pretty good clip, but the foam structure of the pad is compromised. If you don't run you machine in free air, which most experienced technicians do not, this part isn't really a big deal. However, one of BigFoot's biggest selling points is the system can take somebody with no experience and allow them to produce professional results very quickly. It's gotta be safe for everybody.
What causes pads to rotate on an orbital, in the simplest terms, is unbalance. When the pad is applied to a workpiece, the amount of unbalance is multiplied and the rate of rotation will increase dramatically.
In our testing, with our pads, and our compounds, removing the function of the Anti Spin Shroud shows no benefit. However, if you notice a benefit for your polishing style, please keep the considerations about pad rotation in free air that I mentioned earlier in your head.
