On Thu, 15 Oct 2009 16:29:45 -0600, NOPE9 wrote:

>Among motor types, which give the best power ( energy per unit of  
>time )  to weight ratio ?

Hydraulic. 

I did some work on hydraulic power packs recently. 4.5l turbocharged diesel
with a hydraulic gear pump bolted on the end. Gear pumps and motors are
interchangeable. The pump was about 8 inches cube. 

Heavy because it is mostly a lump of steel, I don't think anything
electrical would come close on a continuous rating without some serious add
on cooling. 

I sniffed around looking for gear motors but hard to find weight and power
ratings. Found one something like 37kW continuous for 10kg, and I don't
think it was a particularly high performance one. 


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