Recently, some items drew my attention which might be useful for the discussion of sealing; especially for the solenoids containing moving magnets.

As a simple sample, one can consider Land Rover Defender and its capabilities to cross the rivers and other wet courses.

The more advanced solutions can be found in amphibious vehicles and their mechanisms to insulate the sensitive compartments against water.

So why not inspiring from them to become away from air molecules in the tubes around the moving magnets?

List of inspiring items:

Humdinga - the 4WD amphibious vehicle
Gibbs Aquada - Wikipedia, the free encyclopedia
Gibbs high-speed amphibious motorcycles – ride straight into the lake and out again

AAV:

http://www.albany.marines.mil/News/N...ous-roots.aspx
Assault Amphibious Vehicle - Wikipedia, the free encyclopedia

Weatherproof performance of the Xventure XV-2 trailer from Schutt Industries:

XVENTURE Off Road Trailer
Rugged Xventure trailer sleeps you in the attic, hauls gear below

EarthRoamer will use a new vacuum infusion construction process, different from the way it produces its current XV-LT bodies:

EarthRoamer XV-LT
EarthRoamer reveals its largest off-road expedition vehicle yet
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Even small gadgets:

VSSL Flask hides your favorite tipple inside a flashlight
VSSL Gear - Supplies Survival Kit - Rugged and Made in Canada | Ultimate Survival Tips
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