Egon nailed it... These machines exert only about 4.3psi of ground pressure. A man walking around is about 5.5-6psi. They've never gotten a machine with a lower ground pressure so these beauties just keep on going...
Wow, so does that lower psi mean it COULD travel over thinner ice than a man could or would the sheer weight have a bearing on the thickness of the ice? /forums/images/graemlins/confused.gif
Weight is sorta independent of psi in this case. I think in this application, compaction or lack of compaction was/is the goal. To stay on top of the snow instead of having to pack it down (probably a few feet) so they could go forward. I don't think they do much thin ice crossing with a machine that weighs around 50tons. (guessing)
If you look close it appears to be one of those small operator fans mounted inside pam. I guess thats for those summer heat spells when it breaks above 0 oF. /forums/images/graemlins/smile.gif
I've got one in my pickup truck(the heater blower hasn't worked for several years). Even cold air, moving across the glass, will keep the window defogged.