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8879 Power Functions Speed Control Remote modified

April 30th, 2009 Leave a comment Go to comments

Presentation of the new, speed control-enabled Power Functions handset along with a modification I’ve created to allow easy control of the tracked vehicles. Update: instruction added.

I have been waiting for the 8879 handset for a while, expecting its speed control feature to come really handy. It was obvious that just like the previous handset, this one would see many modifications, so I have planned some on my own beforehand.

The speed control feature implemented into the Power Functions system but never used earlier, offers a number of new possibilities. For instance a heavy model driven by the powerful PF XL motors can speed up or slow down gradually, while with the previous handset it had to be done abruptly, at full motors’ power. Not only does it reduce strain on the drivetrain (thus making it potentially possible to gain greater speed), but it  looks realistic too. Moreover, the tracked vehicles no longer need a subtractor – they can be driven by a single motor for each track and controlled as precisely as if fitted with hydrokinetic transmission. Removing a subtractor results in a much more robust drivetrain system and in substantial savings of the internal hull’s space.

The handset itself is small (the exact size of two previous handset put side-to-side) and complies with the previous handset really well when it comes to putting several handsets together or the general working principles. Just like the previous handset it is powered by three AAA batteries, it has a channel selector with 4 positions available, and two pole reversers, each for a single motor. Instead of two levers present in the previous handset, we have two dials here. Each of them has diameter of a little more than 3 studs, and a 1 stud deep axle hole.  The dials offer 7 levels of speed both forward and reverse. It comes as a surprise that the dials’ movement is not limited – they can be rotated freely, and do not return to a neutral position. Instead, each dial has a red square button that immediately stops the respective motor regardless of the dial’s position. It’s a bit confusing, especially with tracked vehicles, making it hard to synchronize both dials. Fortunately, the dials don’t rotate smoothly, but by small jumps, which is helpful because each jump corresponds to a single speed level.

Another surprise is the fact that the new handset does not require a constant contact with the IR receiver.  While the previous one caused motors to stop upon loosing its signal, with the new handset the motors continue to work uninterruptedly whenever the signal is lost. While it may appear somewhat unsafe (it’s more likely to loose the control of the vehicle that it was with the previous handset), it can be used as an advantage in many situations. Trains builders will certainly appreciate this solution, and so will anyone who chooses to drive his vehicle outdoors. If you think of building a PF-powered vehicle with a degree of autonomy, this handset is a perfect solution, eliminating the need to keep the vehicle’s IR receiver linked to the handset at all times. Instead, it can be given an initial command and then operate on its own.

In order to make controlling the tracked vehicles easier, I have build a simple modification on the handset. It’s a sort of a steering wheel that can be tilted forward / backward to control drive, and works as a regular steering wheel in any position. It does, however, lack some precision, and the gear ratios make it impossible to use the full scale of the handset’s drive control. If we assume that +7 is the full forward speed and -7 is the full reverse speed, the steering wheel offers range from +7 to approximately -2. Therefore it leaves plenty of space for more advanced modifications.

You can see functioning of both original and modified handset from the video below. Additionally, there is my unfinished model of the Caterpillar D9T  tracked dozer used as an exemplary tracked vehicle.


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