Introduction: 100% Recycled Slingshot
If theres one thing I love colleting more than collecting stuff it's collecting hobbies. I'd seen people like zachary fowler and game keeper John on youtube and I was hooked. So I figured, 'I want one of those things... wait I Like making things, I'll just make one!'.
This is a multi-step project so I'll break the tools and materials into those sections.
1. Making your HDPE blank
A deep nonstick tray
2 Nonstick baking sheets
A large wooden chopping board
A rolling pin
An enabling spouse, parent or housemate (the most important).
2. Cutting the slingshot blank:
A saw that will cut tight curves ( scroll saw, bandsaws, fret saws all are great)
A belt sander ( a plane might work but i haven't tried it) or files, sandpaper and patience.
Scissors or an exacto knife.
3. Shaping the frame:
A fine sharpie or marking knife
A set of files, flat, round and half round.
A carving knife.
4.making the bands:
A self-healing cutting board or chopping board
A rolling cutter
5 making the pouch:
Scissors or an exacto knife
A leather hole punch around 5mm
6 Tying the pouch:
Nylon dental floss, smll strips of latex or waxed cotton
Hpde (I used milk bottles, you can ask a cafe to keep them for you if you are lucky)
Latex rubber (I used some from some packaging but the beast type to use comes from thermarest gold exercise bands.
Leather ( thin leather 2mm or so, Cut from an abandonned sofa).
Dental floss, or cotton thread
Double sided tape
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Step 1: Making the HDPE Blank
First you need a lot of hdpe, when you think you have enough, double it. My blank was a little bigger than an A3 sheet of paper and about 2cm thick which weighed about 1.7kg.
The smaller you cut the material, the more solid a block you will get, I went for piceces 1cm by 1cm or there abouts but smaller is better.
So, collect as much hdpe as you can and clean it thoroughly. Cut it into the smallest pieces possible using scissors.
I cut the bottles into long ribbons then chopped the ribbon and that seemed to be the best way.
Hdpe will have 'HDPE' OR a recycle triangle with a no.2 inside, if in doubt, leave it out as you don't want to be melting toxic plastics.
To make the blank you need to line a deep baking tray with a nonstick reusable sheet, make sure the edges stick out of the side as it makes it easier to remove the hdpe block.
Set your oven to 150c and leave to preheat, any hotter and the plastic will burn, you can tell when it burns as it goes an off white-brown colour.
Fill the oven tray with shredded HDPE and place in the hot oven. When the plastic is hot enough lt will go shiney and clear. Be careful ,when handling the hot plastic, it is very sticky and stays hot enough to burn for a long time.
When the plastic in the tray melts down, take the tray out of the oven and flatten it down with something like a potato masher or a rolling pun, top up the tray with more plastic and put it back in the oven.
Repeat until you are well over the thickness you need. The take tray out of the oven, take the plastic out carefully using the edges of the heat proof matt and place on a heat proof board, i then gave the whole thing a once over with a rolling pin.
Over the plastic with a flat board and clamp it flat orncover with weight, this will reduce warping as it cools leave it to cool for a good hour.
Step 2: Making the Frame
I printed the template to scale, roughly cut them out and laid them on the block with a few tabs of double sided tape.The aim was to see how many slingshots I could fit on the slab. I then roughly cut out the slingshot on the band saw, a scrollsaw or fretsaw will be the best for this, as they can cut much tighter curves but you can work with what you've got.
Once you have the rough shape worked out with a bit of extra material. you need to flatten the faces of the slingshot so they are parallel. I did this with a belt sander, which worked really well and quickly.
First, flatten one face, then mark the parallel line on the side of the slingshot, I made mine 13mm as that seemed about right, then sanded to that.
Once I had the faces, flat, parallel and to the dimension you want, you can start to flatten the sides I started by flattening the tops of the forks and the outer sides of the forks so I had two right angles.
I used the two outer corners of the forks as a reference for the templates and stuck them on with double sided tape. .
Then I used a fretsaw to trim the material to the lines on the template.
0nce the lines were all flush to the template I took the templates off and started to shape the frame with hand files and a carving knife. I marked a line around the edge of the sling shot about 6mm and beveled the edges with a carving knife.
I used a round file to cut grooves on the tines of the fork as shown on the template. This will help keep the bands on.
It looked a little plain and HDPE is quite slippy so I added some texture using A small gouge, a round file would also work for this.
I left a circle untextured I then domed the circle and cut my maker mark in with a v gouge, I then melted in some.green hdpe and then shaped it back to flat the dome shape.
