How To Build Your Own Motorized Drawbridge for Your Backyard
If the video player is not working, you can click on this alternative video link.
Drawbridges are undoubtedly amazing feats of engineering, but they tend to be far too large to have one of your own. So, with a little lateral thinking, you can actually build a tiny one in your back garden.
Read on to find out how.
As you can imagine, you'll need some tools and materials before you get started.
Materials and gear needed
- Quikrete cement mix and sand
- Metal tubes and other metal pieces
- Scrap wood or plastic
- Small winch motors
- Steel wire
- Optional - Little remote-controlled toy boat
With all your gear in hand, it is time to get on with this great little build.
Step 1: Prepare the ground
The first step in any project of this nature is to choose the site for the build. Once done, begin to excavate the ground as needed to make room for the bridge and a channel for the "river", if needed.
You'll need two flat-based excavations in the "banks" of the river for the footings of the draw bridge towers. With that done, take your steel rods, and pile them into the ground to define the shape of the bridge towers.
Using more steel wire, build a cage around the wire posts to make the basic frame for what will be the cement tower structures. Watch the video for more details on how to precisely complete this step.
Rinse and repeat to make the second tower frame as needed. With that done, use bits of plastic or wood to make some hoarding for the frames in preparation for pouring the cement.
Once done, mix up your cement as needed and pour it into the molds. With that done, continue to build up the shape of the towers and progressively raise the towers of the bridge as needed.
Ensure you include metal hooks and other metal anchoring points for the draw bridge supports and actuators.
Leave the cement to fully dry,
Step 2: Make the draw bridge decks
Once the cement is dry, completely peel away the molds from the concrete.
Next, take some plastic-card and your old hinges. Assemble them together to make the main hinged decks of the draw bridge and include steel rod reinforcements and other metal parts to attach them to the main towers, as needed.
Build up the sides of the deck so that you can fill them with cement. Rinse and repeat to make a second identical structure.
As with the towers, leave the concrete to dry and then remove the mold from the outside. Mount the decks to the main towers of the bridge using the hinges and attachment rods as shown.
With that done, build up the frames of the ramps on either side of the bridge, and pour in cement as before. Leave to dry and then remove the molds as needed.
Step 3: Make some draw bridge actuators
With the main structure complete, it is now time to make the bridge actually work. Grab your metal parts and assemble the set of cylinders needed for the main actuators. You will need four of them.
Once built, paint them as desired.
Next, build the screw assemblies as shown, connect them to your cylinders, and mount them between the bridge towers and decks. Wire up the motors to the main control box as required.
Step 4: Finish the bridge
With the main electrical and mechanical components finished, you can now move on to making the bridge look nice.
For example, paint the surface of the decks and ramps black to imitate tarmac. Once dry, add on some road markings as desired.
If you want to, you can also include some basic railings on either side of the decks and ramps too. With the bridge complete, you can now flood the "river" portion of the project in preparation for playing with your new toy.
Once done, grab your RC boat, place it in the river, and raise your bridge decks to let the boat pass! Hours of fun are now yours to enjoy.
If you enjoyed this project, you might enjoy making another mini civil engineering-based project? How about, for example, a small dam?