There has been some considerable debate over who exactly came up with the elevating scraper concept, Johnson or Hancock, as both companies were in Lubbock, Texas. By Richard Campbell.
It is generally accepted that it was Hancock who produced the first practical elevating scraper, (and supplying scraper bowls to John Deere as early as 1957).
Caterpillar, who had been cooperating jointly with Johnson since 1964, had acquired the Johnson company outright by 1971.
Caterpillar’s model J621 elevating scraper was a logical development of the company’s previous model J619, which had been introduced in early 1964 and was its first elevating scraper.
As an elevating scraper, the J619 held 20 cubic yards and was powered by a 250-flywheel horsepower Caterpillar diesel.
The J619 was moderately successful but was a victim of rapidly increasing technology in the mid-1960s. As Caterpillar sought to improve the design, some models with unusual builds were dispensed with. For instance, the 619C, which was the only Caterpillar motor scraper to use the four-cylinder D340 engine, was discontinued in mid-1965, so a new prime mover had to be found.
The logical choice was the company’s new 621 tractor.
When the J621 elevator appeared in late 1965, it was powered with the new model D336TA V8 turbocharged and aftercooled diesel engine rated at 300-flywheel horsepower, and considerably more powerful than the previous model J619.
Unusual in being a 60° V8 engine, the D337TA engine was only fitted to one other Caterpillar machine, the early model 980-wheel loader.
Unfortunately it was not the most reliable diesel engine that they had ever produced and made the most horrendous sound during start up, with some users fearing it was about to throw a connecting rod through the engine block!
This noise, according to Caterpillar, was perfectly normal!
However, most long-term users of the J621, when it came to engine rebuild time, repowered the machine with a much more ‘user friendly’ Caterpillar 3306T engine. And I know of at least one machine fitted with a Detroit Diesel 8V-71.
Early production models were fitted with a Caterpillar eight-speed powershift transmission, however, late production machines had Caterpillar’s eight-speed semi-automatic transmission (as fitted to other Cat motor scrapers) as standard equipment.
This allowed greater parts commonality for users.
Caterpillar’s Cushion Hitch was never offered for use with the J621 elevating scraper, with the machine using the standard Caterpillar triangular hitch of the day with two steering cylinders mounted high on the gooseneck.
These allowed 90° steering to either side of centre unless the machine was fitted with a roll overprotective structure (ROPS), which limited the steering angle to the left to about 70° as the structure interfered with the scraper’s draft arms on that side and prevented full steering lock.
The operator was provided with a deeply cushioned seat that featured a hydraulic snubber.
During the colder months, a sliding panel on the left side of the engine cover could be opened to provide heat to the operator’s legs.
While a windscreen was fitted as standard, Caterpillar never offered a factory cab option for the J621, so any machines you see that are still operating, and have a cab fitted, be rest assured that it is an aftermarket item.
Operating controls were grouped together to the operators’ right hand side and were easily accessible as was the transmission shifter.
The Johnson manufactured bowl held 21.5 cubic yards; a slight increase over the previous J619, and was all-hydraulically operated.
Featuring 18 flights measuring 6’ 6” in length, it was driven by a two speed reversible hydraulic motor.
During ejection, which was a two-stage process, the entire front floor including the cutting edge, retracted back on outside suspended rollers to about halfway along the bowls length, allowing the load to drop out, then the ejector bulldozed the remainder of the load out through the now cavernous opening, the retracted cutting edge acting as a strike off or levelling plate.
Upon returning to the cut position the sliding floor was held in place by a hydraulic lock.
Four teeth could be fitted to the cutting edge to aid in breaking up and loading hard or cohesive soils.
Standard tire equipment for a J621 were 29.5×29’s with a 22-ply rating.
Into service
The J621 proved to be a reasonably popular machine for Caterpillar, (elevating scrapers becoming more popular during the late 1960s), and remained in production until 1972, when it was replaced by a further improved model, the 623.
The New Zealand Caterpillar dealer of the day, Gough, Gough & Hamer, imported nine J621 elevating scrapers during the time span the machine was in production.
Most of these original deliveries went to North Island domiciled customers although there were also a couple which went to the South Island and were predominantly used in housing subdivisions and road construction work.
Contemporaries of the Caterpillar J621 included the Michigan 210H, Allis-Chalmers TS-260E and the Wabco 222F.
For the model collector
Regrettably, no model manufacturers have seen fit to produce a model of the Caterpillar J621 in any scale, and scratch building an example (using the old NZG Cat 621 open bowl scraper as a basis) would not be a job for the faint hearted!
As there are currently several boutique manufacturers producing models of out-of-date equipment in resin, it is to be hoped that one of them will realise this oversight in the model elevating scraper market and produce a model of the J621, and hopefully its predecessor, the J619.