Bobcat Snowplow

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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