920-930 Steering System - Barrington Diesel Club · This steering system lets the operator keep control of the machine if the engine stops running. It does not provide steering as

920-930Steering System

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INTRODUCTION

This publication has instructions and procedures for the subject on the front cover. The information, specifications, and illustrations in this publication are on the basis of information that was current at the time this issue was written.

Correct operation, maintenance, test and repair procedures will give this product a long service life. Before starting a test, repair or rebuild job, the serviceman must read the respective sections of the Service Manual, and know all the components he will work on.

Your safety, and the safety of others, is at all times very important. When you see this symbol or this symbol A in the manual, you mustknow that caution is needed for the procedure next to it. The symbols are warnings. To work safely, you must understand the job you do. Read all instructions to know what is safe and what is not safe.

It is very important to know the weight of parts. Do not lift heavy parts by hand. Use a hoist. Make sure heavy parts have a good stability on the ground. A sudden fall can cause an accident. When lifting part of a machine, make sure the machine has blocks at front and rear. Never let the machine hang on a hoist, put blocks or stands under the weight.

When using a hoist, follow the recommendation in the manual. Use correct lift tools as shown in illustrations to get the correct balance of the component you lift. This makes your work safer at all times.

40400X3



920 AND 930 STEERING SYSTEM INDEX

SYSTEMS OPERATION

Amplifier Steering System........................................................................................ 4

Hand Metering Unit (HMU) .....................................................................................6

Operation.................................................................................................................... 4

TESTING AND ADJUSTING

Hydraulic Steering System....................................................................................... 7

Instrument Tests .......................................................................................................7

Operation Checks....................................................................................................... 7

Troubleshooting..........................................................................................................8

Visual Checks............................................................................................................. 7

SPECIFICATIONS

NOTE: For Specifications with illustrations, make reference to the STEERING SYSTEM SPECIFICATIONS FOR 920 & 930 WHEEL LOADERS, Form No. REG01615. If the Specifications in Form REG01615 are not the same as in the Systems Operation and the Testing and Adjusting, look at the printing date on the back cover of each book. Use the Specifications in the book with the latest date.



920 AND 930 STEERING SYSTEM SYSTEMS OPERATION

AMPLIFIER STEERING SYSTEM

A02003XI

SCHEMATIC OF HYDRAULIC STEERING SYSTEM

1. Steering cylinders. 2. Steering control valve. 3. Main spool in steering valve. 4. Valve spool in left neutralizer valve. 5. Valve spool in right neutralizer valve. 6. Ball check valve (one in each neutralizer valve). 7. Left neutralizer valve. 8. Relief valve for main system pressure. 9. Ball check valve. 10. Ball check valve. 11. Ball resolver valve. 12. Flow control valve. 13. Right neutralizer valve. 14. Selector valve spool. 15. Selector valve. 16. Hand metering unit (HMU).

Components in the steering system are the small section (cover end) of an engine driven, two section, vane type hydraulic pump, a hand metering unit (16) a steering control (amplifier) valve (2), two hydraulic cylinders (1) and the hydraulic tank. An explanation of the operation can best be given by dividing the system into two parts. These are: the pilot system and the steering (amplifier) system.

NOTE: Service information for machines equipped with supplemental steering can be found in SUPPLEMENTAL STEERING SYSTEM, Form No. REG00939.

Hand metering unit (HMU) (16), which is a small hydraulic pump, is operated with the steering wheel. The hand metering pump sends pilot pressure oil to operate steering control (amplifier) valve (2). Steering control valve (2) lets the oil flow from

the engine driven pump go to steering cylinders (1) to turn the machine. At high idle, three full turns of the steering wheel will turn the machine from stop to stop. At low idle, additional turns of the steering wheel are necessary to turn the machine from stop to stop.

OPERATION

Machine Moving: Engine Running No Steering Action

The small section of the two section hydraulic pump sends oil to steering control valve (2). The oil cannot go through the valve because main spool (3) for steering is centered. The oil flow then goes in three directions. First, it goes through left neutralizer valve (7) to hand metering unit (16) where it is stopped. Second, it goes to the piston

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end of selector valve (15). At the selector valve, the oil flow moves selector valve spool (14), opening passages for oil flow from the hand metering unit (when steering) to the left and right neutralizer valves. Third, the oil goes to the unloading part of flow control valve (12).

