Engine Model Identification
A brief description of the Lauson Model Numbers and their makeup.
Overhead Valve Engines
Lausons entry into the small engine field was with a group of single vertical cylinder, closed crankcase,
overhead valve, throttle governor controlled engines. These were the first engines Lauson produced that we
can call a “small engine” and they represent the first in a long line of small engines that Lauson would
produce over the following nearly thirty years. These engines are the VA, VR, VW, UA, UR, UW, UAS, UWR, and ZW.
First Generation Engines
In concert with the overhead valve engines, Lauson commenced production of the RA, RAU, RAY, and LA
engines in 1930. Later, a LB model would replace the LA. All these engines were L-head engines of a similar design, varying mostly in size and
I have started calling these RA, RAY, LA, RAU, and LB engines, “first generation” Lauson engines. All
these engines share the same basic engine block design, while the engines that succeed them are based
upon a completely different design. We also need to keep in mind that while Lauson was building these
early small engines, their primary focus was still the manufacture of flywheel engines, which they
continued to build into the early 1940’s.
We should note that with this “first generation” design, Lauson adopted a valve geometry which would be
characteristic of all Lauson engines until Lauson introduced it’s first “third generation” engine design
in 1954. The valve geometry adopted
with the RA series and maintained throughout almost all of the Lauson Manufacturing Company production
places the valves to the right of the piston (as opposed to behind as in many other engine makes) and
perpendicular to the crankshaft. Externally, the result of this design is to have the intake manifold
positioned at the rear of the engine block, while the exhaust manifold is positioned at the front of
the block. This geometry gives nearly all Lauson engines their classic and unique appearance.
With this “first generation design”, the crankshaft is supported by Timken roller bearings in the larger
models (the RAY and up) and an oil pump on most models delivers oil to a pdipper trough, where a dipper
on the connecting rod splashes oil about the crankcase for lubrication. In this design, the camshaft is
placed in a perpendicular plane with the crankshaft and helical crossed gears are used to transmit the
rotary motion of the crankshaft to the camshaft where a separate cam is provided to drive each of the
valves. A governor, if provided, is actuated by a pair of
flyweights on a ring locate at the rear of the camshaft. With All these engines the cam mandrel, which the camshaft
rides upon, protrudes through the front of the crankcase where a nut and lock washer are used to adjust
the "play" of the camshaft casting on this cam mandrel.
Second Generation Engines
These engines began appearing at around 1937 with the introduction of the RLA, RLC, RSC, and TLC models.
The major difference in this design from the “first generation design” is that simple spur
gears drive the camshaft with it now being in a parallel orientation to the crankshaft. This allows a
single cam lobe to service both valves through a pair of cam followers. The governor was also moved to
the crankshaft and operated by a set of flyweights mounted to a collar positioned between a crankshaft
counterweight and the magneto plate. For most models, an oil pump and dipper trough was included with
the design as well as ball bearing main bearings and replaceable connecting rod bearing inserts.
The majority of the small engines that Lauson built fall within this "2nd generation"
group of engines.
Third Generation Engines
In 1954, Lauson brought to market it’s first, what I call, “third generation engine
design” with the model type SLV being the first of this series. This engine was a radical
departure from the engines Lauson had been
building up to that time. This was the first commercial alloy block engine Lauson produced (
though previously, Lauson built many alloy block engines during WWII), and it was the first engine
Lauson had produced with an air vane governor. This engine had a cast iron sleeve and with
this “third generation" design Lauson chose to abandon it’s classic valve placement
and position both the intake and exhaust valves at the rear of the engine block.
These engines were built with a pressurized lubrication system which delivered oil to the top camshaft
bearing, top main bearing, and connecting rod bearing. This 3rd generation design represented a design
would enhance and elaborate upon to build a series of engines that, at one time, made Tecumseh a "name
to be reckoned with" in small engine production.