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 (21 mm) 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.

Speed and efficiency is the strong point 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 baking 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]. 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 pad with 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

Suggestion: use Optimum foam/microfiber pads to reduce heat transfer

Notes

1. Speed, kinetic energy (friction heat), applied pressure, foam pad actual surface contact area, pad and polish / compound grit number (abrasive ability) amount of surface lubrication available, 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 paint surface wither it be a rotary or an orbital polisher; the operative word here is excess kinetic energy (friction heat)

2. As opposed to paint burn, the cause of which is the localized and excessive use of kinetic energy 

Current Information

To be of real practical use, a subject like automotive detailing requires a great deal of research, and updating as new products become available. The advent of materials like detailing clay, micro fibre technologies and finely milled micro diminishing abrasives, suitable for ceramic nanotechnology paints are examples of why it’s so important to monitor the industries new products, chemical technologies and ideas that are constantly being introduced, as are the techniques for applying them, hence all of the in-depth articles will be up-dated and revised on a regular basis

Always be willing to learn; because the more you learn, the more you’ll realize what you don’t know. You should never stop learning, and your quest for information should be part of your everyday process. It is said that knowledge is power, with the caveat that it includes access to a reliable information sources. I would like to think that these articles become an asset to anyone who is new to detailing and to professional’s alike, as well as industry experts who seek to advance their knowledge.

I hope these articles are informative. They are based on the current status of technical development as well as my experience with the products.By having some understanding of the ‘What’ and ‘Why’ as well as the ‘How’ along with a little science to help you understand how the chemicals we use react, you can achieve the results you desire.

I would appreciate it if you would share these articles as it helps other detailers further their knowledge.

As always if you have questions, I’ll do my best to answer; bear in mind the only stupid questions is the one that was unasked. Questions and/ or constructive comments are always appreciated

Copyright © 2012 TOGWT® (Established 1980) all rights reserved