The centered main spool (3) in the steering valve keeps the oil in cylinders (1) and lines from coming out. Variable pressures in the cylinders are felt at the spring end of the unloading valve through ball resolver valve (11). The pilot relief valve (8) for main system pressure, will open when the pressure in the cylinders gets to 2500 ± 25 psi (175.8 ± 1.7 kg/cm2).

SELECTOR VALVE IN MANUAL STEERING (Dead Engine) Position

[Spool moved to left, opening passages (21) and (22)] 17.Main oil pressure inlet. 18. Inlet from metering unit (steer left). 19. Outlet for power steering (left). 20. Inlet from metering unit (steer right). 21. Outlet for manual steering (right). 23. Outlet for power steering (right).

SELECTOR VALVE IN POWER STEERING POSITION

[Spool moved to right, opening passages (19) and (23)] 17.Main oil pressure inlet. 18. Inlet from metering unit (steer left). 19. Outlet for power steering (left). 20. Inlet from metering unit (steer right). 21. Outlet for manual steering (right). 23. Outlet for power steering (right).

Moving Forward: Engine Running Steering Motion

NOTE: The following information is a description of a right turn. The same principle is used for a left turn.

Steering action is controlled by the output of

pilot oil from the hand metering unit (HMU). The HMU is a small hydraulic pump that sends pilot oil to the steering valve at the rate of 1.9 gpm (7.2 lit/min) at one revolution per second of the. steering wheel. When the steering wheel is turned to the right, pilot oil is sent from hand metering unit (16), through selector valve (15) to right neutralizer valve (13) where it is sent to the right end of main spool (3) in steering control valve (2). This flow of oil moves the main spool to the right. This action of the main spool opens a passage for oil flow from the pump to the head end of the left cylinder and the rod end of the right cylinder. As main spool (3) moves to the left, small holes (orifices) drilled in the spool let oil flow go through drilled passages to the opposite end of the spool. This flow of oil through the small holes (orifices) in the main spool causes a decrease in pressure that is balanced by the centering springs of the main spool. The oil flow that goes to the opposite end of the spool returns to the hand metering unit through left neutralizer valve (7) and selector valve (15).

Pressure caused by the flow of oil from the pump to steering cylinders (1) is felt through ball resolver valve (11) to the spring chamber of flow control valve (12). As the pressure increases due to road resistance, valve (12) is moved to the left, increasing the resistance to the flow of pump oil through the valve. This causes an increase in the pressure in the cylinders to balance the increase of pressure caused by road resistance.

The angle that the machine will turn is limited by strikers that are installed on both sides of the front frame. As the machine turns to the right (or left) and nears the frame stops the striker makes contact with the valve spool of the right neutralizer valve. This pushes the spool of the neutralizer valve into the body and stops the flow of oil to the main spool. Stopping the pilot oil lets the main spool, in the steering valve, return to a centered position. This stops the flow of oil from the pump to the cylinders. Steering “off the stop” is possible because the flow of pilot oil is sent around the blocked passage in the right neutralizer valve. It then goes through bypass ball check valve (6) and permits a left turn.

If the pressure in the steering cylinders goes higher than 2500 psi (175.8 kg/cm2) pilot relief valve (8) for main system pressure will open.

Machine Moving, Dead Engine:Steering

When hydraulic pump pressure decreases to less than 30 psi (2.1 kg/cm2) spool (14) in selector valve (15) moves to the left. This stops the flow of pilot oil to either end of main spool (3) in the steering valve. This same action by spool (14)

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opens passages (21) and (22) so that the pilot oil will go to the cylinders. Valves (9) and (10) send oil to the hand metering unit to decrease cavitation and prevent road shocks at the steering wheel when moving over rough surfaces.

This steering system lets the operator keep control of the machine if the engine stops running. It does not provide steering as good as the primary system or a machine equipped with supplemental steering.

HAND METERING UNIT

The hand metering unit (HMU) is a small, hand operated hydraulic pump. Pressure oil from the main hydraulic pump is sent to the inlet (4) where it stopped when the unit is in the neutral position.

