Where's The Mark IV?
Heil's "Mid-Range" Rear Loader
"Where's the new Mark IV?" asked a 1972 Heil advertisement. "It's making tracks to Minneapolis" was the reply, as the new model would be showcased at the American Public Works Association Expo '72 in that city. Press releases of the new model were made as early as June, but it is unknown if they were actually ready for delivery at that time. The reason for the Mark IV being released out of sequence is fairly clear; the dire need for a bulk rear loader to compete with the Leach 2-R had necessitated that Heil put the Mark V into production first (in late 1971) even though both models were derived from the same patent. When the Mark IV arrived, it was smaller than its big brother, with a 2-yard hopper and a shorter body height. It was clearly developed as replacement for the Mark III, although the latter would remain in the lineup for several more years. In the meantime, Heil became the first manufacturer to offer three distinctly different rear loaders, for residential (Mark III), commercial (Mark IV) and industrial (Mark V).
Although related to the bigger Heil, the Mark IV had some major differences. It shared the telescopic slide packer with the Mark V, but instead of swing-links stabilizing the lower end, the Mark IV had sidewall tracks with slide blocks. The blade was connected to the slide blocks through shafts which (like the Mark V) were offset in the front of the panel, resulting in the same elliptical movement of the packer through the tailgate. A pair of 4.5" x 27" cylinders powered the slide movement, while 3.5" x 21" cylinders operated the blade (considerably shorter than the 34" stroke of the Mark V). The Mark IV and was built from the very beginning with Heil's new vertically-ribbed Duo-Press body. This new body construction would be adopted by the Mark III, Mark V and front loader the following year. Body capacities ranged from 16-25 cubic yards, and were shared with the Mark III. Body height was six to twelve inches shorter that the Mark V (depending on size), resulting in a much lower profile.
Electro-hydraulic packer controls were retained, but like the Mark V got optional manual controls by 1977. For smaller containers, a blade-cable container lift was available, as well as the arm-type container hoist (from the Mark III). Roll-bar hoists joined the option sheet at the end of the 1970s. For containers up to 10-cubic yards, there was a version of the 8,000 pound overhead hydraulic winch. The new mid-range Mark gave Heil the widest rear loader lineup in the industry, but would ultimately replace the Mark III as the entry-level rear loader. A seemingly un-spectacular workhorse, the Mark IV would turn out to be Heil's packer for the future, and has been a global best-seller. It has only recently ceased production in the USA and Europe, after nearly four decades of service.
MARK IV PACKER BLADE AND SLIDE
The 3-piece assembly includes packer blade (1), outer slide (10), inner slide (14), packer blade cylinder (11), slide cylinder (13), slide block and pin (35,33), upper hinge pin (15), and bolt-on slide wear plate (20)
The Mark IV used slide blocks and tracks instead of links to stabilize the telescopic slide
16-cubic yard Mark IV with arm-type container hoist system
Interior view of the Mark IV body showing the front the telescopic slide (slide out).
Note the wear marks on the hopper wall from the eccentric action of the pivoting slide
20-cubic yard Mark IV with chain-cable container hoist, powered by movement of the packer slide
VIDEO: 1977 GMC with 18-cubic yard Heil Mark IV
Walk around and body/packer demonstration courtesy of TCS
(Note: This truck has been sold)
Vintage Mark IV on an International Cargostar, still owned by Star Disposal of Jasper, Oregon
Early Mark IV 20-cubic yard
Early models can be identified by heavy reinforcement of the sweep panel, similar to the Mark V
