fmodena said:
Hi Kevin. Thanks for posting this about the "cruise control" as I was curious in Garry's video where he stated he was able to stall the G110V2 on speed 6 but the video is a little fuzzy and was hard to see if the backing plate actually stopped or not.
To me it was hard to tell as there was no black mark on the yellow backing plate to discern the actual spinning under extreme pressure. As per an earlier post by you, it was stated that at lower speeds is where the cruise control really comes into play since there is less centrifugal force to create the rotation of the backing plate.
How much effect does the "cruise control" utilize at the speed 6? Thank you Kevin and thank you Garry for taking the time to post your video comparison.
I am not an electrical or mechanical engineer, so I'm counting on experience gained using the machine (and some brain power). I'd say that at speed 6, there is likely to be
little to
no effect if the machine was being placed under the type of load Garry was putting on it. Seems reasonable to me that in order for
Cruise Control Circuitry to properly function:
A) There
has to be a reservoir of energy available to the motor,
or
B) The motor's RPM
must be limited, so that there will be additional RPM available, should there be a need to boost RPM to increase centripetal force (thus restoring backing plate rotation).
Really, the G110v2's cruise control would have to work similarly to a cruise control installed on a typical car. Imagine you were driving along at
maximum speed (not limited by an intelligent electronic governor), and encountered an uprising hill. If there was no
reserve power or
additional RPM available from the engine, there would be no way to
maintain the previous maximum speed. The motor would
have to have some sort or reserve available (an intelligent electronic governor could limit engine RPM, and lift the limit if there was a need to resotre a predetermined "maximum" speed, under reasonable load conditions).
Back to the machine.
Storage capacitors
could supply some energy, but they would drain rather quickly, and would have to be re-energized in order to supply another burst of current. From what I know about capacitance, there's not much room (if any) inside the machine to mount capacitors that would make any sort of long-term difference.
Regardless, the Cruise Control Circuitry
must be comparing motor RPM to load (aka electrical impedance) in order to know when
more load was placed upon the machine. It would then have to allow more electrical current to flow to or through the motor. There is no real way to guarantee restoration of backing plate rotation, because backing plate rotation is not mechanically driven (it is created by
rotational or
centripetal force). Instead, the circuitry must be trying to restore motor speed, which will then create enough momentum to spin the backing plate.
Again though, depending upon the force placed upon the machine, and depending upon the type of pad and compound being used in any particular situation (grippy, abrasive, slippery, tall, short, etc.), there is a limit to the abilities of
any machine. In regards to the G110v2... the power of its motor, combined with its gearing ratio (used to create up the final drive ratio of the rotating counterweight & spindle assembly) is apparently not capable of overcoming the forces that Garry was placing upon it.
Obviously (I hope), nobody polishes paint in this manner, and more often than not, you'll get much better results using slower rather than faster speeds. This is especially true when the task at hand is final polishing. In fact, I think guys are having more trouble finessing paint rather than cutting defects away. Drop those speeds, keep those pads clean!
In the end... we all know that Garry was simply trying to show how
strong he was anyway. I'm waiting to see his rotary review next. I can see the opening scene now:
Close-up shot of a dented-in wall. The dent resembles the backside of a man. Pan out to a bloodied and bruised Garry Dean, eye taped shut, cast on his right arm. "Hi, I'm Gary Dean, and I just went for a ride. This new-fangled rotary just tossed me into that wall over there with the force of a freakin' freight train..!"