The history of the compactor

From the humble towed roller to the modern self-propelled variety, compactors play an unsung but vital role on jobs where cut-to-fill is involved.   BY RICHARD CAMPBELL

Prior to the invention of the earth compactor, filled areas were either compacted by humans and animals (usually horses pulling a heavy roller) or left to stabilise naturally. This was not always an ideal situation as voids left in the fill could subside over time, sometimes with disastrous consequences. Also, it was not always practical to wait several years before the filled land has compressed enough to be used.

The first purpose built earth compactor was designed and manufactured in 1928 by RG LeTourneau Inc, a company whose innovations in the earthmoving industry are legend. This first roller was known as a “sheepsfoot” compactor (after the design of its feet) and consisted of two oscillating welded steel drums with a series of spaced welded rods projecting from it. Although quite heavy in its own right, extra weight could be added to increase compacting effort. This device worked so successfully that other designs soon followed.

Most significant of the new designs, also by LeTourneau, was the “wedgefoot” compactor. Along with its weight and shape of its feet, it asserted a kneading action on the soil, packing it in tightly. The wedgefoot was more effective than the sheepsfoot in breaking up clumps of earth and small rocks.

It wasn’t long before other manufacturers hopped on the bandwagon, and both sheepsfoot and wedgefoot types were sold in abundance by several companies other than LeTourneau, including La Plant-Choate, Wooldridge, Ateco, Baker and Isaacson, to name but a few. Many of these can still be found in operation today, decades after they were first manufactured.

The beauty of these compactors was that they required practically no maintenance and could be towed behind almost anything that had sufficient floatation and drawbar horsepower to pull them.

It wasn’t until the late 1950s that self-propelled compactors appeared on the scene. Among the pioneers in this field were the Rome Plow Co, which built a series of sheepsfoot discs that could be fitted in place of the scraper bowl on job-weary motor scraper tractor units, thereby turning the machine into a self propelled compactor. Rome called this invention the “Roman Wheel”, and they sold quite a few, especially in California.

Other early adaptations included replacing the rear drive wheels on motor scraper tractors such as Euclid FDTs and Caterpillar DW15s and DW20s with either sheepsfoot or wedgefoot drums.

The Hyster company of Portland, Oregon offered a range of such conversions. Properly ballasted, these conversions worked very well but were a little hard on the operator.

The first purpose-built self-propelled compactor was marketed by the Rex company and was known as the Rex-Pactor. Introduced in 1963, it was of an unusual tricycle design but very maneuverable and highly effective. Powered by a GM Detroit Diesel engine with Allison powershift transmission, the initial model Rex 3-30 Pactor weighed around 15 tons in operating trim.

The operator sat sideways so he could keep an eye on comings and goings in the fill and steered the machine hydraulically with a simple tiller control.

In a stroke of genius the machine was also fitted with a leveling blade so the operator could trim up the fill and drift material into low spots if necessary. The blade could also be used to assist machines that had become stuck in the fill.

The compactor had come of age.

Pretty soon other companies were offering their own self-propelled compactors. Competition came from several quarters:

• Hyster introduced their Caterpillar powered model C-445, which was offered for only a few years before being discontinued. This was a very impressive looking beast and was quite heavy, weighing over 22 tons.
• Bomag began a range of self-propelled compactors around 1969, all of wedgefoot or modified wedgefoot design. These machines were well accepted by the contracting community and can still be seen operating both in New Zealand and overseas.
• FWD-Wagner offered a self-propelled compactor that was basically an adaptation of their W-14 scraper tractor. All wheel driven, this machine was a forerunner of the way the industry was ultimately headed.
• Ray-Go began marketing a small machine aimed more at the private contractor segment of the industry. Ray-Go was absorbed by Caterpillar in the 1990s.
• RG LeTourneau introduced their enormous ‘Power Packer’ series of electrically driven machines. These were very large compactors intended for big projects but, by the time LeTourneau had the bugs ironed out of the design, the market for such large machines had softened and sales were very few.
• In 1969 Caterpillar began introducing their own range of self-propelled compactors commencing with the model 825 followed in 1970 by the  model 815. To start with, these machines were not much more than modified 814 and 824 wheel dozers with wedgefoot compaction drums in place of the tyres. Over time, however, they matured into true purpose-built machines available for general earthworks as well as specialized landfill applications.
• Hard on the heels of Caterpillar, Komatsu also began offering a compactor, the WF22A being the first to come on the market.

Today the self-propelled compactor is a sophisticated piece of equipment, designed to quickly bring fills to strict compaction requirements. 

The New Zealand connection.

New Zealand contractors were not slow in recognising the benefits of the compactor. Along with many LeTourneau imports several New Zealand companies manufactured their own versions of the LeTourneau towed sheepsfoot and wedgefoot compactor. Hewco, Pacific, Moore and CWF Hamilton have all produced home-grown compaction equipment worthy of note.

These compactors can still be found around the country putting in a useful days work. However. New Zealand’s isolation and “No.8 wire” ingenuity has also produced some other rare compaction gems and these are offered here in photo form for your enjoyment.