![[mechanical diagram]](pic/KnexMech.png)
Referring to Figure 1: The components are as follows--Here's an idea, with description:
Referring to Figure 1: The components are as follows--
Mechanically, the operation is as follows:
The motor 5 rotates the winding spool 4 which moves the cables attached to both ends of the catchwagon 1. Both cables are attached to the winding spool 4, and wound in such a way that as one cable is wound onto the spool 4 the other cable is spooled out. In this way the catchwagon 1 is positively driven regardless of its direction of travel.
As the catchwagon 1 reaches the top of its guide assembly 7 the tab on the bottom of the catchwagon 1 contacts the upper end of the actuator mechanism 3. This mechanism reverses the position of the switch 2 thus reversing the polarity of the drive motor 5 which also reverses the direction of rotation of drive motor 5. This also reverses the direction of the winding spool 4 causing the catchwagon 1 to be driven backward down the guide assembly 7.
When the catchwagon 1 reaches the bottom of the lift guide assembly it trips the limit switch 6 which opens, cutting power to the drive motor 5 which stops the winding spool 4 thus stopping the motion of the catchwagon 1.
To restart the cycle, the operator presses the pushbutton (not shown) which electrically bypasses the limit switch. This will cause the drive motor 5 to restart causing the winding spool 4 to restart, causing the catchwagon 1 to continue down the lift guide assembly until it contacts the actuator mechanism 3 which in turn reverses the position of the slide switch 2. As previously noted, this reverses the wiring of the drive motor 5 causing the catchwagon 1 to ascend the lift. Of course when the catchwagon 1 reaches the limit switch 6 at the base of the lift, the mechanism will stop again until the pushbutton is pressed. Ideally the limit switch 6 will be located very close to the point where the catchwagon 1 contacts the switch actuator 3 so that a single press of the pushbutton will cause the catchwagon 1 to reverse, then advance past the limit switch 6.
![[electrical diagram]](pic/KnexElec.png)
Figure
2 shows the electrical arrangement. Power supplied by a battery or other
suitable power supply flows through the normally closed limit switch 6
and the normally-open pushbutton, and then to opposite terminals of the DPDT
slide switch 2. In this diagram, only the contacts of DPDT switch 2
are shown; it should be understood that the top and bottom contacts in the diagram
are electrically separated but mechanically joined, that the center contacts
are the common contact points, and the outer contacts are the A/B throw points.
For safety, the contacts of this switch should be of the "break before make"
type. Note that the motor 5 is powered from the common contacts of the
switch 2. Note also that the two poles of the power supply are cross-connected
so that the switch action effectively reverses the polarity of the common contacts.
Of course, in all cases, the structures need to be built in a manner consistent with the K'Nex roller coaster systems. At the moment, the only K'Nex stuff I own is the 3' Ferris wheel kit, not a roller coaster, so I don't even know if the catchwagon configuration is practical. But the basic idea should work. If you should happen to build on this setup and manage to make it work, please tell me about it. Heck, if you build it, I'll be happy to showcase your work on this page!
--Dave Althoff, Jr.
Last update: April 4, 2003.
