Used Equipment Review: Caterpillar 633C scraper

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  • Earthmovers & Exacavators

A strawberry farm in the granite belt is no match for the tough old Caterpillar 633C scraper that Ron Horner got to witness in action

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Just sitting on the border ranges between Queensland and NSW one will find some unique farming and cropping operations; none more interesting and technically advanced than the Sweet family, who are one of Australia’s leading strawberry runners (plants) suppliers.

Headed up by Wally Sweet and proudly supported by his family, they have continued the dreams of his father who bought the property way back in 1960s. Back then it was a sheep farming operation but over the ensuing years the property has been through many changes to where they now supply one third of Australia’s new strawberry runners to the aspiring strawberry farmers throughout the land.

Now this type of country, although perfect for strawberries, is far from being ideal as to engage in a little bit of clearing, ploughing and sowing. Located in what is commonly known as the granite belt, the area is bound by light to heavy scrub, trees and massive unforgiving numbers of granite rocks.

The family, having a heavy machinery background, were never contemplating sourcing contractors to take a role in clearing and preparing the country for their needs so they continually looked out for suitable used machinery to assist in achieving their end goals.

In an effort to secure an excellent and sustainable water storage facility (or several), the Sweets were in dire needs of several items of earthmoving equipment including dozers, trucks, excavators, graders, tractors with multiple attachments and, of course, scrapers. This brings me to our cover story on the old 1969/70 Caterpillar 633C elevating scraper.

Cat -633C-scraper
Two metre diameter tyres and a blind spot for the operator


One of the first things you will notice is that the 633C Scraper is quite a large machine when you stand beside it. It runs 33x35 tyres both front and rear, however out here on the farm, procurement of used tyres are definitely the go.

At a cost of up to $20k per new Michelin tyre, one would not attempt scrub clearing and risk a stick going through the side wall in one of these, so second hand – and well-used at that – tyres fit the use and hip pocket just nicely. The cubic capacity of the bowl is measured in cubic yards. Determining the size of the scraper is relevant to the volume of the bowl, which in this case is 33 cubic yards when filled.

Identification of Caterpillar equipment is always a combination of numbers and letters, and in the case of a Scraper, one can identify the size – in this case 633C. The ‘6’ is allocated to Caterpillar scrapers, ‘33’ is the cubic capacity of the bowl, and "C" is the model.  

A quick look around the old girl and one can easily see that there is wear and tear at all points of the compass; not to be deterred, as this is not a daily driver, not going to any mine site and definitely not going on contract anywhere in the near or distant future.

The elevator chains are well worn and stretched to the limits as are the 13 hydraulically driven elevator flights now showing signs of welded and plated repairs. The gooseneck between the prime mover and the bowl has been professionally repaired due to severe cracking. These repairs were done in-house at the farm’s fully integrated workshop, filled with all the goodies and the skilled labour to fulfil all of the farm’s mechanical repairs and servicing. This area in between the bowl and the scraper cabin is a ‘no-go zone’ for personnel when the machine is working.

The beauty of the scraper design is that it can turn on a sixpence. The operator can squeeze 90-degree rotation to the left and right very quickly with a flick of the wrist on the steering wheel due to the hydraulic ram steer controls. This is perfectly suited for quick turns or to get out of a bog or some sticky positions requiring diff-lock assistance. Anyone located in this zone when the scraper is operational will be severely injured or killed. Sitting at about 44-feet long, it could almost turn in its own length with a turning circle of 40 feet.

Cat -633C-scraper
Very popular D343T after-cooled engine


Now when these machines were built, the engine was a state-of-the-art Caterpillar D343 turbo after-cooled engine, which went into the production of many of Caterpillar machines and became a very popular favourite amongst earthmovers. Pushing out about that 400hp at 1900rpm, the Cat D343T six-cylinder engine was connected to the  Caterpillar eight-speed semi-automatic transmission with a top speed of about 32mph.

The 633C Scraper runs in at about 40 tonnes empty and, dependent upon the material, would push up to 70 tonnes when fully laden.

Cat -633C-scraper
LHS of dashboard


Once in the cabin, in this case open cab with only an optional extra windscreen sitting between the operator and the elements, you will notice that vision is impaired, restricted or non-existent in some areas of view. The operator sits on a semi-suspension seat located near and above the left wheel with a set of gauges on two panels separated by the steering column.

To the right side of the cabin the operator has very little vision due to the huge exhaust and positioning of the air cleaner located out of the dust, up and high, however when it comes to vision to the bowl Cat has got it sorted with the design of the slightly offset seating arrangement giving the operator a great view of the bowl and the discharge of material and feed.

Controls are quite simple once you get the feel of the movement, side-swaying and power of the Cat: steering wheel central to the seating, foot throttle, brake and diff lock on the floor, eight-speed semi-auto transmission at knee height on the right side forward of the seat.

To the right of the seating and at armpit height were the ejector and elevator control levers. Filling of the bowl with suitable materials could be as quick as 60 seconds for a 33-yard fill … good in anyone’s language, and this is some 50 years ago.

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Cat 633C scraper in action


The old girl may have had a few creaks and groans in her these days but she gets the job done and that’s exactly why the Sweets bought her. Running along the farm access track down to the dam site or borrow pit the mind goes way back to a younger Ronnie and another great era of construction in the 70s and 80s when I ran a couple of scrapers: namely Wabco, International, Cat 633c and I actually owned an old Cat 621J open bowler in another life.

I was never ‘a gun operator’ and had my fair share of close calls but I quickly realised that there were great operators around and I held them in the highest of esteem on the sites. Scraper drivers and D9 and D10 operators were the big guns of the day and one can see why.

Taking into consideration the age, condition and working area of the 633C, it is easy to see why they were and still are so popular. A bit slower on the road, a bit slower through the gears, a bit of slop in the hitch, a bit of wear on the chains, tyres, elevators and a lot of wear on the operator all made for a good afternoon in the sun.

It took a passionate plea for me to get Phil Sweet on the old girl to show us how he does it, and in a flash he tidied up all of the mistakes. Phil is so passionate about the old gear and loves the old scraper and his beloved Cat cable blade D7 dozer (review pending).

When I asked why, he said: "… because they are reliable and we can still get parts for them – it’s that easy."

Cat -633C-scraper
Flights showing wear and tear


There is nothing around that will compete with the efficiency of a fleet of scrapers working the dirt in bulk handling: self-loading of 30 cubic metres in 60 seconds, hauled at a top speed of about 55km/h, dumped and spread in the one movement … it’s awesome to watch but more awesome to be part of.

One thing is for sure: you are going to get dirty and dusty in one of these. So if you don’t have a passion for them, can’t derive any pleasure from the job and can’t handle the pain associated with the hours of being tossed around day after day after day … well this one is not for you.

However, there are blokes out there who have pioneered their way through the ages and laid the groundwork for the younger generations. Suffering ongoing health issues from dust ingestion, crook backs and necks and those legs that just don’t seem to go where you want them once you hit old age, all due to the years of confined seating, those injuries are all forgotten because they would not have it any other way.

Old scraper operators are a dying breed: tough, skilful, cranky (most of ‘em I know), and I’ll bet money on it, every one of them loved their Cat scrapers just like the old 633C I ran today.


1982 Komatsu Dozer

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