Figure 9. John Deere 550 ripping the frozen surface of the test site; total ripping depth is approximately
1 ft (30 cm).
A close-up of the fractured material is shown in
Ripping with the John Deere 550
The John Deere 550 with the model 750-H rip-
Figure 7b. Attempts to immediately go to full
per attachment also effectively ripped frozen
depth (14 in. [36 cm]) usually stopped the tractor
ground at the barrow pit. During these observa-
and caused it to lose traction. The best perfor-
tions, ripping performance was improved with
mance was obtained when three to four passes
less catching and much better control over the
were made to rip a single starting slot to full
ripping depth. The depth of cut was controlled by
depth. This cut to full depth along a 60-ft (18-m)
tilting the blade and using its corner as a skid.
excavation took less than 5 minutes. Parallel off-
This prevented the ripper from pulling down the
set passes were then made with less effort, with
front of the tractor, which increased the depth of
material failing to the prior cut; however, mul-
cut and occasionally stalled forward progress. The
tiple passes (usually two or three) were still re-
ripper was mounted just left of center on the blade,
quired for full penetration. The tractor and blade
as shown in Figure 8, with the right corner placed
were stable and the ripper did not noticeably pull
on the ground and used as a skid. With this con-
down the blade or the front of the tractor. Gener-
trol, a 3- to 4-in. (8- to 10-cm) depth of cut could
ally, forward travel was not smooth, and usually
be maintained at a uniform forward rate. On an
would slow when the ripper caught, loaded, and
average it took 45 seconds to make a 50-ft-long
failed a slab. Occasionally, when the track slipped,
(15-m) pass, ripping to this depth. It took ap-
lifting the blade would help fail the ground and
proximately 10 minutes to rip an 11-in. (28-cm)
restore forward motion. Failure of the frozen
frost layer in a 10- 50-ft (3- 15-m) area, which
ground was often accompanied by a noticeable
is about half of the area required for construction
bang as the ground fractured and the blade un-
of some vehicle fighting positions. The 550 is
loaded. Forward progress was also restored by
shown ripping at this site and some of the large
reversing and starting again, ripping at a shallower
slabs produced can be seen in Figure 9.
depth. At this site 10 to 14 passes were required to
During these observations the ground was flat,
rip the frost to a depth of 14 in. (36 cm) over a
well frozen, and free of snow and ice. Traction
swath approximately the width of the blade.
9
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