- May 17, 2010
just had to shoot this lil arrow at your ballooonFound this research paper that conducted a stress analysis of a harbor freight 4-1/2" angle grinder. The grinder operates at 11,000 rpms and has a rating of 3/4 of a horsepower. A Rockwell Hardness analysis was conducted on the pinion spiral bevel gear. After a conversion was completed, it was estimated that the pinion gear had Tensile Strength of approximately 106,000 psi. Probably what to expect from other replacement grinder spiral bevel gears. My hunch is that the original equipment gears will be of better quality with the name brand grinders. Dewalt makes angle grinders with ratings of 5.3hp.
Considering that the Honda GHX50 output is approximately 2.1 hp and that approximately 1 hp will be split between the front and rear drives, I think the grinder spiral bevel gears will be O.K. Also consider that the gears won't be spinning at 11,000 rpms like the angle grinder.
chains and gears power rating INCREASES with speed. gears for very low speeds have to be a lot stronger than high speed ones. to do with strength of individual teeth, torque requirements, and that transmitted power is a function of rpm and torque.
say it takes a newton of force to bust 10mm of steel. you could either run a tooth thats 11mm thick with one newton and be safe, or spread the load over 11 teeth, all of 1mm... the finer teeth, of course, have to pass each other in the same time as the single fat tooth. each one will also only be loaded to 1/11 of a newton.
now, if you produced 11 newtons of torque in every revolution... and had 11 fat teeth, or 121 fine teeth, all would be well.
double the speed, but retain the same torque over time (power) and the load on each tooth is HALVED.
or , retain the initial tooth loading, and DOUBLE the power rating!
fine teeth make less noise.
cutting 121 teeth is going to cost a lot more than 11 teeth and requires more accuracy... noise versus cost versus speed versus load.
yeah yeah, over technical lecture.
all i can say in favour, is... i havent blown the gears on a grinder yet...and in my work, we replace the brushes every month, a grinder lasts 6 months, tops.
gunna be fun machining the crown gear! they are HARD!