Our customer has hundreds of shipping locations throughout the United
States which employ moveable docking ramps. Many of these facilities are
located in cold weather areas where ice, snow and freezing rain are
standard fare during winter months. To clear snow and ice from ramp
platforms, maintenance personnel employ deicing fluids and rock salt.
Further, in order to provide safe footing for employees, sand is thrown
on the platform plates. All of this makes for a tough, brutal
environment for linear bearings and shafts. I was called to see if LM76
could find a solution that would be a drop-in system, due to the
installed base, it would be too expensive to field retrofit a redesign.
I determined both the shaft and the linear ball bearing were steel -
prone to rapid oxidation. Because of this, bearings and shafts - in
short order - corroded and locked-up, freezing the loading platforms in
position. If the loading platform cannot be adjusted, there's no way to
ensure a safe meeting of the ramp and truck being loaded/unloaded
creating a safety issue. To ensure the balls would not rust/adhere
internally, we nickel coated the balls and used a plastic/resin
retainer. To increase the surface hardness and corrosion resistance of
the shaft, we applied Armoloy® (thin dense chrome coating) to a host 440C stainless.
Armoloy® raised the surface hardness from Rc60 to Rc78 while making
it resistant to deicing fluids, debris and oxidation. After 1 season,
some areas of the ramp are showing signs of corrosion, not
our linear bearings and shafting.
I would have selected our sleeve-style Minuteman Self-Lubricating
bearings (immune to deicing fluids, salt and sand) on an Armoloy coated
shaft but because of high moment loads and poor bearing spacing, the
coefficient of friction was too high - making it difficult to reposition
panel extensions by hand.
A note about the advantages of Armoloy® coatings: Armoloy® is
much more than a surface anodize. This coating forms a layer of nodes,
spherical balls form along the surface being treated. If the shaft
deflects, the nodes realign to mirror the deflection - no chipping or
cracking. Further, the nodes are spherical, they present a point
loading contact to the mating surface - not a line-to-line or sliding
friction. Thus, Armoloy® lowers static friction:
"The coating's nodular finish reduces the
amount of surface area exposed to surfaces in contact with it, thereby
substantially reducing friction and extending wear life. This nodular
finish also retains smaller amounts of industrial lubricants for longer
periods, both further reducing friction and creating a cleaner work
environment."
Lastly, Armoloy® is one of the few materials that can successfully
run on itself. I specify this coating on many naval, FDA, bio/pharma and
other applications where hardness, corrosion resistance, high
temperature (up to 1400F) and FDA/Washdown compliance is required.
Typically, Armoloy® adds about 20% to the cost of shafting.
The other guys have catalogs, we have solutions. For more information on
this application or if you have an application that seems to defy
correction, please call Mike Quinn @ 1-800-513-3163, Cell:
617-538-8756 or email me at
mquinn@LM76.com