Need some help with hydraulics
Posted November 08, 2011 - 11:20 PM
I was figuring I would drive the pump by a pulley from the engine. That would be piped to the motor mounted on the deck. From the motor a belt would turn the main drive pulley of the deck.
Did I say I'm trying to do this as absolutely cheap as possible?
Posted November 09, 2011 - 06:34 AM
Posted November 09, 2011 - 07:48 AM
As for speed, you should be able to get in the ballpark with ratios, but you definitely want a pressure relief in case you get caught up in something.
Edited by MH81, November 09, 2011 - 12:11 PM.
Posted November 09, 2011 - 07:54 AM
Posted November 09, 2011 - 08:36 AM
Posted November 09, 2011 - 07:21 PM
Posted November 09, 2011 - 07:31 PM
Posted November 09, 2011 - 07:38 PM
Posted November 09, 2011 - 07:52 PM
Posted November 09, 2011 - 08:40 PM
Posted November 24, 2011 - 02:36 AM
Posted December 06, 2011 - 01:32 AM
Some hydraulic systems (such as lift cylinders, power steering systems) use relatively high pressure but low flow. These can have fairly small resevours and usually small pumps. You can often "cheat" these systems by using lower horsepower drives for the pump - just increases cycle time.
However hydraulic motors tend to be the exact opposite. Most motors have high flow requirments - think of a water turbine. The "work" happens because of a large volume of liquide flowing through the motor. The high flow requirements generate heat (efficiency loss) through friction, both with the flow volume, and within the motor. This heat buildup, and the high volume of flow require much larger resevours.
In hydraulic motors, think of flow supplying rotational speed, and pressure generating torque - this is not exactly true, but close enough. For a mower blade, you need both - the worst scenario - high flow (gpm) and high pressure (psi) = high horsepower, large pipe lines, large resevour, radiators to dissipate heat. Most hydraulic blade systems tend to use a large flywheel (stump jumper) to retain rotational energy. You can trade off torque (blade takes more time to "spin up to speed"), for speed and lower system overhead. You can use pulleys to multiply your speed, but you also lessen your torque that way.
A single blade often works better on a hydraulic system than 2 or three blades because the single blade is longer (higher cutting tip speed for the same shaft rotational speed) and the assembly is more massive (rotational inertia) than several smaller blade assemblies.
As has been stated, I think you are WAYYYY down on horsepower for this operation, and it would be a large system for a 2 wheel tractor. But work from the end back.
First you need to know the hydraulic motor requirements. Once you know what size motor you need, then you can spec the flow and pressure required to run it. That determines the line size. Flow and pressure requirments lets you spec the hydraulic pump - need one big enough to supply your motor's demand with frictional losses build in. Then pretty straightforward to determine the horsepower required to drive the pump. And finally that gives you minimum size for your resevour. A bit of math, but most hydraulic shops should be able to spec the parts if you give them the starting point - what you want to do!
And finally, you also need a pressure relief system in the line - that flywheel full of energy tends to keep spinning even after the pump shuts off - and would do nasty things to your pump and motor if not planned for.
This aint gonna be cheap..............