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The Little A-Cs - Chapter 3

This book was written exclusively for Yesterday's Tractors Magazine. It is not published in any physical form but only available on this site. No part of this text may be used in any form other than as provided electronically from www.yesterdaystractors.com without express written consent of Yesterday's Tractors. Copyright 1996-1998.

View the table of contents.

3. History in Brief

The B

The first (and last) model to be built was the B. Production began in 1937 with less than 100 units. These early Bs were the only model in the series to use a different engine block. In fact many of the components of the 1937 were not shared with later machines.  The first 100 seemed more as if they were a pre-production prototype to get sales interest going while they tooled up to produce a similar machine in 1938. The 1937 used a Waukesha engine, different sheet metal (though nearly identical in appearance), different front end, steering gear, hubs, spindles and on and on. Needless to say, the 1937 is a rare find and an exception to the normally non-collectable B.

In 1938, the B production began in earnest with a real AC-built engine and finalized components. The initial machine specifications were as given in the Nebraska Tractor Tests.

1938 Allis Chalmers B
Bore & Stroke 3 1/4 x 3 1/2
Cubic Inch Displacement 116.1
Drawbar Horsepower 10.31 (Distillate Fuel)
Brake Horsepower 14.00 (Distillate Fuel)
Governed RPM 1400
Gross Weight 2620 lbs (included added test weight)

Note: Distillate fuel used for testing caused horsepower output to be significantly lower than what people experience in the present when using gasoline.

The specifications would change over the course of the production run as more power was continually needed and improvements in hitching came about. Aside from the this the B remained basically unchanged for nearly 30 years (1937 to 1957 with units sold as late as 1959). The most significant change was in 1947 when it received a major horsepower increase through the use of larger sleeves to increase bore and again in 1950 with governor changes to run at higher RPM. The updated specifications were as follows:

1950 Allis Chalmers B
Bore & Stroke 3 3/8 x 3 1/2
Cubic Inch Displacement125.2
Drawbar Horsepower 15.66
Brake Horsepower 21.17
Governed RPM 1500
Gross Weight 2250 lbs

Though many a Ford N-series or Farmall owner will contest it, several noted references and individuals feel that the B was machine that finally allowed the small farmer to switch to tractor power and retire the horses.  Its original list price certainly would support this at under $500.00. Since so much of a small farmers land would need to be dedicated to providing feed for the working team, a cash outlay such as this would certainly pay for itself shortly in increased farm output.

As with all machines in those days, the B had many implements built specifically for it. Many have followed the tractors through the various owners but most of the time newer implements are retrofitted (read that jury-rigged) to the older machines.

The B was a fairly narrow tread machine with a slightly shorter wheel base than its relatives, the C and CA. This fact makes it easier to move around between farm and shows than all models with the exception of its close brother the IB.

The IB

The IB was produced initially as part of the AC B serial number series but was seperated in 1946 into a completely seperate series. It was born out of the need for industrial machines that could easily move through factories for utility hauling and pushing. Most IBs did not have any options installed for farm work though they are considered an excellent chore tractor now. The most common configuration had simply a heavy front bumper on the front and a stationary drawbar. The IB was quite simple to create. The dropped final drive housings that normally provided the high crop clearance on the B were simply rotated forward one bolt position dropping the entire rear of the tractor down 6 1/2 inches. The front was dropped by building a straight axle with short spindle tubes that bolted directly to the front radiator support. This configuration was exactly duplicated in the mid-50s by International Harvester Corporation with the very popular Farmall Cub Low-boy. While the Low-boy was considered a farm chore tractor, the AC IB was never marketed as such. Instead a heavy bumper arrangement and non-hydraulic rear hitch was used to make it appealing to the industrial market.

Many unusual components had do be developed to accomodate the odd drive train of this machine. As a result, parts are more difficult to locate for the IB. With less than 3000 IBs produced, it is a bit more collectable than the normal B.

The specifications for the IB were the same as for the B with the  exception of its drawbar pull. Since the tractor was never tested at Nebraska and the industrial market had no similar rating organization, only supposition can be made concerning the actual figures. Differences in weight and geometry would indeed alter its pulling characteristics.

