December 26, 2010
I recently purchased a S650
Bobcat skid steer loader and snowblower, primarily for snow removal
operations. I wanted to be able to move my 8 ft. Fisher snowplow that's
normally used on my 1 ton dump truck back and forth between the truck
and the Bobcat. I used a blank Bobcat quick-attach plate and scrap steel
that I had available for the plow attaching mounts. I purchased the
necessary hydraulic components to be able to angle the blade using the
Bobcat's auxiliary hydraulics. The power angling would be initiated via
a thumbswitch on the Bobcat's right hand steering lever. Here's what the
final result looks like:
I disliked the standard Bobcat straight snowplow
arrangement because it made no provision for floating of the blade other
than float of the main lift arms. I definitely did not want the extra
weight of the lift arms applying any down pressure on the blade . I only
plow my own gravel road, which is 1/2 mile long, and any extra down
pressure only serves to aggravate the digging in problem whenever the
ground is not completely frozen. I don't use plow shoes at all as I have
found they can only make such a problem worse. I decided to make the
plow hoist arm a little longer and higher than necessary as I wanted to
be able to use quick attach plate without the plow to do duty as a small
lifting boom (note: see later 2011 modifications below). I located the vertical position of the plow pivot points
to result in the plow A-frame to be level with the ground when the main
lift arms are at the bottom stop and the tilt position is about 30
degrees forward. This is also the tilt location that puts the Bobcat
loader bucket flat on the ground. Normal lifting of the plow blade will
be done with the tilt control. Here's a closer view of the pivot points
that allow the plow to float exactly as it does on the truck:
For the hydraulics involved, I used two adjustable flow
restrictors to keep the angling speed at a reasonable value. The
Bobcat's auxiliary hydraulic flow is far in excess of the Fisher pump on
the truck and the restrictors are needed to prevent slamming caused by
high speed angling of the plow. I also used a cross-over relief valve to
1) prevent overpressure of the Fisher angling cylinders by the Bobcat's
higher pressure system and 2) to provide protection of the plow and
components from unexpected external loads. Such protection is built into
the Fisher control valve on the truck and should be replicated on the
Bobcat to provide that extra margin of safety from damage. I used
1/4" ID 2 wire hydraulic hose after reducing the size from the
standard Bobcat flat-faced quick couplers. Here's a closeup of the
cross-over relief valve:
Here's a diagram of the hydraulic arrangement:
I also changed the Fisher brass fittings at the angling
cylinders to high pressure steel fittings. I was not comfortable with
the lower pressure rating (1200 psig, I think) with the brass ones using
a 2000 psig actuating pressure.
Modifications to above (Oct 2011):
After some use last winter, I found that the lift arm and blank QA plate
design shown above permitted some flex and caused to plow to bounch too much
for my liking when raised and moving over uneven ground. I decided to
revise the design some to stiffen up the QA plate and change the lift
arm arrangement. I also decided to move the restrictors down to attach
directly to the cross-over relief valve rather than at the quick
couplers:
The plow A-frame shown above is on my old 7.5 foot
Fisher blade. The mounting ears on that plow are closer together than
those of my 8 foot blade and do not fit nicely between the attaching
points on the mounting plate. However, it should work fine this way. I
decided not to modify the mounting plate attaching points since I still
wanted the ability to use my primary 8 foot plow with the skid, if
needed. This arrangement avoids the hassle of moving the 8 foot plow
between the truck and the skid mounting plate. I will generally leave
the mounting plate attached to the 7.5 foot plow for use with the skid
and the 8 foot plow attached to the truck for using that.
Here's a side view of the modified arrangement:
Straight on with 7.5 foot plow:
Rod (NH)
October 2011
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