Long throw dual action polishers have become the go-to machines for most professional detailers who offer paint correction services. These machines yield excellent results in a shorter amount of time, making them the clear choice when time is money.
A unique trait that the Rupes Bigfoot and Griot’s BOSS machines share is that they do not spin freely like other free spindle machines do (ie Porter Cable 7424XP). This is because these machines were designed with a shroud that contacts the rear of the backing plate which produces friction, and therefore does not allow the backing plate to spin unless the machine is powered on.
The idea behind this was explored heavily by Kevin Brown of BuffDaddy.com. Kevin explains that this shroud was implemented to slow excessive backing plate rotation when the pad is not under load while the machine is running. So in situations where the pad is not in contact with a polishing surface, or barely in contact with the surface, and the machine is turned on, the ultimate speed of rotation is limited by the friction between the shroud and the backing plate.
This was seen as a potential performance inhibitor, so Kevin went on to develop what is now known simply as “the washer mod”. The idea behind this simple modification is to eliminate the contact between the shroud and backing plate by inserting a thin washer between the mating faces allowing the backing plate to spin freely and therefore increase the backing plate rotation. The benefit here is that more backing plate rotation can lead to an increase in cutting speed while also potentially aiding in your polishing results as well.
As previously mentioned, a small spacer, or washer, is all you need to complete this modification and unleash even more potential out of your long throw polishers (note: The Griot’s BOSS machines include a washer in the supplied parts bag which users can install on their own).
Simply place the washer in between the backing plate and the mounting face on the machine, then reinstall your backing plate. Note that if you are purchasing a washer from your local hardware store to use in this application, do not choose an excessively thick washer as you still need proper thread engagement to hold the backing plate in place. If you’re concerned about adding the spacer, you can replace the mounting bolt with a slightly longer one to make up for the additional height of the spacer.
Thanks to Kevin Brown for allowing me to share this information on the Detailed Image Blog. You can find the complete article by Kevin Brown, which discusses the benefits of long throw machines as well as the performance benefits of the washer mod, on the Autopia.org forums.