The C

The AC C was a natural progression in that for some tasks, such as cultivating, the B had power but too small a dimensions to increase its row crop capability. The B did not have a wide enough stance to handle 2 row work for the majority of crops. Additionally the BE engine had sufficient headroom to increase bore and RPM allowing even more power to be produced. As horsepower eating PTO devices were becoming increasingly important, additional power would be welcome to most small farms. AC had also attempted to downsize its larger machine (the WC) in 1939 by using the B engine on a WC frame. This underpowered machine did not sell and was generally a failure. This left a hole in the AC line that would better be filled by upscaling the B. Thus the C was released.

The C had used a wider set of final drive castings, conical cast hubs and wide pinion axles to  obtain the necessary width to effectively work 2 rows. The front end was offered standard as a tricycle model as these were becoming the row crop front end configuration of choice.  An adjustable wide front was also offered that was compatible with the wide rear end. These items combined with the increase in horsepower from bore and RPM increases, made the C a full 2 row tractor for most farm purposes.

Specifications as tested were:

1940 Allis Chalmers C
Bore & Stroke 3 3/8 x 3 1/2
Cubic Inch Displacement125.2
Drawbar Horsepower 14.15
Brake Horsepower 20.27
Governed RPM1500
Gross Weight

The differences between the B and C go further than the width of the stance and power productions. Many subtleties have resulted in the mixing of parts that just dont fit or look rather odd. For example, the retrofit of a wide C front axle on a B may look straightforward when one picks up the parts at a salvage yard but will result in a lot of head scratching, cutting and welding, when one tries to actually mount them. They are so different that the grill, radiator support, steering gear and drag link must all be swapped. Looking at the rear fenders quickly, you might think they are the same but when placed side by side, they share no similarities.

The C sold between the years of 1940 and 1950 before coming into stiff marketing competition from other manufacturers who were producing significantly more complex and capable hydraulic hitch systems, live PTO, and of course ever more power.

The CA

The introduction of the AC WD brought many engineering improvments to the AC line that in some cases surpassed anything else on the market. Many of these items could be transferred directly to the series covered in this book. The AC CA was the implementation of these features in a smaller tractor. To the casual observer, the CA may look identical to to a C with different rims. On closer inspection, it is a different machine from the engine back (with a few exceptions) and for that matter from the engine forward. Still the changes were subtle enough that appearances could easily deceive. The fact that this machine had heavy rear axle castings, axles, hydraulic pump from the WD, a 4 speed transmission, draft control and over twice the power of the original B, made it a very desirable working machine. All this and the weight is only a few hundred pounds above the C.

Specifications as tested were:

1951 Allis Chalmers CA
Bore & Stroke 3 3/8 x 3 1/2
Cubic Inch Displacement 125.2
Drawbar Horsepower 17.83
Brake Horsepower 24.79
Governed RPM 1650
Gross Weight 2763 lbs

The most important features necessary to be competitive in 1950 were live PTO and more powerful hydraulics. The CA provided both with the the split and clutched rear right pinion axle and the 4 piston WD hydraulic pump. In order to use the increased volume of hydraulic fluid, it was fitted with heavier rams and a redesigned hitch known as the "Snap Coupler". This easy to use hitch could not win over the growing standardization of the Ferguson System hitch known as the 3 point but did have advantages when it came time to hook up an implement. Features like the Power Adjust Wheels were an AC original and available only on the CA and WD at that time. This feature would eventually be applied to every major tractor brand before the end of the decade. Ergonomics were improved with the addition of a shock absorber pan seat. This was a departure from the rest of this series but necessary to compete since every other brand had already gone this way.

The CA was an excellent method of quickly marketing a tractor with the features of the later D-14 without having to retool.

Prev Page  Table of Contents   Next Page
1. Introduction
2. What are they?
3. History in Brief
4. Competing Tractors
5. Appearance
6. Identifying Numbers
7. Similarities and Differences
8. Cosmetics: What did they really look like?
9. Tips, Tricks and Maintenance
10. Using the Little Allis'
11. Tune-up Data, Quantities, and Specifications

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