Steering action is started by turning the steering wheel. The control spool is turned by a direct connection with the steering column shaft (9). Turning the spool opens passages that send oil to the metering (pump) (10) section.

The oil that is pumped by the HMU is sent through connecting lines to the steering valve. The opposite chamber on the HMU is connected to tank.

HAND METERING UNIT IN NEUTRAL POSITION

1. Meter section. 2. Control section. 3. Column section. 4.Inlet for main system oil. 5. Outlet to tank. 6. Right turnoutlet. 7. Left turn outlet.

The faster the steering wheel is turned the faster the machine will turn. This is due to the rate of flow from the HMU. The fastest steering time is when the steering wheel is turned at a rate of 1.1 seconds per revolution with the engine at high idle. The fastest time with the engine at low idle is 2.25 to 1.75 seconds per revolution of the steering wheel.

If the engine should stop when the machine is moving, the HMU will give the operator the ability

HAND METERING UNIT IN RIGHT TURN POSITION

4. Inlet for main system oil. 5. Outlet to tank. 6. Right turn outlet. 7. Left turn outlet. 8. Ball check valve. 9. Steering column. 10. Metering pump. 11. Spool and sleeve.

to manually control the steering until he can come to a stop. When manual steering is used, the HMU sends oil directly to the steering cylinders. Steering oil is kept in the system through the action of ball check valve (8).

HAND METERING UNIT IN LEFT TURN POSITION

4. Inlet for main system oil. 5. Outlet to tank. 6. Right turn outlet. 7. Left turn outlet.

CAUTION: Manual steering is slower than power steering. Turning from stop-to-stop is impossible. Extra care must be taken by the operator at all times when this method of steering is used. Pushing the machine is possible but towing should not be used unless at very slow speeds.

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920 AND 930 STEERING SYSTEM TESTING AND ADJUSTING

HYDRAULIC STEERING SYSTEM

During an analysis of the hydraulic steering system, remember that correct oil flow and pressure are necessary for correct operation. Pump output (oil flow) is a function of engine speed (rpm). Oil pressure is caused by resistance (by the system) to the flow of oil.

Visual checks and measurements are the first step when troubleshooting a possible problem. Then do the operation checks and last the instrumentation tests.

Use the 5S5123 Hydraulic Test Group, a stop watch and a magnet or the 9S2000 Flow Meter for basic tests to find:

1) The opening pressure of the relief valve for main system pressure. When the opening pressure of the relief valve is too low, it will cause a decrease in the steering ability of the machine. When the opening pressure is too high it will cause a decrease in the life of hoses and components.

2) Cycle times in the steering circuit. The time needed to steer from straight ahead to either the right or left stop should be approximately the same. Differences in these times will result in poor control of the machine.

3) Oil flow in the different parts of the circuit. This includes the flow of oil from the pump to the steering valve; from the hand metering unit to the neutralizer valves; from the selector valve to the steering valve (manual steering).

VISUAL CHECKS

Let the oil become cool and do the following inspections:

1. Check the level of the oil in the tank. Slowly loosen the tank filler cap. Release all pressure in the tank before removing the cap. Remove the cap.

2. Remove the filter element and check for foreign materials. A magnet will separate ferrous metals from non-ferrous materials not made of metal (sealing materials such as: piston rings, O-ring seals, etc.). 3

3. Inspect the hand metering unit, all lines and the steering cylinders for damage or leakage.

OPERATION CHECKS

A WARNING: When testing and adjusting the hydraulic system, move the machine to a smooth horizontal location on a dirt sur

face. Move away from the job traffic pattern and

away from other personnel. Do not let more than one man on the machine at a time. Keep all other personnel off to one side and in view of the operator at all times.

The operation checks of the system can be used to find leakage in the system. They can also be used to find a valve or pump that is not working correctly. The time needed to steer from stop to stop can be used to check the condition of the cylinders and the pump.

Turn the machine from stop to stop several times.

1. Watch the movement of the cylinders as they are extended and retracted. The movement must be smooth and regular.

2. Listen for noise from the pump.

3. Listen for the sound of the relief valve opening. The relief valve must not open until the system pressure reaches 2500 ± 25 psi. (175.8 ± 1.7 kg/cm2).

