Replacing an old, mechanical steering gear (with half a turn of play in the steering wheel) and installing a hydraulic orbitrol is the dream of every owner of an older tractor (e.g., Ursus or Zetor).
Unfortunately, after installing the desired kit, the magic often fades. The steering wheel turns very heavily, the system jerks, or – even worse – the steering wheel can be turned endlessly, but the wheels don't budge. Where does the problem lie? A faulty orbitrol, a weak pump, or perhaps human error?
BRhydraulic experts break down the most common steering system failures and debunk the biggest myth about orbitrol selection!
1. The biggest myth: "I'll buy a bigger orbitrol, it will turn lighter"
This is a mistake that costs mechanics the most stress (and money). Many customers believe that replacing a 100 cm3 orbitrol with a 160 cm3 one will make the steering wheel turn "with one finger". It's exactly the opposite!
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How does orbitrol capacity work? A value of e.g., 100 cm3 means that for one full turn of the steering wheel, the orbitrol will pump 100 cubic centimeters of oil into the cylinder.
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Bigger orbitrol = fewer turns. If you install a 160 cm3 orbitrol, the wheels will turn faster (you will make e.g., only 2 turns of the steering wheel from lock to lock instead of 4).
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The catch (Physics): To push more oil with one turn, you need to use significantly more arm strength! A larger orbitrol always means heavier steering wheel operation, unless you have a powerful hydraulic pump that can handle this output.
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Golden rule: For standard agricultural tractors (Ursus C-330, C-360, T-25), an 80 cm3 or 100 cm3 orbitrol is ideal. Larger ones are installed in powerful machines with efficient pumps.
2. The steering wheel spins endlessly without resistance, but the wheels remain stationary
This is a classic symptom which in 90% of cases does not mean a faulty orbitrol at all (although it is usually blamed and sent for warranty).
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Main culprit: Cylinder seals. If the steering wheel offers no resistance and the wheels don't turn, it most often means that the seals on the piston inside the steering cylinder have completely failed (known as internal leakage). The orbitrol pumps oil into the cylinder, but instead of pushing the piston, the oil simply flows freely to the other side and returns to the reservoir.
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How to check? Block the wheels, disconnect one hose from the cylinder and try to turn in that direction. If oil squirts from the disconnected cylinder port, you can be sure – the cylinder is leaking and needs regeneration.
3. The steering wheel "jerks" and kicks back
This symptom most often appears immediately after starting the machine or during quick steering wheel movements.
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Cause 1: Air in the system. Hydraulic steering hates air. For the system to work smoothly, you must bleed it thoroughly (turning the steering wheel from lock to lock a dozen times on a raised axle).
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Cause 2: Insufficient pump. The orbitrol has a specific flow requirement (e.g., 10 l/min). If your old pump only provides 6 l/min, then with a quick steering wheel movement, the orbitrol "drinks" all the oil from the hose. A vacuum is created, the system seizes up and offers enormous resistance until the pump can catch up and pump oil.
Summary
A well-chosen steering system is a guarantee of safety and immense comfort. Do not buy parts haphazardly. If you don't know how to match the orbitrol capacity with the size of your cylinder and pump efficiency – contact us. We will calculate it for you!
