I have worked with hydraulic systems in both military Aircraft and 
industrial equipment.
all of them that I worked with used a air charged accumulator.  They 
were a cylinder with a piston in it, Capped at both ends, one end gets 
the hyd. fluid, the other gets an charge of nitrogen gas.  regular 
compressed air can also be used also but dry nitrogen is better
This type could be made very light weight. It would depend on much 
pressure was needed, the volume of fluid .  Higher system pressure would 
cause the tube to be made of heavier material.

Also this type can be mounted in any position and still work OK.

>Bill,
>
>On Sun, 6 Aug 2006 15:29:48 -0700, William "Chops" Westfield wrote:
>
>  
>
>>On Aug 6, 2006, at 3:13 PM, Howard Winter wrote:
>>
>>    
>>
>>>a hydraulic accumulator consists of a piston in a vertical
>>>cylinder on top of a column of hydraulic fluid, with a heavy
>>>weight resting on it.
>>>      
>>>
>>Are we still talking about transportation?  "Heavy weight" and
>>"mobile" don't mix very well...
>>    
>>
>
>
>
>  
>
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