Dear Mr. Nicky,

It is usual practice that one should always check for mechanical rating of gearbox as well as thermal rating of gear box. The slewing gearbox used in bucket wheel on boom reclaimer or stacker-cum reclaimer should also be checked on the same guidelines. The slewing drive will be operating continuously, few hours at a stretch, and it will be also subjected to very frequent reversal operation. That means the drive will start, stop and again start very frequently as a continuous operation. Also, it will be subjected to high starting torque etc. Therefore, gearbox should be selected to suit this drive duty, incorporating the recommendation from gearbox manufacturer who only will have the intrinsic knowledge about the design of their gearbox.

Regards,

Ishwar G Mulani.

Author of Book : Engineering Science and Application Design for Belt Conveyors.

Author of Book : Belt Feeder Design and Hopper Bin Silo

Advisor / Consultant for Bulk Material Handling System & Issues.

Email : parimul@pn2.vsnl.net.in

Tel.: 0091 (0)20 25882916 ■

you have not really answered a lot of questions with your question.

Is the slewing drive gear a spur or worm gear drive?

Is the gearbox drive hydraulic or electric?

what are the gear ratios if any?

If the gearbox drive is hydraulic:

1.The main pump can be of any type.

2. Be sure there is a case drain line draining

the oil pressure away from the shaft seal of the pumps or pumps-this gaurantees the seal will not be blown out and maintains a maximum pressure of 15 psi against the seal and keeps it flushed out and clean to reduce wear of the driven shaft of the pump.

3. If the motor you select has a case drain be sure it is connected and drains back to the oil tank for the reasons stated above. you will know if it has a case drain if you see a pipe plug in the neck of the gear hydraulic motor or pump

4. The drive motor for the gearbox should be a radial piston motor-maximum torque with little power used-but that is not to say a gear or vane motor cannot be used in its place.

5. Hydraulic drives are easily done as a central power pack for hydraulic power for the stacker functions uncomplicates things greatly as each function can powered by the use of pilot operated hydraulics and anadequately sized powerpack eliminating a lot of extra wiring and controls for the stacker reclaimer.

By keeping the system as dumb and simple as possible you will icrease reliability and availability of the unit.

6. Lastly and just as important, the bearing surface of the slewing gear should be oiled with an oil metering system to reduce friction, reduce torque loads and increase bearing surface life. ■

If you intend revving up the boom then thermal capacity of the gearbox is a minor issue. You say improve performance; not reliability. Will the boom structure take the extra inertial loads? Will the slew motor brakes take the loads? Will the bucket wheel have to be revved up to suit? What about the slewing gear tooth loads. A right can of worms here.

If you take the trouble to pore through the machine documentation you will get some idea of the possibilities.

When I used to prepare machine specifications & manuals in my younger days I somehow suspected that nobody was ever going to read the voluminous documentation that accompanied the machines. My suspicions are constantly vindicated. ■