4. Check the time needed to steer the machine from a full left turn to a full right turn. The fastest steering time is when the steering wheel is turned at the rate of one revolution in 1.1 seconds with the engine at high idle.

INSTRUMENT TESTS

Tools needed: 5S5123 Hydraulic Testing Group and 9S2000 Flow Meter.

Tests can be made with oil at operating temperatures of 90° to 120°F. (32° to 49*C).

NOTE: Testing with the 9S2000 Flow Meter should always be done with the oil temperature at 150 ± 5°F (65 ± 5°C). To keep oil loss to a minimum, remove the filler cap on the tank and replace it before opening the system.

1. Install a 0 to 4000 psi (0 to 281.2 kg/cm2) pressure gauge with necessary fittings and hose.

2. Remove the strikers on both neutralizer valves.

NOTE: The safety link can be installed instead of removing the strikers.

3. Get the engine to 2200 rpm. Turn the steering wheel (left or right) until you get a maximum reading on the pressure gauge.




4. The gauge must read 2500 ± 25 psi (175.8 ± 1.7 kg/cmI. 2).

5. Keep the engine speed (rpm) at 2200 and turn the steering wheel in the opposite direction. The maximum pressure reading must be 2500 ± 25 psi (175.8 ± 1.7 kg/cm2).

6. Add or remove shims (1) to get the correct pressure.

CHANGE IN PRESSURE BY REMOVALOR ADDITION OF ONE SHIM (1)

CHANGE IN psi.SHIM PART NO. THICKNESS (kg/cm2)

3H2549 .010 in. 94.(0.25 mm) (6.61)

3J7473 .005 in. 47.(0.13 mm) (3.30)

7. Tighten plug (2) to 30 ± 5 lb.ft. (4.1 ± 0.7 mkg).

1. Shims. 2. Plug.

TROUBLESHOOTING

To find the cause of a problem in the steering system, use the following procedures:

I. Check the pilot circuit between hand metering unit (HMU) (12) and spool (6) in steering control valve (7) with the engine running.

A. Remove plug (9).

B. Turn the steering wheel for a right turn.

C. The flow of pilot oil must be smooth and free of air.

D. Replace plug (9).

E. Remove plug (4).

F. Turn the steering wheel for a left turn.

G. The flow of pilot oil must be smooth and free of air.

H. Replace plug (4).

NOTE: When the plugs are removed, there will be small flow of oil. If the steering wheel is not turned this flow will stop. After the flow has stopped, turn the steering wheel at a constant rate (2 to 3 seconds per revolution). If the flow of oil does not stop or is not smooth and free of air check the following possible causes.

POSSIBLE CAUSE:

Oil flow is not smooth and has air in it.

Oil supply has air in it. Check the lines, valves and tank for an air leak. Check oil level in the tank. Check for restrictions in the drilled passages of the valves or in the pilot lines.

HMU is not working correctly.The pull needed to turn the steering wheel should be low, 18 to 22 lb. in. (20.7 to 25.4 cm.kg) when the oil is warm and the wheel is turned at a rate of 15 to 20 seconds per revolution. If steering is more difficult check for a restriction in the pilot lines or the drilled passage ways in the HMU or valves. Check the HMU to be sure it is installed correctly.

II. Check the circuit between the HMU (12) and steering cylinders (1) with the engine shut off.

A. Remove plug (3).

B. Turn the steering wheel for a right turn.

C. The flow of oil must be smooth and free of air.

D. Replace plug (3).

E. Remove plug (2).

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SCHEMATIC OF STEERING SYSTEM

1. Steering cylinders. 2. Plug. 3. Plug. 4. Plug. 5. Reverse flow ball check valve. 6. Main spool in steering valve. 7. Steering control valve. 8. Pilot relief valve. 9. Plug. 10. Ball check valve. 11. Ball check valve. 12. Hand metering unit (HMU). 13. & 14. Supply line for pilot pressure to hand metering unit. 15. Ball resolver valve. 16. Flow control valve. 17. Spool in selector valve. 18. Pilot line for right turn. 19. Pilot line for left turn. 20. Supplemental steering valve. 21. Supplemental steering pump.

