">
 
Keep it simple... keep it going... and keep it!
 

Up

Search for Manuals
at Simplicity's Technical Publications Site

Enter the MFR Number:

Shirts, hats, mugs & more in the

You can make a contribution to support Simple trACtors online, safely and securely, using our PayPal account.

 

LUBRICATION

Lubrication in pump and motor components is vital to the operation of the hydrostatic system. (Fig. 7) illustrates the design of a typical piston. A slipper is crimped to the end of the piston and works as a ball and socket keeping a flush contact with the swash plate, regardless the angle. The center of the piston and slipper is drilled with a small hole to allow a metered amount of oil to flow to the ball and slipper contact areas so these parts always float on a thin cushion of oil. As oil pressure behind the piston increases, flow through the port increases to provide more oil to maintain the oil cushion. Additionally, the piston and  cylinder walls are finished to very close tolerances which allows the hydraulic oil to lubricate and seal this critical area.

 

Click for a closer view

VARIATIONS ON HYDROSTATIC TRANSMISSIONS

Another transmission using the same hydrostatic principles utilizes radial ball piston pump and motor rotating blocks. In this design, the cylinder bores are positioned like spokes around a central hub, and the pistons are large hardened steel balls instead of cylindrical in shape. (See Fig. 8)
 

The stationary center hub contains the passages necessary to transfer the oil between pump and motor cylinder blocks. The ball piston positions are determined by a bearing like raceway encircling the cylinder block. When the pump race is positioned so the stationary hub is at its center, no movement of the ball pistons occurs in their cylinders.

Oil pressure and flow to the motor block begins when the pump race is moved away from its centered position by the tractors control apparatus. This causes the ball pistons to stroke in and out of their cylinders which are filled with oil, thus creating the necessary pressure. The motor race is permanently positioned off center to provide the fixed angle which results in the motor piston block rotation when the pistons react to the pressure applied to their cylinders. It should be noted that efficiency of the ball piston hydrostatic depends upon the close fit of each ball to its own cylinder. Extreme care must be taken when making repairs to these units to assure the original position of those parts are  maintained.

Lubrication of the ball piston increases as system pressures rise, providing more oil when lubrication requirements rise. Oil that is utilized for lubrication would soon cause the hydrostatics to cease functioning if there were no way to replenish that volume of fluid “lost’ to lubrication. We have seen that two passages are required between pump and motor rotating groups for flow to take place. Check valves leading to each passage allows additional oil to enter either passage when in a negative pressure (vacuum) condition.


[Source: Simplicity publication, Hydraulic Systems Training Information, #840172, Principles and Operation of Tractor Hydraulic Systems]
 

 

 

NOTE: This site is designed to be viewed in at least 1024 x 768 resolution in Internet Explorer v6 or later, Mozilla Firefox v4 or later, and Google Chrome.  It may not display correctly in other resolutions or on other devices.  Links on this site are monetized.  We assume NO liability or responsibility for the accuracy of ANY data on this site.    
©
1998 - 2011 by Simple trACtors LLC, North Brookfield, MA. All rights reserved.

 

Please support our sponsors  . . . 
and help keep this site free for your use.