Michigan motor scrapers are probably unfamiliar to a lot of earthmovers these days, but they occupy a place in the development of this type of machine, especially when it comes to elevating scrapers. By Richard Campbell.
Unlike a lot of other companies who gained their motor scraper technology by acquisition of other builders, the Michigan Division of Clark Equipment decided to ‘go it alone’, and build a range of open bowl motor scrapers by itself.
Michigan’s first motor scraper was introduced in 1957 and the initial offerings were the model 110 (10 cubic yards struck), model 210 (15 cubic yards struck) and model 310 (24 cubic yards struck).
Subsequently, a very large scraper was offered for a short time, the model 410, but this was not considered a success and suffered from many teething problems that were never satisfactorily addressed before the type was discontinued with less than 30 units being manufactured.
In later years, Clark-Michigan would buy the Hancock company, a pioneer in the design and development of elevating scrapers, and ironically, the one type of scraper with which Clark-Michigan would have its greatest successes.
However, our subject for this month is the Michigan 210, a 15 cubic yard open bowl scraper with a very clean and modern design for 1957.
Clark-Michigan offered a choice of engines for the model 210 depending on the customers preference – a 290 flywheel horsepower General Motors 8V-71 naturally aspirated V8 diesel, or a 262 flywheel horsepower Cummins NTO-6-CI 6-cylinder turbodiesel.
Clark chose one of its own powershift transmissions for the model 210, a 4-speed powershift type which was mounted at the tail end of the tractor unit’s chassis and driven by an extension shaft which passed through the hitch, quite a novel arrangement for the time.
A drop box extended down from the transmission and fed transmission output directly into the machine’s differential via a short drive shaft.
This arrangement was very accessible for servicing, and the entire transmission/drive train and hub-mounted planetary axles package was manufactured by Clark.
In top gear, the Michigan 210 could zip along at almost 30 mph.
The whole general layout of the model 210 was logical and well thought out.
The machine’s braking system was air operated and consisted of conventional expanding shoe type brakes on all four wheels.
Tyre recommendations were 26.5×29 22-ply E3 earthmover type, but other types could be had from the factory on special order.
One area in which Clark-Michigan copied a competitor’s idea was the bowl raise/lower and apron hydraulics, which were operated by single acting hydraulic cylinders with levers and linkage (or a cable in the aprons case).
These closely followed a Euclid design but were a little lighter in construction, being manufactured from pressed steel plate as opposed to Euclid’s use of castings in critical stress areas.
This minimalist philosophy followed on to the hitch assembly which was also a fabrication and not a casting.
One area where Clark-Michigan did deviate from Euclid design was the ejector, which was of conventional dozer design with a double acting hydraulic cylinder powering in and out as opposed to Euclid’s roll out type floor with a single acting cylinder (the floor being returned to loading position by gravity).
The bowl held 15 cubic yards struck and 20 cubic yards heaped, a useful load for both large and smaller jobs.
The Michigan 210 used twin, double-acting hydraulic cylinders for steering which gave the machine 90-degree turns to either side of center.
Twin steering cylinders were mounted low down on the hitch (as opposed to other manufacturers machines) and were a little harder to get at for servicing, but did keep the weight down low for added stability.
The 210-H elevator.
In 1965, Clark-Michigan introduced an elevating scraper version of its model 210 with a bowl manufactured by Hancock of Lubbock, Texas, the combination being known as the Michigan model 210-H.
The 210-H was designed to self-load 23 cubic yards.
A larger tyre was required to support the extra payload and provide adequate traction for loading, so the 26.5×29 tyres were replaced by 29.5×29 34-ply E2 or E3 types.
Michigan offered an upgraded version of the model 210-H a couple of years before production ceased entirely known as the model 210-HB but the type was never really manufactured in any great quantity.
Clark subsequently bought out Hancock in 1966 and ironically, it was with the Hancock elevating scraper that Clark had the most success in the motor scraper industry, offering a raft of different models until ceasing production entirely in 1981.
Michigan in New Zealand.
Michigan scrapers were not a common sight on New Zealand construction sites and the author can find no trace of any model 210s being imported, either conventional or elevating types.
There were Michigan scrapers imported, but these were all the later (Hancock designed) elevating type, namely the models 110-11, 110HT, and 110-15.
For the model collector.
A fairly grim outlook here as the only known model of a Michigan 210 scraper to date was made by Mercury Toys of Italy to 1:130 scale.
The model is crude and way out of scale to place in most collections of earthmoving equipment.
Mercury went out of business in 1978 so not only is the model rare these days, it is also expensive!
A “sand-pit” model of the Michigan 210H with Hancock elevating scraper bowl was offered by Nylint Toys in the USA, but this is more of a curio rather than a collector’s piece.
Brief Specifications Michigan 210
Engine: Cummins NTO-6-CI, 6-cylinder, turbocharged inline diesel rated at 262 flywheel horsepower at 2100 rpm. or General Motors 8V-71, naturally aspirated V8 diesel rated at 290 flywheel horsepower at 2100 rpm.
Transmission: Clark 4-speed powershift with integral torque converter
Top speed: 29 mph
Brakes: Air operated expanding shoe type on all wheels
Standard tyre: 26.5 x 29 22-ply E-3
Steering: Full hydraulic, 90° each way
Turning circle: 34’ 1”
Length: 38’ 1”
Width: 11’ 3”
Height: 11’ 2”
Capacity: 15 cubic yards struck, 20 cubic yards heaped
Operating weight: 24.5 tons (empty) 46 tons (loaded)