Have You Got Enough Torque?

The most important parameter in rock cutting with a diamond tipped rocksaw is speed of the blade. Ideally, the speed of the diamond tip as it scrapes the rock should be 40-50m/s for efficient cutting.

The maximum power that is available is, theoretically, the power of the diesel engine in the excavator. In reality, it is much less, depending on the efficiency of the power transfer system all the way from the engine to the rock. A 24t excavator typically has about 140KW engine and let's assume we have a 2.5m diamond blade on our saw.

If the efficiency of the system right up to the blade is 80% (a very optimistic scenario!), than the diamond blade power is ca 120kW. This power is the product of speed and torque. This means that the torque we end up with for a properly designed rocksaw is:

 T = P x D / 100 = 3 KNm

In all truth, when all the real world constraints are taken in consideration, we are unlikely to get more than some 2.4 KNm. This torque, however, is very difficult to maintain on the edge of a 2.5m wheel from a 24t excavator. Excavators are not made for fine control. And so they keep stalling the blade - an apparent lack of torque.

The only way most manufacturers see to improve the situation is to increase the torque and that is only possible by sacrificing cutting speed, i.e. cutting productivity.