Power FunctionsLEGO®

Power Functions Servo Motor

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Product rating. 4.13 out 5 stars
8 Reviews
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Power realistic steering with the Servo Motor!

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Drive Enhance your LEGO® Technic vehicles with 4-wheel steering capability and using the 90-degree turning features of the Servo Motor!

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Drive your LEGO® Technic creations to a whole new level with the LEGO Power Functions motor made for the ultimate 4-wheel steering experience. Power through the turns like never before with ultra-realistic steering.  Steer your Technic vehicle left, right or straight ahead with any one of 15 steering axle positions. Rotates 90 degrees clockwise or counterclockwise. It’s easy to add 4-wheel steering to your models with the Servo Motor’s front and back power outputs!

  •  Servo Motor features 90-degree rotation clockwise or counterclockwise
  •  Designed for use with LEGO® Technic elements and vehicles
  •  Includes front and back power output ports for easy 4-wheel steering functionality
  •  Steer 90 degrees in either direction with a total of 15 fixed positions!
  •  Requires a Power Functions Battery Box (sold separately)
  •  Add 4-wheel steering functionality to your models!
Power Functions Servo Motor is rated 4.1 out of 5 by 8.
Rated 3 out of 5 by from Does not return to center It has plenty of tourque but after a while,it broke. It will not return to it's center.
Date published: 2017-11-11
Rated 5 out of 5 by from At last LEGO has a Servo! Have waited a long time for this, many years whilst RC cars and aircraft developed and then many months since the first release of the LEGO servo motor in sets. Bought two Crawlers 9398 in 2012, built one and used the other for motor experiments. It didn't take long to think of some applications for the servo motor but a Crawler revamp (41999) and a problem meant that we had to wait till now, in 2014, for the servo motors to be available separately in significant numbers. It was worth the wait - I would rather have best quality; it is what we have come to expect from LEGO. The servo motor is not quite the same as an RC car or aircraft servo. Instead of direct proportional control it has 7 positions either side of centre if you use the train remote handset 8879 or an NXT or EV3 to drive it. This is great for vehicle steering and any kind of proportional control. I used an NXT and IR Link sensor with an IR Receiver 8884 to test the first servo motors, the program moving each one through all its positions in a sequence by setting the motor speed in the program block to different values. As well as steering or aircraft flight surfaces, the proportional function can be used for robot limbs or facial features, or to drive a pneumatic servo for proportional pneumatic control. When used with the pole reverser switch 8869 or bang-bang remote 8885, the servo motor has just 3 positions - the centre position and the end-stop positions 90 degrees either side of it. This is great when you know you want a 90 degree movement. I used this function to control rail points (on the right in the picture) and also a points junction for a new type of monorail (on the left in the picture). The rail points application (7895 or the previous 9-Volt version 4531) does not need any modification to the points because the servo motor has plenty of torque. It just needs a long rack to actuate the slider, available in Jet Plane 9396, Mobile Crane 42009 and other sets, with a 12:20 gear ratio to make the 90 degrees of servo movement correspond to the slide length of the point mechanism. You can make a control panel for many points and signals with the 8869 switches. The great thing about the servo motor in 2- or 3-position applications is that it has built-in electronic end-stops. This replaces a gearmotor or PF medium motor used with a white clutch gear. When changing the rail points with a pole reverser switch (centre position for point straight, down for point curved, up position blocked with a 1x2 slider plate) the servo will move the points to exactly the right position without the operator having to watch or listen for the clutch gear slipping and the wow-wow sound of the gearmotor when it does so. This means it is OK to have the points out of sight because the position reliability is good. Other previously-motorised 12-Volt train functions suit the servo motor well, like decoupling (onboard the train or trackside) or level crossing barriers or gates. As an upgrade from the 12-Volt level crossing 7866 you have the choice of smooth barrier control by using the train remote handset or NXT. You can connect servo motors in parallel electrically, such as to control two rail points together, one at each end of a loop, to change trains. I will use these loops several times on my layout - 12 points to select from 4 trains each way. Quick changes of trains are better at exhibitions because people can see the new train sooner - the changeover speed is enabled by the servo motor. I tested the servo motor parallel operation. When controlled together with very weak batteries or high loads the two servos might not actuate at exactly the same time but they will both keep retrying and get to their destinations unless the load is too great. With just two motors in parallel the effect is minimal but I tested it with 10, 15 and 20 servo motors driven from a single pole reverser switch with deliberately-weak batteries (at the bottom of the picture). All the motors got to their destinations eventually, one after the other - as one moved and drained the weak supply (shown by the battery box LED dimming) it affected the others so they tried again. Parallel performance will be much better with either fresh batteries or a mains-derived supply, which could be from a 9-Volt train controller or the PF LiPo battery 8878 with charger 8887. I will use either of the last two solutions when exhibiting a railway layout. Under high load the servo will do its best to get to the destination but if it detects an overload it will release the torque so as not to damage itself. If you find this happening in your model then you should either gear it down or use two servos in parallel. Look out for another Technic set containing a servo motor in the autumn of 2014 or buy these up to 5 at a time! These servo motors are a serious but worthwhile investment and will enhance your control functions in all types of LEGO creations.
Date published: 2014-02-08
Rated 3 out of 5 by from Will not return to center I got a Lego servo motor and it worked fine. It was very easy to fit into a model and worked great. I used on a monster truck once and now it sometimes hesitates or does not return to center. It works fine for a while but every once in awhile it will not return to center and you have to turn the battery box off and then on again. I did not do anything wrong to it and used it very little on one car that I only drove inside like I said above. i think the price is very high for 9 volt motor. Like I said I am very disappointed. I looked it up and other people had the same problem. I would recommend this to someone else though because mine was probably one in a 100 servo motors that has that problem. Other than that it is very helpful for building your Lego creations because you do not have to make gears for the steering to slow it down.
Date published: 2016-05-11
Rated 5 out of 5 by from Purchased with the 8885 remote to make steerable cars for the kids more easily. Works great with the 8879 remote as well but haven't fully realized its potential yet.
Date published: 2015-03-19
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