F. Turn the steering wheel for a left turn.

G. The flow of oil must be smooth and free of air.

H. Replace plug (2).

NOTE: When the plugs are removed, there will be a small flow of oil. If the steering wheel is not turned this flow will stop. After the flow has stopped, turn the steering wheel at a constant rate, 15 to 20 seconds per revolution. The pull needed to turn the steering wheel should be low 18 to 22 lb. in. (20.7 to 25.4 cm.kg) when the oil is warm. If the steering

is more difficult, check for restrictions in the pilot lines or drilled passages in the valves. Check the HMU to be sure it is installed correctly.

III. Check the performance of the Hand MeteringUnit (HMU).

A. To check the performance of the HMU, loosen fittings on lines (18) and (19). These are the pilot lines for steering right and left respectively.

B. With the engine running and the steering wheel stationary, there will be a small loss




CROSS SECTION OF BALL RESOLVER VALVE

15. Ball resolver valve. 20. Flow control dampening pin.

LEFT HAND NEUTRALIZER VALVE

4. Plug. 5. Reverse flow ball check. 10. Ball check valve.

of oil. The flow should stop after all of the oil in the lines runs out.

C. The amount of pull needed to turn the steering wheel must be low; 18 to 22 lb. in. (20.7 to 25.4 cm.kg) with warm oil and the wheel is turned at a rate of 15 to 20 seconds per revolution.

D. Pilot flow at the opened lines must be smooth and free of air when the steering wheel is turned at 2 to 3 seconds per revolution.

E. Connect fittings removed in Step IIIA.

IV. The HMU can cause the following problems:

A. Steering wheel turns by itself with the engine running.

RIGHT HAND NEUTRALIZER VALVE

9. Plug. 11. Ball check valve.

1. HMU is dirty causing the sleeve valve to stick. (The pull needed to turn the steering wheel is usually higher than normal).

NOTE: If there is dirt or foreign materialin the HMU, the rest of the hydraulicsystem should be flushed.

2. The length of the bolts holding the HMU to the steering column is too long. These bolts may not be tightened evenly. The surfaces of the HMU and the part it is mounted on are not flat.

3. The centering springs (7J8010) in the HMU are broken.

4. The sleeve valves in the HMU have too tight a fit.

B. Steering wheel is hard to turn with the engine running.

1. Steering wheel steers normal with cold oil but becomes harder to steer as oil warms up.

2. Check the pilot lines for restrictions.

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3. The bolts (7J6835) in the HMU assembly are too tight or have not been tightened evenly. Correct torque is 20 ± 1 Ib.ft. (2.8 ± 0.14 mkg).

4. Steering pump has a defect. Flow should be 23.0 U.S. gpm, (87.1 lit/- min) at 1000 psi (70.0 kg/cm2) and 2000 rpm.

5. The clearance between ball check valve (10) and spring pin is too small. The minimum measurement is .10 in. (2.54 mm).

6. The timing on the HMU drive is not correct. Drive pin (7J8009) must be parallel with the groove in the star gear.

C. Steering wheel is hard to turn when machine is against one of the stops (neutralizer valves).

The clearance between the reverse flow ball check valves (11) or (5) and spring pin is too small. The minimum measurement must be .10 in. (2.54 mm).

V. Troubleshooting the Steering Control Valve (Engine must be at High Idle unless a different indication is given).

A. Machine steering is correct with an empty bucket but it steers slow when the bucket is loaded or the brakes are being used.

1. The fit between flow control valve (16) and body of the steering control valve (7) is too loose.

2. One or both of the seats in the ball resolver valve (15) has a leak.

a. If steering is slow in both directions, both seats have a defect or the fit between flow control valve (16) and body of the steering control valve (7) is too loose. The flow control valve may be sticking or there is leakage across pilot relief valve (8) or its seal.

b. If steering is slow in one direction only, there is a defect in only one of the seats in the ball resolver: right turn slow: upper ball resolver seat, left turn slow: lower ball resolver seat.

