[Steam-engine] Traction Engine Evolution

[Andy glines]

I started a this thread on Harry's but I also want to
hear from the folks at ATIS.  
I have been thinking about how traction engines
evolved during the years when they were being built to
provide power for many different pursuits. I'd guess
that most engines were built between 1880 and 1930.
The fact that the technology remained effective and
popular for so long is impressive. I like to compare
older engines with the newer version just to see how
things changed over the years. Often traction engines
were simplified by removing "features" rather than
adding them. 
The change in features is easy to see with and engine
like my Huber 16 #8213. My engine was built around
1905. Hubers were built with square rear axles until
about 1906. Square axle Huber engines featured special
spring mounted rear wheels to absorb shock from the
road and the front axle has a large coil spring in the
bolster for the same purpose. The bull gear rode on a
different hub than the wheel and were attached to the
wheel via a spring shock absorber device to lessen
jerking when starting a load. The whole rear wheel
arrangement is rather elaborate for a traction engine.
I suspect that the suspension system was abandoned
because it had to expensive to build and I doubt the
suspension was a big advantage on something that only
goes 3-4 mph. The rear drawbar is also spring loaded
to reduce jerking a load. Square axle Hubers also
featured a superheater. Superheater engines are easy
to spot because there will be 2 large diameter pipes
coming from the dome where there is usually just one.
The superheater must have been a rather expensive
feature becaue it required installing a verticle
"flue" from the top of the dome to the fire flue and
another from the bottom of the fire flue to the bottom
of the barrell for a superheater drain. I think that
the superheater was advertised as providing about 8%
greater efficiency. If you didn't remember to driain
the superheater after sitting idle for awhile you
risked getting a slug of water to the cylinder. You
also had to remember to keep it drained during cold
weather for obvious reasons. Firing with extra long
pieces of wood required special care so as not to hit
the superheater in the middle of the fire flue. It is
not uncommon to see the superheater abandoned on one
of these engines. Like the wheels I suspect that cost
and potential for trouble coupled with little gain
resulted in the feature being dropped. Even thought
the double-walled, telescoping stack is still
advertised in the 1913 catalog most of the newer
Hubers I see don't have it. Usually the stack is
straight gauge tube of fixed length. My engine is
missing the stack but I hope to work with Tracy Porter
to make a reproduction. I've gone on long enough. What
changes have you noticed over the years of traction
engine production?

Andy Glines
Evansville, IN


		
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