In the previous article, I explained about the new Delivery Station for Lego World 2016. In this article, I will give an update about the progress.
The new Delivery Station will consist of five parts:
- Container Push: a mechanism that pushes the containers with the candies from the four wagons to the platform.
- Rolling Platform: a mechanism that transports the containers to the fork lifts.
- Fork lifts: four separate lifts that can lift the container (still with candy) up, rotates the container to get the candy out and drops the container as well at two different locations.
- Container and Candy split: The container and the candy are dropped at two different conveyor belts. The containers are moved outside to a container bin where it can be picked up manually and the candies are moved to four separate lockers.
- Candy locker: The visitor can feed his or her ticket to the card reader. The corresponding locker will be unlocked and the visitor can get the candy.
The last three weeks, I have been working on the first four parts. All parts are designed and built as a module to make it also relatively easy to transport.
This part of the Delivery Station pushes the containers with candies from the wagons onto the rolling platform. The pushing is done by 40 axles, shifting sideways. To do this in one movement, I use a grooved cam that is moved from left to right and back (to redraw the axles). In the picture below you see how it looks in LDD.
And a detail of the grooved cam:
A video of the Push mechanism is posted at our Youtube channel: https://www.youtube.com/watch?v=y-SzjWnaRMQ.
Note: the new Delivery Station assumes that the train can stop within ± 4 studs accuracy.
The rolling platform is quite simple and is used to move the containers (that were just pushed from the wagons) to the fork lifts. Since it is not clear what the exact position is of the containers, guide rails are used to get the containers to the fork lift location.
The Lift Mechanism was the most difficult part to design. The first proof of concept as described in the article “Engineering the new delivery station” was not stable enough.
For the second proof of concept, I designed a mechanism that pushed the forks of the fork lift outwards. Otherwise, the containers got stuck at the forks if they entered the forks not completely straight. The forks should first make an upwards movement, and at the top the forks should rotate. In that way, the container and the candy would be released.
In the next Youtube movie, you’ll see this second proof of concept:
In one movement, when the forks make the upwards movement, the two forks make an inner movement to grab the container. At the top, the forks make a small rotation. It is enough to get the candy out of the container, but is not enough to get the container released as well.
A third proof of concept was designed using a gear mechanism that takes care of the rotation:
As you can see in the video, when the fork reaches the top, it hits a rotating gear. This makes the complete fork including the container, rotate. A splitting mechanism pushes the two forks outwards, thus enabling the container to be released from the fork.
From a mechanical point of view, this design just works fine. However, there are some major drawbacks:
- It is too complex. It if is (too) complex, it will make the mechanism unreliable especially in an environment where it needs to run for days (Lego World)
- There is no way to automate this in a simple way: how does the rotating part ‘know’ that the rotation has completed and that it can reverse its direction to rotate the forks in the other way. And how does the lifting mechanism ‘know’ that this back rotation has finished and that it can lower the forks to the start position?
- Due to the weight of the container with candy, the forks bend down a little but when it is going up. Too often, the container fell off during the lift.
I put the idea of ‘lift first, then rotate’ aside and tried to design a mechanism that does all the work in one mechanical move. And I succeeded, as can be seen in the fourth (and final) proof of concept:
As you can see, in one movement:
- the forks ‘grab’ the container when the lifting starts
- the rotation starts immediately, thus minimizing the risk that the container falls off during the lift
- at the top of the rotation, the forks are pushed outside releasing the container (and the candy)
I also designed the Container & Candy Split to check if the movement is not too fast or too slow. A test with 20 runs, resulted in 18 successful splits and 2 runs where the candy landed on the conveyor belt of the containers.
The next step is to order additional bricks to build the four lifts and the complete C&C split part. Meanwhile, I will start to design the lockers for the candies.