What is the main difference between an 'air over hydraulic system' and a 'full air system'.?
Answers:
"This system combines the use of compressed air and hydraulic pressure for brake operation. The air-over-hydraulic brake system has an air-over-hydraulic power cylinder (fig. 3-48) that contains an air cylinder and a hydraulic cylinder in tandem. Each cylinder is fitted with a piston and a common rod. The air piston is of greater diameter than the hydraulic piston. This difference in the two pistons ."
http://www.tpub.com/eqopbas/39.htm.
I hope this helps you,friend.
"The air brake is the standard, fail-safe, train brake used by railways all over the world. In spite of what you might think, there is no mystery to it. It is based on the simple physical properties of compressed air. So here is a simplified description of the air brake system."
http://www.railway-technical.com/air-bra.
'air over hydraulic system'
http://www.tpub.com/content/engine/14081.
Full power hydraulic brake systems have been used on heavy-duty off-highway vehicles for more than 30 years. The first applications for full power hydraulic brake systems were in mobile mining equipment mining loaders, haul trucks, etc. It was in these first applications that full power hydraulic brake systems demonstrated their superiority over common air over hydraulic brake systems.
Since their introduction in mining, full power hydraulic brake systems have become common in a large variety of other industries including earthmoving, material handling, and agriculture. Some examples of machines using full power hydraulic brake systems include wheel loaders find excavators, forklifts, telescopic handlers, logging forwarders, and agricultural harvesters. The full power hydraulic brake systems for these machines may have slightly different features, but their underlying concept remains the same.
A full power hydraulic brake system may use the machine's existing hydraulic system as a power source. An accumulator charge valve directs the machine's hydraulic system flow into one or more hydraulic accumulators to maintain the accumulator pressure between a high and low limit. The hydraulic accumulators store energy for "power-off" (when the machine is off) braking. A low pressure warning switch warns the operator when the accumulator pressure is below the low limit. Hydraulic brake pressure is controlled by a pedal modulating valve.
http://www.findarticles.com/p/articles/m.
An dif you're asking about SUSPENSION / DAMPING and not braking..
air over hydraulic pricipally uses the air as the 'spring' and the oil as the damper. The oil flows through restrictor valves in the compression (to slow speed) and on rebound (to slow return & damp the return rate) to prevent 'pogo-ing'.
A full air system works the same as above - but uses the restricted air flow to attenuate the compression & rebound rates.
Both systems work well - but I personally prefer air/oil as the tollerances can be less exacting when setting up the rates (due to oil having a viscocity v's air with none!)
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