Free Piston Tractor

By Staff
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Figure 2
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Figure 1

1408 N. Van Buren, Ottumwa, IA 52501.

Reprinted with permission from the August 1957 issue of
Doane’s Agricultural Report, 11701 Barman Dr., St. Louis, MO
63146.

Free Piston Tractor perfected by Ford was demonstrated at the
Nebraska Tractor Day. For a discussion on how this tractor works,
note box.

The power stroke compresses air at b. This air bounces the
pistons back for the compression stroke. During the compression
stroke, air at c. is shoved through reed valves into the air
‘box at a. Entrapped air in the combustion cylinder also is
compressed, reaching ignition temperature at the time fuel is
injected. On the power stroke (drawing 1), the pistons are forced
outward by the expansion of burning gases. This movement uncovers
the exhaust ports first allowing most of the heated gas to leave
the cylinder through the exhaust tube. Then the intake ports are
uncovered (drawing 2), and air from the air ‘box’ flows
through the cylinder, thoroughly scavenging it and mixing with the
exhaust gases. The diluted hot gases flow into a surge tank (not
shown) and are released under even, steady pressure to the turbine
wheel. The revolving turbine powers the tractor through reduction
gears.

This tractor was developing around 50 horsepower as
demonstrated. Ford engineers say it has a potential of over 100 HP
without extensive changes. Noise level was not objectionable even
without mufflers. It sounded similar to a 2-cylinder, 2-cycle
Maytag engine.

Only a slight turbine whine was heard and this did not seem at
all objectionable.

Another very interesting feature about the tractor was the
transmission. Shifting could be done ‘on the go’ between
all ranges. Work is continuing on this type power. However, it will
definitely not be available in the near future, say the
engineers.

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