Knex Automatic Drawbridge Element

Introduction: Knex Automatic Drawbridge Element

I created an instructable for Oblivion's drawbridge element since even I was having trouble following the pictures. I hope this helps you build Oblivion or just the element itself!

Step 1: Lower Framework

This step contains the ramp the ball waits on until the bridge allows it to roll.

Step 2: The Main Motor

This step contains the 1st motor and the mother switch that interacts with the pulley systems.

Step 3: Upper Framework

This step contains the spool that controls the bridge movement.

Step 4: Secondary Motor

This step contains the second motor that pulls the mother switch upwards to raise the bridge. It will then automatically turn off. This is a complex step so take your time.
IMPORTANT NOTICE!!!! - Te motor in this step is a slow-turning motor found in the knex amusement part series " Drop And Swing" set.
Other motors may bee too fast for the mechanism.

Step 5: The Drawbridge

Basically it!

Step 6: Pulley Tires

My shortest step!

Step 7: Pulleys

This step is probably the longest in terms of how much adjusting you will have to make! Pay close attention to how the pulleys are attached.

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Tip 2 years ago on Step 5

I clipped the string under a blue clip, rather than tying it around the rod. I find this much easier than tying string, and it's much easier to adjust.


2 years ago

Could you maybe link this on the drawbridge step on Oblivion's instructable?

Good job! I really like this element: it looks very complex, but the mechanism isn't that difficult.

Excellent work bringing the drawbridge element to fuller life! ;-) Much more exhaustive than an in-step piece. One question, though. I remember when originally watching Oblivion that the bridge would make a short up-down at the bottom between lowering and raising, and still does here. It's fine, I just wondered what caused that motion. :-D


Reply 8 years ago on Introduction

The reason for that is when the bridge goes all the way down, the string starts to wind back up raising the bridge because motor two has a slight delay before it reverses the rotation making the bridge go down then raise back up. Just a little delay I purposefully implemented to give the ball a little more time to roll off the bridge.