Graders

The earth sculpting machine we see here:


is often called just a grader, or sometimes a road grader, or sometimes just a blade, but its formal name is motor grader. You can in fact see that on the nameplate of the one shown above:


Why is that? What other kind could there be - hand pushed?

In fact, when this kind of machine was introduced, it was not self-propelled. Rather, they were drawn by tractors - substantial tractors, at first steam powered (or sometimes even by teams of horses, mules, or oxen). Here we see such a rig in about 1918 on a farm in North Dakota:


Note the shaft that goes at an angle to the center of the tongue; we'll talk about that in a later section.

The tractor is a Twin City "25" (internal combustion).

Here's one running in modern times:

http://www.youtube.com/watch?v=zCJU8tYkIMY

When the self-propelled version first appeared, it warranted the name motor grader. Today, even though there are few, if any, tractor-drawn graders in use (at least in the U.S.), the name perseveres, and many people in the business call them just that ('cuz that's their name).

We are fortunate to have here in Weatherford, Texas two lovely examples of graders (the tractor-drawn kind) on exhibit. We'll see them in the following parts of this series.

[To be continued.]

Best regards,

Doug

Graders - part 2

Here we see a nice Caterpillar grader (model number unknown), probably from about 1919:


This is on exhibit at the property of a local earth moving contractor.

Here we see the bull wheel, which supports the blade, allowing it to be articulated in almost any way you can imagine:


The mechanisms are all very clever. For example, the wedge-shaped part seen toward the right, actuated by a pull rod from the operator's position, lifts a pin that locks the azimuth position of the blade.

Here we see the grader from the front so we can examine the steering arrangement.


Basically, the grader "trails" the tractor, since the tongue is conceptually connected to the front axle. But the operator can modify the grader's path with a steering wheel.

We see that the wheel leads, via a sequence of long shafts, connected by universal joints, to a gearbox located on the tongue. The tongue can actually pivot with respect to the front axle. but the two are held in a consistent relationship by two radius rods leading to the ends of a length of roller chain wrapped around a sprocket driven by the gearbox. When the steering wheel is turned, one of these radius rods is pulled and one relieved, changing the angle of the axle with respect to the tongue.

[To be continued]

Best regards,

Doug

Doug Kerr said:

The earth sculpting machine we see here:
{SNIP for brevity}
is often called just a grader, or sometimes a road grader, or sometimes just a blade, but its formal name is motor grader.

Click to expand...

Hi Doug,

Thanks for sharing these. It brings (fond) memories of the 70's when I lived in a house in the forest in the outskirts of a village in the Netherlands. The dirt/sand roads had to be treated a couple of times every year to keep them accessible for normal traffic (off-the-road vehicles were scarce in those days, just some quads and Jeeps). Unfortunately I have no pictures of them, but they were blessed. They incorporated a plow (of sorts) and a grading mechanism in one operation.

Fond memories, and my first real photochemically based darkroom with a Durst film "enlarger".

Cheers,
Bart

Graders - Part 3

Just a block away from that Caterpillar grader, on display by the City of Weatherford in front of the old city generating station (we still have city-provided power - no deregulation, no choice of providers, and about the lowest rate in the state) is this Adams Leaning Wheel Grader No. 10. made by the J. D. Adams Manufacturing Company, Indianapolis, Indiana:


I suspect this is from 1919 or the early 1920's.

As you might think from the name, its novel feature was that both the front and rear wheels could be (separately) leaned to one side or the other, assisting the achievement of good lateral traction when operating on a sloping ("superelvated") grade (these machines often had to operate in almost "mountain goat" fashion).

Here we see the arrangement on the front.


A gearbox moves the "tie rod" from side to side, working levers that tilt the wheel spindles. You might wonder why there is a circular gear portion on the tie rod rather than a straight toothed rack, given that the intent is just lateral movement, not rotation of the tie rod. But the center of the tie rod follows a circular path (as the levers on the spindles rotate on their pivots), and thus to maintain engagement with the driving pinion the "rack" has to become an actual portion of a circular gear.

A similar arrangement is seen on the rear:


Also seen here is an actual straight toothed rack, used to move the whole rear axle assembly from side to side, allowing the operator to "find two good tracks" for the rear wheels to follow. (The Caterpillar grader we saw earlier has a similar rear axle lateral shift arrangement, but no tilt.)

Modern motor graders (such as the big Volvo seen at the beginning of this thread) usually have tiltable front wheels only.

Here we see the steering arrangement:


The lower tongue actually pulls the grader, and can pivot laterally independently of the front axle.

The upper tongue is articulated, and the rear portion is connected by fixed radius rods to the axle. A gearbox at its point of articulation, operated by the steering wheel over the familiar arrangement of long shafts and universal joints, "bends" the upper tongue, changing the relative azimuth of the front axle, changing the "steering" from just simple "trailing" after the tractor.

I don't know which of these two steering arrangements came first, but it is likely that the common location of the gearbox between them is a result of the evolution of one manufacturer's design from one arrangement to the other!

The tractor seen in this shot is a Fordson Model F, probably from about 1924, also on display at this site. I doubt that it was used to pull this grader (or any grader), but it is a fascinating machine. I will report on it in a separate thread.

Best regards,

Doug

Hi, Bart,

Bart_van_der_Wolf said:

They incorporated a plow (of sorts) and a grading mechanism in one operation.

Click to expand...

Indeed, graders with a second blade at the front are quite common, especially in Europe (supposedly most especially in Finland)

Best regards,

Doug

These sketches show how wheel tilt and rear axle lateral shift (along with extremes of bull wheel angling and lateral shift, although I did not discuss that) can be employed in grader operation:


This shows tractor-drawn graders. It is from a report showing the economic advantages of using tractor-towed graders, rather than motor graders, in low-volume road maintenance (especially, for example, in third world countries). It was published by a US government agency in connection with an international conference, but the original report was done by British engineers.

Don't you love the cap on the operator? In fact, I was wearing just that sort when inspecting the graders today (suspenders, too)!

I had meant to wear my Basque beret (gets less in the way of the camera), but I forgot and grabbed my usual cap. I had no idea I was wearing a grader operator's cap!

Best regards,

Doug

Best regards,

Doug

Interesting to see these. The first motor graders were pretty basic as well. I remember seeing an Allis Chalmers model with manual controls similar to those you show. It was still working for the Alberta government about 1962. A more modern version with hydraulics is shown here,
http://www.machinerytrader.com/listingsdetail/detail.aspx?OHID=7245953

Hi, Clayton,

Clayton Lofgren said:

Interesting to see these. The first motor graders were pretty basic as well. I remember seeing an Allis Chalmers model with manual controls similar to those you show. It was still working for the Alberta government about 1962. A more modern version with hydraulics is shown here,
http://www.machinerytrader.com/listingsdetail/detail.aspx?OHID=7245953

Click to expand...

Thank you so much. That is the smaller "tractor-pattern" motor grader style. I did not have a good picture of such before.

The larger pattern (of which the Volvo I showed is perhaps an extreme example) has the engine at the rear.

Smaller ones of this pattern have two driving wheels, but four driving wheels are much more common.

However, the very first motor grader (the Russell Motor Hi-Way Patrol of about 1919) had the engine (and the large driving wheels) at the front. (This line was later absorbed by Caterpillar.)

Best regards,

Doug