[jimbob1603]

Hi,
All linear compressors are oil-less. But, I do not believe that all oil-less compressors are linear:

Linear compressor:
low power consumption
low pressure (1 - 10 psi) / high volume output
quiet operation
designed for continuous operation
linear magnet drive
purchased at specialty shops & commercial suppliers

Oil-less compressor:
high power consumption
high pressure (50 - 150 psi) / low volume output
very noisy operation
designed for intermittent operation
motor driven diaphragm
purchased at Home Depot

I don't think the ice has any particular direction it will push/drag the pilings. Its probably mostly influenced by water current and wind direction. The 'thermal expansive properties' of water/ice are tremendous; nothing will stop the ice from compressing/damaging (however minimal) any piling. The thicker the ice, the more potential for damage.

Wood is the cheapest material; then steel; and aluminum being the most expensive. Concrete pilings, without some sort of steel reinforcing, is a bad choice. Concrete has superb compressive strength, but poor tensile and shear strength.

I would never use steel in a marine environment, for obvious reasons; and probably not even in fresh water .... just too much maintenance. I'd use a 6063 alloy aluminum in fresh water (if cost was not an issue ..... a 4x4x3/16 Al tube is 4 times the price of a 4x6 PT timber). All said and done, wood is the preferred material; and wood is probably the most forgiving when it comes to ice damage.
j