After years of planning and testing in secrecy, Caterpillar finally unveiled its first hydraulic excavator a fair bit later than a lot of the competition. By Richard Campbell
Caterpillar’s first hydraulic excavator, the model 225, was launched in 1972 after a lengthy testing period.
Caterpillar was quite a late entrant into the hydraulic excavator market, with many of its homegrown competitors, notably Koehring, Link-Belt and Warner & Swasey, having already had machines in the marketplace for a number of years. There was also the threat from foreign imported machines, especially from Japan, which included the likes of Hitachi, Kato and Komatsu. Bucyrus-Erie, a US manufacturer of large cable excavators and draglines had already entered into a joint venture with Komatsu to develop hydraulic excavators in the mid 60s.
Caterpillar wasn’t about to take all this lying down and initial studies of layout, potential powerplants and machine configurations were begun in great secrecy during 1968. Testing of the first prototypes was conducted at the Arizona proving grounds during 1970.
The wholly Caterpillar designed machine was put into production as the 51U series during 1972 and also manufactured by Caterpillar at its plants in Brazil (20S series) and Belgium (76U series).
During its fourth year of production some changes were made to the operator’s cab to make it a little more user friendly. These modifications included redesign and repositioning of the two operating joysticks and a shape revision to the cab from a ‘V’ front to a straight taper which deleted the lower front glass in favour of a single sheet. This slid on rollers and rails, and could be stored above the operator’s head.
Initially these changes to the glassware featured a new product called “Lexan” which Cat had high hopes for and it was fitted to all the 225s windows except those in the door.
Lexan was a polycarbonate plastic with extremely high impact resistance and was cheaper to produce than the toughened safety glass from which the previous windows had been manufactured. However Lexan did not live up to expectation, scratching relatively easily and being particularly susceptible to UV radiation, which caused it to “yellow” quite rapidly
Needless to say the Lexan equipped 225s were not in production very long before Caterpillar reverted to toughened safety glass.
Following some improvements and a horsepower increase a 225B came along in 1986 followed by the short lived model 225D around 1989.
However, the original design had now reached the peak of its development potential and was replaced in 1990 by the even shorter lived Caterpillar-Mitsubishi joint venture model E240.
Today’s modern equivalent of the 225 is the Caterpillar 320D.
The Caterpillar 225 described
The heart of the Cat 225 was a Caterpillar model 3208 direct injection V8 diesel rated at 125 horsepower.
Derived from the 1160 series of truck engines originally developed for Ford Motor Co. and used extensively in its “Louisville” range of medium trucks, the 3208 featured a very low weight to horsepower ratio and two-ring pistons.
Early industrial models of the 1160 destined for earthmoving applications were known as the model 3160 and did not have a very favourable reputation due to the fact that they did not have replaceable cylinder liners, making the cylinder block virtually a throw away item. This was addressed in the 3208 by cylinder liners that could be replaced.
The 3208 engine was also used in the Caterpillar 613 elevating scraper.
Caterpillar chose a two-section variable displacement hydraulic pump with load proportioning for powering all the major machine functions. Flow rate of these units was in the order of 56 gallons per minute.
A further double section pump assembly was also provided for travel control and pilot pressure functions.
The entire engine and pump assembly plus a myriad of pipes was housed in a very squared off carbody, with two access doors on each side and a further two at the back to allow servicing the diesel engine. All the roof panels of the hood could also be opened for access to the machine’s innards.
The undercarriage was all by Caterpillar and featured 22” triple grouser shoes as standard. Two speed travel motors allowed the 225 to trundle along at approximately two-and-a-half miles an hour.
A feature of the travel motors was that disc brakes within the motors applied automatically when the travel controls returned to neutral or the engine was shut down.
Operators were well looked after with the cab being very spacious with good visibility and noise control. All the controls fell readily to hand and were easily manipulated. Early machines had a fairly basic instrument layout but later models incorporated system monitoring and a revision of the instrument panel which made it much easier to keep an eye on machine functions.
Working tools
Customers could choose between a single piece gooseneck boom or the European-style two piece boom. A great variety of what Cat called ‘sticks’ but what are more commonly known in this part of the world as arms or dippers were also available in various lengths, depending on the task at hand.
Standard bucket of the 225 was one cubic yard although, of course, many other options could be fitted depending on machine application.
Early 225s were not equipped with extra piping or valves to accept powered attachments such as hammers or rotators. This was rectified on later machines, which were far more flexible in the type of extras that could be accommodated.
A New Zealand connection
New Zealand was one of the first countries in the world to receive the 225 and local Caterpillar dealer Gough, Gough & Hamer imported approximately 50 examples. There were also some private imports.
Users included Warren Fowler, Green & McCahill, Lendich Construction and McConnell-Dowell, all of whom had fleets of the excavators.
A great many of them were used in the construction of the New Plymouth to Auckland gas pipeline during the mid 1970s.
Many working examples are still out there earning a dollar.
For the die-cast model collector
Examples of the Caterpillar 225 excavator have been manufactured in 1:50th scale by Winross and Joal. Both are generic Caterpillar 225s and neither are particularly well detailed with the Winross model being the older of the two.
It has also been issued as the larger 235.
The Joal model, which features the optional two-piece boom, is still generally available and reasonably priced while the Winross model is found only on eBay and usually fetches ridiculous prices despite its poor detail and advancing age.
At the moment, however, they are still the only game in town.
Brief specifications – Caterpillar 225 excavator (mid production)
Engine: Caterpillar 3208, V-8 direct injection, naturally aspirated diesel rated at 135 flywheel horsepower at 2000 rpm
Pumps: Caterpillar 2-section, variable displacement
Travel: Variable, hydrostatic
Speed: Up to 2.5 mph
Track Gauge: 106”
Std.Track Shoe: 22” (many options)
Length: 32’ 3”
Width: 10’ 3” (on std.22” shoes)
Height: 10’ 7”
Bucket Capacity: 1 cubic yard (many options available)
Max.Dig.Depth: Up to 23 feet
Operating Weight: 25 tons (standard fit out)