To ensure smooth, trouble free operation of the auxiliary hydraulic systems in its cold planers, Roadtec uses overhung load adapters from Zero-Max.
Repaving asphalt streets and highways requires heavy equipmentincluding cold planers, which cut 2.5m wide by 300mm deep swathsin old asphalt surfaces in order to remove them. These coldplaner systems work at speeds up to 125cm/min cutting,granulating and conveying the loose asphalt into waiting trucksfor recycling.
By necessity, the power transmission systems inthese cold planers are ruggedly designed to handle large amountsof asphalt and to operate for long periods without service ormaintenance.
Roadtec, An Astec Company, is a world leadingmanufacturer of pavement placement equipment for over 30 years.Used for asphalt removal, its cold planers are designed toprovide the optimum balance between horsepower, production andmanoeuvrability.
These are versatile machines capable of cuttingdepths to 30cm and widths from 0.2 to 2.5m.
They also provideside-cutting operations and have bidirectional operationcapabilities to achieve down cutting in the reverse direction oftravel.
Roadtec's largest cold planer, the RX 50B, operateson three D-4 size tracks providing a 2.5m cutting radius withcrab steer, front-track steer and rear-track steer.
It has a twostage covered 86.4cm-wide front load-out conveyor with 50-degreeswing to either side providing high volume loading capacity.Power from the main shaft of the 600HP Caterpillar diesel enginetravels into a hydraulic clutch and then to the grinding drum bybelt drive.
A second pump on the same shaft provides thehydraulics for propulsion.
To ensure smooth, trouble freeoperation of the auxiliary hydraulic systems in these coldplaners, two overhung load adapters (OHLAs) from Zero-Max areemployed, one mounted on each side of the engine.
The larger OHLA(800 series) drives the pump that provides hydraulic pressure tooperate the components that move the ground asphalt to theconveyor.
The smaller OHLA (600 series) drives a pump thatprovides hydraulic pressure for other system operations such assteering and discharge conveyors.
'Without the overhung loadadapters, too much stress was transmitted to the pump'sbearings which could result in premature and costly pumpfailure', reports Chris McSharry, Design Engineer forRoadtec.
'We'd heard about the overhung load adaptersand did a bearing life scenario for our system usingZero-Max's estimated working life formula from their onlinecatalogue.
The numbers looked good, plus we liked the idea ofusing a proven off-the-shelf module rather than trying to designa bearing support setup or our own from scratch, which would havebeen more expensive and time consuming'.
The drive setupMcSharry and the Roadtec engineers devised positions the OHLAunits at 180 degrees from each other.
This balances the forceapplied to the front of the engine's crankshaft.
The model600 has two V-belts on one pulley connecting it from the engine,while the model 800 has three V-belts on one pulley connecting itto the engine.
By choosing just the OHLA size needed to do thejob, only essential space and weight was used in the enginecompartment.
The OHLA 600 used in Roadtec's system has anSAE-B face mount and weighs 13.5kg, and the 800 has an SAE-C facemount and weighs 25kg.
Both sizes feature rugged housings madefrom 25,000lb/in2 tensile cast iron with shafts of 130,000lb/in2stress-proof steel.
Both have heavy-duty tapered roller bearingsand operate the Roadtec system at a 1-to-1 ratio at speeds up to2100rev/min.
'The OHLAs give us a solid, permanent mountingsurface, which aids in the overall stability of the system',reported McSharry.
'By eliminating the stress and overhungloading, both the pump motor and bearings perform nicely withoutany threat of failure for either.
The entire drive system runsfreer with the OHLAs, and with less power used.
These coldplaners put out a lot of power so the added stability from theOHLAs really promotes a smoother operating system'.
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