Sunday, 6 August 2017

Flex vs. Rupes

The throw (or eccentric offset) [: Centripetal force is a force that makes a body follows a curved path: it is always directed orthogonal to the velocity of the body, toward the instantaneous centre of curvature of the path]

Stroke Diameter (Offset)
All other parameters being equal, a machine featuring a large stroke (or offset) will create more centripetal force than a machine featuring a small stroke, because centripetal force is the primary element that causes the backing plate to rotate. The higher centripetal force will add a higher shearing force than what other machines would transfer to the pad. You need to slow it down a little and ease off applied pressure

Why is a large diameter stroke or orbit beneficial?
[To better understand why a large stroke machine can deliver better and faster polishing results, imagine hand sanding a panel of wood with a typical sanding block & paper using very short 1mm back and forth strokes.  Although sanding would be concentrated and exact, most of the sanding debris would remain positioned between the sandpaper and wood panel.  

Rapid clogging of the sandpaper would likely occur, effectively limiting cutting power and finishing potential.  

However, if the length of each sanding stroke was increased (within a similar time frame), the sandpaper would move along at a more rapid pace.  The increased speed of motion would assist in loosening any stuck-on debris from the sandpaper, all the while helping to eliminate sanding debris residing between the paper and wood surface. The exact same principles of extending the stroke apply when using the LHR21ES, except its motion is rotational (not linear), and we use buffing liquids (not sandpaper) to accomplish our work.

High speed + lots of motion = very fast polishing.

A majority of the buffing liquids available today utilize abrasive particles that are engineered to assist in polishing the surfaces we're working on.  To work efficiently, these particles must occasionally shift and tumble in order to keep them free of debris, minimize clumping of the abrasives, and slow contamination of the buffing pad.  

The LHR21ES's large-diameter stroke (21mm) and high-speed capability (4,200 RPM) combine to deliver unrivaled performance in this regard, utterly stomping the performance mustered by other competitor's machines] – Kevin Brown

Therefore, if you use a machine with a large stroke size, you should generally see an increase in random pad rotation versus an identical machine featuring a short stroke. If the orbit offset is doubled, the speed of the backing plate is also doubled; however, the abrasive ability is increased by more than double.

If you are a professional detailer you will probably have both machines, but the Flex® 3401 (the rotation rate is 1/10 of the orbit rate) is definitely going to speed up the correction process. (OEM) production line paint finishing and correction use a large eccentric offset machines. Flex® Dual Action Machine Polishers are designed and built in Germany, they are the preferred choice of Porsche Body Shops and RUF Automobiles GmbH. Use a thicker waffle foam pad 1.25-inch pad thickness, which allows constant contact over the whole pad surface and promotes an even pad temperature

Speed and efficiency are the strong points of the forced rotation of the Flex®. It’s really easy to handle, and the power of the Flex with curved vertical panels actually resulted in a substantial decrease in detailing time since the pad never stopped spinning. A slightly stiffer backing plate along with Menzerna polishes, Lake County Hybrid pads are an ideal polish/pad combination

The Rupes Bigfoot has a large 15 or 21mm eccentric offset and has an indirect drive, making it virtually impossible to cause a strikethrough on the paint [2]. A thicker d 7/8-thickness or a waffle type surface allow constant contact over the whole pad surface, promote an even pad temperature and allows backing plate rotation at lower machine speeds 

The Flex 3401 has a standard 8mm eccentric offset and uses a direct drive motor, allowing the user to apply more downward pressure.Flat pads, on a long stroke orbital polisher, will create localized surface hot spots, nor do they exert an even pressure A thin pad 7/8 -thickness or a waffle type surface allow constant contact over the whole pad surface, promote an even pad temperature and allows backing plate rotation at lower machine speeds

 When polishing you shouldn't have to apply heavy pressure to the point where the Rupes would stall and the long throw would allow the polishes and compounds to work better as it abrades the surface. All that is required with either machine is that the pressure is sufficient to compress the pad 50% < but not flatten it

While the long throw dual action polishers make paint polishing a whole lot easier, they have become a detailer’s worst nightmare for pads. The amount of centre heat build-up has been disintegrating pads from the inside out causing a foams cell structure to flatten and no longer have the proper structure to finish the task

Washer Mod:
The mod is just installing another washer between the backing plate and mounting pad. Completely reversible. The Rupes machines have an anti-spin feature built in. Disabling this, plate rotation and cutting speed are dramatically increased.

Exact Fit Compression Pads (Americana Global Inc.) were designed to alleviate this problem by incorporating a hole structure to allow heat to disperse evenly and allow the pad to run at cooler temperatures and still provide maximum cutting and finishing abilities over a longer period of time.

1. Speed, kinetic energy (friction), applied pressure, foam pad actual surface contact area, pad and polish / compound grit number (abrasive ability) amount of surface lubrication available, the area being polished, and material (paint, especially paint edges, plastic, metal, etc.) heat conductivity of the material being polished

The above will, given the right circumstances, 'friction burn' (strikethrough) a painted surface whether it be a rotary or an orbital polisher; the operative word here is excess friction

2. As opposed to painted surface burn, the cause of which is the localized and excessive use of kinetic energy (friction heat) 

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