MQ PS4030 SAW — CHOOSING PROPER BLADE SIZE
Choosing Proper Blade Size
To select the proper size blade for the job requires an understanding of the cutting capability of your saw and its relationship between engine power, (as reflected in the engine RPM), and the speed (RPM)oftheBladeShaft. ThedieselengineoftheMQPS4030runs at 2800 RPM (full load). If 2800 RPM was a desirable Blade Shaft speed for the average conditions in which you work, we would use thesamesizesheaveontheengineshaftandthebladeshaftmaking the resulting ratio between the two of 1:1. (See figure 8.)
1 : 1 Ratio | 1.4 : 1 Ratio |
2800 (engine RPM) / 2000 (desired BS RPM) = 1.4
This is the ratio 1.4 : 1, which means that for every 1.4 revolutions of the engine, the Blade Shaft only turns once.
Ratios greater than 1 : 1 also have the beneficial effect of increasing thetorqueoftheBladeShaft bythesamefactor(1.4inourexample). The manufacturer advertises the Deutz 2011 Series diesel engine develops 133 ft. lbs. (max) of torque. To find the theoretical Blade Shaft torque of our example saw setup:
133 x 1.4 = 186.2 ft. lbs.
Actualtorqueofthesawwillvarysomewhat. Ingeneral,moretorque means more cutting power.
Figure 8. Blade Shaft Ratios
If,however,foryourcuttingconditions,youneedaBladeShaftspeed slower than the engine speed (and this usually is the case), we then need to INCREASE the ratio between the two speeds by using a larger diameter sheave on the Blade Shaft, which will cause the BladeShafttorunslowerthantheenginespeed. If,forexample,you know from experience that you need a Blade Shaft speed of 2000 RPM for the size of blade you normally use, divide the engine speed RPM by the desired blade speed RPM (refer to the Blade RPM vs. SFPM Chart,Table 7.)
Typically, however, the ratios are not used to design a level of torque; they are used to create optimum blade speed (Blade Shaft RPM) for your application.
The major factors are:
■diameter of blade(s) you commonly use
■cutting conditions
MQ PS4030 SAW • OPERATION MANUAL — REV. #0 (02/29/08) — PAGE 23
