Snowplow--Why two hydraulic cylinders for angling?

[npalen]

I'm looking at adding hydraulic angle control to my vintage York landscape rake is the reason I'm asking. I see the dual cylinder setup on most snow plows/blades and they are usually plumbed as single acting but controlled with a double acting directional valve. Is there a stability advantage of doing it this way or what?

 

[Zebrafive]

You're talking about snow plows on trucks?
My guess is they handle the abuse better. Large diameter rams in small compact diameter cylinders, plus equal force for either direction.
On AG rear blades you will find double acting cylinders, that's what I'd put on your rake.

 

[V1Rotate]

I'm only guessing at this but I would think that the reason for two cylinders is strength.
When the angle valve is in the neutral position (closed), both cylinders are unable to move. this means that the plow will hold its angle when a side load is put upon it. By having two cylinders, you are splitting the load between the two, instead of all the force going to only one cylinder.

 

[SSdoxie]

I think it is done mostly for equal speed of angle. If it was 1 double acting cylinder it would move considerably faster angling what ever direction the cylinder retracted. A larger the rod diameter, in same size cylinder barrel, is going to much than a smaller rod. Using 2 equal sized single acting cylinders with larger diameters gives equal angle speed and more stability of the blade at either angle. The steering on my tractor is the same concept. It uses 2 single acting cylinders, 1 pressurized for each direction, with a stabilizer link between the front wheels.

 

[Leejohn]

Snow plows use 2 single acting cylinders becaues of the break away if you hit something real hard. The plows have cross over relief valve.

 

[94BULLITT]

I think most truck plows have single acting cylinders so you need 2 so you can angle it.

This SSQA plow only has 1 cylinder.

HLA Snow

 

[LD1]

I also believe it has to do with the crossover relief / safety.

the cross over relief works on pressure. IF you used a single DA cylinder, it would would take more force to collapse the cylinder as it would to extend. So if you set it up to protect the components when the cylinder is collapsing, it wouldnt hold an angle well when it ram were extending cause it would take less force.

Probably the speed of angle is also a factor.

 

[RickB]

I also believe it has to do with the crossover relief / safety.

the cross over relief works on pressure. IF you used a single DA cylinder, it would would take more force to collapse the cylinder as it would to extend. So if you set it up to protect the components when the cylinder is collapsing, it wouldnt hold an angle well when it ram were extending cause it would take less force.

Probably the speed of angle is also a factor.

+1 on all of that, and add the disparate displacement volumes of rod and base ends of a double acting cylinder as it relates to the effectiveness of a crossover relief.