Used equipment review: Cat 637 scraper
RON HORNER climbs into the cab of a Caterpillar 637 scraper and finds that having two working in tandem in a push-pull operation is still the most efficient method of moving dirt.
Danny Hope of Hope Civil operates out of Munruben in South East Queensland, and has a number of scrapers, graders and excavators available for work throughout Queensland and New South Wales.
The late-1970s and ’80s 637Ds and 637Es are good rigs, he says, and are built to last and be rebuilt.
"Do you know, Ronnie," he says, "I can still go into Caterpillar and buy any part I require to keep these old girls going? I maintain them to the highest level at all times."
When I ask him about the costs of running such equipment he replies, "Well … disregarding fuel and labour costs, tyres would have to be a big cost to keep them running. I have spent $18,000 on one single Michelin tyre for these old girls but then again spending $10,000 on a scraper is akin to spending $200 on your family car for a service."
Danny goes on to say that work for these big girls has been patchy for a few years as the number of flatter, larger parcels of land suitable for subdivisions has diminished in many areas … the steeper the country the more the clients look for excavators and dump trucks to complete the bulk earthworks jobs.
In the cab
As you claw your way up into the cabin of the Cat 637D scraper you could be excused for becoming nauseous and nervous. The cabin sits several metres off the ground and has a slightly skewed seating arrangement so the operator can view both the front and the rear of the machine and keep an eye on how the material is being loaded and discharged from the trailing bowl.
On the right side of the operator’s panel beside the seat are the controls used for dropping the bowl for loading and elevating it for travel and discharging.
The 55 km/h, eight-forward-speed (and one reverse) power-shift transmission stick is within easy reach of the operator and the steering wheel can be controlled by the operator’s legs if need be.
It’s all power steering; with a quick flick of the wrist you can get the nose of that machine whipping from one side to the other in quick fashion.
Gauges are easily viewed from the operator’s seat and the throttle, brake and tow hitch controls are all located on the floor. The roar of the big Cat engines front and back just make the hair on your arms stand on end!
It’s been such a long time since I felt and heard power like this … sadly, and for some unknown reason, I feel l am witnessing the end of a magnificent era in earthmoving.
On the job
These 637s are twin-engine, or tandem powered, push-pull scrapers and can be very efficient on short hauls where the cut and fill areas are close together and have sufficient length to fill the bowls of both scrapers.
One of the two big Cat engines drives the front wheels and the other drives the rear wheels, combining to develop up to 750 horsepower (560kW). With the lead scraper loading and the rear scraper pushing there is the combined power of an incredible 1500 horses (far from the one-horsepower model developed over 100 years ago).
Once the leading scraper is loaded it takes over assisting the trailing scraper to fill by using a hitch joining the two machines. Once both scrapers are filled, the hitch is disconnected and they make their way to the fill zone.
After watching Danny’s crew work like a well-oiled machine I’m itching to give it a go for myself.
The big cat engines roar into action, I lift the bowl off the ground, slap into gear, throttle down and immediately the cabin lurches and sways as I get the power steering under control. I’m off!
A quick look confirms that I am closely followed by my tandem mate for the day in the other 637.
As we approach the borrow pit I take a line which has already been pre-ripped by a Komatsu D155A dozer. The pit is a good, long one and there’s plenty of room for both 637s to load up.
As I have taken the lead position it is imperative that I don’t take the wrong line or dig too deep or too shallow. I need to squeeze the power into the big girl so as not to spin the drive wheels (hitting a sharp rock with spinning tyres will only end in $18,000 worth of grief).
As I begin filling the bowl I can adjust the amount of material by the positioning of the apron.
I feel my mate in the second 637 give me a push up the bum as he immediately converts the 750hp (560kW) of my scraper into 1,500 horsepower (1,120kW) with both scrapers combined.
With the bowl filled in under a minute I feel the tugging on my rear as I feel the scrapers combine together to get the second one filled, again in under a minute.
The ‘umbilical cord’ is detached and we’re on our way to the fill zone where we are met with a spotter, a Cat 825 compactor, a water truck and a grader.
I take the line of discharge, the spotter gives me the thumbs up, the apron is up and the ejector engaged. This part of the operation has to be done at speed and, if done correctly, caps off a very efficient operation. A good scraper operator will make the compactor’s job much easier.
As I roll and heave and get jolted in the seat, I wheel the big girl’s nose out of the fill and back towards the haul road to the borrow pit. The whine of the transmission and the roar of the big Cat engines sound fantastic as we gear up towards top speed. We won’t hit the 55 km/h top speed but we will hit the 8th gear before hit the borrow pit and start the process over again.
So why use scrapers?
Having twin-engine scrapers working in tandem in a push-pull operation is the most efficient method of moving dirt providing you have a longer cut, the haul route is reasonably short and access is kept in good condition.
The running costs of these massive earthmovers don’t come cheap — they have a 1200-litre fuel tank and use an average of 800 litres of fuel in a 10-hour shift — but the 637s can load up in one minute for a full-capacity load of 26 cubic metres heaped or almost 19 cubic metres solid in the bowl.
Although scrapers in this configuration do not require a dozer to push-fill them it is advisable to have a dozer rip rock or any tighter material ahead of the scrapers to keep the pit clean and the material plentiful and easy to load.
Discharging of material is extremely efficient as the scrapers can drop the material from the bottom of the bowls at speed to a depth of up to 480mm. This enables the compactor to trim, level and compact the material at optimum speed, creating a very efficient work environment.
Hauling up to 90 tonnes in overall weight, these big rigs just chew up the haul roads. From pit to pad it is advisable to have a grader to trim the haul road for greater speed and efficiency. However, scrapers do have the ability to trim the haul roads on the return journey to pit if and when required.
Although they’re fitted with a good cushion hitch to minimise the rough conditions, bad haul road conditions can cause the operators of these rigs a great deal of discomfort and pain which, over time, can develop into a workplace injury..
Also, they create so much dust that it is advisable to use a water truck, or several, on these projects.
The bottom line
Although there are fewer suburban bulk earthworks projects throughout Australia and contractors are moving to dump trucks and excavators, scrapers are still the most efficient method of moving bulk dirt.
Quick loading times, high travel speeds and the ability to load and dump on the run yield fast cycle times, allowing these Caterpillar 637 scrapers to consistently deliver high productivity at the lowest cost per tonne.
Danny Hope has kept these scrapers in really good nick. It’s quite apparent that he ‘walks the walk’ as I can’t find anything markedly out of place or in need of repair.
They run well, there are no oil leaks, the tranny and drive line looks and performs perfectly, the machines are well presented, the tyres are good and they’re still earning good money. Not bad for 1978/80 models!
As Danny says, the Cat 637 scrapers are "built to be rebuilt, and built to last". I must say I have to agree with him on this one.
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