The difference between rolling and sliding friction in camera sliders. Mike Quiunn 4.7.2011
Take a quarter and roll it on its edge across a table - goes forever and moves quickly. Now take that quarter and lay it on its side and
push it...that's the difference. Sleeve bushings inherently have much more surface area under load. Simply put, they have big feet.
Conversely, a ball and roller have much smaller feet ensuring them a meaningfully lower co-efficient of friction.
A ball offers point contact
loading and loosely reside in 4 rows within a steel or plastic shell:
These balls literally kick each other along as the balls roll down the shaft. Because they have so little contact area, the coefficient
of friction is as low as .001 - they roll easily and smoothly. The drawbacks in a camera slider are readily recognizable:
|1. Resonance - noise - ZING! ZING! ( Metal on metal contact and because they push each other from load to preloads, they create resonance, noise and vibration.
2. They are made from steel and can rust - they require lubrication.
Rollers have internal ball or needle bearings at their core, between the inner and outer race. They are separated in a retainer, unlike
linear ball bushings which run loose in their track ways.
These are sealed and lubricated for life. They have more contact area but the coefficient of friction remains low approximately .003 -
not as low as the ball - but very close. These rollers come in dual angular contact ( gothic arch ) or V geometries. They are very smooth,
take high loads/moment loads ( overhanging loads )and provide great stiffness. They are however steel and they run on steel shafting
or V groove rails. They can produce noise and are vulnerable to the elements.
Plastic Sleeve Bearings are truly all weather and can run very smoothly and tolerate debris. However, the real world coefficient of friction
is around .2 - factors higher than ball and rollers. They are also prone to a phenomena called edge loading. This effect can cause the carriage plate ( slider ) to ratchet or get sticky due the bearings digging into the shaft. This is particularly troublesome when you attempt to slide the carriage plate with top heavy rigs like a DSLR with a Red Rock
system. You will need two hands.
There is an answer...Camera Motions new " Silent Slider "
Why? Because we offer a solid, 1 piece precision machined aluminum carriage block that is black anodized. Not an extrusion that is
cheap and has varying tolerances one lot to another. We have selected the best industry urethane cam followers with needle bearing
rollers - tight and true.
Moreover, the rollers damp any noise or vibration yet hold a 25 pound load. Smooth, quiet and solid. The Silent
Slider is a product of linear motion engineering - pure and simple. It was was designed to run on the igus size 16mm twin extruded rail
which is ubiquitous in the the camera slider industry. Keep your rail and tripod shoe and move to the future - The Silent Slider!
Let engineering win - not salesmen. Only $ 230.00. Call Mike Quinn @ 1-800-698-5820.