You might have some air bubbles at this point, you.can melt small strips.of.plastic and fill them in but i wasn't worried as this was a proof of concept project for me, if I was to redo it, at this point I would fill all the pockets. File.to shape and run through wet and dry grits 1000 or more for a nice finish.
Step 3: Making the Bands
Making the bands is a fairly straight forward process. You need a chopping board, idealy a self healing one.
A roller cutter,
A straight metal ruler
A fine sharpie (other brands are available.)
You also need to do some maths.
You need to work out your draw length and the extension ratio, this sounds worse than it is.
Draw length is how far the elastic is pulled back (slingshot frame to pouch, when full drawn).
Extension ratio is how much stretch you want, it is the ratio of band length at rest to band length at full draw length.
The larger the ratio, the more the band will stretch and the more power you will get, you will also be more likely to break the band.
For the most efficient extension a ratio of 1:6 is recommended, if you want your band to last longer 1:5 or 1:5.5 is fine.
E.g. if you have a draw length of 75 cm or 30 inches, and you have a ratio of 1:6 you will need bands at 5 inches or about 12.5 cm.
So, to make your bands, lay your latex on the cutting matt, measure an extra 2cm or so at on end, you will need this to tie the band to the frame. From that mark, measure out the band length, mark it with a sharpie and add 2cm again, then cut.
You can also add a taper, which improves acceleration, to do this cut your bands as usual, then make a mark on each side the end of the band depending on how much taper you want e.g. 0.5cm in on each side on a 2cm wide band.
Lay the band flat and straight on a cutting board, place a steel rule from the mark, down the band to the corner on the other side. Then use a roller cutter to cut down the band in one continuous cut. This is important, any nicks or cuts in the band may cause it to snap when stretched.
You can buy bands online with pouches attached, or you can buy latex, a popular option is thermaband gold.
If you buy bands online, check the length and if they have the recommended ammo size.
Also check if the pouch is tied for TTF ( Through the forks) or OTT ( Over the top). The slingshot i made is over the top.
Step 4: Making the Pouch
The pouch is 2mm scrap leather from an old sofa, I copied the pouch that came with my scout slingshot. Which is about wcm wide and 7cm long, I folded it half length ways and drew a line along the crease, then did the same the other way to find the center, using a 6mm leather punch, i made a hole.in the center, then one 5mm in from each end.
I then rounded the corners. Sharp scissors work well for this or a roller cutter, if you are making your own bands, a roller cutter is very useful
Step 5: Tying on the Bands/pouch
To tie on the bands you need a small piece of latex apromimately 10 cm long and anywhere between .5 and 1 cm wide.
First place the mark you made after 2cm over the edge of the top of the band fork.
You then hold the extra elastic over the groove on the back of the fork. Then take the latex strip and put one end under your thumb, on top of the band and groove, pull the latex tie taut and start to wrap it round the fork, following the groove, wrap it 3/4 times. Then do one more wrap round over your thumbnail, lift your thumb and place the end of the tie under it in a small loop, then pull your thumb out so the latex pins the loop into the groove, if you have done this right, you can pull the loose end and the whole lashing will come off. Repeat for the other side.
To tie on the pouch you need to fold the end of the latex band in half and thread it through the hole in your pouch so the rough side of the leather is facing the slingshot. Then fold it over itself on the outside of the pouch. Have someone pinch the leather pouch in one hand and the latex loop in the other and strech it. Then with waxed cotton thread or elastic ( i used dental floss to keep myn100% recycled challenge alive), lash the latex just before and after it goes through the pouch. 3/4 wraps round and then you can place a piece of looped string over the lashing, thread your loose end through the loop, wrap 2 more times over the loop and then use the loop to pull the loose end through the lashing, tieing it off.
Simple shot have a great video on how to set up your slingshot, as it is a visual task.
Now.you are ready to shoot it!
Step 6: Optional: Adding a Lanyard Hole
Having a lanyard is an added feature that is especially useful if you are using powerful bands as the lanyard can help the strain and stop you dropping the slingshot on release.
It's worth noting that hpde does not glue well, so anything you need to attach to the plastic needs to be done by melting or by mechanical means eg bolts rivets or screws.
To add a lanyard hole, Icut a small section of brass tube the same length as the sling shot is thick and some change. I then drilled a hole in the handle of the slingshot the same diameter as the tube. Then I hammered the tube section through the hole with a wooden mallet. Once it was all the way through, I filed the brass down to a mm above the surface of the slingshot.
To make the fit even stronger, I took 2 10mm ballbearings and placed them in either end of the tube, put them in a vice and tightened it to open the holes up a little and made a rivet of sorts.
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