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Trapdoor Counterbalance
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Page 12 of 13
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How to make a trapdoor counterbalance for the
Kid's Play Fort.
This will help stop the trapdoor accidentally falling shut and reducing the possibility of a mishap such as the trapdoor falling on heads or fingers while kids are climbing up the ladder.
There is a description of all the parts below the drawing, followed by some explanatory pictures.
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The following is reference to the above drawing.
Scroll down for some explanatory pictures.
[a] The trapdoor. There are instructions on how to make the trapdoor in
"How to build a Kid's Play Fort"
, however, there will need to be an additional piece of 45x45 (1 1/2x 1 1/2) wood added to the underside of the trapdoor to give the rope something strong to tie around.
[b] The pulley. The pulley must be able to swing freely and be big enough to take the rope. The pulley must be positioned directly above the casing so the weight will hang vertical. The pulley must not have any parts that a kid can dismantle or undo with hands.
[c] The bolt. The bolt goes through the rafter above the case and supports the pulley. A number of washers and/or shackle/s may be needed to serve the purpose.
[d] The steel weight. The weight used for this project is a piece of steel 50x50x200 (2"x2"x8") with an eye welded to the top. The weight is about 4 kilo (9lb). Most engineering shops will have a bit of scrap steel lying around that you can generally obtain at a reasonable cost and if you're willing to pay a bit extra, you should also be able get an eye welded on the top or at very least, a hole drilled through the top. Any shape steel weight will suffice as long as the case is tailor-made to suit the weight.
[e] The rope. The rope must be of a strong and lasting quality. Thread the rope through holes drilled in the trapdoor and around the piece of 45x45 (1 1/2x 1 1/2) wood underneath, positioned (as shown in the drawings) approximately central lengthwise and about 25mm (1") in from the edge of the trapdoor on the ladder side. Tie well at both the trapdoor end and the steel weight end and then cover the knots with a PVC adhesive tape so kids cannot undo the knots.
[f] The case. The case is the wood structure made to house the weight. When making the case ensure the cavity is larger than the thickness and width of the steel weight. Bolt the case to the wall directly below the pulley.
[g] Metal strap. Screw a metal strap (or similar type bracket) across the top opening of the case so that the steel weight cannot be pulled out. Kids will be kids, you know!
[h] Metal strap Screw a metal strap (or similar type bracket) across the bottom opening of the case so that the steel weight cannot fall out should the rope break or knots come undone.
The case. Ensure the cavity is bigger than the thickness and width of the weight.
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The pulley hanging loosely from a bolt through the rafter.
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The weight before being dropped in the casing. Tie the weight well.
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Metal strap across top of case to ensure weight cannot be pulled out. Put one on the bottom as well.
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A little kid wondering what all the fuss is about.
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Wow! It actually works.
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NOTE: This complete plan-set can be immediately purchased in downloadable PDF format free of advertising and print friendly for only $5.
click here for more info
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