Yeah , the Echo models you provide are the most economical & performance for the dollar . Although not the proper tool for the application , at least the most cost effective lmao . P.S. a carbide tooth chain or "Mount St. Helen" style chain would survive the task best " not so sure about the bar or roller tip which are not designed for continuous dirt intrusion !
Excellent summary Bob , actually any Construction cut off saw with an appropriate abrasive carbide cutting wheel would be much more efficient & safe for such work , that routinely are used on demolition & fire rescue teams . Although , actually reciprocating saws with an appropriate blades (teeth per inch) are normally used for such tasks also by competent demolition & construction crews . Not sure the op qualifies as either though ?
"No chainsaw will work to cut roots buried in the ground, the chain will be blunt in seconds."
Reciprocators are good for many roots, but for anything larger than around 3 inches the power draw from the batteries is too much for them or their motors cannot handle it. Also, and this has just been my experience, recirocators go through their batteries rather quickly when cutting anything harder to slice than pipe.
So , you intend to intentionally damage the chain & bar of the chainsaw , not to mention potentionally injure yourself or someone else by using a chainsaw improperly . However , do not have the resources to purchase a few xtra 20 volt , 40 volt or 60 volt or even 80 volt batteries for a more appropriate reciprocating saw or construction / demolition cut off saw along , with perhaps 4 or 6 xtra blades ? P.S. To answer you original question the 450 Rancher home owner grade saw is not what failed , the bar & chain designed to cut wood not gravel , rocks or sand is what potentionally fouled & eventually would have caused the internal drive mechanizium to become contaminated & also fail . The torgue converter that you refer to is more commonly & correctly called a " clutch " . Even much more expensive and powerful world class saws would have been damaged by such improper usage . Numerous qualified & experienced saw users refrain from cutting downed trees for the same reason , dirt or sand & gravel contaminated bark will destroy a chain & bar very easily . Only when a necessity , will they carefully attempt such cutting activities & recognize the potential for damage to equipment or personal injury !
Are you aware of the kickback positions of a saw bar ? If not , enlighten yourself pdq. Your video of cutting with the Kolbalt is an accident waiting to happen friend !