3. Steering pump has a defect. Flow should be 23.0 U.S. gpm (87.1 lit/- min) at 1000 psi (7.0 kg/cm2) and 2000 rpm.

B. Steering wheel turns by itself.

1. Check the HMU (See paragraphIV. A.)

2. The alignment of the metering orifice and pump-to-cylinder slots on main control spool (6) with the lands in valve body (7) is not correct. Remove spool (6) and install it in the reverse direction. Be sure to install the retainers and spacers correctly. Steering time from stop-to-stop may need an adjustment. This can be done by using the 6J6517 or 6J6576 Shims. Add shims to increase right turn cylinder flow. Remove shims to increase left turn cylinder flow.

3. Main control spool (6) is sticking in a shifted position. Check the valve for dirt or foreign matter, body valve bolt torques that are not the same on each bolt, deep scratches in the bore of the valve body or rough particles on the spool.

C. Steering time is too slow in both directions. Normal steering time from stop-to- stop is 2.5 to 2.9 seconds with the engine at high idle and turning the steering wheel at 1 revolution per second.

1. Check the steering time with and without brake application. The steering times will be approximately the same.

2. Make an adjustment to flow control valve (16) by adding 5S7018 Shims. A maximum of 10 shims is permitted to keep the pressure on the pump from being too high in neutral.

3. Check the performance of the steering pump. Flow should be 23.0 U.S. gpm (87.1 lit/min) at 1000 psi (7.0 kg/cm2 ) and 2000 rpm.

D. Steering time too slow in one direction only.

1. Leakage in one of the ball resolver seats. Check steering with and without brake application. (See paragraphV. A.2.)

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2. Make an adjustment in the shims atthe end of the control valve spool.(See paragraph V.B.2.)

3. Check the steering wheel slip (movement of the steering wheel withoutmachine movement) to check thealignment of the control valve spoolwith the body. Maximum permissibleslip (engine at low idle, warm oil,brakes released, bucket off theground) is 15 seconds per revolutionof steering wheel with a very smallmovement of the machine. If thesteering wheel can be turned fasterthan 15 seconds per revolution withno movement by the machine, remove the control valve spool fromthe steering control valve body andinstall it in the reverse direction.Make a shim adjustment on the control spool until the steering times arethe same.

E. Machine does not steer when steeringwheel is turned.

1. Flow control valve (16) is stuck inthe open position.

2. The 1J8497 Relief Valve has a defector a failure of a seal.

3. The timing land in the main controlvalve body is not machined correctly.

4. The spline end of the steering columnhas been pushed into the HMU toofar causing the inner and outer sleevevalves to stick.

5. Check the performance of the steering pump. Flow should be 23.0 U.S.gpm (87.1 lit/min) at 1000 psi (7.0kg/cm2 ) and 2000 rpm.

F. Machine steering is not smooth.

1. The flow control valve (16) is notworking correctly.

2. The flow control dampening pin (20)is not installed. (8J430 Valve onmachines 41K1876—UP and 62 V-2906—UP).

3. The timing slots and metering orificeof the main control spool are not tospecifications. (See paragraph V.D.3.).

4. Check the performance of the steering pump. Flow must be 23.0 U.S.gpm (87.1 lit/min) at 1000 psi (7.0kg/cm2 ) and 2000 rpm.

G. Lip seal leakage on the right hand neutralizer valve. The seal can come out of thebore and the stem on the neutralizer valvewill not move freely. The relief valve seatmay be installed wrong or the O-ring sealis leaking.

H. No manual steering; power steering isworking correctly. Selector valve spool(17) is stuck in the power steering position.

I. The steering wheel can be turned after themachine has made contact with a framestop.

1. The frame stop adjustment is notcorrect. It does not contact the neutralizer valve spool.

2. Valve seat (5) or (11) has a defect ordirt is keeping it from working correctly.

J. Noise caused by vibration. (Can be heardbest at lower engine rpm).

Replace tube assemblies (13) and (14) with a 1V2774 Hose Assembly.

□ CATERPILLARCaterpillar, Cat and □ are Trademarks of Caterpillar Tractor Co.

CATERPILLAR FUNDAMENTAL ENGLISH FORM NO. REG00513-03

JANUARY 1974 PRINTED IN U.S.A.



Documents

920-930 Steering System - Barrington Diesel Club · This steering system lets the operator keep control of the machine if the engine stops running. It does not provide steering as