As technology has progressed, so have lawn mowers. Hydrostatic drive and transmission aren’t just for professional lawn mowers and big equipment anymore. Most manufacturers have now given us the choice of picking between standard and hydrostatic drive for residential mowers too. I’ve tried both types of drive and can tell you there is definitely a difference. Let’s find out what a hydrostatic transmission actually is and if you will benefit from having one.
What is a Hydrostatic Transmission on a Lawn Mower? (The Short Answer)
A hydrostatic lawn mower has a pump that pushes hydraulic fluid to a hydrostatic motor and produces movement in both a forward and backward motion. They have a high power-to-weight ratio with infinitely variable speed control, resulting in greater power, maneuverability, responsiveness, and outperforming conventional drive systems.
The Various Parts of a Hydrostatic Transmission
Let’s take a closer look at the parts that make up a hydrostatic transmission and their functions.
Power Input Belt & Pulley
Hydrostatic transmissions or “Hydro’s” receive their power from the engine via a belt and pulley system, similar to a conventional drive system. The difference is that the belt and pulley aren’t directly driving the wheels. Instead, the pulley is located on the engine’s drive shaft before the clutch that drives the deck. The pulley is then connected to the pump via a drive belt. (Yes, you unfortunately still have a belt.) This pulley rotates at the same speed as the engine; therefore, the engine is always set to its highest power level so that the hydro can use whatever power it requires.
Hydrostatic Pump
Pumps create the pressure needed to drive hydro motors. The belt transfers the engine power into the hydro pump and creates pressure. This pressure is then transferred to the motors as needed. The pump has two valves for the oil to pass through. Each valve determines the direction the motors will drive in; either forwards or backward. It’s important to understand that the pump will produce consistent pressure since it is being provided with consistent power from the engine. This means that even at low speed, there is still power and maneuverability.
Oil Reservoir
Like other hydraulic systems, there is a need for stored oil. Lawn mowers have a small oil reservoir to hold hydraulic oil. The pump can call upon this reservoir if the oil becomes low.
High-Pressure Hoses
Depending on the lawn mower design, the pump and motors may be two separate components. As a result, they are connected by high-pressure hoses that are capable of withstanding the pressure of a hydraulic system.
Hydrostatic Motor
This is the final piece in the hydro drive. The motor receives oil from the pump in two possible directions, depending on what the operator requires for forward or reverse. A drive piston within the motor converts the oil pressure and flow direction into drive direction and ground speed.
How All the Parts Work Together in a Hydrostatic Transmission
So, to summarize, the engine provides power to the hydro pump via the drive belt and pulley. This spins a shaft that spins the internal pump pistons within the hydro pump. Pressure is formed with the pump, which can be released in two directions and at varying speeds depending on the operator using the accelerator pedal or control levers. The oil then travels via the hoses to the hydro motor and spins the motor pistons. The pistons are connected to a drive shaft which is also connected to the wheels. As a result, the flow of oil through the motor pistons will generate the power to spin the wheels.
It’s similar to passing water over a water wheel. The volume and speed of water passing over the wheel will determine the output ability.
Now as previously mentioned, hydrostatic transmission comes in a variety of designs depending on the application. Lawn tractors tend to have single transmission systems as the wheels always turn together in the same direction, whereas zero-turns have two separate motors that can turn in different directions at different speeds. This setup requires a hose to connect to the pump. Having this independent control means you no longer require a steering wheel to govern direction, you have the power of the wheels.
When I Think It Makes Sense to Consider a Hydrostatic Mower
I’ll be the first to admit that hydrostatic lawn mowers are definitely an improvement over standard drives. However, your wallet might not agree. You’ll have to be prepared for the extra cost and weigh the pros and cons and apply them to your particular situation to see if it’s a cost that makes sense.
If you’re cutting a lawn with lots of turning, then a zero-turn with hydros is a definite time-saver. This is why you see all the professionals using them. Additionally, tractors with hydro’s also offer a much-improved ride. Say goodbye to jerky maneuvers at slow speeds. Simply put, they are an all-around easier drive system without any gears to worry about.
The only real downside is that the engine is always running at full power to drive the hydro. As a result, you will get through a tank of gas quicker. Then again, you will cut the lawn a lot quicker too.
Leave a Reply